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Power Network Application Trainer

– Insulation Analysis

199

7.2.3 Dielectric discharge

It is difficult to determine the polarization index if polarization absorption current I

RCpi

is small compared to the others.
Rather than measuring the polarization current during an insulation test, the

dielectric discharge

(DD) test can be performed. DD test is carried out after the

completion  of  the  insulation  resistance  measurement.  Typically,  the  insulation
material  is  left  connected  to  the  test  voltage  for  10  ...  30  min  and  then  discharged
before  the  DD  test  is  carried  out.  After  1  min  a  discharge  current  is  measured  to
detect  the  charge  re-absorption  of  the  insulation  material.  A  high  re-absorption
current indicates contaminated insulation (mainly based on moisture).

DD value

Tested

material

status

> 4

Bad

2

– 4

Critical

< 2

Good

Table 68-3: Values of dielectric discharge

Idis (1 min) Discharging current measured 1 min after the voltage was

switched off

U

Test voltage

Ciso

Capacitance of tested object

Table 69-3: Typical values of dielectric discharge

Figure 111-3: The current/time diagram of a good and bad insulation tested with dielectric discharge

method

The dielectric discharge test is very useful for testing a multi-layer insulation.

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Summary of Contents for MI 3298

Page 1: ...Power Network Application Trainer MI 3298 Instruction manual with exercises Ver 1 0 1 Code no 20 752 871 ...

Page 2: ...l metrel si http www metrel si Mark on your equipment certifies that it meets European Union requirements for EMC LVD ROHS regulations 2018 METREL Electrical power installations testing and verifications METREL 2018 No part of this publication may be reproduced or utilized in any form or by any means without permission in writing from METREL ...

Page 3: ...wer Network Application Trainer Introduction MI 3298 3 TABLE OF CONTENTS Introduction 4 Earth Ground network impedance analysing 36 Power generators transformers coils 162 Insulating material analyses 191 ...

Page 4: ... specification 19 1 8 2 2 MI 3298 P1 Training Module 23 1 8 2 3 MI 3298 P1 Warnings and safe rules 24 1 8 3 MI 3298 T Power Transformer Cables and Power Loads 25 1 8 3 1 1 MI 3298 T Technical specification 28 1 8 3 2 MI 3298 T Training Module 29 1 8 3 3 MI 3298 T Warnings and safe rules 30 1 9 Test methods 31 1 9 1 Auto sequence 32 1 9 1 1 Auto Sequence groups menu 32 1 10 Safety precautions 33 1 ...

Page 5: ...ce measurements 46 Figure 28 2 Placement of measuring probes 62 method 48 Figure 29 2 Definition of parameter a 49 Figure 30 2 Straight line measuring probes placement 49 Figure 31 2 Equilateral placement 51 Figure 32 3 Different measured voltage drops at low and high probe resistance 52 Figure 33 2 MI 3290 Earth Analyser and MI 3295S Step Contact Voltage Measuring System 53 Figure 34 2 MI 3123 Ha...

Page 6: ...90 2 Selection of test point for GPR measurements 154 Figure 91 2 Graphical presentation of GPR measurements 157 Figure 92 2 GPR measurement with MI 3290 158 Figure 93 2 Graphical presentation of GPR measurements 161 Figure 94 3 Set of Metrel measuring instruments which could be used with MI 3298 T 162 Figure 95 3 Single phase VT PT transformer and CT transformer turn ratio measurement connection ...

Page 7: ...easurement setup for insulation testing 208 Figure 119 3 Diagnostic test measurement setup 212 Figure 120 3 Step voltage test measuring setup 215 Figure 121 3 Transformer insulation resistance measurement setup primary secondary side 217 Figure 122 3 Transformer Insulation resistance test setup primary side pe terminal 221 Figure 123 3 Transformer Insulation resistance test setup secondary side pe...

Page 8: ...asurements on the MI 3298 P1 module between selected terminals 21 Table 4 1 Resistance measurements on the MI 3298 P1 module between selected terminals 21 Table 5 1 Resistance measurements on the MI 3298 P1 module between selected terminals 22 Table 6 1 Turn ratio related to the switch position 28 Table 7 1 Resistance of primary windings U V W related to the switch position 28 Table 8 1 Technical ...

Page 9: ...nal institute or other partners Institutes Training centres Electricity Safety Boards Trainers for Power environment All training modules should be equipped with A Catalogue of Knowledge A Catalogue of Exam A Certificate for supplementary qualification and competences Certified Training Modules and Seminars are supported by the Metrel Academy Within the Knowledge section we make recommendations an...

Page 10: ...and modules together with knowledge and certificates Figure 1 1 Organizations included in certification The whole package includes Knowledge Guideline Handbook Registered Training Program Certified Training Test Equipment Safety Precautions on Screen Module Puzzle s Figure 2 1 Training module road map ...

Page 11: ...r the Electro Technical Safety and Low voltage electrical installations NNELI as a partner company through eTest scheme in Slovenia We are a partner company of E Check Association of electrical installers in Germany and cooperate with similar associations in other countries 1 5 References Through our own participation in providing and supporting national vocational qualification programs in the fi...

Page 12: ... sent on the following addresses o help metrel si o info metrel co uk o metrel metrel de Bespoke product training for an individual customer or larger groups of people Complete distributor set up training product repair and calibration training B2B web support provides specific technical information for Metrel partners Download centre enables you downloading product technical data Manuals Datashee...

Page 13: ...know how about troubleshooting maintaining and caring out different measurements on the real field It is aimed as well to be used at sale demonstration for presentation of different measurements techniques Note When using training modules in technical schools we suggest the presence of a qualified person during the practice Applications Education trainings and seminars with theoretical and practic...

Page 14: ...tance measurements Transformers Turn Ratio Analysing Different modules could be evaluated separately as an independent system and or connected together to express the interconnectivity problems and influences between them This type of approach could give the trained personnel clear information on testing methods measured values and results on known systems and overview over situations where system...

Page 15: ...use the HV training module if any damage is noticed Consider all generally known precautions in order to avoid risk of electric shock while dealing with hazardous voltages Service intervention is only allowed to be carried out by competent authorized personnel Do not use the HV training module in a wet environment around explosive gas vapour or dust For the training purposes and for your safety us...

Page 16: ... switch selection of different resistance pylon foots earthing condition 5 Selection switch selection of different earth character resistive inductive type 6 Connection for the next neighbourhood Training module puzzle concept 7 Soil simulation semi conductive material for GPR step and contact voltage measurements 8 Fuse 250V T1A 9 Connection point for S P1 clamp for ground resistance measurement ...

Page 17: ...mber 4 Explanation for selection switch Nm 4 simulation of pylon fault earthing conditions Figure 6 1 Pylon foots grounding simulation Pos 0 regular pylon foots condition different earth resistance for each foot Pos 1 broken earth connection for pylon foots 2 and 3 Pos 2 simulation of earthing ring connection for GPR Step Contact measurements Pos 3 broken pylon foots connection ...

Page 18: ...nts available with MI 3290 and MI 3295M Visual check Safety precautions Before During and After tests Ground Networks Impedance Pylon ground impedance Pylon legs impedance with flex clamps HF resistance measurement Passive flex clamps measurement Impulse impedance measurement Pylon Ground Wire Test PGWT Ground Potential Rise GPR Earth Surface Potential Fault Simulated Step Contact Voltage List of ...

Page 19: ...Step Contact Voltage 1 8 2 1MI 3298 P1 Technical specification 1 Resistance between Earth terminal and accessible test terminals Figure 10 1 MI 3298 P1 resistance test between selected terminals Test terminal Low limit Ω High limit Ω 1 14 25 15 75 2 9 5 10 5 3 19 21 4 4 5 5 5 5 450 550 6 84 6 103 4 7 450 550 Table 1 1 Resistance measurements on the MI 3298 P1 module between selected terminals ...

Page 20: ... P1 resistance test between selected terminals Position of Switch 5 Low limit Ω High limit Ω 1 2 16 2 64 2 2 40 3 20 Table 2 1 Resistance measurements on the MI 3298 P1 module between selected terminals 3 Resistance between Earth terminal and pylon foots terminals Figure 12 1 MI 3298 P1 resistance test between selected terminals ...

Page 21: ...ce measurements on the MI 3298 P1 module between selected terminals 4 Resistance between Earth terminal and pylon foots terminals Figure 13 1 MI 3298 P1 resistance test between selected terminals Test terminal Low limit Ω High limit Ω 1 4 5 5 5 2 4 5 5 5 3 4 5 5 5 4 4 5 5 5 Table 4 1 Resistance measurements on the MI 3298 P1 module between selected terminals ...

Page 22: ...High limit Ω 1 0 L 0 L 2 0 L 0 L 3 0 L 0 L 4 4 75 kΩ 5 25 kΩ Table 5 1 Resistance measurements on the MI 3298 P1 module between selected terminals General data Dimesnions w x h x d 40 cm x 11cm x 33 cm Pollution degree 2 Weight 3 94 kg Degree of protection IP 40 Operation conditions Working temperature range 10 C 50 C Maximum relative humidity 90 RH 0 C 40 C non condensing Working nominal altitude...

Page 23: ...age probes code 20 052 009 Pylon code 20 052 006 Ground wire connection code 20 692 042 Puzzle interconnection part code 20 052 010 Set of measuring cables Coax measurement cable black code 20 692 124 Measurement cable red code 20 691921 Measurement cable blue code 20 691923 Measurement cable green code 20 691924 Flex current clamps A 1612 phi 14 cm code 20 051 222 1 pcs Optional Flex current clam...

Page 24: ...ion trainer and leave it to dry totally before use Do not use liquids based on petrol Do not spill cleaning liquid over the demo board 1 8 2 3 MI 3298 P1 Warnings and safe rules Note Follow the instructions for safety work Warnings Never touch test terminals during the measurements Connect instrument according the instructions described in this manual For the training purposes and for your safety ...

Page 25: ...er connection terminals and its technical data Voltage ratio 10075 V 1000 V Vector group Yyn0 Note For measuring the transformer isolation use max test voltage 1kV 2 Test point for cable insulation resistance testing Max test voltage 5 kV DC 3 Tube Fuse 250V T1A 4 Switch for selecting different transformer winding conditions 5 Ground terminal 6 Connection for the next neighbourhood training module...

Page 26: ...ion on winding w List of measurements and instruments which could be done with MI 3298 T module with MI 3280 instrument Figure 18 1 List of measurements available on MI 3280 Visual check Safety precautions Before During and After tests Transformer s Turn Ratio measurement Transformer s winding resistance measurement List of measurements and instruments which could be done with MI 3298 T module wit...

Page 27: ...ostic Test o Dielectric Absorption Ratio DAR o Polarisation index PI o Dielectric Discharge DD Voltage dependence test Step Voltage Test Withstanding Voltage Test Measurement and instrument which could be done with MI 3298 T module with Micro Ohm MI 3250 Voltage insulation testers MI 3200 MI 3201 MI 3205 MI 3210 Figure 20 1 Inductive measurements mode available on MI 3250 instrument ...

Page 28: ...tion 2 2 200 2 400 RXv switch position 1 2 3 4 400 4 650 RXw switch position 1 4 400 4 650 RXw switch position 2 3 999 9 999 9 Table 7 1 Resistance of primary windings U V W related to the switch position HV Test Un 500 V Low limit High limit Riso 5 GΩ 12 GΩ DAR 1 2 PI 2 6 DD 4 8 Co 54 nF 66 nF HV Test Un 5 kV Riso 2 GΩ 12 GΩ DAR 1 2 PI 2 6 DD 4 8 Co 54 nF 66 nF Table 8 1 Technical data of the HV ...

Page 29: ...nction or any damage notice the module must be serviced by a competent service department Contact your dealer or producer for further information Producer s contact details Address METREL d d Ljubljanska 77 SI 1354 Horjul Slovenia Europe Tel 386 1 755 82 00 Fax 386 1 754 92 26 URL http www metrel si E mail metrel metrel si Use a soft patch slightly moistened with water or alcohol to clean the surf...

Page 30: ...this manual For the training purposes and for your safety use Metrel instruments described in this manual Never apply AC voltage on primary or secondary winding terminals marked as H terminals U V W or X terminals u v w risk of electric shock Never apply AC voltage to pe terminal This terminal represents housing of transformer Never touch the test terminals during the performed measurement Risk of...

Page 31: ...rding to the IEEE Std 81 2012 item 8 2 2 1 Three point Z earth method according to the IEEE Std 81 2012 item 8 2 2 2 Staged fault test method according to the IEEE Std 81 2012 item 8 2 2 3 Fall of potential method according to the IEEE Std 81 2012 item 8 2 2 4 Clamp on or stake less method according to the IEEE Std 81 2012 item 8 2 2 5 Resistance by fall of potential FOP flex clamp on method accor...

Page 32: ...Auto Sequence groups menu In Auto Sequence groups menu lists of Auto Sequences are displayed Only one list can be opened in the instrument at the same time The list selected in the Auto Sequence groups menu will be opened in the Auto Sequence main menu Pre programmed sequences of measurements can be carried out in Auto Sequence menu The sequence of measurements their parameters and flow of the seq...

Page 33: ...edures and practices adopted by the particular organization involved shall be strictly followed 1 10 1 Station ground tests Reduced the hazards by wearing gloves and dielectrically rated footwear Exposed test leads and electrodes are isolated from workers and the general public Short test periods assured and all test leads promptly removed after the test is completed Remote probes and test leads a...

Page 34: ...according IEEE 81tm 5 Operator needs to go through the precautions test to be sure that all safety equipment and measures are used during the performed tests and all regulations are taken into account Visual test is used as guidance to maintain safety standards prior testing and they are available under icon Main purpose is to make all safety checks before performing any test 1 11 1 Inspectors gui...

Page 35: ...connecting neutral and shield wires Hazard can occur due to current flow through the interconnected shield wires High voltages can occur if neutrals are disconnected from energized equipment 1 11 3 Inspectors guide after test reminder After completing the tests operator is responsible that All test leads promptly removed after the test is completed ...

Page 36: ...t 36 Earth Ground network impedance analysing Figure 23 1 Set of Metrel measuring instruments which could be used with MI 3298 P1 Topics covered Lightning protection Substations Transformers Transmission lines Towers Pylons Measurement instruments used MI3290 MI3295S MI3295M MI 3123 ...

Page 37: ...rement 72 4 Exercises on MI 3298 P1 training module 75 4 1 Earth resistance measurement exercises 81 4 1 1 3 Pole and 4 Pole earth resistance measuring method 81 4 1 1 1 Measurement with MI 3290 Earth Analyzer 81 4 1 1 1 1 3 Pole measuring method 81 4 1 1 1 2 4 Pole measuring method 84 4 1 1 2 Measurement with MI 3123 SmartTEC Earth Clamp meter 87 4 1 1 3 Measurement with MI 3295S Step Contact Vol...

Page 38: ...hod resistance type simulated broken foot resistance resistive earthing type 121 4 1 6 2 Auto Sequence procedure 4 Pole HF measuring method S Flex broken earth connection with simulated GW connection 125 4 1 7 Impulse measuring method 131 4 2 Step Contact Voltage Measurement exercises 135 4 2 1 Step voltage measurement with Earth Analyser MI 3290 135 4 2 2 Step voltage measurement with Step Contac...

Page 39: ...ulty earthing system 69 Figure 51 2 Example of ground potential measurement 71 Figure 52 2 Potential gradient measurements example straight line 71 Figure 53 2 Test step contact voltage plates and 25kg probes 73 Figure 54 2 Step voltage measurement with MI3290 instrument 73 Figure 55 2 Step voltage measurement with MI3295S MI3295M instruments 74 Figure 56 2 Contact voltage measurement with MI3290 ...

Page 40: ...oltage setup with MI 3290 142 Figure 86 2 Contact Touch voltage setup with MI 3295S 145 Figure 87 2 GPR measuring method with MI 3290 149 Figure 88 2 Test point selection for GPR measurement 150 Figure 89 2 GPR measuring method with MI 3290 MI 3295M 153 Figure 90 2 Selection of test point for GPR measurements 154 Figure 91 2 Graphical presentation of GPR measurements 157 Figure 92 2 GPR measuremen...

Page 41: ...tion 104 Table 28 2 Pylon foot s impedance 106 Table 29 2 S Flex measurement setup result presentation 106 Table 30 2 Pylon foot s impedance 108 Table 31 2 Flex clamp installation 108 Table 32 2 S Flex measurement setup result presentation 109 Table 33 2 Pylon foot s impedance 110 Table 34 2 S Flex measurement setup result presentation 111 Table 35 2 S Flex measurement result comparison 112 Table ...

Page 42: ...ypically is done from Strips tubes underground earth loop metal strip or cable sunk into the building concrete metal plates in different form like star ring shaped network meshes Earth resistance is not concentrated in one point but it is distributed around whole electrode If a faulty current flow through the earth electrode then a typical distribution of the voltage occurs around it voltage funne...

Page 43: ...pped with earth wires HF Earth Resistance 25 kHz IEEE Std 81 1983 High Frequency Earth Resistance Meter CIGRE Working Group C4 2 02 Methods for measuring the earth resistance of transmission towers equipped with earth wires Pylon ground wire test Wenner Method Schlumberger Method IEEE Std 81 2012 Four point method Equally Spaced or Wenner Arrangement Unequally Spaced or Schlumberger Palmer Arrange...

Page 44: ...re and salt content in soil radically affects to its resistivity Since the amount of water in the soil varies related to the weather conditions groundwater level seasons different layer soil structure as well as temperature increase of temperature leads to decrease of resistance the earth resistance vary a lot during the year s seasons Indicative values of specific earth resistances for a few typi...

Page 45: ...ng Grounding network impedance measurement 45 Figure 25 2 Specific resistance measurement probe distance vs depth of measurement With such measurements it is also possible to determine more different layer soil structure and also layer depth ...

Page 46: ... Measured earth resistance in 4 pole method a Distance between earth probes b Depth of earth probes π Number π is a mathematical constant 3 1416 2 2 2 Schlumberger method measurement ES and S earth probes are located at a distance d from one another and other two earth probes E and H at distance a from ES and S probes see Figure 13 3 below All probes must be placed on a straight line and to a dept...

Page 47: ...lectrodes a and d as well as the depth b of electrodes By changing the electrodes depth b also deeper ground layers will be taken into account Simplified formulas for calculation of earth resistance for different earthing types a Earth resistance for square metal plate with the page of the square a b Earth resistance for vertical rod with the length l c Earth resistance for the metal strip with th...

Page 48: ...In the practice it is not always easy to acquire earth electrode which ensures sufficient earth resistance We must be aware that the earth resistance is changing during the yearly seasons Metrel recommends periodical testing of earth resistance to ensure safety operation in case of fault 2 3 1 Functionality and placing of test probes For a standard earthing resistance two test probes voltage and c...

Page 49: ...between the electrodes is pretty constant Parameter a represents the maximum dimension of the earthing electrode or a system of electrodes and can be defined according to Figure 17 3 Figure 29 2 Definition of parameter a Buried metal objects water pipeline nearby railway lakes river etc cause local deviations and could influence to the measurements 2 3 1 1 Straight line placement Figure 30 2 Strai...

Page 50: ...lower than 10 Higher differences or non symmetric results mean that the voltage funnels influence the measurement and the distance d1 should be increased Notes Initial uncertainty of measured resistance to earth depends on distance between electrodes d1 and size of earthing electrode a d1 a1 Uncertainty 5 10 10 5 50 1 Table 10 2 Measurement result uncertainty vs d1 a1 It is recommended to repeat t...

Page 51: ...an average of two or more partial results It is advisable for the measurement to be repeated at different placements of test probes The test probes shall be placed in the opposite direction from tested electrode 180 or at least 90 MI 3290 gives you the status about performed measurement in case of present disturbances Consider warnings presented on the display when starting the measurement Take ca...

Page 52: ...ce Increasing test probe size or paralleling of probes METREL test equipment displays appropriate warnings in such case according to IEC 61557 5 All METREL Earth testers measure accurate at probe resistances far beyond the limits in IEC 61557 5 Figure 32 3 Different measured voltage drops at low and high probe resistance Notes High impedance of S and H probes could influence the measurement result...

Page 53: ...arth Analyser MI 3290 is able to carry out earth measurement using different measuring methods The appropriate one should be selected by the operator depending on the particular earthing system to be tested Metrel offers different type instruments which could be used for earthing measurements Figure 33 2 MI 3290 Earth Analyser and MI 3295S Step Contact Voltage Measuring System Figure 34 2 MI 3123 ...

Page 54: ...Power Network Application Trainer Earthing Grounding network impedance measurement 54 Earth resistance measurement methods available on METREL instruments MI 3290 and MI 3123 ...

Page 55: ...Power Network Application Trainer Earthing Grounding network impedance measurement 55 ...

Page 56: ...Power Network Application Trainer Earthing Grounding network impedance measurement 56 ...

Page 57: ...t Notes AC test current Ie is injected through the test probe H fixed or sweep mode 55 Hz 15 kHz Impedance of probe H should be as low as possible to inject higher test current Existing grounded system conductive water pipeline should be good enough that its resistance is negligible Measured earthing system should be far enough away from the water pipeline system to be outside its influence 2 3 2 ...

Page 58: ...ort test lead E to minimize its influence in the final result 2 3 2 3 4 pole measurement single frequency and sweep mode up to 15 kHz The advantage for using of 4 pole test is that the leads and contact resistances between measuring terminal E and tested item do not influence the measurement Figure 37 2 4 pole measurement Notes AC test current Ie is injected through the test probe H fixed or sweep...

Page 59: ...AC test current Ie is injected through the test probe H fixed or sweep mode 55 Hz 1 5 kHz Impedance of probe H should be as low as possible to inject higher test current Voltage drop is measured between probe S and ES Selective current Ic is measured through the selected earthing electrode Ze1 by current clamps Selected impedance Ze1 is determined by the voltage measured on the S ES terminals and ...

Page 60: ...much lower than the impedance of tested electrode Ze4 then the result can be considered as Ze4 Other individual impedance could be measured on the same manner Notes AC test current Ie is injected through the generator current clamps fixed or sweep mode 82 Hz 329 Hz 2 3 2 6 HF Earth Resistance 25 kHz measurement The high frequency measuring method offers the advantage of eliminating the influence o...

Page 61: ...nt method automatic compensate inductive components of the adjacent pylons Figure 41 2 Compensation of inductive component with HF 25 kHz method Note Typical ground wire inductance in power lines 0 2 mH 200 mH 2 3 2 7 Selective Flex Clamps 1 4 measurement single frequency and sweep mode up to 1 5 kHz This measurement is applicable for measuring selective earth resistances of individual earthing po...

Page 62: ... arrow marked on the clamp coupling points toward the correct orientation for correct phase measurement Make sure that the number of turns is correctly entered in the test parameters window 2 3 2 8 Passive Flex Clamps Measurement The passive measuring method use the Inductive current or grounding wire current Igw flowing in the earthing system to determine the selected earth resistances of individ...

Page 63: ... is measured through the earthing electrode Zsel1 4 1 pylon foots selected by the user The selected earth impedance Zsel1 4 1 is determined from the voltage US E and selected current external current clamp If1 4 ratio When using only one two or three flex clamps always connect one clamp to F1 terminal synchronization port Make sure that the arrow marked on the clamp coupling points toward the corr...

Page 64: ...ected into the earth through an auxiliary probe H The resistance of the auxiliary probe H should be as low as possible in order to inject a high test current The resistance Rc can be decreased by using more probes in parallel A higher injected current improves the immunity against spurious earth currents In the example following current Ig_w is measured according to following equation where Ig_w O...

Page 65: ...n actually break down decreasing the resistivity of the soil during the surge Measurement of earth resistance with low frequencies may not provide results which are indicative of the ground response to a lightning discharge In complex installations many earths are interconnected and the whole network is measured as one Lightning first strokes normally have 1 to 10 μs impulse current rise times Hig...

Page 66: ...into the earth through a shielded auxiliary probe H Figure 47 2 Typical Impulse shape short circuit Impedance of probe H should be as low as possible to inject higher test current Voltage peak is measured between probe S and E Use short test lead E to minimize its influence in the final result The current probe resistance Rc and potential probe resistance Rp are measured using 3 Pole measurement a...

Page 67: ...Example Influence of inductive impedance part to the test object measured with impulse impedance measurement and 3 pole measurement method Screenshot for Re1 Screenshot for Re2 Screenshot for Re3 Screenshot for Re4 Figure 48 2 Influence of inductive impedance part at impulse measurement ...

Page 68: ...urement 68 Figure 49 2 Influence of inductive impedance part at 3 pole measurement From this example it is visible that increased impedance during voltage strike could cause significant problems if earthing system is not properly done and serious hazard to people or equipment ...

Page 69: ...through the earth electrode then a typical distribution of the voltage occurs around it voltage funnel Maximum voltage drop is concentrated around the earth electrode A typical voltage distribution occurs around the electrode so called voltage funnel Fault currents close to power distribution objects substations distribution towers plants could be very high up to 200 kA This can result in dangerou...

Page 70: ...rth Analyse of ground potential rise is important in the design phase of electrical substations because the high potential may be a hazard to people or equipment Potential gradient voltage change over distance may be so high that a person could be injured due to the voltage between two feet s Step voltage or between the ground on which the person is standing and a metal object Contact voltage In c...

Page 71: ...tion unit is powered by 230V 50 60 Hz MI3295M volt meter measuring unit 0 01 19 99 mV 20 0 199 9 mV 200 1999 mV 2 00 19 99 V 20 0 V 59 9 V MI3295 is intended to perform measurements on bigger test objects power stations substation Figure 51 2 Example of ground potential measurement Notes AC test current Ie is injected through the test probe H frequency range 55 Hz 329 kHz Impedance of probe H shou...

Page 72: ...ounding network impedance measurement 72 3 1 2 Step contact voltage measurement At critical locations like transmission towers the fence around substation hazardous step and contact voltages can occur which can be life threatening to living beings ...

Page 73: ...ound points at a distance of 1 m For performing the test two step voltage plates where operator stands during measurement or two 25 kg measuring probes feet simulation should be used The voltage between the probes is measured by a voltmeter with an internal resistance of 1 kΩ that simulates the body resistance Figure 53 2 Test step contact voltage plates and 25kg probes Note The surface of step S2...

Page 74: ...me having a handin contact with a grounded structure or object The measurement of contact voltage is performed between an earthed accessible metal part and ground 1 meter apart from the tested object The voltage between the probes is measured by a voltmeter with an internal resistance of 1 kΩ that simulates the body resistance test step contact voltage plates or 25kg probes should be used Figure 5...

Page 75: ...ifferent earth impedance measurements methods as well as simulation of different conditions on the pylon which helps to understand different conditions on the real field This chapter describes basic principles of measuring methods for measuring Earth resistance impedance Impulse impedance Pylon Ground Wire test Step voltage Contact voltage Ground Potential Rise Figure 59 2 Available measurement on...

Page 76: ...ing measurements Instrument used MI 3290 Earth Analyser MI 3295S Step Contact Voltage Measuring System MI 3295M MI 3123 Note Take care by using MI 3295S instrument Connect the current probes according the instructions in this manual Wrong connection of current probes could damage the module or burn the fuse Explanation of switch positions example For more details please check Item 1 8 1 Table 12 2...

Page 77: ...ox 22 4 Ω 329 Hz Foot Nm 2 approx 10 9 Ω 329 Hz Foot Nm 3 approx 22 1 Ω 329 Hz Foot Nm 4 approx 5 47 Ω 329 Hz Ztot calc 2 74 Ω Simulated broken foot Nm 2 3 connection simulated resistive earth character flex measurement one flex clamp single foot MI 3290 Foot Nm 1 approx 17 8 Ω 329 Hz Foot Nm 2 approx 391 Ω 329 Hz Foot Nm 3 approx 283 Ω 329 Hz Foot Nm 4 approx 5 33 Ω 329 Hz Ztot calc 3 99 Ω Regula...

Page 78: ... connection MI 3290 Re 2 7 Ω at 25 kHz R type Regular measurement place condition simulated inductive earth character simulated ground wire connection MI 3290 Re 6 2 Ω at 25 kHz L type Item 4 1 6 Regular measurement place condition simulated inductive earth character single and frequency measurement MI 3290 S Flex Ztot 2 66 Ω 329 Hz 4 pole Ze 2 68 Ω 329 Hz Simulated broken foot Nm 2 3 connection s...

Page 79: ...pedance measurement 79 Regular measurement place condition simulated resistive earth character simulated ground wire connection MI 3290 Zp 3 7 Ω Regular measurement place condition simulated inductive earth character simulated ground wire connection MI 3290 Zp 74 Ω ...

Page 80: ... voltage measurement MI3290 MI3295M Result depends on the position of test probes Item 4 2 4 Contact voltage measurement MI3295S MI3295M Result depends on the position of test probes GPR Item 4 3 1 GPR straight line measurement MI3290 Note MI3290 is used as current generator and volt meter Result depends on the position of test probes Item 4 3 2 GPR straight line measurement MI3290 MI3295M Note MI...

Page 81: ...on installation without connected ground wire 3 pole method uses three wire connection with the possibility of frequency selection from 55 Hz to 15 kHz fixed sweep mode In this exercise fixed frequency measurement is used 329 Hz Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character single frequency measurement Indust...

Page 82: ...t probe to E C2 terminal and other part to the pylon connect the green test probe to the S P1 terminal and other part to the voltage probe RP 4 Set the parameters by clicking the bottom left dark grey corner Since exercises on the training module are used only for training purposes distance to current R and voltage r probes is not needed Select Single test mode and 329 Hz test frequency 5 Start th...

Page 83: ... 83 Expected result for 3 Pole method Simulated resistance of current and voltage probe was around 496 Ω so the injected current into the system was quite low approx 61 mA Presented earth impedance and earth resistance are the same since selected load character is the resistance type ...

Page 84: ...329 Hz in first step and frequency sweep in the second one Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character single and sweep frequency measurement Industrial areas Transformer stations Radio towers Pylons without ground wire connection Solar power plants Wind water turbine Ze 2 55 Ω 329 Hz single mode Ze 2 55 Ω ...

Page 85: ...est probe to ES P2 terminal and other part to the pylon 4 Set the parameters by clicking the bottom left dark grey corner single mode at 329 Hz Since exercises on the puzzle uses only for training purposes distance to current R and voltage r probes is not needed Select Single test mode and 329 Hz test frequency 5 Start the measurement by pressing START key on the instrument or icon on the LCD Expe...

Page 86: ...there is practicaly no difference Measuring procedure sweep frequency measurement Same measurement could be repeated usingsweep mode frequencies in the range from 55 Hz to 15 kHz Parameter setup Expected result Impedance measurement in whole frequency range shows resistance character practically no change in the frequency range from 55 Hz to 15 kHz If there is status on the LCD which shows that th...

Page 87: ...h position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character single and sweep frequency measurement Residential areas Radio towers Pylons without ground wire connection Solar power plants Wind water turbine Re 2 66Ω 125 Hz Table 16 2 Measurement setup result for 4 wire measurement method with MI 3123 Measuring procedure 1 Select...

Page 88: ...nal and other parts to the pylon connect the green test probe to the S terminal and other part to the voltage probe RP 4 Select limit value to evaluate the measured result To enter into the limit window press TAB button and select the limit by using Up Down navigation buttons In this case limit value 2 Ω is used 5 Start the measurement by pressing TEST key Expected result Measured eath resistance ...

Page 89: ...r test current needs to be generated Test current up to 7 5 A could be generated and test voltage up to 50 V Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character single and sweep frequency measurement Radio towers Pylons without ground wire connection Solar power plants Wind water turbine Power transmission Power di...

Page 90: ...d Summary Presented exercise shows the usage of three different METREL instrument MI 3290 MI 3123 and MI 3295S for measuring earth resistance usig 3 Pole and 4 Pole measuring method Measurement selection and method selection depends on the object size and surrounding Earth Analyzer MI 3290 supports different measurement methods as well as measurements could be performed at different frequences so ...

Page 91: ...ork impedance measurement 91 Results comparison 3 Pole 329 Hz MI 3290 2 56 Ω 4 Pole 329 Hz MI 3290 2 55 Ω 4 Pole 125 Hz MI 3213 2 66 Ω 4 Pole 55 Hz MI 3295S 2 94 Ω Table 18 2 Result comparison for 3 pole and 4 pole measurement done with different instruments ...

Page 92: ...on Expected result Regular measurement place condition simulated inductive earth character single and sweep frequency measurement Industrial areas Transformer stations Radio towers Pylons without ground wire connection Solar power plants Wind water turbine Ze 3 32Ω 329 Hz single mode Ze 3 31Ω sweep mode Table 19 2 Measurement setup result for 4 pole method Measurement setup and procedure is the sa...

Page 93: ...exercise Nm 1 item 4 1 1 1 2 Measuring procedure sweep frequency measurement Measurement setup and procedure is the same as under exercise Nm 1 Item 4 1 1 1 2 so check the details for proper connection Expected result Earth impedance measurement in frequency range from 55 Hz up to 15 4 kHz shows prominent inductive character of measured object We propose to use sweep mode measurement for analysing...

Page 94: ...ive earth character single frequency measurements Industrial areas Transformer stations Radio towers Pylons without ground wire connection Solar power plants Wind water turbine Ze 3 94Ω 329 Hz single mode Table 20 2 Measurement setup result for 4 pole method with simulated error Measuring procedure Select proper switch position on the training module Measurement setup and procedure is the same as ...

Page 95: ...ue of 3 94 Ω is too high for the selected object Measurement with S Flex method will show us that result 3 94 Ω is not acceptable due to the broken foot s connection Four pole measurement method does not show us the separate foot condition so differen measurement method should be choosen 4 1 2 3 Simulation of resistance inductive earth character regular foot s condition and simulated Ground Wire c...

Page 96: ...rial areas Transformer stations Radio towers Pylons without ground wire connection Solar power plants Wind water turbine Ze 1 46 Ω 4 Pole at 329 Hz R type Ze 1 48 Ω 4 Pole at 329 kHz L type Table 21 2 Measurement setup result for 4 pole method with different test object condition Measuring procedure resistance earth character Select proper switch position on the training module Measurement setup a...

Page 97: ...neighbourhood pylons is included in our case simulated inductance connected to the earth From the results we can see that the 4 Pole method is not proper one for measuring pylons earth impedance connected via ground wire Result comparison Table 22 2 Result comparison same test method vs different test object setup 4 Pole 329 Hz 3 32 Ω 3 94 Ω 1 46 Ω 1 48 Ω ...

Page 98: ...omplete earth measurement on the transmission pylon with four foots with only one flex clamp Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character one flex clamp Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Foot Nm 1 approx 22 4 Ω Foot Nm 2 approx 10 9 Ω Foot Nm ...

Page 99: ...t to the current probe RCE connect the red and blue test probe to E C2 terminal and other part to the pylon connect the green test probe to the S P1 terminal and other part to the voltage probe RP Fit the flex clamp around the first pylon foot 4 Set the parameters by clicking the bottom left dark grey corner Single measurement at test frequency 329 Hz is selected Number of turns should correspond ...

Page 100: ... was not set there is no PASS FAIL indication Use the proper limit value if you need to evaluate the result Since this measurement gives result only for the single foot measurement needs to be repeated also on the other foots Move the clamp to the next foot sequential to foot 2 3 and 4 and repeat the measurement Expected result for foot number 2 Expected result for foot number 3 Expected result fo...

Page 101: ...lon resistance with single flex clamp is time consuming measurement since for each measurement we need to move flex clamps to the next foot To speed up the measurement and skip the manual pylon earth resistance calculation we propose to use four flex clamp optional accessories 4 1 3 2 S Flex measuring method by using one Flex clamp with simulated broken foot resistance and resistive earthing type ...

Page 102: ...easurement setup result presentation From the Expected results column it is visible that total foot earth impedance is in expected range but foot Nm 2 3 are total out of scope S Flex method is suitable measurement method for analysing the selective foot conditions Measuring procedure 1 Repeat the connection setup and MI 3290 setting procedure as it is presented under 4 1 3 1 exercise Select proper...

Page 103: ...t Results may be impaired Expected result for foot number 4 To get total object impedance we need to calculate it from the individual values Four foots pylon could be presented as parallel connection of four impedances so the calculated object impedance is Foot Nm 1 17 8 Ω Foot Nm 2 390 Ω Foot Nm 3 283 Ω Foot Nm 4 5 33 Ω Total impedance 3 99 Ω Table 26 2 Pylon foot s impedance Measuring pylon resi...

Page 104: ...ar measurement place condition simulated resistive earth character flex measurement simulated ground wire connection Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Foot Nm 1 approx 30 1 Ω Foot Nm 2 approx 11 7 Ω Foot Nm 3 approx 23 6 Ω Foot Nm 4 approx 5 63 Ω Ztot calc 2 95 Ω Table 27 2 S Flex measurement setup result presentation Measuring proc...

Page 105: ...ted also on the other foots Move the clamp to the next foot sequential to foot 2 3 and 4 and repeat the measurement Expected result for foot number 2 Expected result for foot number 3 Expected result for foot number 4 To get total object impedance we need to calculate it from the individual values Four legs pylon could be presented as parallel connection of four impedances so the calculated object...

Page 106: ...ulated ground wire connection Figure 70 2 S Flex measurement setup Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character flex measurement simulated ground wire connection Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Foot Nm 1 approx 47 2 Ω Foot Nm 2 approx 16 1 Ω...

Page 107: ...ect setup switches and ground wire accordingly Expected result for foot number 1 Since this measurement gives result only for the single foot measurement needs to be repeated also on the other foots Move the clamp to the next foot sequential to foot 2 3 and 4 and repeat the measurement Expected result for foot number 2 Expected result for foot number 3 Expected result for foot number 4 ...

Page 108: ... regular pylon s foot condition and resistance earth character Depends on the tower dimensions different approach could be used related to the measurement object 1 Mono pylon one flex clamp 2 Four 4 legs pylon one flex clam 3 Four 4 legs pylon four flex clamps One 1 flex used One measurement One 1 flex used Four 4 one by one measurements Time consuming complex post analyses with additional calcula...

Page 109: ...etup for measuring two pylon foot s Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character flex measurement simulated ground wire connection Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Foot Nm 1 2 approx 6 27 Ω Foot Nm 3 4 approx 4 61 Ω Ztot calc 2 65 Ω Table 32 ...

Page 110: ...mpedance we need to calculate it from the individual values Four legs pylon could be presented as parallel connection of four impedances so the calculated object impedance is Foot Nm 1 2 6 27Ω Foot Nm 3 4 4 60 Ω Total impedance 2 65 Ω Table 33 2 Pylon foot s impedance Comparing to the prevoius exercises this method requires only two measurements and it is faster than previous ones Since two foots ...

Page 111: ...d condition Application Expected result Regular measurement place condition simulated resistive earth character flex measurement simulated ground wire connection Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Ztot calc 2 65 Ω Table 34 2 S Flex measurement setup result presentation Measuring procedure 1 Follow the measurement setup connection des...

Page 112: ...ely Measurement method shows direct single foot condition METREL propose to use four flex clamps for detail analyse From presented examples we can conclude that broken foot earthing has no big influence to total earth resistance but could cause serious problem on the object in case of fault Ground wire connection causes that part of current is terminated through the ground wire and other adjacent ...

Page 113: ... adjacent towers and then via earth back to the source Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistive earth character flex measurement simulated ground wire connection MI 3290 Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Ig_w 0 10 mA at 329 Hz Regular measurement place co...

Page 114: ...es according the connection diagram connect the black test probe to H C1 and GUARD terminal and other part to the current probe RCE connect the blue test probe to E C2 terminal and other part to the pylon fit the S Flex clamp around all four foots Note Current for all tower foots have to be measured 4 Setup the parameters test frequency and number of turnings 5 Start the measurement by pressing ST...

Page 115: ...ork impedance measurement 115 Expected result Since ground wire was not connected in this case current is zero Figure 74 2 PGWT measurement setup with connected ground wire Select proper switch position on the module and start the measurement Expected result ...

Page 116: ...ificant part of current flows to adjacent tower In real case we can compare the current flows via ground wire for different towers and determine the actual state related to the ground wire connection Result comparison Table 37 2 PGWT result comparison In case of connected ground wire significant part of current flows to adjacent towers ...

Page 117: ...s the inductive component Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistance inductive earth character simulated ground wire connection Pylons mono and multi leg with and without protective earth cable connection Ski lifts Radio towers Re 2 7 Ω HF at 25 kHz R type Re 6 2 Ω HF at 25 kHz L type Table 38 2 HF measurement method set...

Page 118: ...ltage probe RP 9 Parameters does not need to be set since the probe distance is not relevant for the HF measurement Since exercises on the puzzle uses only for training purposes distance to current R and voltage r probes is not needed 10 Start the measurement by pressing START key on the instrument or icon on the LCD Expected result Since limit value was not set there is no PASS FAIL indication Us...

Page 119: ...arison test object setup vs measurement method Since transmission pylons are connected via ground wire connection the HF 25kHz method is most appropriate one since it automatically exclude the impedance od adjacent towers due to high measurement frequency Ground wire inductance cause that impedance of adjacent towers became negligible and only small test current flows through ground wire connectio...

Page 120: ...ods could be analysed later to find out the existing situation of measured object The sequence of measurements their parameters and flow of the sequence can be programmed The results of an Auto Sequence can be stored in the memory together with all related information Auto Sequence can be pre programmed on PC with the Metrel ES Manager software and uploaded to the instrument On the instrument para...

Page 121: ...Ski lifts Radio towers S Flex Ztot 2 66 Ω 329 Hz 4 pole Ze 2 68 Ω 329 Hz Table 40 2 4 pole and S Flex setup result presentation Two measurement methods 4 pole and S Flex executed under single Auto Sequence is used under same test object for comparing the results and executed with single press on Start button To join two measuring methods under single Auto Sequence we need to prepare appropriate on...

Page 122: ...icence for MI 3290 instrument Figure 78 2 Auto sequence setup 4 pole and S Flex Measuring procedure 1 Connect the test object for performing S Flex and 4 pole measurement Connection details could be found under 4 1 3 and 4 1 2 Item 2 Select the Auto Sequence menu and select already prepared 8 2 2 6 Tower FOP 1xFlex Clamp IEEE 81 test sequence ...

Page 123: ...Network Application Trainer Earthing Grounding network impedance measurement 123 Start the measurement by pressing START key on the instrument or icon on the LCD Follow the instructions appears on the screen ...

Page 124: ...Power Network Application Trainer Earthing Grounding network impedance measurement 124 ...

Page 125: ... earth cable connection Ski lifts Radio towers 4 pole Ze 1 78Ω 329 Hz HF Re 6 7Ω 25kHz S Flex Foot Nm 1 approx 14 76 Ω 329 Hz Foot Nm 2 approx 348 Ω 329 Hz Foot Nm 3 approx 1 767 kΩ 329 Hz Foot Nm 4 approx 6 62 Ω 329 Hz Ztot calc 4 49 Ω Table 41 2 4 pole HF and S Flex setup result presentation Three measurement methods 4 pole HF 25 kHz and S Flex method executed under single Auto Sequence will be ...

Page 126: ... setup 4 pole HF and S Flex Measuring procedure 1 Connect the test object for performing 4 pole HF 25 kHz and S Flex measurement Connection details could be found under 4 1 2 4 1 3 and 4 1 5 Item 2 Select the Auto Sequence menu and select already prepared 8 2 2 6 Tower FOP HF 25 kHz 1xFlex clamp IEEE 81 sequence ...

Page 127: ...by pressing START key on the instrument or icon on the LCD Follow the instructions appears on the screen To continue press key on the instrument or on the LCD Information about the selected measurement and short reminder about the proper connection Result presentation for the 4 pole measuring method sweep mode ...

Page 128: ...last selected method S Flex will proceed Take care that number of current clamp turns corresponds to the entered parameter Start the measurement with press on button Measurement for the first pylon leg finished successfully Reposition flex clamp to the second leg and press to procced with measurement Measurement for the second pylon leg finished successfully Reposition flex clamp to the third leg ...

Page 129: ...resented as parallel connection of four impedances so the calculated object impedance is Foot Nm 1 14 76 Ω Foot Nm 2 348 Ω Foot Nm 3 1 767kΩ Foot Nm 4 6 62 Ω Total impedance 4 49 Ω Table 42 2 Pylon s foot impedance calculation Measurement for the third pylon leg finished successfully Reposition flex clamp to the fourth leg and press to procced with measurement Measurement finished succesfully ...

Page 130: ...prepare in advance the planned measuring methods with all necessary parameters to be executed in one step First example with regular object conditions both methods give almost same result In second case where object conditions are not correct inductive type connected ground wire two pylon foots not earthed the results differ greatly from one to another and this should lead to deeply analyse to fin...

Page 131: ...s such as direct lightning strike into the tested object Switch position Simulated condition Application Expected result Regular measurement place condition simulated resistance inductive earth character Impulse measurement Industrial areas Transformer stations Radio towers Pylons with without protective earth cable connection Solar power plants Wind water turbine Zp 3 7 Ω Zp 112 Ω Table 44 2 Impu...

Page 132: ...rrent probe RCE connect the blue test probe to E C2 terminal and other part to the pylon connect the green test probe to the S P1 terminal and other part to the voltage probe RP Since exercises on the puzzle uses only for training purposes distance to current R and voltage r probes are not needed 3 Start the measurement by pressing START key on the instrument or icon on the LCD Expected result Swi...

Page 133: ...surement place condition simulated resistive earth character simulated ground wire connection Industrial areas Transformer stations Radio towers Pylons with without protective earth cable connection Solar power plants Wind water turbine Zp 3 7 Ω Regular measurement place condition simulated inductive earth character simulated ground wire connection Zp 74 Ω Table 45 2 Impulse measuring method setup...

Page 134: ...d result Results comparison Table 46 2 Result comparison Impulse method vs different test object setup Comparing results we can see that inductive earthing type has huge impact to impulse earth impedance which could be critical check explanation of inductive influence explained under item 2 5 in case of lightning strike damage on the object and equipment ...

Page 135: ...ese exercises MI 3290 is used only as current generator MI3295M is used in this application as Volt meter with selected internal resistance of 1 kΩ simulation of human body resistance Simulated conditions do not present same situation as it is in the real field MI 3295M meter re calculates measured Step voltage to the real Step voltage which could appears in case of fault lightening condition Gene...

Page 136: ...tage setup with MI 3290 MI 3290 instrument 1 Select Potential S T Current source test 2 Connect measuring cables according the connection diagram connect shielded cable to H C1 GUARD terminal other part to the current probe RCS connect the blue test probe to E C2 terminal and other part to the pylon ...

Page 137: ...t for calculated the real Step voltage MI 3295M instrument 5 Select STEP VOLT function by using buttons 6 Set the parameters by using the navigation buttons Iset generated current from the MI 3290 instrument 0 15 A in our test case Iflt expected fault current defined for the test object 5 kA for the test object Rinp MI 3295M input impedance defined in standard IEEE 81 1 0 kΩ for measuring step con...

Page 138: ... for selected case 7 Placement of measuring probes Note for measuring step voltages different directions around test object should be tested 8 Press TEST button on the MI 3295M instrument to start measurement Where Um measured voltage between test probes U calculated real step voltage Um Iflt Iset Measured Step voltage is below the specified limits so there is PASS indication ...

Page 139: ...man body resistance Generated current is limited with the design of MI 3298 P1 Connect MI3295S only to training module terminals which are indicated in this manual Switch position Simulated condition Applications Expected result Industrial areas Transformer stations Radio towers Pylons with without protective earth cable connection Solar power plants Wind water turbine Related to the position of t...

Page 140: ...th MI 3295S Hint Check the time on the MI 3295S before performing synchronization After the test the results made with the meter can be updated with the real generator current that were measured at the same time with the Station so additional synchronization should be performed 2 Under SETTINGS menu set POWER RANGE to 50 3 Press HELP button on the MI 3295S to check the connection diagram connect c...

Page 141: ...trument 1 Select STEP VOLT function by using buttons 2 Set the parameters by using the navigation buttons Iset generated current from the MI 3290 instrument 1 5 A in our test case Iflt expected fault current defined for the test object 1 0 kA for the test object Rinp MI 3295M input impedance 1 0 kΩ for measuring step contact voltage selected value 2 0 kΩ for measuring step contact voltage for Aust...

Page 142: ...ed only as current generator MI3295M is used in this application as Volt meter with selected internal resistance of 1 kΩ simulation of human body resistance Switch position Simulated condition Applications Expected result MI3290 MI3295M MI 3290 is used as current generator MI 3295M is used as volt meter Industrial areas Transformer stations Radio towers Pylons with without protective earth cable c...

Page 143: ...erminal and other part to the pylon 3 Set the parameters by clicking the bottom left dark grey corner test frequency 55 Hz Select the test frequency to 55Hz since the DSP filter on MI 3295M is setup to 55 Hz 4 Start the test current by pressing START key on the instrument or icon on the LCD Generated current by the MI 3290 is 151mA This value should be entered into MI 3295M meter as reference curr...

Page 144: ...ect Rinp MI 3295M input impedance defined in standard IEEE 81 1 0 kΩ for measuring step contact voltage selected value 2 0 kΩ for measuring step contact voltage for Australia market by using special adapter 1 0 MΩ for measuring ground potential rise GPR Ulim limit Step voltage Limit depends on the type of object 200 V for selected case 7 Placement of measuring probes Note for measuring contact vol...

Page 145: ...uch voltage measurement with Step Contact instrument MI 3295S and MI 3295M Instrument used for current generation MI 3295S Instrument used forcontact voltage measurement MI 3295M Figure 86 2 Contact Touch voltage setup with MI 3295S Note MI3295S could generate maximal current of 55 A so it is intended for measurement bigger objects comparing to MI 3290 MI3295M is used in this application as Volt m...

Page 146: ...e and date on the Volt meter MI 3295M and station MI 3295S The main purpose of the Time Current synchronization is to enable a correction of the step and contact voltage results after the test During the test the step and contact voltage results are calculated on base on the set current Iset in the meter 2 After the test the results made with the meter can be updated with the real generator curren...

Page 147: ... to make recalculation of Step voltages with the exact generated current MI 3295M instrument 6 Select U CONTACT TOUCH function by using buttons 7 Set the parameters by using the navigation buttons Iset generated current from the MI 3290 instrument 0 49A in our test case Iflt expected fault current defined for the test object 5 0 kA for the test object Rinp MI 3295M input impedance 1 0 kΩ for measu...

Page 148: ...5M Ground potential rise is carried out for properly design of electrical substations because the high potential may be a hazard to people or equipment Measurements are performed circular around the tested object to measure equipotential lines determination of line strips circular earthing loops in straight line from the tested object to measure the gradient step voltage Presented exercise will tr...

Page 149: ...itch position Simulated condition Applications Expected result Industrial areas Transformer stations Radio towers Pylons with without protective earth cable connection Solar power plants Wind water turbine Result depends on the position of test probes Table 51 2 GPR measuring method setup result presentation Figure 87 2 GPR measuring method with MI 3290 1 Measuring procedure On the MI 3290 instrum...

Page 150: ...be used for simulation as voltage test probe Prepare test point plan as it is presented on the picture bellow Figure 88 2 Test point selection for GPR measurement Setup test parameters Select the test frequency range from 55Hz to 329Hz Step Size and Direction Note Step Size present index at which point measurement is done number of measurement Note Since potential earth spike could not be used on ...

Page 151: ...0 Next steps 1 Perform all measurements till the last test point and stop the measurements by pressing icon on the LCD and after data save the results by pressing icon on the LCD Measured results could be presented on the instrument s LCD graphical or numerical point by point presentation or by downloading to Metrel MESM software for post process analyse Stop the measurements and save data Go to n...

Page 152: ...sed MI 3290 used as current generator and MI 3295M as volt meter Switch position Simulated condition Applications Expected result Industrial areas Transformer stations Radio towers Pylons with without protective earth cable connection Solar power plants Wind water turbine Result depends on the position of test probes Table 52 2 GPR measuring method setup result presentation Note MI3295M is used in...

Page 153: ...procedure MI 3290 1 On the MI3290 instrument select function I Potential 2 Test probes connection and parameter settings connect the black test probe to H C1 terminal and other part to the current probe RCS connect the blue test probe to E C2 terminal and other part to the pylon Prepare test points plan as it is presented on the picture bellow ...

Page 154: ... the test frequency to 55Hz since the DSP filtering on MI 3295M is setup to 55 Hz 3 Press START key on the instrument or icon on the LCD to generate the current through the test object Measuring procedure MI 3295M 4 Select POTENTIAL function by using buttons and setup measurement parameters Iset generated current from the MI 3290 instrument 0 151A in our test case ...

Page 155: ...ints useful in case that we measure GPR in more different directions 5 Start potential measurements in the first point by pressing button TEST button Measurement for test point d 0 0m is ready to be performed Press again TEST button once to execute the measurement Possible manipulations by buttons TEST button repeat measurement at same point again Right arrow button go to next measurement point n ...

Page 156: ...etwork impedance analysing 156 Results could be presented directly on the MI 3295M LCD by pressing MEM button Result presentation Measured results could be downloaded to Metrel MESM software for post process analyse and graphical result presentation ...

Page 157: ...ork Application Trainer Earth Ground network impedance analysing 157 Figure 91 2 Graphical presentation of GPR measurements Where the voltage gradient is steep a hazard of electric shock is present for passers by ...

Page 158: ...r measurement bigger objects comparing to MI 3290 MI3295M is used in this application as Volt meter with internal resistance of 1 MΩ Generated current is limited with the design of MI 3298 P1 Connect MI3295S only to training module terminals which are indicated in this manual Switch position Simulated condition Applications Expected result Industrial areas Transformer stations Radio towers Pylons ...

Page 159: ... generator current that were generated at the same time with the Station 3 Under SETTINGS menu set POWER RANGE to 50 4 PressHELPbutton on the MI 3295S to check the connection diagram connect current cable to C1 H terminal and other part to the current probe RCS connect current cable to C2 E terminal and other part to the pylon Note total cable must be totally unwrapped from the cable reel due to t...

Page 160: ...or the test object 5 0 kA for the test object Step Step present index at which point measurement is done number of measurement Same test points are used as under Item 4 3 2 Dir orientation of test points useful in case that we measure GPR in more different directions 8 Start potential measurements in the first point by pressing button TEST button 9 Measurement for test point d 0 0m is ready to be ...

Page 161: ...esult presentation Measured results could be downloaded to Metrel MESM software for post process analyse and graphical result presentation Figure 93 2 Graphical presentation of GPR measurements Where the voltage gradient is steep a hazard of electric shock is present for passers by ...

Page 162: ...ransformer coils 162 Power generators transformers coils Figure 94 3 Set of Metrel measuring instruments which could be used with MI 3298 T Topics covered Transformer Turn Ratio Transformers Winding Resistance Measuring instruments used MI 3280 MI 3250 ...

Page 163: ...MI 3280 172 6 1 Visual test performed before during after measurements exercises with MI 3280 175 6 1 1 Safety precautions before performing measurements with MI 3280 175 6 1 2 Safety precautions during measurements with MI 3280 175 6 1 3 Test reminder after performing measurements with MI 3280 175 6 2 Turn ratio and winding resistance measurements exercises with MI 3280 177 6 2 1 Transformer Turn...

Page 164: ...3250 187 Figure 104 3 Winding resistance measurement setup with MI 3250 189 Table 54 3 Exercises measurements on MI 3298 T training module transformer turn ratio and winding resistance testing 172 Table 55 3 Transformer turn ratio measuring setup result presentation 178 Table 56 3 Transformer vector group Yyn0 presentation 179 Table 57 3 Transformer turn ratio measuring setup result presentation w...

Page 165: ...ase transformer consists of three sets of primary windings one for each phase and three sets of secondary windings wound on the same iron core The primary windings are connected in one of several ways Two most common configurations are used Delta D configuration the polarity end of one winding is connected to the non polarity end of the next Star Y configuration all three non polarities or polarit...

Page 166: ... html Selection of transformer vector group depends on different factors Parallel operations All transformers should have same vector group polarity of the winding Removing harmonics Dy vector group y winding nullifies the 3rd harmonics Earth fault Relay z or y vector group on secondary side should be used with neutral and possible earth fault relay Type of transformer application power export tra...

Page 167: ...e measurement If you do not have specific reason to operate at specific excitation frequency it is highly recommended to set fex to 70 Hz Consider displayed warnings when starting the measurement If error notification appears on screen at the beginning of the measurement for example V H1H2 10 0V transformer might be supplied with auxiliary power source Inspect what might be the cause for that erro...

Page 168: ...easurement basic transformer data should be entered into the instrument H X configuration Vector group this info could be found on the transformer name plate and is fundamental parameter for performing correct measurements excitation voltage excitation frequency primary secondary voltage TAP position Notes MI 3280 DT Analyser has a single AC source so multiple phases of the three phase transformer...

Page 169: ...rent protection notification appears on screen decrease the excitation voltage and try again 5 2 Winding resistance R RA RB RC MI3280 measures winding resistance by applying a stable DC current to the appropriate winding or winding combination After detecting steady state of winding current the voltage is measured and resistance is calculated by Ohm s law When measurement is finished the transform...

Page 170: ... might be supplied with auxiliary power source Inspect what might be the cause for that error eliminate the fault and try again If error notification appears on screen during the measurement for example I X1 X2 1 mA at least one clip indicated in the message is disconnected or too high winding resistance is detected Inspect what might be the cause for that error eliminate the fault and try again 5...

Page 171: ... testing equipment Notes Consider displayed warnings when starting the measurement If error notification appears on screen at the beginning of the measurement for example V H1 H2 10 0V transformer might be supplied with auxiliary power source Inspect what might be the cause for that error eliminate the fault and try again If error notification appears on screen during the measurement for example I...

Page 172: ...nd through the simulation of different fault conditions understand the nature of the tested object on the field With the MI 3298 T training module it is possible to simulate different condition on the three phase transformer like partial short cut or broken winding condition on the transformer Explanation of switch positions Table 54 3 Exercises measurements on MI 3298 T training module transforme...

Page 173: ...rtcut and broken connection on winding C MI3280 rA 20 217 Ω r 100 rB 10 089 Ω r 0 14 rC 8000 Ω r 100 Uex 80V fex 70 Hz Measurement of turn ratio on the three phase transformer with simulated problem on winding C broken connection MI3280 rA 10 106 Ω r 0 31 rB 10 089 Ω r 0 14 rC 8000 Ω r 100 Uex 80V fex 70 Hz Item 6 3 Measurement of winding resistance measurement on the three phase transformer regul...

Page 174: ...rmer coils 174 Transformer Winding resistance measurement Item 6 1 4 Winding resistance measurement for three phase transformer Measurement of winding resistance on the three phase transformer MI3250 RHA 397Ω RXA 4 50 Ω RHA 397Ω RXA 4 46 Ω RHA 403Ω RXA 4 51 Ω ...

Page 175: ...cautions before performing measurements with MI 3280 Before performing measurements on the transformer some basic rules need to be considered related to the safety work and pre test condition of the test object 6 1 2 Safety precautions during measurements with MI 3280 During the measurements on the transformer some basic rules need to be considered related to the safety work 6 1 3 Test reminder af...

Page 176: ...ore during and after performing the measurements on the tested objects Usually these warnings seem to be self evident but Metrel feels responsible for appealing to consider the safety rules and safe work With the use of Auto Sequences we can include these Visual tests into the regular procedure as an additional warning to observe safety rules while performing measurements ...

Page 177: ...e used MI 3298 T 6 2 1 Transformer Turn ratio measurement Exercise 1 Figure 100 3 Transformer turn ratio measurement setup with MI 3280 Transformer turn ratio and phase angle are basic transformer data Based on deviation related to standard values eventual open circuits broken connections and short cuts short turns could be detected Note Warnings related to safety Connect instrument according the ...

Page 178: ...lectric shock For measuring Transformer turn ratio use Metrel instruments described in this manual Setup switch Nm 4 to position 1 Method used Simulated condition Expected result rA 10 107Ω r 0 32 Uex 80V rB 10 090Ω r 0 15 Uex 80V rC 10 109Ω r 0 34 Uex 80V Table 55 3 Transformer turn ratio measuring setup result presentation Measuring procedure 1 Under RATIO test menu select r A B C measurement fu...

Page 179: ...eference Turn ratio Calculated Turn ratio from Voltage ratio VH VX and appropriate factor that depends on vector group example for the tested power transformer Table 56 3 Transformer vector group Yyn0 presentation 4 Connect the test cables to the measured transformer according the connection diagram Connection diagram is available under button Measured cables have Kelvin clamps crocodiles which au...

Page 180: ... etc this contact could be critical Grab the connector s jaw and turns it slightly left and right as it is presented on the picture bellow Figure 101 3 Proper crocodiles mounting to ensure good contact In case of weak bad contact following message will appear on the display Check contacts again and repeat the measurement 5 Start the measurement by pressing START key on the instrument or icon on th...

Page 181: ...PASS indication Hints Measured values should not deviate more then 0 5 from the nominal ratio according IEC 60076 1standard Exercise 2 Setup switch Nm 4 to position 2 Method used Simulated condition Expected result rA 20 217 Ω r 100 Uex 80V fex 70 Hz rB 10 089 Ω r 0 14 Uex 80V fex 70 Hz rC 8000 Ω r 100 Uex 80V fex 70 Hz Table 57 3 Transformer turn ratio measuring setup result presentation with sim...

Page 182: ...ot cause problem on windings C turn ratio was not calculated so this is direct point to open circuit broken connection We also propose to perform additional winding resistance measurement in such case Exercise 3 Setup switch Nm 4 to position 3 Method used Simulated condition Expected result rA 10 106 Ω r 0 31 Uex 80V fex 70 Hz rB 10 089 Ω r 0 14 Uex 80V fex 70 Hz rC 8000 Ω r 100 Uex 80V fex 70 Hz ...

Page 183: ... was problem during measurements Comparing results with the reference data on the transformer nominal plate following problem was detected a problem on windings C turn ratio was not calculated so this is direct point to open circuit broken connection We also propose to perform additional winding resistance measurement in such case ...

Page 184: ...280 Same connection setup as in previous exercises Setup switch Nm 4 to position 1 Method used Simulated condition Expected result RHA 401 0 Ω RXA 4 492 Ω RHB 400 3 Ω RXB 4 460 Ω RHC 405 0 Ω RXC 4 508 Ω Table 59 3 Winding resistance measuring setup result presentation 1 Under Rwind test menu select RA B C measurement function 2 Set the parameters by clicking the bottom left dark grey corner ...

Page 185: ...strument or icon on the LCD Expected result Winding resistance measurement does not have any limit specification so there is no FAIL PASS indication Metrel recommends to perform regularly measurements on the transformer and monitor eventuel deviations Exercise 2 Same connection and configuration setup as in previous exercise with simulated error switch on position 2 Method used Simulated condition...

Page 186: ... evident from the turn ratio measurement exercise under Item 6 2 1 where was turn ratio almoast half larger then in normal situation b winding resistance in phase C exceeds the measuring range of the instrument We can conclude that there is definitely broken windings C Exercise 3 Same connection and configuration setup as in previous exercise with simulated error switch on position 3 Method used S...

Page 187: ...tion Expected result Winding resistance measurement for current transformer RHA calc 397Ω RXA calc 4 50 Ω RHA calc 397Ω RXA calc 4 46 Ω RHA calc 403Ω RXA calc 4 51 Ω Table 62 3 Winding resistance measuring setup result presentation Measuring procedure 1 With MI 3250 it is possible to measure the resistance of one winding at a time Based on the transformer vector group it is necessary to define the...

Page 188: ... 3 between windings B C measured resistance R3 RHB RHC After finishing the measurement it is necessary to calculate winding resistance for the individual winding RHA calc 2 2 3 1 R R R RHB calc 2 1 2 3 R R R RHC calc 2 2 1 3 R R R Connection diagram for measurement of secondary side od transformer winding resistance Measurement needs to be done for each winding part separately winding resistance f...

Page 189: ...stance measurement setup with MI 3250 2 Under Main Menu menu select Measurement mode and confirm it with SELECT button and setup the measurement parameters in the bottom left corner 3 Connect test probes to primary side of transformer step 1 windings A B step 2 windings A S and step 3 windings B C ...

Page 190: ...ct test probes to secondary side of transformer step 1 winding XA between winding cennection and common point Measured result will direct correspond to windings resistance Setup the parameters as it is described under point 3 take care that optimal test current and Resistance range is achieved Conclusion From the presented example we can conclude that MI 3250 MicroOhm 10A meter is more intended fo...

Page 191: ...ng instruments for insulation measurement which could be used with MI 3298 T Topics covered Transformers Cables Measurement instruments used MI 3210 TeraOhmXA 10 kV 2 24 MI 3205 TeraOhm 5 kV 2 26 MI 3201 TeraOhm 5 kV Plus 2 28 MI 2077 TeraOhm 5 kV 2 30 MI 3202 GigaOhm 5 kV 2 32 MI 3121H 2 5 kV Insulation Continuity ...

Page 192: ...ge 199 7 2 4 Step voltage insulation resistance test 200 7 2 5 Withstanding voltage test 201 7 2 6 Using the GUARD terminal 201 7 2 7 Test voltage selection 202 7 3 Safety considerations before during after insulation testing 203 7 3 1 Protecting device under test DUT and test equipment 203 7 3 2 Protecting the operator 203 8 Exercises on MI 3298 T Insulation resistance measurement 205 8 1 Insulat...

Page 193: ...ement setup 212 Figure 120 3 Step voltage test measuring setup 215 Figure 121 3 Transformer insulation resistance measurement setup primary secondary side 217 Figure 122 3 Transformer Insulation resistance test setup primary side pe terminal 221 Figure 123 3 Transformer Insulation resistance test setup secondary side pe terminal 223 Table 64 3 Applied test voltage table 194 Table 65 3 The four par...

Page 194: ...is the reason why insulation has to be measured Insulation is measured in the initiating phase of electrical device and also later during maintenance works or repairing and measurements are of simple and diagnostic type 7 1 Basics of Insulation Measurements According to Ohm s law the current does not depend on time But a simple measurement of insulation resistance shows that the current does indee...

Page 195: ...e insulation resistance measurement instrument does not include an ideal voltage source At the start all available instrument power is used to charge the capacitor Ciso for a short period The voltage on connection points drops because of this Figure 108 3 Current diagram for an ideal voltage source When DC voltage is suddenly applied to the insulation the test current will start at a high value gr...

Page 196: ... whether the replacement of the insulation system is required Typical examples of where testing insulation resistance and its diagnosis are recommended are transformer and motor insulation systems cables and other electrical equipment 7 2 1 Basic insulation resistance test Spot reading test Virtually every standard concerning the safety of electrical equipment and installations requires the perfor...

Page 197: ...V measurement period 1 min Minimum insulation resistance for basic insulation 2MΩ Minimum insulation resistance for supplementary insulation 5MΩ Minimum insulation resistance for reinforced insulation 7MΩ 7 2 2 Time rise method polarization index dielectric absorption ratio When test voltage is applied a bad insulation causes drop of the value Riso and the increasing in the insulation leakage curr...

Page 198: ... Considered as good insulation older types 4 Very good insulation Modern type of good insulation systems Table 66 3 Typical values of polarization index The results of this method don t depend on temperature and the method can give a conclusive information without comparing records of past tests Dielectric absorption ratio DAR is similar to the polarization index method The only difference are per...

Page 199: ...hen discharged before the DD test is carried out After 1 min a discharge current is measured to detect the charge re absorption of the insulation material A high re absorption current indicates contaminated insulation mainly based on moisture DD value Tested material status 4 Bad 2 4 Critical 2 Good Table 68 3 Values of dielectric discharge Idis 1 min Discharging current measured 1 min after the v...

Page 200: ...sults even in case we are not able to stress insulation with nominal electrical voltages The device under test is exposed to different test voltages that are applied in steps The voltage starts at the lowest value and increases with defined steps up to the highest level The application of increased voltage creates electrical stresses on internal insulation cracks Results can also be corrected to w...

Page 201: ...n coordination purposes Keeping the voltage for the predefined period performs this test The device under test must withstand this voltage without breakdown of the insulation In this case the slope of increasing voltage must be low enough to prevent breakdown indication due to charging current of tested object capacitance Test time with defined test voltage is usually 1 min for type tests and 2 s ...

Page 202: ...egative terminal Since the leakage resistance is effectively in parallel with the resistance to be measured the use of guard terminal causes the current flowing through surface to be diverted from the measuring circuit The unwanted surface leakages are drained by the guard terminal and are not considered in the measuring result Result without using the GUARD terminal IA IRiso IRiss The result is i...

Page 203: ...the DUT is disconnected from other equipment and circuits if possible Discharge the insulations that will be tested METREL testers will give a warning in case of energized DUT To prevent the damage of the DUT it is recommended to short accessible connections of circuit on both sides of tested insulation Select correct test voltage and method Pay attention to grounded DUT Some insulation testers ar...

Page 204: ...tested insulation versus test voltage Select threshold current limit as low as possible Don t touch any part of the test system during the measurement and do not disconnect test leads until the measurement is finished and the DUT discharged Figure 116 3 Discharging of insulating material Ciso 100 nF Utest 5 kV METREL test equipment makes automatic discharge of the test circuit at the end of the te...

Page 205: ...gnostic test Polarization Index Dielectric Absorption Ratio Dielectric Discharge Step Voltage Test Note maximum insulation test voltage on the emulation of power cable is 5 kV and transformer where it is possible to train the insulation resistance between Primary and Secondary windings Primary windings and Ground point Secondary windings and Ground point Note maximum insulation test voltage on the...

Page 206: ...or before it is fully discharged Risk of electric shock In case that automatically discharge was not successfully discharge the test object manually Risk of electric shock Notes Consider displayed warnings when starting the measurement A high voltage warning symbol appears on the display blinking red light appears on the instrument as well as sound optional during the measurement to warn the opera...

Page 207: ...D ON AVG 0 Cable insulation resistance testing Step Voltage Test MI3205 Note max test voltage 5 kV R1 1 94 GΩ U1 1 03 kV R2 2 59 GΩ U1 2 02 kV R3 3 09 GΩ U1 3 02 kV R4 3 66 GΩ U1 4 01kV R5 4 08 GΩ U1 5 01 kV Un 5kV Timer 05 00 Insulation resistance measurements transformer Item 8 2 Insulation resistance testing between transformer Primary and Secondary site regular condition on the transformer MI3...

Page 208: ...of operating voltage but not less than one mega ohm For example a motor rated at 5 kV working voltage should have a minimum resistance of 5 MΩ Exercise 1 Insulation resistance test Spot test This is the simplest and fastest way of insulation resistance testing Unfortunately only one test with no prior tests can be only a rough guide as to how good or bad the insulation is In this test the instrume...

Page 209: ...ge step 50 V 50 V 1 kV and 100 V 1 kV 10 kV Note Maximum test voltage is 5 kV Timer1 Duration of measurement mm ss step 1 s max time 99 min Lim Limit value selection OFF 0 50 MΩ 1 0 TΩ If limit is not set there is no PASS FAIL indication after performed measurement AVG Averaging of the result value OFF 5 10 30 60 3 Connect the test leads to the instrument and to the test object Connect the red tes...

Page 210: ... result and graph window is done by pressing SELECT button Measurement result averaging Filters and additional averaging are built in Metrel insulation measurement devices in to reduce the influence of noise on measurement results This option enables more stable results especially when dealing with high Insulation Resistances In Insulation Measurement the status of the averaging option is shown in...

Page 211: ...ults 30 s Moving average of 30 results 60 results 60 s Moving average of 60 results Example of measurement with averaging option of 5 results Measurement setup Expected result with the usage of averaging function of 5 results The averaging function eliminates the impact of rapid jumps on the measurement result ...

Page 212: ...sults of this test enable the decision to be made on the preventive replacement of the insulation material Method used Simulated condition Expected result Un 5 kV T 1 min AVG 0 Riso 9 14 GΩ DAR 1 36 PI 3 66 DD 5 44 Table 73 3 Diagnostic test measuring setup result presentation Measuring procedure 1 Connection set up is the same as it is performed under Exercise 1 2 Under MAIM MENU MEASUREMENTS men...

Page 213: ... min Standard value should be 1 minute Timer3 Duration of measurement mm ss step 1 s max time 99 min Standard value should be 10 minutes DD Enable or disable dielectric discharge testing AVG Additional averaging of the result value OFF 5 10 30 60 Time1 Time2 Time3 Timer1 Timer2 and Timer3 are timers with the same starting point The value of each presents the duration from the start of the measurem...

Page 214: ...Power Network Application Trainer Insulation Analysis 214 Expected result Based on the result for DAR PI and DD parameters we could conclude that tested material insulation state is good condition ...

Page 215: ...nction illustrates the relationship of a materials Insulation resistance and its applied voltage Method used Simulated condition Expected result Un 5kV Timer 05 00 R1 1 94GΩ U1 1 03kV R2 2 59 GΩ U1 2 02 kV R3 3 09 GΩ U1 3 02 kV R4 3 66 GΩ U1 4 01kV R5 4 08 GΩ U1 5 01 kV Table 74 3 Step voltage test setup result presentation Measuring procedure 1 Connection set up is the same as it is performed und...

Page 216: ...ameters by clicking the bottom left dark grey corner Un Set test voltage step 50 V 50 V 1 kV and 100 V 1 kV 10 kV final value Timer1 Duration of measurement mm ss step 1 s max time 99 min total one AVG Additional averaging of the result value OFF 5 10 30 60 Expected result ...

Page 217: ...ation resistance test Spot test between primary and secondary side of transformer Figure 121 3 Transformer insulation resistance measurement setup primary secondary side Method used Simulated condition Expected result RISO 17 5 GΩ RISO 18 1 GΩ Table 75 3 Transformer insulation resistance test setup result presentation primary secondary side Measuring procedure 1 Under MAIM MENU MEASUREMENTS menu s...

Page 218: ...al U or V or W Connect the black crocodile Rx to the secondary side of transformer on the MI 3298 T training module X terminals u or v orw Connect GUARD terminal to the pe terminal of the transformer on the MI 3298 T training module Note Test connection for the specific test object could be checked under HELP menu Connection diagram should serve as an example Note with the connection of GUARD term...

Page 219: ...ormer together otherwise you need to check each combination U u U v U w V u V v V w W u W v W w Exercise 1 2 Step voltage test between primary and secondary side of transformer Measuring procedure 1 Under MAIM MENU MEASUREMENTS menu select Step Voltage Test measurement function 4 Set the parameters by clicking the bottom left dark grey corner Un Set test voltage step 50 V 50 V 1 kV and 100 V 1 kV ...

Page 220: ...Power Network Application Trainer Insulation Analysis 220 one AVG Additional averaging of the result value OFF 5 10 30 60 5 Use same connection setup as in previous Exercise 1 1 ...

Page 221: ...ation resistance test setup result presentation primary side pe terminal Measuring procedure 1 Measurement and parameter setup is the same as it is presented in Exercise 1 1 2 Connect the test leads to the instrument and to the test object Connect the red test probe Rx to the primary side of transformer on the MI 3298 T training module H terminal U or V or W Connect the black test probe Rx to the ...

Page 222: ...2 Expected result Exercise 2 2 Step voltage test between between primary side of transformer and pe terminal representing transformer housing Measuring procedure 1 Measurement and parameter setup is the same as it is presented in Exercise 1 2 Expected result ...

Page 223: ...ation resistance test setup result presentation secondary side pe terminal Measuring procedure 1 Measurement and parameter setup is the same as it is presented in Exercise 1 1 2 Connect the test leads to the instrument and to the test object Connect the red test probe Rx to the secondary side of transformer on the MI 3298 T training module X terminal u or v orw Connect the black test probe Rx to t...

Page 224: ...oltage test between secondary side of transformer and pe terminal representing transformer housing Measuring procedure 1 Measurement and parameter setup is the same as it is presented in Exercise 1 2 Conclusion We suggest to perform test on each single winding to test all different combinations ...

Page 225: ...sformer DTA Digital transformer analyser DUT Device under test E C2 Current terminal 2 on the instrument EN Europe norm ES P2 Voltage terminal 2 on the instrument FFT Fast Fourier Transform FOP Fall of Potential GF Ground Funnel profile GL Ground Lightening profile GP Ground Pylon profile GX All profiles GPR Ground Potential Rise GW Ground Wire H Primary side of transformer H C1 Current terminal 1...

Page 226: ...probe step contact measurement RC Connection for current probe RP Connection point for voltage probe Rwind Winding resistance S P1 Voltage terminal 1 on the instrument SD Secure digital S T Step and Touch U Voltage u v w Secondary voltage terminals U V W Primary voltage terminals Vex Excitation voltage VT PT Voltage transformer Power transformer X Secondary side of transformer Z Impedance Ze Earth...

Page 227: ...nstruments used in presented exercises 10 2Literature 1 General catalogue 2012 May Good to know 2 Guide for Modern Insulation Testing version 1 1 20 750784 3 Earth Analyser MI 3290 version1 2 3 20 752 597 4 Digital Transformer Analyser MI 3280 version 1 1 1 20 752 598 5 MicroOhm 10A MI 3250 version 1 1 2 20 751 893 6 TeraOhmXA 10 kV MI 3210 version 1 3 1 20 752 185 7 Step Contact Voltage Measuring...

Page 228: ...MI 3290 Earth Analyser 228 ...

Page 229: ...MI 3280 Digital Transformer Analyser 229 ...

Page 230: ...MI 3280 Digital Transformer Analyser 230 ...

Page 231: ...MI 3250 MicroOhm 10A 231 ...

Page 232: ...MI 3205 TeraOhmXA 5kV 232 ...

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