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Tettex MIDAS 2881, Operating Instructions Manual

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Tettex MIDAS 2881 Operating Instructions Manual Download Page 36

 

 

 

26  

Operation Elements

 

 

6.4

 

Instrument Side Panel 

 

Figure 12 - Side panel 

 

 

 

The instrument’s right side panel is devided into  
two main parts: 

 

1. Measuring 

connections 

2.  High Voltage and safety ground connections 

 

 

6.4.1

 

Measuring Inputs 

 

 

The Safety Switch should be used at all times.  Never short circuit it and do not use 
fixed mechanical locking devices for depressing the switch button.  The switch button 
must be manually operated at all times

. 

 

 

 

The instrument must be disconnected from all voltage sources if a fuse has to be 
replaced.  When replacing the mains fuse always use a replacement fuse with the same 
specifications and current rating.   

 

 

Summary of Contents for MIDAS 2881

Page 1: ...Operating Instructions HAEFELY TEST AG MIDAS 2881 Mobile Insulation Diagnosis Analysing System Version 2 0 LAN version only 4843930...

Page 2: ...Art Nr 4843930 Operating Instructions MIDAS 2881 Date Version Responsible Changes Reasons 04 16 2 0 SG 2881 LAN Version replace the firewire model...

Page 3: ...nt serial number and firmware version number With the exception of the firmware version number this information can be found on the registration plate on the right panel of the instrument The firmware...

Page 4: ...operations failure to follow the instructions could result in errors in measurement Indicates hazards There is a risk of equipment damage or personal injury or death Carefully read and follow the inst...

Page 5: ...ience with this kind of equipment will find this document to be of assistance as an extended help A keyword index at the end of the operating manual greatly eases use If you find a mistake or inconsis...

Page 6: ......

Page 7: ...on Factor 11 4 5 Apparent Power Real Power Reactive Power 11 4 6 Test Instruments 12 4 7 Evaluation of Test Results 12 4 8 Supplementary Test Methods 16 4 9 Standard Capacitor Measuring Current Limits...

Page 8: ...t 58 7 5 3 Formulas in Measuring Grids 59 7 5 4 Menu Signal Analysis 61 7 6 Tab sheet SEQUENCE 65 7 6 1 Definition of Spreadsheet Sequence 65 7 6 2 Sequence Measurement 68 7 6 3 Edit Sequence Limiters...

Page 9: ...2 14 3 1 Test Procedure 132 14 3 2 Measuring Data Interpretation 133 14 3 3 Measuring high cap values using the Resonating Inductor 135 14 3 4 Operation of Resonating Inductor with Midas 136 14 4 Liqu...

Page 10: ......

Page 11: ...offers optimal user friendliness Operation is simple thanks to the user dialogue system and on line help The system is ideal for high and low voltage measurements over a wide frequency range The test...

Page 12: ...ng hardware and HV supply MIDAS standard type supplies 12kV MIDAS G type supplies 15kV Control Computer 1 Fully installed Laptop in shell case MIDAS 2881 Cables in rugged trolley including Shielded me...

Page 13: ...tank providing additional visual warning of high voltage presence MIDAS OFFICE MIDAS software for customer personal office PC Used for data visualisation staff education test planning and preparation...

Page 14: ...actor tan 0 10 000 0 001 0 5 rdg 0 01 Power Factor cos 0 100 0 001 0 5 rdg 0 01 Quality Factor 0 01 10000 0 0001 0 5 rdg 0 0001 Capacitance 0 01pF 0 2 rdg 0 2pF Inductance 0 1mH 0 5 rdg 0 5 mH Test Cu...

Page 15: ...PF cos 20 C PF cos PF cos 20 C QF quality factor QF quality factor 20 C CP ZX CP RP RP ZX CP RP CS ZX CS RS RS ZX CS RS LS ZX LS RS RS ZX LS RS LP ZX LP RP RP ZX LP RP Standard capacitor Cn URMS URMS...

Page 16: ...recommendations The MIDAS generates high voltage and is capable of causing serious even lethal electrical shock If the instrument is damaged or it is possible that damage has occurred for example duri...

Page 17: ...with a HV GND connection surveillance The high voltage can only be switched on when the earth circuit is properly connected The instrument indicate the status Grounded or Open by LED and by software A...

Page 18: ...re disconnected from the instrument The green yellow safety ground cable should be the LAST lead to be disconnected from the set Do not disconnect the voltage cables from unless the MIDAS Voltage is s...

Page 19: ...order to define acceptable loss factor values a data record service was developed based upon statistical data that related to specific equipment types and models Standard measurements of capacitance a...

Page 20: ...terial 0 r dielectric constant In an ideal capacitor the resistance of the insulation material dielectric is infinitely large That means that when an AC voltage is applied the current leads the voltag...

Page 21: ...Factor to specify the power losses in the insulation Because the angles are complimentary it is unimportant whether tan or cos is used as with very small values the difference is negligible However t...

Page 22: ...ratus failures are due to a deteriorated condition of the insulation Many of these failures can be anticipated by regular application of simple tests and with timely maintenance indicated by the tests...

Page 23: ...of Typical Apparatus Insulation Values of insulation dissipation factor for various apparatus are shown in this table These values are useful in roughly indicating the range to be found in practice ho...

Page 24: ...factor temperature characteristics as well as dissipation factor measurements at a given temperature may change with deterioration or damage of insulation This suggests that any such change in temper...

Page 25: ...locity will increase the severity and variability of the interference field The lower the specimen capacitance and its dissipation factor the greater the difficulty with possible reduction in accuracy...

Page 26: ...ulting load range use these basic conditions and rules 1 Maximum test voltage shall be less than the nominal voltage of the standard capacitor UTestmax UCN Current through standard capacitor CN N Test...

Page 27: ...0 01 f 50Hz internal AC source used built in CN used IX 251mA within IX range OK 150mA Only intermittent testing allowed due to max supply output current limit Psupply 2513VA within P range OK ICN 31...

Page 28: ...IX through the unknown test object CX Both branches are energized by the built in HV AC power source UTest and both currents are measured by the adjustable high accurate shunts RX and RN and then dig...

Page 29: ...alled V potential which is the low voltage point reference of the high voltage supply All capacitances connected to this reference point are bypassed and are therefore not influencing the measuring va...

Page 30: ...ace is measured in parallel and therefore causes a minor error on the measurement The measured value is CHG Cstray Figure 8 Measurement with connected V Potential point to the powered bushings guardin...

Page 31: ...of the system All capacitances connected to this reference point are bypassed and are not influencing the selected measurement Figure 9 Measuring setup on a single phase transformer with two low volt...

Page 32: ...exceeded When measuring power transformers and HV current transformers this configuration determines the capacitance and dissipation factor between the various winding groups In this mode the highest...

Page 33: ...orithms to reduce the noise and extract the measuring signal These algorithms has to be selected whenever readings are not stable or high armonics content can be detected in the measuring signals The...

Page 34: ...l Parts The MIDAS system can be dismounted to individual transportable parts The system consist of following elements 1 Measuring Instrument 2 Trolley 3 Laptop These parts can be mounted dismounted by...

Page 35: ...sing the system 6 3 Computer connection Figure 11 Comunication and mains plug location Computer conection plugs are located at the top side in the instrument back panel black coloured inside the glove...

Page 36: ...ing Inputs The Safety Switch should be used at all times Never short circuit it and do not use fixed mechanical locking devices for depressing the switch button The switch button must be manually oper...

Page 37: ...l the HV transformer and the entire HV circuit is enclosed Guard It s also the low voltage point of the HV supply NOT the system earth 7 SAFETY SWITCH INPUT Plug receptacle for connecting the handheld...

Page 38: ...t cable yellow respectively the test object Note The matching plug has a locking ring that should be fastened by hand 14 RESONATING INDUCTOR CONTROL Receptacle to connect the control link to the optio...

Page 39: ...nd Earthing Figure 15 Safety ground connection Wing nut ground terminal for connecting the safety ground lead to earth ground connected to the instruments housing and the ground pin from the mains con...

Page 40: ...nt side panel indicates the actual high voltage state of the MIDAS No light The system is in a safe state The emergency stop is pressed the Safety Switch is released or HV GND lead is not connected Il...

Page 41: ...lease go to the chapter 6 3 7 1 General 7 1 1 Start up Once the system has been started the following Start up window comes in which two options could be selected for different operations Select to st...

Page 42: ...d for manual operation such as setting the measuring connection voltage and frequency and storing the measuring results in a spreadsheet See section Tab sheet MANUAL for details Tab Sheet Sequence Thi...

Page 43: ...s shown in the title bar The Simulated mode provides the same functionality as on the MIDAS itself but no system hardware is needed The measuring values are simulated Document Name The actual active l...

Page 44: ...possible to get more stable measurement results This alarms shows if Ext Noise Reduction is activated For more information see Button Extended Noise Reduction Alarm Watchdog This error message appear...

Page 45: ...rotected by password Button About Pressing this button will pop up the following message window with information about software version calibration time and instrument serial number Button Signal anal...

Page 46: ...log pops up where you can load an existent file to continue your work Button Save To save the actual test file press this button Button Save As With this button the actual file can be saved with a dif...

Page 47: ...alog two possibilities will arise Button Show Report By pressing this button the Internet Explorer with the actual file will pop up An example is shown in below Button Show Actual Diagram When this bu...

Page 48: ...led It is possible to hide or display the test sequences the measurement values and the analysis window Clicking on the Logo on the right side of the explorer window will show or hide the menu The Pri...

Page 49: ...or the report Overwrite the file with your company logo to replace the default Tettex logo 7 3 Display of Measurement Values In the tabs sheets MANUAL and SEQUENCE four measuring values are displayed...

Page 50: ...tion Factor temperature corrected to 20 C with the selected Temperature Correction Table DF tan Actual measured Dissipation Factor in percentage format DF tan 20 C Dissipation Factor in percentage for...

Page 51: ...ed to the test object multiplied by 3 E g to get Line Line voltage from the Line Ground value Ieff Ref Effective Current through CN Ieff Test Effective Current through CX Frequency Measured frequency...

Page 52: ...l equivalent circuit RS ZX LS RS Resistive part of the test impedance inductance ZX in serial equivalent circuit LP ZX LP RP Capacitive part of the test impedance inductance ZX in parallel equivalent...

Page 53: ...d type of insulation Connection Actual selected connection mode Scope Waveform display The voltage value applied at the shunts in function of the time This selection is only available at the fourth ri...

Page 54: ...hange the temperature unit Celsius or Fahrenheit and the languages Currently the user interface is available in English and Chinese Menu Auxiliary You can enter additional information for your special...

Page 55: ...bjects and therefore results can automatically be corrected to the reference temperature 20 C 68 F To do so the corresponding test object has to be slected in the menu As information the correction ta...

Page 56: ...e The correction factors given above are valid for insulation systems that use mineral oil as the insulating fluid Other insulating fluids may require different correction factors Modify the Temperatu...

Page 57: ...B and HV GND Only supplied cables can be used The standard length is 20m 66 ft AC Supply If you need higher test voltage or current to energize your test object an external 50 60 Hz power supply can b...

Page 58: ...Standard Capacitor Cn This option allows using the Midas with an external standard capacitor e g Tettex types 3320 or built in the Current Booster 5287 The corresponding values of the external nominal...

Page 59: ...ce will apply high voltage please follow the safety rooles as while performing the test By pressing Evaluate Parameters the evaluation procedure will be started You are guided with the connection diag...

Page 60: ...uring the Capacitance CHL HV LV Side The capacitance CHG HV Gnd Side will turns the phase if the test current is small If this field is checked this case will be detected and automatically switched to...

Page 61: ...mode File Manager System will start automatically with File Manager dialogue Load Last File The file with which you have worked the last time will be automatically loaded The system will continue at t...

Page 62: ...all stored values So it is very easily to make you inputs Button Load Factory Settings After leaving the factory or after a recalibration the values of standard capacitor or cable length are tested an...

Page 63: ...rface Here can you set the interface for controlling 2820 by remote The 2820 can be controlled by LAN or by RS 232 Be aware that the set parameters of the interface correspond with the host computer o...

Page 64: ...54 Software...

Page 65: ...orded stored in the MEASUREMENTS spreadsheet by clicking the Record button The main elements in this tab sheet are Element Description Field Measuring Values The displayed measuring value can be selec...

Page 66: ...n one row and change them simultaneously Button Tools Clicking this button will open a list with elements described below This list will also pop up if you click the right mouse button somewhere in th...

Page 67: ...se which measured value should be recorded and at which position displayed For information about the pop up window see the chapter Definition of Columns for Measuring Spreadsheet Button Edit Descripti...

Page 68: ...ns of the measuring system is displayed Each recorded test series have their own test conditions so it is possible to trace back test condition over years even with different measuring de vices and op...

Page 69: ...all data can be moved or removed With and you can move the position of a specific active column Note The columns in the measuring spreadsheet itself can also be moved in position with simple drag and...

Page 70: ...rmula when a measurement is recorded Where C 0 0 is the actual cell C 4 1 means 4 columns leftside of column tan This is cell DF tan and one row above the actual row All relations are relative to the...

Page 71: ...spectrum of the measured signals The amplitudes are related to the amplitude of the first harmonic in Percent The first 15 harmonics are shown Tab Sheet Reference Channel Cn If this Tab Sheet is sele...

Page 72: ...nly for visualization purposes and will not change the devices ranges By pressing Button Up the signal amplitude is shown larger while By pressing Button Down the signal amplitude is shown smaller The...

Page 73: ...n without the Midas hardware Button Inc Dec Time Base By pressing ms Button the time scale will increased As a result there are more recorded data visible By Pressing s Button the time scale will be d...

Page 74: ...of the scope If it is unchecked higher and lower values than the maximum range of the scope are not shown anymore Button Save Pressing this button will store the recorded raw data of the ADC A dialog...

Page 75: ...can be defined by the voltage applied the test mode UST or GST and a picture with some comments The bitmap and the text will be displayed before the test sequence will start At the bottom half of the...

Page 76: ...A B Test mode definition If one of these fields is not empty a measurement will be done with the appropriate test mode connection The field can be labelled by an identifier e g Cs for stray capacitanc...

Page 77: ...to all of these rows If this button is pressed on the selected column Bitmap a file selection dialog will appear where the desired picture can be chosen Button Edit Limit s With this button the param...

Page 78: ...whole dialog the high voltage is switched off 7 6 2 Sequence Measurement In the second half of the tab sheet SEQUENCE the measured values of a sequence are stored All technical feasible data are reco...

Page 79: ...will select the measurement signal you want to use for limits for example DF tan To perform this operation the sequence number SqNr and the connection in table MEASUREMENTS must be equal to the values...

Page 80: ...n area absolute Parameter DF tan Relative to ref Not selected Expected Value 0 005 MinTol 0 002 MaxTol 0 002 2a Pass area absolute Parameter DF tan Relative to ref Not selected Expected Value 0 005 Mi...

Page 81: ...evious By pressing this button the previous limiter can be read If there is a previous cell at the SEQUENCE spreadsheet which is marked with a limiter sign the limits of this cell is selected Button N...

Page 82: ...leased Safety Switch pressed etc are fulfilled the high voltage with its specified voltage and frequency will be switched on For the specified test mode all measurements are collected After each chang...

Page 83: ...Software 73 Button Start At Selected Pressing this button will start the sequence at the selected row of the spreadsheet SEQUENCE...

Page 84: ...ter that the sequence will execute the next cell in the spreadsheet SEQUENCE The actual measured voltage will be shown at the left or right hand side of the needle Button Apply Pressing this button wi...

Page 85: ...easurement Button Analysis Columns With the buttons at the top of the spreadsheet you can change the amount of displayed measuring data The graphical output is automatically adjusted By pressing the c...

Page 86: ...selected measured data 7 7 2 Graphic Analysis Description Button X Y Axis By pressing the labels of the X or Y axes a popup occurs where all possible axes values can be selected Tab sheet predefined V...

Page 87: ...les at the same time The feature is especially helpful if you want to analyze the measured data from different test objects Analysis File Selection Pressing the button will open the following dialog i...

Page 88: ...files All selected measurement files are shown here By pressing the column name File Name you can manage this list See related chapter for details 7 8 Remote Operation This section first describes th...

Page 89: ...ogether Separates command headers from one another Separates arguments from one another Attached to the command header for interrogating an argument Separates individual commands from one another Comm...

Page 90: ...delete operation something has changed in the Event Status Register 4 MAV Message Available Set if there is still data to read through the controller 3 Not in use always 0 2 Not in use always 0 1 Not...

Page 91: ...syntax error that occurred while processing the interface buffer Bit 7 0 6 0 5 0 4 0 3 General error 2 Illegal syntax 1 Illegal argument 0 Unknown command EXR Execution Error Register Holds the last...

Page 92: ...is allowed RS setting or executing in remote control mode is allowed RA querying in remote control mode is allowed 7 8 2 General Commands This section describes the common commands defined in the IEE...

Page 93: ...collective error ESE NR1 X X Returns the contents of Event Status Enable Registers ISR NR1 X X Returns and then clears the contents of the Internal Status Register ISE NR1 X Sets the Internal Status E...

Page 94: ...ctivated only if the high voltage is switched off The RHE Remote High Voltage switched ON and RHA Remote HV switched OFF columns give information about the necessary states of the system If a command...

Page 95: ...GSTAB GST gA GST gB GST gAB X X X X Sets or Returns the test mode of the system RefCAP INTERN Nx X X Returns the value of the internal reference capacitor in F EXTERN EXTERN Nx X X Sets or returns the...

Page 96: ...tted in the same way as on the display as f e 12 44 kV for Voltages 99 43 pF for Capacitances 0 0033 for Dissipation Power Factor a s o Following units are possible p Pico 10 12 n Nano 10 9 u Mikro 10...

Page 97: ...304 mA RESX Nx X X Resistor parallel to Capacitance CX in parallel equivalent circuit Answer similar as 1 20 kOhm PWRA Nx X X Apparent Power Answer similar as 277 35 VA PWRP Nx X X Real Power Answer s...

Page 98: ...WR10 INDX RINDX ZX YX For description see above f e you can send MSET URMS PF CAPX ITEST and you will get with the command MeasDATa a similar string as 957 V 0 00119 106 21 pF 31 25 uA for answer Meas...

Page 99: ...Software 89 HVGnd NO YES X X Signals YES if High Voltage Ground is not connected ANY NO YES X x Signals Yes if any of the alarms above is set to true...

Page 100: ...ight optional warning lamp it is possible to position a second high voltage indicator where all involved personnel can see it immediately e g on top of the transformer tank The function no light illum...

Page 101: ...atics of test current extension with resonating inductor Lk A variable reactor coil is connected in parallel with the capacitive test object CX This configuration constitutes a parallel resonating cir...

Page 102: ...ted output poer over a 16h periode Max ON time 15 min PD level max output 500 pC Operating temperature 5 C 50 C Storage temperature 20 C 70 C Humidity 5 95 r h non condensing Weight Approx 135 kg 297...

Page 103: ...Accessories and Options 93 Schematics Overview of the 5288A inductor and it s shielding Operation Activate the use of a Resonating Inductor in the Menu Menu Settings...

Page 104: ...180 can be used when the direction of the controls depending on how the inductor is wired works inverted Increase the high voltage in small steps 2 kV and optimize balance as required Always wait unt...

Page 105: ...black 3m 1 PE connection cable 5289 MIDAS yellow green 3m 1 Baseload capacitor 400nF 15kV with HV connection cable and PE connection cable Specification 50Hz 60Hz Maximum Output Current 7 35A 6 12A L...

Page 106: ...onnect the additional power supplies built into the 5289 to the Midas to enforce the Midas output power 4 Prepared access for a future automation of the inductor 5 HV Out connector for the High Voltag...

Page 107: ...on the bottom of the 5289 and the ground at one end and to the station grounding system at the other end Connect the MIDAS HIGH VOLTAGE OUTPUT with the supplied short yellow HV cable to the HV In of...

Page 108: ...Options Figure 3 Rotating Machine Stator Test connections to Midas using the resonating inductor and the baseload capacitor With UST B the baseload can be checked with UST A the connected rotor capac...

Page 109: ...Accessories and Options 99 Schematics Overview of the 5289 inductor and it s shielding...

Page 110: ...L or Press L The phase shift should be as small as possible 10 To work with the Inductor start at low voltages 1 2kV and tune for resonance Wait until the measured value is stable light green display...

Page 111: ...menu Setup to reactivate the Midas high voltage transformer over current protection which is disabled while 5289 operation Set the inductance gap back to a medium position This protects the end posit...

Page 112: ...mple of use of the Current Booster type 5287 Option Current Booster 5287 Option Current Booster 5287 schematics Connections Connect the MIDAS Power Output LV Out to Booster with the supplied 2m cable...

Page 113: ...field which correspond with the 10V respectively 100V booster output level The following items are supplied with this option 1 Current Booster 5287 1 High current connection cable to DUT with clamp 20...

Page 114: ...protective measures cannot be provided then the instrument should be periodically checked for contamination and promptly cleaned with suitable cleanser when required This kind of service work is parti...

Page 115: ...tch located above the mains socket on the rear panel of the instrument If the instrument is to remain unused for any length of time it is recommended to unplug the mains lead In addition it is advisab...

Page 116: ...uld be taken when transporting the instrument If return of the instrument is necessary and the original packing crate is no longer available then packing of an equivalent standard or better should be...

Page 117: ...be disassembled and recycled No special instructions are necessary for dismantling The instrument is constructed of metal parts mostly aluminum and synthetic materials The various component parts can...

Page 118: ...Customer Support Department can be reached at the following postal address HAEFELY TEST AG Customer Service Tettex Lehenmattstrasse 353 CH 4052 Basel Switzerland Tel 41 61 373 4111 Fax 41 61 373 4914...

Page 119: ...Conformity 109 13 Conformity...

Page 120: ...110 Appendix Appendix...

Page 121: ...ngs is contained in a weatherproof housing usually porcelain or silicone The space between the primary insulation and the weather shed is usually filled with an insulating oil or a compound plastic fo...

Page 122: ...potential taps the C2 capacitance is much greater than C1 For bushings with power factor tap C1 and C2 capacitances may be the same order of magnitude In the dissipation factor tap design the ground...

Page 123: ...ted to the terminals Tests should not be performed with the bushings mounted in wooden crates or lying on a floor Otherwise the test results can be affected by the wood or the cement floor It is also...

Page 124: ...lange If a bushing is mounted on an equipment the overall measurement method would include all conduction and insulation elements connected between the bushing center conductor and ground Therefore th...

Page 125: ...ature C1 Insulation test of bushing in transformer During measurements on bushings in transformers all terminals of the windings to which the bushings are connected must be tied together electrically...

Page 126: ...igned to fit closely to the porcelain surface usually directly under the top petticoat and applying a high voltage to the band This test provides a measurement of the losses in the section directly be...

Page 127: ...should be the nominal frequency 50 or 60 Hz Test can be combined with the standard measurement at nominal frequency The C1 insulation is measured by the UST A mode The connection is shown in the figur...

Page 128: ...of 1 Results should be compared with those of earlier tests or with results of tests on similar bushings Capacitances recorded for tests on potential taps should also be checked against nameplate val...

Page 129: ...indings bushings and liquid insulations Power and distribution transformers exist as single phase or three phase design For insulation purposes transformers can be further classified as dry type which...

Page 130: ...not exceed one half the low frequency test voltage given in IEEE C57 12 00 The lowest low frequency test voltage given in C57 12 00 is 10 kV which correspond to a nominal system voltage of 1 2 kV Ther...

Page 131: ...ions Sequence Line DUT INPUT A to INPUT HV GND to Test Mode High Voltage to 1 CHL LV Tank GND UST A HV 2 CHG LV Tank GND GST gA B HV 3 CLG HV Tank GND GST gA B LV 4 CLG CHG Tank GND GST gA B LV HV Not...

Page 132: ...nly an overall test to ground can be performed CHG If an autotransformer is equipped with a tertiary winding which is accessible the test procedure is exactly the same as described in section Two Wind...

Page 133: ...winding is to effectively eliminate the interwinding capacitance except for stray capacitances between bushing leads 3 phase 3 winding transformer in Yn Yn formation with tertiary winding Measurement...

Page 134: ...ct of the winding capacitance It is imperative that separate tests should be performed on all transformer bushings The Transformer windings must remain short circuited for all bushing tests and all bu...

Page 135: ...equence Line DUT INPUT A to INPUT B to INPUT HV GND to Test Mode High Voltage to 1 C1G 2 3 Tank GND GST gA B 1 2 C12 2 3 Tank GND UST A 1 3 C13 2 3 Tank GND UST B 1 4 C23 1 3 Tank GND UST B 2 5 C2G 1...

Page 136: ...sequence of 2 kV 10kV and 12kV may be used Test Procedure Current transformers are tested in the same manner as two winding transformers see section Power and Distribution Transformers As for all tra...

Page 137: ...e inductive unit of a capacitor voltage transformer can be disconnected from the capacitor voltage divider This allows beside the overall test voltage ratio phase displacement separate measurements ab...

Page 138: ...or stack shall not differ by more than 5 from the reciprocal ratio of the rated voltages of the units The capacitor losses tan should be agreed upon between manufacturer and purchaser If the dielectri...

Page 139: ...tual short circuit impedance measurements are taken If there are built in current transformers they must be shorted during the test to avoid saturation of their iron cores and over voltages at the sec...

Page 140: ...rns poor electrical connections core de laminations core lamination shorts tap changer problems and other possible windings and core problems in the transformer In principle the test measures the curr...

Page 141: ...UST B LXP2 2 3 1 Tank GND UST A LXS1 4 7 Tank GND UST A LXS2 5 7 Tank GND UST A LXS3 6 7 Tank GND UST A Measuring Data Interpretation On a three phase star delta or delta star transformer the excitat...

Page 142: ...pation factor measured at the lower test voltage from that measured at the higher test voltage When the dissipation factor increases significantly above a certain voltage it is evident that ionization...

Page 143: ...rate at the highest voltage to ground and are therefore most affected by ionization The remaining life in a winding can often be extended by obtaining dissipation factor versus voltage curves on all c...

Page 144: ...factor tip up test is in the measuring of individual stator coils to determine whether they conform to a purchase specification or are within a range deemed to be acceptable The tip up technique is a...

Page 145: ...lues the test voltage has to be further reduced which is in most cases not desirable With the optional resonating inductor a parallel resonating circuit can be created In this resonant configuration t...

Page 146: ...the HV output of the resonating inductor Some of the connections described can be seen in Figure 47 Before starting the measurement some adjustments in the software have to be done On the Setup page...

Page 147: ...t 2cm of liquid above the top of the cylinder inside the cell when the cover is replaced the cylinder of the inner cell should be covered with liquid If there is an insufficient amount of liquid in th...

Page 148: ...d either reconditioned or replaced Should be investigated to determine the cause of the high power factor 1 0 2 0 1 0 Note High dissipation factors indicates deterioration and or contamination with mo...

Page 149: ...sting of cables generally requires additional precautions because the entire device under test is not always visible Both ends of the cable under test should be clearly identified and isolated Avoid p...

Page 150: ...test procedure as outlined for a single conductor unshielded cable can be performed Supplementary it is possible by an UST mode to perform dissipation factor measurements between two conductors which...

Page 151: ...same conditions Comparison with previous test results Comparison of results obtained from both ends Comparison with available manufacturer data 14 6 Capacitors Capacitor test do check the insulation...

Page 152: ...Inductor With the MIDAS built in supply capacitances up to a maximum of CX 100nF 50 60Hz Smax 3kVA can be measured For capacitances with higher values the test voltage has to be reduced or a parallel...

Page 153: ...The power factor of the earth insulation is expected to be in the order of 0 5 or less The main capacitor should have a much lower power factor An increase in capacitance of several percent is an ind...

Page 154: ...ing chambers For uniformly distributed voltage above the interrupting sections these breakers need grading capacitors across the interrupting chambers The following sections will give two examples of...

Page 155: ...ST gA B 1 open C2G 1 Tank GND GST gA B 2 open C12 1 Tank GND UST A 2 open C1G C2G Tank GND GST gA B 1 2 closed Note Test line 4 can be used to inter check the measurement results 4 1 2 Additional meas...

Page 156: ...1 2 Additional measurements in other test modes can be executed to inter check the measurements results Although pre insertion resistors and their switches are included in the sum capacitances of the...

Page 157: ...eutralizing discharge transient currents which are the result of lightning and switching The function of a surge arrester is similar to that of a circuit breaker If a discharge transient current occur...

Page 158: ...he arrester is returned to service Test Procedure on a Single Unit Arrester Arrester assemblies consisting of single units per phase can be tested by the grounded specimen test method GST The line con...

Page 159: ...Applications Guide 149...

Page 160: ...en power losses are measured It can usually be minimized by wiping the porcelain with a plain dry cloth In some circumstances it might be necessary to use cleaning agents and waxes or to heat the porc...

Page 161: ...te Row s 58 68 70 77 Delete View 78 Difference 64 Edit 68 73 Edit Comment 70 77 Edit Description 58 Edit Limit s 68 Evaluate Parameters 49 Ext Noise Reduction 35 Extended Noise Reduction 57 File Manag...

Page 162: ...e 63 Use as Limit s 70 User Configuration 35 Voltage Max 56 X Y Axis 65 X Y Axis 77 C Cell marked as Attention 70 marked as Failed 70 Check box use external Supply 47 Check box use Booster 5287 48 Che...

Page 163: ...ge 75 Test Voltage Stray Capacitance 49 L Label Action 75 M Measuring Value Ambient Temp 43 Apparent Power S 42 Connection 43 Cp parallel 42 Cs serial 42 DF 40 DF 20 C 40 DF 40 DF 20 C 40 Frequency 41...

Page 164: ...Sheet Analysis 32 Attention 72 Auxiliary 44 Conditions 43 DUT Info 43 Manual 32 Noise Channel 62 Options 44 Pass 72 predefined Views 77 Reference Channel Cn 62 Sequence 32 Settings 44 Setup 32 Test C...

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