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Howard Industries HI-105, Instructions Manual

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Howard Industries HI-105 Instructions Manual Download Page 20

Document 2.4.126, Revision 4

October 2017

20

Three-Phase Padmounted Distribution Transformers

Surge Arresters

Surge arresters can be used in three-phase 

padmounted transformer installations to protect the 

transformer and underground cable from damage 

due to voltage surges.

Surge arresters should be installed only on 

systems where the power frequency voltage at the 

arrester does not exceed the published maximum 

continuous operating voltage (MCOV) values. 

Disconnect surge arresters before performing 

impulse, induced-potential or applied-potential 

tests; otherwise, the arresters may be damaged. 

Reconnect surge arresters after testing and before 

placing the transformer into service. 

Internal MOV Arresters

Internal metal-oxide-varister (MOV) surge arresters 

are designed to be fluid immersed and mounted 

inside the transformer tank. It is recommended that 

fluid-immersed MOV arresters not be exposed to an 

average oil temperature exceeding 90°C (194°F) 

and a maximum oil temperature exceeding 125°C 

(257°F). 

Disconnect fluid-immersed MOV surge arresters 

before performing impulse, induced-potential or 

applied-potential tests; otherwise, the arresters 

may be damaged. Reconnect surge arresters after 

testing and before placing the transformer into 

service. 

Optional arrester disconnectors provide a means 

to disconnect the fluid-immersed MOV arrester 

grounds for transformer testing without entering 

the transformer tank. Individual disconnectors are 

provided for each MOV arrester.  Two different styles 

of disconnectors are available, one manufactured 

by ERMCO Components Inc. (ECI) and one 

manufactured by Cooper Power Systems (CPS).  

These two styles operate differently as indicated 

below.

Before testing the transformer, disconnect the 

arresters using the following procedure for the 

disconnector on each phase.

1.    Make sure the transformer tank is properly 

grounded. 

2.    De-energize the transformer from a remote 

location. 

3.   Ground all bushings and terminals. 

4.    Disconnect the MOV arresters by operating 

the disconnectors as described below.

       For the CPS disconnector (identified by a 

black plastic external cap):

 

   a.    Unscrew the black disconnector cap 

from the shaft. 

   

   b.    Re-attach the small diameter end of 

the disconnector cap to the shaft. 

 

   c.     Push the handle and shaft toward 

transformer until the shaft flange is 

flush to the sealing gland. 

       For the ECI disconnector (identified by a 

7/16” square brass metal head):

   a.    Unscrew the 7/16” square metal head 

until the thread disengages.

   b.    Pull the shaft out to its full extent 

(approximately 2”).

5.     It is now safe to perform impulse, induced-

potential or applied-potential tests. 

After testing the transformer, reconnect the MOV 

arresters using the following procedure.

1.   Make sure the tank is properly grounded. 

2.    De-energize the transformer from a remote 

location. 

3.   Ground all bushings and terminals. 

4.    Reconnect the MOV arresters by operating 

the disconnectors as described below.

      For the CPS disconnector:
 

   a.    Pull the disconnector handle and shaft 

fully away from transformer.

 

DANGER

FAILURE TO FOLLOW THE INSTRUCTIONS 

BELOW WILL RESULT IN DEATH OR SERIOUS 

PERSONAL INJURY, AND DAMAGE TO THE 

EQUIPMENT.
•    De-energize the transformer from a 

remote location and make sure all 

transformer terminals and bushings 

have zero voltage before connecting or 

servicing surge arresters. 

•    Disconnect all surge arresters before 

performing impulse, induced potential or 
applied potential tests.

 

Summary of Contents for HI-105

Page 1: ...7 1 Three Phase Padmounted Distribution Transformers Howard Industries Distribution Transformer Division Instructions HI 105 Installation Operation and Maintenance of Three Phase Padmounted Distribution Transformers 45 kVA through 10 000 kVA ...

Page 2: ... voltage bushing terminals have been properly grounded Only qualified personnel should install maintain and operate this equipment Qualified personnel are those who are trained in the installation maintenance and operation of high voltage equipment trained in the proper use of personal protective equipment such as rubber gloves safety glasses protective clothing hard hats etc and trained in approp...

Page 3: ...and After Initial Energization 12 Pre Energization Inspection and Tests 12 Ratio Test 12 Insulation Resistance Test 12 Tap Changer Setting 12 Series Multiple or Delta Wye Switch Settings 13 Grounding 13 Bolted Connections 13 FluidLevel 13 Fluid Temperature 13 Internal Fault Detector 13 Current Transformers 13 Accessory Wiring 13 Tank Finish 13 Tools 13 Internal Inspection 13 Post Energization Insp...

Page 4: ... Flip Top Terminal Compartment Cover 24 Door Handle Padlock and Security Bolt 24 Lift Off Door Hinges 24 Other Accessory Devices 24 Section 7 Maintenance 25 Periodic Inspection 25 Inspection Checklist 26 Electrical Tests 27 Exterior Paint Finish 28 Fluid Leaks 28 Audible Sound Level 28 Molded Case Circuit Breakers 29 Other Accessory Devices 29 Sampling and Testing the Fluid 29 Filtering the Fluid ...

Page 5: ...designs Standard and optional features are subject to change without notice The instructions contained herein are applicable to transformers operated in normal conditions as specified in the Usual Service Conditions section of IEEE Standard C57 12 00 Questions regarding installation operation and maintenance particularly when encountering unusual or special circumstances not sufficiently covered b...

Page 6: ...l Inspection Although all transformers components and accessories are carefully inspected and tested prior to shipment a thorough receiving inspection should be conducted to detect any damage or loss that might have occurred during shipment The receiving inspection should be completed upon receipt and before unloading from the truck Note any damage or discrepancies on the bill of lading file a cla...

Page 7: ...h and Low marks For transformers supplied with a fluid sight plug the fluid level can be directly observed if it is within acceptable range If the transformer does not have a fluid level gauge or sight plug the fluid level can be checked by removing the liquid level plug located at the 25 C mark Exercise caution when checking the fluid level using the fluid level plug as the fluid may spill out an...

Page 8: ...rea in their original shipping containers Do not store the transformer in a corrosive environment If the transformer is to be stored for an extended period of time before being placed into service it should be stored on a firm level surface The gas space above the insulating fluid should be pressurized with dry nitrogen to a pressure of 2 3 PSIG This will prevent a negative internal pressure that ...

Page 9: ...ting Consult local and national codes to ensure that the installation meets all applicable requirements Location of the transformer must permit it to operate in conditions that meet the requirements specified in the Usual Service Conditions section of IEEE Standard C57 12 00 Operation not meeting these service condition requirements will compromise transformer capacity and reliability unless the t...

Page 10: ...hat all mating connector surfaces are clean and smooth Connections must be tightened appropriately to prevent overheating and possible failure of the connection Refer to the nominal torque guidelines contained in Table 3 Connections should be made with care to avoid placing undue stress on the bushings High Voltage Connections Three phase padmounted transformers with live front construction are us...

Page 11: ...October 2017 11 Three Phase Padmounted Distribution Transformers Low Voltage Connections Three phase padmounted transformers are normally supplied with externally clamped molded low voltage bushings with or without spade terminals ...

Page 12: ...ce test must not be performed on a wye wye connected transformer with an Ho Xo bushing without first disconnecting the internal connection between the primary and secondary neutrals This connection can be found on a terminal board located below the fluid level in the transformer tank Refer to Opening the Transformer Tank for instructions 3 Tap Changer Setting Check the tap changer setting to ensur...

Page 13: ... checked by temporarily removing the liquid level plug located at the 25 C mark 8 Fluid Temperature Observe the fluid temperature gauge and make sure the temperature is no lower than indicated below before the unit is energized 20 C 4 F for conventional transformer oil 0 C 32 F for R Temp fluid 10 C 14 F for FR3 fluid 9 Internal Fault Detector If the transformer is supplied with an Internal Fault ...

Page 14: ...ound levels and factory sound testing Unusual sounds should be investigated as this might indicate a potential problem 6 Locking the Terminal Compartment Before leaving the installation site make sure the terminal compartment is secure using the following procedure Lower the flip top cover if supplied and engage the center mounted cover security bolt Close the primary compartment door and engage e...

Page 15: ... DANGER FAILURE TO FOLLOW THE INSTRUCTIONS BELOW WILL RESULT IN DEATH OR SERIOUS INJURY AND DAMAGE TO THE EQUIPMENT Do not operate load break equipment if a fault condition is suspected Use a live line tool hot stick or shotgun stick to operate transformer load break equipment After operating transformer loadbreak equipment check that voltages at transformer terminals are the expected values Check...

Page 16: ...former front panel and shown on the nameplate diagram Rotary load break switches are designed to be operated with a live line tool hot stick or shotgun stick and should not be operated by hand The two position switch is operated by inserting the live line tool into the operating handle and rotating the switch to either the ON or OFF position The three or four position switch is operated by inserti...

Page 17: ...n fuse device is equipped with a series connected fluid immersed isolation link or if specified by the customer a series connected partial range current limiting fuse Isolation links and partial range current limiting fuses are designed to blow in the event of an internal transformer fault A transformer with a blown isolation link or partial range current limiting fuse cannot be re energized and m...

Page 18: ... firmly into the Bay O Net housing 2 Twist the locking handle latching it to the shoulder of the Bay O Net housing Make sure that the metal washer is positioned tightly on the end of the Bay O Net housing 3 Inspect the fuse holder carefully to make sure it is fully seated and latched properly Dead Break Dry Well Canister Fuse The dead break dry well canister is a fluid tight single pole current li...

Page 19: ...itch insert the live line tool in the operating hook and pull forward swinging the Arc Strangler open To remove the Arc Strangler insert the live line tool in the hinge opening and lift up S C Fused Switch S C fused switches should be operated according to instruction provided by S C S C tools should be used to operate an S C fused switch Vacuum Fault Interrupter The vacuum fault interrupter VFI t...

Page 20: ... by Cooper Power Systems CPS These two styles operate differently as indicated below Before testing the transformer disconnect the arresters using the following procedure for the disconnector on each phase 1 Make sure the transformer tank is properly grounded 2 De energize the transformer from a remote location 3 Ground all bushings and terminals 4 Disconnect the MOV arresters by operating the dis...

Page 21: ...tential or applied potential tests The following procedure should be followed to manually reconnect the arrester leads 1 Reconnect each of the three arrester leads to their junction points 2 Re install the tank cover Refer to Opening the Transformer Tank for instructions Molded Case Circuit Breakers Molded case circuit breakers use an automatic trip system to help protect the transformer and conne...

Page 22: ...can be used to provide a remote alarm of low fluid level Transformers may also be supplied with a sight plug which provides direct observation of the fluid level Fluid Temperature Gauge The fluid temperature gauge is a dial type bi metal instrument that indicates the fluid temperature at the top of the fluid column in degrees centigrade The temperature gauge is mounted on the front panel in a dry ...

Page 23: ...gized The IFD also includes a standard pressure relief device that is integrated into the sensor to relieve excessive tank pressures that might occur during normal operation of the transformer The IFD incorporates a removable shipping lock for transportation and storage The shipping lock must be removed after transformer installation Always transport IFD equipped transformers with the shipping loc...

Page 24: ...or pulling cables into the terminal compartment To open the cover disengage the center security bolt and rotate the cover upward A latch is provided to secure the cover in the open position Door Handle Security Bolt and Padlock Three phase compartmental padmounted transformers are designed and constructed to be tamper resistant according to the requirements of IEEE Standards C57 12 28 or C57 12 29...

Page 25: ...ve typically require no maintenance except replacement in the event of damage Gauges should be checked periodically to make sure they are operating properly Periodic Inspection The transformer s terminal compartment interior all exterior surfaces and the transformer s surroundings should be inspected Inspection frequency should be governed by operating conditions at the installation site More seve...

Page 26: ...eplacing a gasket carefully clean mating surfaces to remove any rust dirt transformer fluid old gasket material or other contamination that might prevent a good seal Use appropriate gasket cement when installing new gaskets Do not reuse old gaskets Six months after replacing a gasket check and re tighten if necessary 6 Maintain a clean and unobstructed area around the transformer including suffici...

Page 27: ...the condition of the transformer Comply with instructions and precautions provided by the test equipment manufacturer Contact the Howard Industries Transformer Division to discuss any of these tests DANGER FAILURE TO FOLLOW THE INSTRUCTIONS BELOW WILL RESULT IN DEATH OR SERIOUS PERSONAL INJURY AND EQUIPMENT DAMAGE Energize the transformer from a remote location Do not energize the transformer usin...

Page 28: ...luid residue a low reading on the fluid level gauge and a constant zero reading on the pressure vacuum gauge which does not vary over time as a function of transformer loading and ambient temperature are also indications of a possible fluid leak To verify that a fluid leak exists clean the suspected leak area with an appropriate solvent to completely remove the fluid and observe the area for reapp...

Page 29: ...article contaminates as well as small amounts of moisture Follow the operating instructions provided by the filter press system manufacturer Continue to filter the fluid until the dielectric test result is 26kV or greater When filtering any particular type of insulating fluid make sure the filter press system is not contaminated with any other type of fluid Contamination of the fluid may alter its...

Page 30: ...into the tank All tools should be accounted for after work is completed It is recommended that any tools used on top of the transformer or inside the tank be attached with safety cords to prevent them from being lost inside the transformer Personnel must not stand directly on any electrical insulation Clean drop cloths should be used under working areas in the transformer to prevent objects from d...

Page 31: ...orque values for any devices or connections not listed below Use the manufacturer s recommended torque values for any customer supplied devices Fastener Type Nominal Torque in lbs Torque Range in lbs Penta head security bolt 100 80 120 3 8 bolt 550 500 600 Hand hole cover bolt 190 170 210 Table 1 Torque Guidelines for External Cabinet Fasteners Mounting Type Nominal Torque in lbs Torque Range in l...

Page 32: ...ess of gasketed components the measured torque will normally be less than the nominal torque listed in the table above due to relaxation of the gasket material Additional tightening of bushing mounting hardware may cause the component to crack or the gasket to become over compressed Table 4 Torque Guidelines for Accessories Component Nominal Torque in lbs Torque Range in lbs Bay O Net fuse cartrid...

Page 33: ...vision should be notified immediately when problems are discovered during the warranty period All warranty repairs must be made or approved by the Howard Industries Transformer Division Transformer Disposal Comply with all local state and federal regulations when disposing of any insulating fluid Fluid type and volume can be determined by referring to the transformer nameplate Contact Howard Indus...

Page 34: ...Document 2 4 126 Revision 4 October 2017 34 Three Phase Padmounted Distribution Transformers NOTES ...

Page 35: ...Document 2 4 126 Revision 4 October 2017 35 Three Phase Padmounted Distribution Transformers NOTES ...

Page 36: ...ions for Installation Operation and Maintenance of Three Phase Padmounted Distribution Transformers 45 kVA through 10 000 kVA Document 2 4 126 Revision 4 October 2017 Copyright 2017 Howard Industries Inc Laurel Mississippi Telephone 601 425 3151 Fax 601 649 8090 Email mkt howard com Web howardtransformers com ...

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