HIGH VOLTAGE CIRCUIT BREAKER

SUB - OBJECTIVE

At the end of the lesson the Trainee will be able to analyze the high voltage circuit breakers faults find it out and fix it.

CIRCUIT BREAKER

No	Symptoms	Cause	Remedy
1.	Overheat of Contact.	(I) Poor contact.	Replace wiper spring.
		(2) Ingress of foreign substances to contact surface or rough main contact.	(a) Remove foreign substances. (b) Polish contact surface (replace, if remarkably roughened).
2.	Failure in inter- Rupting      operation.	(1) Broken wire or erroneous wiring of opening circuit.	Recheck circuit
		(2) Poor contact of auxiliary switch.	(a) If auxiliary switch lever of          ON/OFF shifting operation is found improper, adjusting shifting. (b) If auxiliary switch contact wipe is poor, increase wipe or replace auxiliary switch. (c) Should incomplete contact of auxiliary. switch be caused by looseness of mounting bolts, retighten           them.
		(3) Broken wire of layer short of tripping coil.	Replace coil.
		(4) Breakage of link, on control system.	Replace broken parts.
		(5) Malfunction fo electromagnetic valve.	Repair increased friction parts and defective parts or replace electro – magnetic valve.
		(6) Operating air pressure drop.	(a)   Check setting pressure of reducing valve. (b)   Check air supply source and air leak.
		(7) Gas pressure drop.	Repair leak places and supply gas.

No	Symptoms	Cause	Remedy
3.	Failure of closing operation	(1)    Broken wire or erroneous wiring of closing control circuit.	Recheck circuit
		(2)   Poor contact of Trip free          Contactor.	Replace contactor or repair rough contactsurface.
		(3)   Broken wire or layer short of  coil.	Replace coil.
		(4)   Malfunction of hook.	Eliminate increased friction and replace defective parts.
		(5)   Breakage of closing spring.	Replace spring
		(6)   Gas pressure drop.	Supply gas and repair leak places.
4.	Pumping operation	(1)  Erroneous operation of.trip free contactor or poor contact of auxiliary switch (for trip free contactor). (2) Defective arrangement of hook and roller on closing link mechanism.	Check trip free contactor. Check and repair link mechanism.
5.	Gas leakage	(1) Incomplete insertion of packing into groove or hole on seal, or damaged gasket.	Reweld seal part gasket.
		(2)  Defective welding or defective               material.	Reweld or replace parts.
		(3)  Loose joints.	Check fastenings.
		(4)  Mulfunction of gas density detector.	Readjust or replace gas density detector.
		(5) When gas density detector issues heavy fault alarm due   to broken gas piping etc.	Turn off the backup circuit breaker immediately, and also turn off the disconnecting switch from both ends of circuit breaker to be separate from the circuit. contact with the nearest sale office of Hitachi Ltd. or Kokubu Works directly

 

No	Symptoms	Cause		Remedy
6.	Air leakage	(1)Electromagnetic valve	(a) Damaged valve   gasket due to ingress of  foreign substances.	(a) Replace valve         packing. (b) Eliminate foreign         substances.
			(b) Damaged valve seat due to ingress of foreign substances.	Replace valve body.
			(c) Broken electro-magnetic valve lever.	Replace lever.
		(2) Main valve Same as (a) and (b) above.		Same as (a) and (b) above.
		(3) Air leakage from piping sysem.		Check fastenings for looseness.
		(4) Increase of air leakage from airing   valve.		Measure discharge of airing valve,and if the measured valve does not complete with the specified value, replace it.
		(5) Others.		Check gaskets and fastening at joints.

  

 

HIGH VOLTAGE CIRCUIT BREAKER PART 2