TROUBLESHOOTING OF TRANSFORMER

TROUBLE SHOOTING OF TRANSFORMER

TROUBLE SHOOTING OF TRANSFORMER
NO.	TROUBLES	CAUSE	ACTION
1	Stop of transformer (Except OLTC)	Internal fault of main tank	(1) Check on relay        operation. (2) Electrical tests -1  Measurement of insulation resistance -2 Measurement of winding resistance -3 Measurement of voltage ratio. -4 Measurement of exciting current (3) Gas analysis of          transformer
1-1	Operation of differntial relay and buchholz relay or pressure relief device operate simultaneously	(1) Internal fault	Action shall be same as internal fault procedures.

1-2	Operation of buchholz relay and pressure relief device	(2) Internal fault	Action shall be same as internal fault procedures.
1-3	simultaneously Operation of differential relay only	(1) Internal fault  (2) Inrush current               at time of              energyization	(1) Action shall be same        as internal fault      procedures. (2)-1 Setting values of         relays.   (2)-2 Value of inrush              current.
1-4	Operation of buchholz relay (trip) only	(1) Internal fault  (2) Faulty          operation	(1) Action shall be same as internal fault procedures. (2)-1 Check wiring. (2)-2 Check contacts.
1-5	Operation of pressure device Only	(1) Interal fault  (2) Faulty Operation	(1) Action shall be same as internal fault procedures. (2)-1 Check wiring. (2)-2 Check contacts.
1-6	Winding temp. indicator or oil temp. indicator	(1) Internal fault  (2) Faulty operation  (3) Stop of cooling          fan.	(1) Action shall be same as internal fault procedures.  (2)-1 Check wiring  (2)-2 Sudden variation of oil  temperature. (3)    Check cooling fan.
2	Operation of buchholz: relay (alarm) only	(1) Internal fault  (2) Trapped air or          evoluation of          dissolved gases	(1) Action shall be same as           internal fault procedures.   (2) -1 Analysis of gas               accumulated   in Buchholz Relay.  (2)-2 Sudden variation of oil               temperature.
3	Operation of relays such as overcurrent relay, ground relay, arrestor etc.	(1) Internal fault (2) External faults such as short- circuit In the system	(1) Action shall be same as           internal fault procedures. (2) -1 Check any sign of          Heavy current             circulation in the             windings. (2) -2 Check any sign of           on-load tap changer interrupting heavy short-circuit current. (2) -3 Short-circuit current value, its duration time.

4	Abnormality is found in recording devices	- ditto -	- ditto -
	High     temperature rise	Period required to Reach the maximum temperature and ambient temperature, Load factor or type of load. Connection diagram of bank and internal connection tap voltage.	If the oil temperature is about 80`C over, the transformer must not be operated continuously.
	Burned coil	Date and time of burning.       Installation site. Perod of use(immediately after operation period). Cause of failure:    Overload     Lighting Short circuiting (internal or external) Others Existence or absense of copper powder. Operation of protective devices (primary and secondary)
	Local heating	Heated point. Load factor or type of load. Smoke.   Discoloration.

	Insulation resistance failure	Insulation resistance:         High voltage winding to low voltage winding and tank. Low voltage winding to high voltage winding and tank. High voltage winding to low voltage winding. Temperature and humidity at which mea surement is made. Installation site (indoors or outdoors). History of the transformer. Dielectric strangth of the insulation oil.
	Noise	Operating conditions (overload, normal)