TROUBLESHOOTING OF TRANSFORMER
TROUBLE SHOOTING OF TRANSFORMER
NO.
01.
TROUBLE
Stop of transformer
(Except OLTC)
CAUSE
Internal fault of
main tank
ACTION
Check on relay operation.
Electrical tests
Measurement of insulation resistance
1-1
1–2
1–3
Operation of
differntial relay and
buchholz relay or
pressure relief
device operate
simultaneously
Operation of
buchholz relay and
pressure relief
device
(1) Internal fault
Operation of
buchholz relay and
pressure relief
device
Measurement of winding resistance
Measurement of voltage ratio.
Measurement of exciting current
Gas analysis of transformer
Action shall be same as internal
fault procedures.
(2) Internal fault
(1) Internal fault
Action shall be same as internal
fault procedures.
(2 Internal fault
Action shall be same as internal fault
procedures.
(1) Internal fault
Action shall be same as internal
fault procedures.
(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) Internal fault
(2) Faulty
Operation
) 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.
TROUBLE SHOOTING OF TRANSFORMER
NO.
02.
TROUBLE
Operation of
buchholz: relay
(alarm) only
CAUSE
ACTION
(1) Internal fault
(2) Trapped air or
evaluation 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.
03.
(1) Action shall be same as
internal fault procedures.
04.
Operation of relays
such as over current
relay, ground relay,
arrestor etc.
(1) Internal fault
(2) External faults
such as short- circuit
In the system
Abnormality is found
in recording devices
- ditto -
High
temperature rise
Burned coil
(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.
Short-circuit current value, its duration
time.
- ditto -
Period required to
If the oil temperature is about 80`C over,
Reach the maximum
the transformer must not be operated
temperature and
continuously.
ambient temperature,
Load factor or type of
load. Connection
diagram of bank and
internal connection tap
voltage.
Date and time of
burning. Installation
site. Period of use
(immediately after
operation period).
Cause of failure:
Overload Lighting
Short circuiting
(internal or external)
Others
Existence or absence
of copper powder.
Operation of
protective devices
(primary and
secondary)
Local heating
Heated point. Load
factor or type of load.
Smoke.
Discoloration.
Insulation resistance:
Insulation resistance
failure
Noise
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 strength of
the insulation oil.
Operating conditions
(overload, normal)