There are following test
to be performed before commissioning of power transformers as per Indian
Standard Code.
Inspection
|
- Junction
box and marshalling kiosks
- Control
panel, relay panel etc.
|
Primary
injection test
|
- To
check operation and stability of earth fault relay on high voltage side and
low voltage side
- line
directional elements of high voltage relays
- Over-current
relays on low voltage side
- Over-current
relay on high voltage side ( when current transformers are not in transformer
bushings )
- Earth
fault relay on low voltage side
- Test
on high speed neutral ammeter
- Voltage
compensation
|
Secondary
injection
|
- Performed
on transformer protection relay
|
Ratio
test
|
- When
415 V applied on high voltage side, measure the voltage between all phase on
low voltage side for every tap position of high voltage
- Measure
the voltage
A
to a , b and c
B
to a , b and c
C
to a, b and c
Where
A, B and C are three phase terminals of high voltage side whereas a, b and c
are terminals of low voltage side
|
Tripping
tests
|
- High
voltage
- Low
voltage
- Inter-tripping
tests
- Winding
temperature trips
|
Calibrate
earth resistance
|
|
Buchholz
relays
|
- Check
that there is no air in protector before commissioning
- When
energizing transformer, close in on – trip – etc.
- Test
for angle, air injection etc
- Check
for stability when oil pumps are started – at ambient temperature and at
winding temperature of 80 degree or above
|
Alarm
circuit
|
- Buchholz
relay
- Oil
and winding temperature thermometer
- Cooling
gear failure
|
Fan
& pumps
|
- Check
that oil valves are open in cooling circuit.
- Check
that rotation of pumps, automatic starting overloads devices etc.
- Check
stability of Buchholz relay
|
Tap
changing test
|
- Check
mechanism, indication, buzzer , lamp etc.
|
Phasing
tests
|
- At
415 V
- Between
transformers in a bank
- To
prove internal and external connections for parallel operation
- On
auxiliary supply and voltage transformers
|
Insulation
test
|
- High
voltage winding and low voltage winding
- On
current transformer and voltage transformers
|
Oil
test
|
- Check
oil level
- Dielectric
test
- Volume
resistivity
- Acidity
- Tan
delta
- Water
content
|
Load
test
|
- Voltmeter
and ammeter on both high voltage and low voltage side
- Over
current
- No
spill in high voltage star point
- No
creeping of contacts on both high and low voltage earth fault relays
- Directional
elements – low voltage directional over current and earth fault relays
- Voltage
compensation
|
Voltage
compensation test ( If compensating CTs are fitted )
|
- Primary
injection test
- Load
test
|
Check
neutral earthing switches are closed before connect with live
|
|
Check
transformer on equal taps before switching in
|
- For
transformer in bank
- For
transformer in parallel
|
If
necessary, arrange temporary protection for soaking and switching in (
example – unrestricted earth fault, if soaking from low voltage side 113 V
and 213 V open )
|
|
Tap
changing test on load over full range of taps
|
|
When
transformer rating above 1000 MVA, energizing of transformer for the first
time, voltage should be build up gradually
|
|
Low
voltage excitation current measurement
|
|
Single
phase magnetic balance test
|
|
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