| Items |
Objective |
Method |
Capacity / Equipment |
| 1. Voltage ratio test |
To measure voltage
ratio between
windings of
transformer |
1.Voltmeter method
2.Comparision
method
3. Ratio bridge
method |
Tira Thai transformer
have ratio and phase
deviation not more
than +- 0.5%
/Transformer ratio
meter Multi-Amp
TR800 |
| 2. Polarity |
To determine polarity
(sub. or additive ) |
1. Inductive kick
2. Alternating
voltage
3. Comparison 4.
Ratio bridge |
Measures polarity of
transformer. / Volt-Amp-Watt meter |
| 3. Phase relation test |
To determine angular
displacement and
relative phase
sequence |
1. Phasor diagram
2.ratio bridge
3. excited voltage |
Measures angular
displacement and
phase sequence
(vector group) of the
transformer |
| 4. Resistance
measurements |
To measure
resistance of
transformer winding |
1. Bridge method
2. Voltmeter-ammeter
method |
Measures resistance
of transformer
winding /Volt-Amp-Watt meter |
| 5. No-load loss test |
To measure no-load
loss at specified
excitation voltage
and specified
frequency |
1. Average-voltage
voltmeter method |
Measures core loss of
transformer/ PT ,CT,
Volt-Amp-Watt meter |
| 6. Exciting current
test |
To measure current
that maintain the
magnetic flux
excitation in the core
of the transformer |
1. Average-voltage
voltmeter method |
Measures exciting
current of the
transformer / PT ,CT,
Volt-Amp-Watt meter |
| 7.Load loss and
impedance test |
To measure losses
occurring at rated
load , including I2R
loss and stray loss
and measured
voltage required to
circulate rated
current through one
winding when the
other winding is
short-circuited |
Wattmeter-voltmeter-ammeter method |
Measures load loss of
the transformer /
PT,CT, Volt-Amp-Watt meter |
| 8.Induce potential
test |
To check insulation
turn to turn and
between layers of the
winding |
Applied greater than
rated volts per turn
to the transformer ,
the frequency of the
impressed voltage
must be high enough
to limit the flux
density in the core |
1. Generator 500 kW
Max. frequency 500
Hz
2. Generator 250 kW
frequency 200 Hz
3. Testing
Transformer 4000 kVA
1.5/6.9/50 kV |
| 9. Applied potential
test |
To test the
transformers ability
to withstand
application of
voltage associated
with the specified
insulation level
(insulation between
winding -winding
and winding -
ground) |
Applied potential at
power frequency to
specified value and
held for the time
specified. |
1. HV Testing
Transformer (3 x 75
kVA) 400V/0-250 kV 2.
Reactor |
| 10. Oil test |
To determine oil
dielectric strength |
Oil Tester (applied
high voltage until
gap in oil breakdown
and measure this
voltage ) |
Measures dielectric
strength of
transformer oil. / Oil
Tester |
| 11. Insulation
resistance test |
To determine the
insulation resistance
from individual
windings to ground
or between
individual windings |
Mega ohmmeter
(applied dc voltage) |
Measures insulation
resistance of the
transformer. / Mega
ohmmeter |
| 12. Leakage test |
Check leakage of
tank |
Pressurize tank by
applying dry
nitrogen. if after 6
hours no pressure
drop is registered the
transformer tank is
leakage free |
Check for tank leakage |
| Items |
Objective |
Method |
Capacity /
Equipment |
| 13. Temperature-rise
test |
To measure
temperature rise of
oil and winding of
transformer |
1. Actual loading
2. Simulated loading
2.1 short circuit
method
2.2 The loading back
method |
Measures temperature
rise of oil and winding of
transformer. /PT ,CT,
Volt-Amp-Watt meter |
| 14. Dielectric type
test (Lightning and
switching Impulse
test, BIL) |
To certify that the
transformer has
been designed and
constructed to
withstand the
specified
(BIL)insulation
levels |
Marx's multiplier
circuit |
Measures dielectric of
the transformers (BIL ) /
Impulse Generator
Haeferly Series E Max.
Voltage 1400 kV 70 kJ |
| Items |
Objective |
Method |
Capacity |
| 15. Dielectric special
test BIL FW&CW |
To certify that the
transformer has
been designed and
constructed to
withstand the
specified insulation
levels |
Marx's multiplier
circuit |
1. Impulse Generator
Haeferly Series E Max.
Voltage 1400 kV
2. Chopping Gap 1200
kV |
| 16. Determination of
capacitance
winding-to-earth,
and between
windings |
To measure
capacitance of
transformer |
Bridge method |
Measures capacitance
of the transformer.
/Bridge capacitance
meter |
| 17. Measurement
Zero-sequence
impedance on three
phase transformer |
To measure Zero
phase sequence
impedance |
Winding shall be
excited at rated
frequency between
the neutral and three
line terminal
connected together |
Measures Zero phase
sequence impedance of
the transformer. /PT ,CT,
Volt-Amp-Watt meter |
| 18. Determination of
sound level |
To measure sound
level originating
from active part of
transformer which is
transmitted, either
through the
dielectric fluid or the
structure supports,
to the outer shell or
to other solid
surfaces from which
it is radiated as
airborne sound |
1. Measuring
continuous sound
pressure levels, In
term of either A-weight
2. Rating
transformer sound
emissions
3. Report the result
in a standard
manner |
Measures sound from
active part of
transformer. /sound
level meter |
| 19. Measurement of
the dissipation
factor (tan d) of the
insulation system
capacitance |
To determine ratio
of the power
dissipated in the
insulation in watts
to the product of the
effective voltage
and current in volt-amperes when test
under a sinusoidal
voltage |
Bridge circuit |
Measures the
dissipation factor (tan d)
of the insulation system
capacitance . /Bridge
capacitance meter |
| 20. Determination of
partial discharge on
transformer |
To measure the
radio-influence
voltage (RIV)
generated by any
internal partial
discharge |
Measures partial
discharge in terms
of RIV and will be
measured at the line
terminal of the
winding under test |
Measures partial
discharge level of
transformer. /PD
Detector and PD
analyzer, Haeferly |
