5-90 T35 Transformer Protection System GE Multilin
5.4 SYSTEM SETUP 5 SETTINGS
5
The loss of life function calculates the insulation aging acceleration factor using the settings entered in this section, by
following equation:
(EQ 5.7)
where is the rated hottest-spot temperature as per the table below,
and is the actual computed winding hottest-spot temperature.
The aging acceleration factor is computed every minute. It has a value of 1.0 when the actual winding hottest spot tem-
perature is equal to the rated temperature, is greater than 1 if the actual temperature is above the rated temperature,
and less than 1 if the actual temperature is below the rated temperature.
• NO LOAD LOSS: This setting is obtained from the transformer data and is used to calculate the aging acceleration
factor.
• TYPE OF COOLING: The setting defines the type of transformer cooling and is used to calculate the aging accelera-
tion factor. The values and their description for this setting are as follows:
“OA”: oil-air
“FA”: forced air
“Non-directed FOA/FOW”: non-directed forced-oil-air/forced-oil-water
“Directed FOA/FOW”: directed forced-oil-air/forced-oil-water
• TOP OIL RISE OVER AMBIENT: This setting should be available from the transformer nameplate data
• THERMAL CAPACITY: The setting should be available from the transformer nameplate data. If not, refer to the follow-
ing calculations. For the “OA” and “FA” cooling types:
C = 0.06 (core and coil assembly in lbs.) + 0.04 (tank and fittings in lbs.) +1.33 (gallons of oil), Wh/°C; or
C = 0.0272 (core and coil assembly in kg) + 0.01814 (tank and fittings in kg) + 5.034 (L of oil), Wh/°C
For the “Non-directed FOA/FOW” (non-directed forced-oil-air/forced-oil-water) or “Directed FOA/FOW” (directed
forced-oil-air/forced-oil-water) cooling types, the thermal capacity is given by:
C = 0.06 (core and coil assembly in lbs.) + 0.06 (tank and fittings in lbs.) + 1.93 (gallons of oil), Wh/°C; or
C =0.0272 (weight of core and coil assembly in kg) + 0.0272 (weight of tank and fittings in kg) + 7.305 (L of oil), Wh/°C
For dry-type power transformers:
C = 0.048 × (weight of copper winding); or
C = 0.015 × (weight of core and copper windings from the nameplate); or
C = 0.12 × (weight of aluminum windings); or
C = 0.02 × (weight of core and aluminum coils from the nameplate)
• WINDING THERMAL TIME CONSTANT: Required for insulation aging calculation. If this value is not available from
the transformer data, select “2 min.”.
RATED WINDING
TEMPERATURE
POWER
CAPACITY
NORMAL LIFE
EXPECTANCY
AT Θ
H_R
Oil 55°C ≤ 500 kVA 180000 hrs 95°C
≤ 100 MVA 6.5 × 10
4
hrs 95°C
65°C ≤ 500 kVA 20 years 110°C
≤ 100 MVA 6.5 × 10
4
hrs 110°C
> 100 MVA 6.5 × 10
4
hrs 110°C
Dry 80°C Any 20 years 140°C
115°C Any 20 years 175°C
150°C Any 20 years 210°C
F
AA
t() e
15000
Θ
H_R
273+
-----------------------------
15000
Θ
Ht()
273+
----------------------------
–
=
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