Sel 2414 - Page 100

5.32
SEL-2414 Transformer Monitor Instruction Manual Date Code 20130214
Metering and Monitoring
Monitoring
Equation 5.21
The default value from Table 5.14 ranges from 1.25–3.0 hours. You can select
other values from within a range of 0.1–20 hours. The default values for this
variable listed in Default Transformer Constants are from IEEE C57.92-1981,
Tables 2 and 4.
Oil Exponent (T[x]EXPn[y]).
Range: 0.1–5.0, in 0.1 steps
This exponent is a constant that the thermal element uses in calculating ultimate
top-oil rise over ambient temperature (ΔΘ
TO
).
The default values listed in Table 5.14 are from IEEE C57.92-1981, Tables 2 and
4. If specific values for a particular transformer are known, you can enter values
from within a range of 0 to 5.
Winding Exponent (T[x]EXPm[y]).
Range: 0.1–5.0, in 0.1 steps
This exponent is a constant that the thermal unit uses in calculating ultimate hot-
spot conductor rise over top-oil temperature (ΔΘ
H
).
The default values listed in Table 5.14 are from IEEE C57.92-1981, Tables 2 and
4. If specific values for a particular transformer are known, you can enter values
from within a range of 0 to 5.
where:
P
r
= total loss at rated load (watts)
THor = top-oil rise over ambient at rated load
The formula for the calculation of C depends on the cooling method used.
For natural-oil cooling modes—
C = transformer thermal capacity (watt-hours/degree)
= 0.06 • (weight of core and coil assembly in pounds)
+0.04 • (weight of tank and fitting in pounds)
+1.33 • (gallons of oil)
OR
C = 0.1323 • (weight of core and coil assembly in kilograms)
+0.0882 • (weight of tank and fitting in kilograms)
+0.3513 • (liters of oil)
For forced-oil cooling modes (either directed or nondirected)
C = transformer thermal capacity (watt-hours/degree)
= 0.06 • (weight of core and coil assembly in pounds)
+0.06 • (weight of tank and fitting in pounds)
+1.93 • (gallons of oil)
OR
C = 0.1323 • (weight of core and coil assembly in kilograms)
+0.1332 • (weight of tank and fitting in kilograms)
+0.5099 • (liters of oil)
where:
1 kg = 2.2046 pounds
1 gallon = 3.785 liters
OTR C
THor
P
r
--------------
• =