5.31
Date Code 20130214 Instruction Manual SEL-2414 Transformer Monitor
Metering and Monitoring
Monitoring
Cooling Stage n Constants
Top-Oil Rise Over Ambient Temperature (T[x]THor[y]).
Range: 0.1°–100°C, in 0.1°C steps
Top-oil rise over ambient temperature is the difference in degrees Celsius of the
top-oil temperature of a transformer above the ambient temperature, at steady-
state, full-rated load.
The default values listed in Default Transformer Constants 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 100°C.
Hot-Spot Conductor Rise Over Top-Oil Temperature (T[x]THgr[y]).
Range: 0.01°–100.0°C, in 0.1°C steps
Hot-spot rise over top-oil temperature is the difference in degrees Celsius of the
temperature of the hottest spot on the conductor winding over the top-oil
temperature at steady-state, full-rated load. If not provided, THgr can be
calculated from the following equation.
Equation 5.20
Table 5.14 lists default values. The setting range for THgr is 0 to 100°C.
Ratio Losses (T[x]RATL[y]).
Range: 0.1–100.0, in 0.1 steps
RATL is the ratio of load loss at rated load to no-load loss. 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 0.1 to 100.0.
Oil Thermal Time Constant (T[x]OTR[y]).
Range: 0.1–20.0 hours, in 0.1-hour steps
The oil thermal time constant is the time it takes the top-oil temperature rise over
ambient temperature to reach 63.2 percent of the difference between final rise
and initial rise during a load change. If not provided, OTR can be calculated from
the following equation.
where:
THwr = average winding rise over ambient at-rated load
(55°C or 65°C)
Θ
hswr
= hot-spot winding rise over average winding rise
(10°C if THwr = 55 or 15°C if THwr = 65)
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