Schweitzer Engineering SEL-387-0 - Figure 3.15 Thermal Element Logic

3.33
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Thermal Element (SEL-387-6 Relay)
Figure 3.15 Thermal Element Logic
The thermal element operates in one of three modes, depending upon the
presence or lack of measured temperature inputs:
➤ Measured ambient and top-oil temperature inputs
➤ Measured ambient temperature only
➤ No measured temperature inputs
If the relay receives measured ambient and top-oil temperatures, the thermal
element calculates hot-spot temperature (Figure 3.16 (A)). When the relay
receives a measured ambient temperature but not a measured top-oil
temperature, the thermal element calculates the top-oil temperature and hot-
spot temperature (Figure 3.16 (B)). In the absence of any measured ambient or
top-oil temperatures, the thermal element uses a default ambient temperature
setting (DTMP) that you select and calculates the top-oil and hot-spot
temperatures (Figure 3.16 (C)). Top-oil temperature is always calculated from
the applied currents for the cooling system efficiency element.
Relay
Word
Bits
Setting
Θ
TO
TOT1
TO1
_
+
TOT2
TO2
_
+
Θ
H
HST1
HS1
_
+
+
HST2
HS2
_
FAA
FAAL1
FAA1
_
+
FAAL2
FAA2
_
+
RLOL
RLOLL
RLL
_
+
TLOLL
TLOL
TLL
_
+