Schweitzer Engineering SEL-387-0, Instruction Manual

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3.42
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Thermal Element (SEL-387-6 Relay)
Transformer De-Energized (TRDE)
Transformer heating consists of heating resulting from transformer losses and
heating resulting from load. IEEE standard C57.91-1995 assumes the
transformer is energized and calculates an increase in oil and winding
temperatures resulting from transformer losses. Relay Word TRDE provides
the thermal element a way to distinguish between the de-energized and
energized stages. For example, wire a “52b” (normally closed) circuit breaker
auxiliary contact to input
IN101
and enter the SEL
OGIC
control equation TRDE
= IN101. When IN101 asserts (circuit breaker main contacts open and the 52b
auxiliary contacts closed), the thermal element considers the transformer de-
energized and the ambient, top-oil, and hot-spot temperatures all have the
same value.
It is the user’s responsibility to make up an “effective external contact” from
one or more 52a or 52b contacts (from one or more breakers) indicating that
all the “source” breakers are open. If the user fails to assign a properly
configured digital input to TRDE, then the top-oil and hot-spot temperatures
will increase over the ambient temperature even when the power transformer
is de-energized.
Number of Thermal Inputs (NTHM)
Range: 0–4
The maximum number of thermal inputs is four. The number of available
thermal inputs depends on your data acquisition system and the construction
of your transformer (XTYPE).
Thermal Function (THMz) (SEL-387-6 Relays With
Firmware Versions R404 and Earlier)
Range: AMB, OIL1, OIL2, OIL3
This setting determines how the SEL-387 uses the thermal inputs it receives.
The choices are AMB (ambient temperature), OIL1 (top-oil temperature 1),
OIL2 (top-oil temperature 2), and OIL3 (top-oil temperature 3). If NTHM is
set to 0, the relay assumes that it is not receiving any temperature inputs and
will use only currents for its calculations. The COMFLG bit is cleared when
NTHM is set to 0.
Ambient Temperature Input (AMB) (SEL-387-6 Relays
With Firmware Versions R606 and Later)
Range: THM1... THM4, RTD1A...RTD12A, RTD1B ...RTD12B
This setting assigns one of the selected temperature inputs to the ambient
temperature variable in the SEL-387-6 thermal model.
Top Oil 1 Temperature Input (OIL1)
(SEL-387-6 Relays With Firmware Versions R606 and Later)
Range: THM1...THM4, RTD1A...RTD12A, RTD1B...RTD12B
This setting assigns the selected temperature input to the top oil 1 temperature
variable in the SEL-387-6 thermal model. Use this setting for single tank,
three phase transformers, or as one of three top oil inputs for single tank,
single phase transformers.
NOTE:
z = 0, 1, 2, ... NTHM. There are
as many THM settings as there are
thermal inputs. Each thermal input
must be properly designated.
NOTE:
Thermal Model
temperature inputs
assigned as RTD inputs
require temperature inputs
from the SEL-2600 RTD
Module via one of the
SEL-387 serial ports.
Thermal Model
temperature inputs
assigned as THM inputs
require an external device,
such as an SEL-2030,
communicating thermal
information directly to the
SEL-387 via the relay
serial port. For more
information on using the
THM type thermal inputs,
see SEL Application Guide
AG2006-05 “Connection
and Configuration of an
SEL Communications
Processor and an SEL-2410
I/O Processor to Obtain
Measured Ambient and
Top-Oil Temperatures for
the SEL-387-6 Relay
Thermal Element”.