Schweitzer Engineering SEL-387-0, Instruction Manual

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3.48
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Overcurrent Element
The SEL-387-6 obtains temperature information via one of its serial ports.
The relay may receive data from as many as four temperature transducers: a
single ambient temperature transducer and one transducer for top-oil
temperature from each of three single-phase transformers. These data could
come from an SEL-2032 or an SEL-2030 Communications Processor, which
receives the temperature data from either an SEL-2600A RTD Module or a
PLC (see
Figure 3.17 ). The SEL communications processor must receive the
temperature data in Modbus
®
, SEL Fast Messaging, or ASCII protocol. The
SEL communications processor passes these data on to the SEL-387-6 in the
form of an SEL Fast Message. While the SEL-387-6 can receive temperature
data at any rate, the thermal element uses these data only once a minute.
Please refer to SEL Application Guide 2000-07, Connection and
Configuration of an SEL Communications Processor and SEL -2600A to
Obtain Measured Ambient and Top-Oil Temperatures for SEL-387 -6 Relay
Thermal Element for information about how to set the SEL communications
processor to communicate with the SEL-2600A RTD Module and the
SEL-387-6.
Figure 3.17 Example System Block Diagram
Overcurrent Element
Application
Description
The SEL-387 provides numerous overcurrent elements, as many as 11 per
winding, 44 total. Four levels of phase instantaneous/definite-time elements
are available for single- or three pole feeder protection, breaker failure
protection, overcurrent phase selection for targeting, transformer backup
protection, etc. Two levels of negative-sequence and residual instantaneous
elements provide protection against unbalanced conditions and ground faults.
A phase, negative-sequence, and residual time-overcurrent element are
available for system backup protection.
Operating
Characteristic
Each winding input of the SEL-387 has 11 overcurrent elements (see
Table 3.4 ). Nine of these 11 are torque-controlled elements, of which there are
one definite-time element, one instantaneous element, and one inverse-time
element per each of three categories. These categories are phase, negative-
sequence, and residual current. Two of the 11 overcurrent elements, 50P
n 3
and 50P n 4, are not torque controlled. These two elements are phase
instantaneous overcurrent elements that provide output information per phase
SEL-2600A or PLC
SEL
Communications Processor
SEL-387-6
SEL Fast Messaging
Temperature Inputs
Power Transformer
Station Computer
Modbus ® , SEL
Fast Messaging,
or ASCII protocol