P.11.6
SEL-411L Relay Protection Manual Date Code 20151029
Testing and Troubleshooting
Testing Features and Tools
Remote Relay Behavior (Characteristic Test)
When the characteristic test is active at the local relay, a signal is permanently
keyed over the 87L channel(s) to all remote relay(s) to block the 87L element
in those devices. Note that other protection functions such as the distance
elements are free to operate at the remote terminals.
Note: The 87L TEST command can also be used to inhibit the 87L element
entirely. This prevents local and remote operation of the 87L element during
testing of other protection functions in the local relay.
Loopback Test
The second option in the test mode is the loopback test. The 87L Test
command can be used to facilitate loopback testing of communications
channels to isolate a problem with a communications channel. When the
loopback test is active, the relay substitutes the address of the remote relay
with its own address in order to allow the 87L element to respond to the data
transmitted by itself.
Testing Features and Tools
The relay provides the following features to assist you during relay testing:
➤ Metering
➤ High-resolution oscillography
➤ Event reports
➤ Event summary reports
➤ SER (Sequential Events Recorder) reports
Certain relay commands are useful in confirming relay operation. The
following commands, for example, aid you in testing the relay:
➤ TAR
➤ PUL
➤ TEST DB
➤ TEST FM
➤ TEST DB2
In addition, the relay incorporates a low-level test interface where you can
interrupt the connection between the relay input transformers and the input
processing module. Use the low-level test interface to apply reduced-scale test
quantities from the SEL-4000 Relay Test System; you do not need to use large
power amplifiers to perform relay testing.
Test Features
Metering
The metering data show the ac currents and voltages (magnitude and phase
angle) connected to the relay in primary values. In addition, metering shows
many other quantities including the power system frequency (FREQ) and the
voltage input to the station dc battery monitors (Vdc1 and Vdc2). Compare
these quantities against quantities from other devices of known accuracy. The
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