10.2
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Testing and Troubleshooting
Testing Methods and Tools
Low-Level Test
Interface
The SEL-387 has a low-level test interface between the calibrated input
module and the separately calibrated processing module. You can test the
relay in either of two ways:
➤ Conventionally, by applying ac current signals to the relay
inputs
or
➤ By applying low magnitude ac voltage signals to the low-level
test interface.
Access the test interface by removing the relay front panel.
Figure 10.1 shows the low-level interface connections. Remove the ribbon
cable between the two modules to access the outputs of the input module and
the inputs to the processing module (relay main board).
You can test the relay processing module using signals from the SEL RTS
Low-Level Relay Test System. Never apply voltage signals greater than 9 V
peak-to-peak to the low-level test interface. Figure 10.1 shows the signal
scaling factors.
The relay contains devices sensitive
to Electrostatic Discharge (ESD).
When working on the relay with the
front panel removed, work surfaces
and personnel must be properly
grounded or equipment damage may
result.
!
CAUTION
You can test the input module two different ways:
➤ Measure the outputs from the input module with an accurate
voltmeter and compare the readings to accurate instruments in
the relay input circuits;
or
➤ Replace the ribbon cable, press the front-panel {METER}
pushbutton, and compare the relay readings to other accurate
instruments in the relay input circuits.
Figure 10.1 Low-Level Test Interface
Test Methods
Test the pickup and dropout of relay elements using one of three methods:
➤ Front-panel target LCD/LED indication
➤ Output contact operation
➤ Sequential Events Recorder (SER)
Target LED Illumination
During testing, use target LED illumination to determine relay element status.
Using the TAR F command, set the front-panel targets to display the element
under test. Monitor element pickup and dropout by observing the target LEDs.
For example, the Winding 1 phase definite-time overcurrent element 50P11
appears in Relay Word Row 2. When you type the command TAR F 50P11
<Enter>, the terminal displays the labels and status for each bit in the Relay
1.25 Vdc AT NOMINAL 125 Vdc BATTERY
PROCESSING MODULE INPUT (J10) : 9 V p-p MAXIMUM
INPUT MODULE OUTPUT (J13) : 100 mV AT NOMINAL CURRENT (1 A OR 5 A)
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