13-4 Testing and Troubleshooting Date Code 20001006
SEL-351 Instruction Manual
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 volts peak-peak to the low-level test
interface. Figure 13.1 shows the signal scaling factors.
CAUTION
!
The relay contains devices sensitive to Electrostatic Discharge
(ESD). When working on the relay with front or top cover
removed, work surfaces and personnel must be properly grounded
or equipment damage may result.
You can test the input module two different ways:
1. Measure the outputs from the input module with an accurate voltmeter (measure signal
pin to GND pin), and compare the readings to accurate instruments in the relay input
circuits, or
2. Replace the ribbon cable, press the front-panel <METER> button, and compare the relay
readings to other accurate instruments in the relay input circuits.
Figure 13.1: Low-Level Test Interface
Delta-Connected Voltages
For SEL-351 Relays with delta-connected voltages, the following applies to the input module
output (J1) in Figure 13.1:
1177.6 mV AT NOMINAL VOLTAGE (120 V
LL
)
A measurement made from VA pin to GND pin reflects voltage VA - VB (VB pin to GND pin
reflects voltage VB - VC; VC pin to GND pin reflects voltage VC - VA).
Sensitive Earth Fault (SEF) Channel IN (0.05 A Nominal)
For SEL-351 Relays with SEF channel IN, the following applies to the input module output (J1)
in Figure 13.1:
50 mV AT NOMINAL CURRENT (0.05 A, channel IN)
Test Methods
Test the pickup and dropout of relay elements using one of three methods: target command
indication, output contact closure, or sequential events recorder (SER).
Courtesy of NationalSwitchgear.com
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