Date Code 20150401
SEL Application Guide 2015-12
Application Guide
Volume I
AG2015-12
Testing a Two-Terminal Application
of the SEL-411L in Test Mode
Ashwin Vashist and George Alexander
I
NTRODUCTION
The SEL-411L Advanced Line Differential Protection, Automation, and Control System has a
built-in test mode with flexible single-terminal and multiterminal testing options. This mode
allows you to perform acceptance, commissioning, and maintenance testing on a line differential
application that uses SEL-411L Relays in an easy and efficient manner. The
TEST 87L
command makes it possible to test the differential element on an in-service line from only one
terminal or from all terminals at the same time (the latter requires the test sets to be satellite-
synchronized).
Figure 1 shows a typical line differential protection arrangement where the exchange of local and
remote operating data between the relays in the scheme takes place over two channels. Bay 1
(Channel 1) uses a dedicated fiber direct connection between the two relays and a channel-based
data synchronization method (ping pong). Bay 2 uses multiplexers to create a hot standby
channel. This has the potential for channel asymmetry, so a time-based synchronization is used
for Channel 2. When external time-based synchronization is used, both SEL-411L Relays must be
connected to an external, high-precision, IEEE C37.118-compliant time source.
This application guide is a test guide for the scenario presented in Figure 1. The goal of this guide
is to provide the ability to test the characteristics of the differential elements in an SEL-411L and
to provide the tools to calculate the currents to be injected into the relay to validate the
differential scheme.
SEL-411L
SEL-411L
Bay 1
Bay 2
Dedicated Fiber
Hot Standby
Channel
Digital
Multiplexer
Digital
Multiplexer
Bay 1
Bay 2
Figure 1 Typical two-terminal SEL-411L application
