Sel 411L - Page 719

P.11.5
Date Code 20151029 Protection Manual SEL-411L Relay
Testing and Troubleshooting
Test Mode
TEST 87L Command
In general, this command provides two testing options, viz. an 87L element
characteristic test and a loopback test.
Initiate an 87L test mode by typing the following relay command at access
level B:
=>>TEST 87L <Enter>
An 87L test can be terminated by typing:
=>>TEST 87L OFF <Enter>
With the default settings, you can also terminate the test by pressing the front-
panel pushbutton labeled RELAY TEST MODE. For security reasons, the E87L
setting and the 87TMSUP setting supervise the TEST 87L command. Relay
Word bit 87TMSUP asserts when the 87TMSUP SEL
OGIC control equation
asserts to a logical 1. If this equation is true (and E87L = Y) then the TEST
87L command can be executed. If 87TMSUP is not asserted, and you type the
TEST 87L command, the following message is generated:
87 Test Mode Supervision is not asserted, test aborted
=>>
Similarly, if E87L = N, the following message is generated:
87L function not enabled, test aborted
=>>
The default setting for 87TMSUP is PLT04—the same protection latch that is
used to implement the relay Test Mode. As a result, the TEST 87L command
cannot be executed unless the relay is already in Test Mode.
Instead of using PLT04 in the 87TMSUP SEL
OGIC control equation, you can
use other functions such as a key switch wired to an input, for instance. If you
do not want to supervise the TEST 87L command, then set 87TMSUP = 1 to
permanently defeat the supervision. However, without PLT04 in the
87TMSUP SEL
OGIC control equation, pressing the pushbutton will not
terminate the 87L TEST; you now have to terminate the test by typing in the
TEST 87L OFF command.
Characteristic Test
Once in the test mode, you can select to test the characteristic or to do a
channel loopback test. The characteristic mode is used to facilitate testing of
the 87L characteristic or to prevent the 87L element from interfering when
testing other protection functions.
Local Relay Behavior (Characteristic Test)
When doing the characteristic test at the local relay, the output of the
differential element is blocked from driving the Trip Logic, effectively
preventing the relay from closing its tripping contacts when the tested 87L
operates. At the same time, the output of the element-under-test (87LA, 87LB,
87LC, 87LQ, or 87LG) is routed to the 87TOUT Relay Word bit. This Relay
Word bit is assigned to OUT206 under the default settings as shown in
Table 11.4. Note that other protection functions such as the distance elements
are free to operate at the local terminal.