![Schweitzer Engineering Laboratories SEL-421-4 Instruction Manual Download Page 217](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_1216726217.webp)
5.57
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Functions
Out-of-Step Logic (Zero Settings)
Swing Center Voltage (SCV) Processing and Analog Variables
The detection of a network power swing condition is based on monitoring the
rate-of-change of the positive-sequence swing-center voltage. For the purpose of
implementing the function, the following analog variables are used:
➤
SCV1: per-unit positive-sequence swing-center voltage
➤
dSCV1_Unflt: unfiltered derivative of the positive-sequence swing-
center voltage
➤
dSCV1_UF: ultra-fast derivative (filtered) of the positive-sequence
swing-center voltage
➤
dSCV1_F: fast derivative (moderately filtered) of the positive-
sequence swing-center voltage
➤
dSCV1_S: slow derivative (most filtered) of the positive-sequence
swing-center voltage
➤
d2SCV1_UF: ultra-fast second derivative (not filtered) of the
positive-sequence swing-center voltage
Swing Center Voltage Slope Detector
, the top four comparators determine whether the swing is fast
(dSCV1_F remains asserted for 1.75 cycles) or slow (dSCV1_S remains asserted
for 5 cycles) for both negative and positive slopes, if the supervision condition
are met. The supervision conditions are:
➤
No power swing is in progress (OSB_I is de-asserted), and no Zone 2
through Zone 5 distance elements are asserted
or
➤
The absolute value of dSCV1_UF is greater than 0.55)
or
➤
The absolute value of dSCV1_UF is lower than 0.55 but greater than
0.2
and
the absolute value of d2SCV1_UF is greater than 0.23.
Therefore, if OR Gate OR 1 does not assert, one of the timers (Timer 1 through
Timer 4) starts timing. If the conditions prevail, the top input of AND Gate
AND 5 asserts after the appropriate timer expires.
Summary of Contents for SEL-421-4
Page 6: ...This page intentionally left blank ...
Page 14: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 104: ...This page intentionally left blank ...
Page 128: ...This page intentionally left blank ...
Page 536: ...This page intentionally left blank ...
Page 584: ...This page intentionally left blank ...
Page 616: ...This page intentionally left blank ...
Page 696: ...This page intentionally left blank ...
Page 750: ...This page intentionally left blank ...
Page 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Page 776: ...This page intentionally left blank ...
Page 932: ...This page intentionally left blank ...
Page 976: ...This page intentionally left blank ...
Page 1024: ...This page intentionally left blank ...
Page 1038: ...This page intentionally left blank ...
Page 1064: ...This page intentionally left blank ...
Page 1128: ...This page intentionally left blank ...
Page 1206: ...This page intentionally left blank ...
Page 1316: ...This page intentionally left blank ...
Page 1350: ...This page intentionally left blank ...
Page 1464: ...This page intentionally left blank ...
Page 1468: ...This page intentionally left blank ...
Page 1492: ...This page intentionally left blank ...
Page 1518: ...This page intentionally left blank ...