![Schweitzer Engineering Laboratories SEL-421-4 Скачать руководство пользователя страница 396](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_1216726396.webp)
6.60
SEL-421 Relay
Instruction Manual
Date Code 20171021
Protection Applications Examples
345 kV Tapped Overhead Transmission Line Example
Occasional loss-of-potential to the distance relay, while unavoidable, is detect-
able. When the relay detects a loss-of-potential condition, the relay can block dis-
tance element operation, block or enable forward-looking directional overcurrent
elements, and issue an alarm for any true loss-of-potential condition.
If line-side PTs are used, the circuit breaker(s) must be closed for the LOP logic
to detect an LOP condition. Therefore, if three-phase potential to the relay is lost
while the circuit breaker(s) is open (e.g., the PT fuses are removed while the line
is de-energized), the relay cannot detect a loss-of-potential condition when the
circuit breaker(s) closes again. At circuit breaker closing, the relay can detect one
or two missing potentials that occurred while the circuit breaker was open. See
Loss-of-Potential Logic on page 5.28
for more information.
lists the three choices for enabling LOP.
Set ELOP to Y1 for this application example. This choice reduces the chances of
false tripping because of a loss-of-potential condition.
ELOP :=
Y1
.
Loss-of-Potential (Y, Y1, N)
You do not need Advanced Settings for this application example.
EADVS :=
N
.
Advanced Settings (Y, N)
Phase-Distance Elements (21P)
Mho Phase-Distance Element Reach
Employ each zone of mho phase-distance protection as follows:
➤
Zone 1—Instantaneous underreaching tripping
➤
Zone 2—DCB scheme tripping
➤
Zone 3—DCB scheme blocking
Zone 1 Phase-Distance Element Reach
Zone 1 phase-distance protection provides instantaneous protection for phase-to-
phase, phase-to-phase-to-ground, and three-phase faults for 80 percent of the dis-
tance from Station S to Station R because this is the shortest line segment from
one terminal to another. Errors in the current transformers, potential transform-
ers, modeled transmission line data, and fault study data do not permit Zone 1 to
be set equal to 100 percent of the distance to Station R. Otherwise, unwanted trip-
ping could occur for faults just beyond the remote terminal.
Set Zone 1 phase-distance protection equal to 80 percent of the positive-sequence
impedance from Station S to Station R.
Table 6.16
LOP Enable Options
Option
Description
N
The LOP logic operates but does not disable voltage-polarized directional ele-
ments, distance elements, and forward-looking directional overcurrent ele-
ments. Use LOP in this case for alarm only.
Y
The relay disables all voltage-polarized directional elements and distance ele-
ments, but enables forward-looking directional overcurrent elements. These
forward-looking directional overcurrent elements effectively become nondirec-
tional and provide overcurrent protection during an LOP condition.
Y1
The relay disables all voltage-polarized directional elements and distance ele-
ments. The relay also disables the overcurrent elements controlled by the volt-
age-polarized directional elements.
Содержание SEL-421-4
Страница 6: ...This page intentionally left blank ...
Страница 14: ...This page intentionally left blank ...
Страница 30: ...This page intentionally left blank ...
Страница 104: ...This page intentionally left blank ...
Страница 128: ...This page intentionally left blank ...
Страница 536: ...This page intentionally left blank ...
Страница 584: ...This page intentionally left blank ...
Страница 616: ...This page intentionally left blank ...
Страница 696: ...This page intentionally left blank ...
Страница 750: ...This page intentionally left blank ...
Страница 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Страница 776: ...This page intentionally left blank ...
Страница 932: ...This page intentionally left blank ...
Страница 976: ...This page intentionally left blank ...
Страница 1024: ...This page intentionally left blank ...
Страница 1038: ...This page intentionally left blank ...
Страница 1064: ...This page intentionally left blank ...
Страница 1128: ...This page intentionally left blank ...
Страница 1206: ...This page intentionally left blank ...
Страница 1316: ...This page intentionally left blank ...
Страница 1350: ...This page intentionally left blank ...
Страница 1464: ...This page intentionally left blank ...
Страница 1468: ...This page intentionally left blank ...
Страница 1492: ...This page intentionally left blank ...
Страница 1518: ...This page intentionally left blank ...