Schweitzer Engineering Laboratories SEL-421-4 - Page 1049

8.11
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Monitoring
Circuit Breaker Monitor
The relay makes a further check on the auxiliary circuit breaker (52A) contacts
by testing whether these circuit breaker contacts have changed state within
approximately 100 ms after the end of the trip or close threshold times. Thus, this
additional check serves as the trip time-out and close time-out condition. This
check verifies that the circuit breaker actually closed or opened, and it alerts you
if maintenance is required on the circuit breaker mechanical linkages or auxiliary
(52) contacts.
Electrical Operating Time
The electrical operating time is the time between trip or close initiation and an
open-phase status change. For both circuit breakers, the relay measures the trip-
ping time for each phase from the assertion of the BM1TRP Relay Word bit to
the time the relay detects an open-phase condition. Similarly, the relay measures
electrical operating time for closing each phase from the assertion of BM1CLS
to the restoration of phase quantities. The relay compares these tripping or clos-
ing times to the electrical slow operation time thresholds for tripping and closing,
B1ESTRT and B1ESCLT, respectively. The relay issues an electrical slow opera-
tion alarm, B1ESOAL, for 5 seconds when trip or close times exceed these thresh-
olds. Figure 8.6 shows the timing diagram for the A-Phase pole of Circuit Breaker 1.
BM1CLSA := BK1CL OR IN304 Breaker Monitor A-Phase Close—
BK1 (SEL
OGIC Equation)
BM1CLSB := BK1CL OR IN305 Breaker Monitor B-Phase Close—
BK1 (SEL
OGIC Equation)
BM1CLSC := BK1CL OR IN306 Breaker Monitor C-Phase Close—
BK1 (SEL
OGIC Equation)
Assertion of the Relay Word bit B1MSOAL indicates any one of the follow-
ing four conditions:
➤ The mechanical operating time for a trip operation exceeds
30 ms (the slow trip alarm setting)
➤ The mechanical operating time for a close operation exceeds
70 ms (the slow close setting)
➤ No 52A1 status change occurred during the time B1MSTRT
plus approximately 100 ms after trip initiation (a trip time-out
condition)
➤ No 52A1 status change occurred during the time B1MSCLT
plus approximately 100 ms after close initiation (a close time-
out condition)
Example 8.5 Mechanical Operating Time Settings (Continued)