GE L90 Instruction Manual page 255

5 SETTINGS
EXAMPLE 1: BREAKER TRIP CIRCUIT INTEGRITY MONITORING
In many applications it is desired to monitor the breaker trip circuit integrity so problems can be detected before a trip oper-
ation is required. The circuit is considered to be healthy when the voltage monitor connected across the trip output contact
detects a low level of current, well below the operating current of the breaker trip coil. If the circuit presents a high resis-
tance, the trickle current will fall below the monitor threshold and an alarm would be declared.
In most breaker control circuits, the trip coil is connected in series with a breaker auxiliary contact which is open when the
breaker is open (see diagram below). To prevent unwanted alarms in this situation, the trip circuit monitoring logic must
include the breaker position.
Assume the output contact H1 is a trip contact. Using the contact output settings, this output will be given an ID name, e.g.
"Cont Op 1". Assume a 52a breaker auxiliary contact is connected to contact input H7a to monitor breaker status. Using the
contact input settings, this input will be given an ID name, e.g. "Cont Ip 1" and will be set "On" when the breaker is closed.
Using Digital Element 1 to monitor the breaker trip circuit, the settings will be:
# DIGITAL ELEMENT 1
#
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
The setting should be greater than the operating time of the breaker to avoid nuisance
PICKUP DELAY
alarms.
NOTE
GE Multilin
UR Relay - Form-A
H1a
I
I = Current Monitor
H1b
V
V = Voltage Monitor
H1c
827073A1.vsd
Figure 5–100: TRIP CIRCUIT EXAMPLE 1
DIGITAL ELEMENT 1
FUNCTION: Enabled
DIG ELEM 1 NAME:
Bkr Trip Cct Out
DIG ELEM 1 INPUT:
Cont Op 1 VOff
DIG ELEM 1 PICKUP
DELAY: 0.200 s
DIG ELEM 1 RESET
DELAY: 0.100 s
DIG ELEM 1 BLOCK:
Cont Ip 1 Off
DIGITAL ELEMENT 1
TARGET: Self-reset
DIGITAL ELEMENT 1
EVENTS: Enabled
L90 Line Differential Relay
5.6 CONTROL ELEMENTS
DC+
52a
Trip
Coil
DC–
5
5-165