GE t60 Instruction Manual page 200

5.6 CONTROL ELEMENTS
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.
5
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
The
PICKUP DELAY
alarms.
NOTE
5-122
I = Current Monitor
V = Voltage Monitor
827073A1.vsd
Figure 5–72: TRIP CIRCUIT EXAMPLE 1
DIGITAL ELEMENT
FUNCTION: Enabled
DIG ELEM
MESSAGE
Bkr Trip Cct Out
DIG ELEM
MESSAGE
Cont Op 1 VOff
DIG ELEM
MESSAGE
DELAY:
DIG ELEM
MESSAGE
DELAY:
DIG ELEM
MESSAGE
Cont Ip 1 Off
DIGITAL ELEMENT
MESSAGE
TARGET: Self-reset
DIGITAL ELEMENT
MESSAGE
EVENTS: Enabled
setting should be greater than the operating time of the breaker to avoid nuisance
T60 Transformer Management Relay
DC+
UR Relay - Form-A
H1a
I
H1b
V
H1c
52a
Trip
Coil
DC–
1
1 NAME:
1 INPUT:
1 PICKUP
0.200 s
1 RESET
0.100 s
1 BLOCK:
1
1
5 SETTINGS
GE Multilin