GE B30 UR Series, Instruction Manual

Page: 286 / 582

5-164 B30 Bus Differential System GE Multilin
5.7 CONTROL ELEMENTS 5 SETTINGS
5
Figure 5–72: DIGITAL ELEMENT SCHEME LOGIC
CIRCUIT MONITORING APPLICATIONS:
Some versions of the digital input modules include an active voltage monitor circuit connected across form-A contacts. The
voltage monitor circuit limits the trickle current through the output circuit (see technical specifications for form-A).
As long as the current through the voltage monitor is above a threshold (see technical specifications for form-A), the “Cont
Op 1 VOn” FlexLogic operand will be set (for contact input 1 – corresponding operands exist for each contact output). If the
output circuit has a high resistance or the DC current is interrupted, the trickle current will drop below the threshold and the
“Cont Op 1 VOff” FlexLogic operand will be set. Consequently, the state of these operands can be used as indicators of the
integrity of the circuits in which form-A contacts are inserted.
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.
Figure 5–73: TRIP CIRCUIT EXAMPLE 1
SETTING
DIGITAL ELEMENT 01
FUNCTION:
Disabled = 0
Enabled = 1
DIGITAL ELEMENT 01
BLOCK:
Off = 0
FLEXLOGIC OPERANDS
DIG ELEM 01 DPO
DIG ELEM 01 PKP
SETTING
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DIGITAL ELEMENT 01
INPUT:
Off = 0
SETTING
INPUT = 1
RUN
t
PKP
t
RST
DIGITAL ELEMENT 01
PICKUP DELAY:
SETTINGS
DIGITAL ELEMENT 01
RESET DELAY:
AND
SETTING
DIGITAL ELEMENT 01
NAME:
DIG ELEM 01 OP
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