GE UR T60 Instruction Manual page 382

5.7 CONTROL ELEMENTS
ETT NG
DIGITAL ELEMENT 01
FUNCTION:
Disabled = 0
Enabled = 1
ETT NG
DIGITAL ELEMENT 01
INPUT:
Off = 0
ETT NG
DIGITAL ELEMENT 01
BLOCK:
Off = 0
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-
5
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.
5-244
ETT NG
DIGITAL ELEMENT 01
NAME:
AND RUN
INPUT = 1
Figure 5–135: DIGITAL ELEMENT SCHEME LOGIC
Figure 5–136: TRIP CIRCUIT EXAMPLE 1
T60 Transformer Protection System
ETT NG
DIGITAL ELEMENT 01
PICKUP DELAY:
DIGITAL ELEMENT 01 FLEXLOG C OPE AND
RESET DELAY:
DIG ELEM 01 DPO
t
DIG ELEM 01 PKP
PKP
DIG ELEM 01 OP
t
RST
5 SETTINGS
827042A1.VSD
GE Multilin