5-180 F60 Feeder Protection System GE Multilin5.6 CONTROL ELEMENTS 5 SETTINGS5As long as the current through the voltage monitor is above a threshold (see technical specifications for form-A), the Flex-Logic™ operand “Cont Op # VOn” will be set (# represents the output contact number). If the output circuit has a high resis-tance or the DC current is interrupted, the trickle current will drop below the threshold and the FlexLogic™ operand “ContOp # VOff” will be set. Consequently, the state of these operands can be used as indicators of the integrity of the circuits inwhich Form-A contacts are inserted.EXAMPLE 1: BREAKER TRIP CIRCUIT INTEGRITY MONITORINGIn 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 contactdetects 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 thebreaker is open (see diagram below). To prevent unwanted alarms in this situation, the trip circuit monitoring logic mustinclude the breaker position.Figure 5–94: TRIP CIRCUIT EXAMPLE 1Assume 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 thecontact 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.The settings to use digital element 1 to monitor the breaker trip circuit are indicated below (EnerVista UR Setup exampleshown):The PICKUP DELAY setting should be greater than the operating time of the breaker to avoid nuisancealarms.TripCoil52aVIH1aH1bH1cUR Relay - Form-AV = Voltage MonitorI = Current MonitorDC+DC–827073A1.vsdNOTE
