GE Multilin L90 Line Differential Relay 5-1655 SETTINGS 5.6 CONTROL ELEMENTS5EXAMPLE 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 5ñ100: 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.ìCont 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. ìCont Ip 1" and will be set ìOnî when the breaker is closed.Using Digital Element 1 to monitor the breaker trip circuit, the settings will be:The PICKUP DELAY setting should be greater than the operating time of the breaker to avoid nuisancealarms.# DIGITAL ELEMENT 1#DIGITAL ELEMENT 1FUNCTION: EnabledMESSAGE DIG ELEM 1 NAME:Bkr Trip Cct OutMESSAGE DIG ELEM 1 INPUT:Cont Op 1 VOffMESSAGE DIG ELEM 1 PICKUPDELAY: 0.200 sMESSAGE DIG ELEM 1 RESETDELAY: 0.100 sMESSAGE DIG ELEM 1 BLOCK:Cont Ip 1 OffMESSAGE DIGITAL ELEMENT 1TARGET: Self-resetMESSAGE DIGITAL ELEMENT 1EVENTS: EnabledTripCoil52aVIH1aH1bH1cUR Relay - Form-AV = Voltage MonitorI = Current MonitorDC+DC–827073A1.vsdNOTE
