3-14 C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUALWIRING CHAPTER 3: INSTALLATION3Figure 3-13: Form-A and solid-state contact outputs with voltage and current monitoringThe operation of voltage and current monitors is reflected with the corresponding FlexLogic operands (CONT OP # VON, CONT OP# VOFF, and CONT OP # ION) that can be used in protection, control, and alarm logic. The typical application of the voltagemonitor is breaker trip circuit integrity monitoring; a typical application of the current monitor is seal-in of the controlcommand.See the Digital Elements section of chapter 5 for an example of how form-A and solid-state relay contacts can be appliedfor breaker trip circuit integrity monitoring.WARNING Consider relay contacts unsafe to touch when the unit is energized. Death or serious injury canresult from touching live relay contacts.NOTEUSE OF FORM-A AND SOLID-STATE RELAY OUTPUTS IN HIGH-IMPEDANCE CIRCUITSFor form-A and solid-state relay output contacts internally equipped with a voltage measuring circuit acrossthe contact, the circuit has an impedance that can cause a problem when used in conjunction with externalhigh-input impedance monitoring equipment such as modern relay test set trigger circuits. These monitoringcircuits can continue to read the form-A contact as being closed after it has closed and subsequently opened,when measured as an impedance.The solution is to use the voltage measuring trigger input of the relay test set, and connect the form-A contactthrough a voltage-dropping resistor to a DC voltage source. If the 48 V DC output of the power supply is usedas a source, a 500 Ω, 10 W resistor is appropriate. In this configuration, the voltage across either the form-Acontact or the resistor can be used to monitor the state of the output.NOTEWhere a tilde “~” symbol appears, substitute the slot position of the module. Where a number sign “#” appears,substitute the contact number.LoadI~#a~#b~#cV827862A4.CDR+++++a) Voltage with optionalcurrent monitoring Voltage monitoring onlyLoadIVBoth voltage and current monitoringLoadIVb) Current with optionalvoltage monitoring Current monitoring only Both voltage and current monitoring(external jumper a-b is required)LoadVLoadc) No monitoring~#a~#b~#c~#a~#b~#c~#a~#b~#c~#a~#b~#cI
