GE Multilin B30 Bus Differential System 3-153 HARDWARE 3.2 WIRING3Figure 3–16: 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 ) which can be used in protection, control, and alarm logic. The typical application ofthe voltage monitor is breaker trip circuit integrity monitoring; a typical application of the current monitor is seal-in of thecontrol command.Refer to the Digital elements section of chapter 5 for an example of how form-A and solid-state relay contacts can beapplied for breaker trip circuit integrity monitoring.Consider relay contacts unsafe to touch when the unit is energized.USE 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 across thecontact, the circuit has an impedance that can cause a problem when used in conjunction with external high inputimpedance monitoring equipment such as modern relay test set trigger circuits. These monitoring circuits may con-tinue to read the form-A contact as being closed after it has closed and subsequently opened, when measured asan impedance.The solution to this problem is to use the voltage measuring trigger input of the relay test set, and connect the form-A contact through a voltage-dropping resistor to a DC voltage source. If the 48 V DC output of the power supply isused as 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.Wherever a tilde “~” symbol appears, substitute with the slot position of the module; wherever a numbersign “#” appears, substitute the contact number.When current monitoring is used to seal-in the form-A and solid-state relay contact outputs, the Flex-Logic™ operand driving the contact output should be given a reset delay of 10 ms to prevent dam-age of the output contact (in situations when the element initiating the contact output is bouncing, atvalues in the region of the pickup value).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~#cIWARNINGNOTENOTENOTICE
