3-14 F60 Feeder Protection System GE Multilin3.2 WIRING 3 HARDWARE3A relay configured for high impedance fault detection element includes two CT/VT modules: one type 8F, 8G, 8H, or 8Jmodule and one type 8Z module. For correct operation of the high impedance fault detection element, the ground currentterminals of the two CT modules must be connected to a ground current source, either a zero-sequence CT (see the Typi-cal wiring diagram with high impedance fault detection earlier in this chapter) or, if a zero-sequence CT is not available, tothe neutral conductor of the phase CTs (see diagram below).Figure 3–16: TYPICAL 8Z MODULE WIRING WITH PHASE CTS3.2.5 CONTACT INPUTS/OUTPUTSEvery digital input/output module has 24 terminal connections. They are arranged as three terminals per row, with eightrows in total. A given row of three terminals may be used for the outputs of one relay. For example, for form-C relay outputs,the terminals connect to the normally open (NO), normally closed (NC), and common contacts of the relay. For a form-Aoutput, there are options of using current or voltage detection for feature supervision, depending on the module ordered.The terminal configuration for contact inputs is different for the two applications.The digital inputs are grouped with a common return. The F60 has two versions of grouping: four inputs per common returnand two inputs per common return. When a digital input/output module is ordered, four inputs per common is used. The fourinputs per common allows for high-density inputs in combination with outputs, with a compromise of four inputs sharing onecommon. If the inputs must be isolated per row, then two inputs per common return should be selected (4D module).The tables and diagrams on the following pages illustrate the module types (6A, etc.) and contact arrangements that maybe ordered for the relay. Since an entire row is used for a single contact output, the name is assigned using the module slotposition and row number. However, since there are two contact inputs per row, these names are assigned by module slotposition, row number, and column position.Some form-A / solid-state relay outputs include circuits to monitor the DC voltage across the output contact when it is open,and the DC current through the output contact when it is closed. Each of the monitors contains a level detector whose out-put is set to logic “On = 1” when the current in the circuit is above the threshold setting. The voltage monitor is set to “On =1” when the current is above about 1 to 2.5 mA, and the current monitor is set to “On = 1” when the current exceeds about80 to 100 mA. The voltage monitor is intended to check the health of the overall trip circuit, and the current monitor can beused to seal-in the output contact until an external contact has interrupted current flow.Block diagrams are shown below for form-A and form-A / solid-state relay outputs with optional voltage monitor, optionalcurrent monitor, and with no monitoring832752A3.CDR7c8c8b8a5c5b5a7b7a3c4b4a4c1c2b2a6b6a6c2c1b1a3b3aCURRENT INPUTS NOT USED8ZMMMMMMMMMMMMMMMMMMMMMMMMIAIBICIGIA5IA1IB5IC5IG5IB1IC1IG1ABCPOSITIVE WATTS (5 Amp CT)528F / 8G8c8a7c5a5c6a7a6cVXVAVBVCVOLTAGE INPUTSVXVAVBVC1cFFFFFFFFFFFFFFFFFFFF3c3bCURRENT INPUTS2c4c1a4b4a1b2a3a2bIAIBICIGIA5IA1IB5IC5IG5IB1IC1IG1
