GE Multilin F60 Feeder Protection System 3-133 HARDWARE 3.2 WIRING3A 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 3–15: TYPICAL 8Z MODULE WIRING WITH PHASE CTS3.2.5 PROCESS BUS MODULESThe F60 can be ordered with a process bus interface module. This module is designed to interface with the GE MultilinHardFiber system, allowing bidirectional IEC 61850 fiber optic communications with up to eight HardFiber merging units,known as Bricks. The HardFiber system has been designed to integrate seamlessly with the existing UR-series applica-tions, including protection functions, FlexLogic, metering, and communications.The IEC 61850 process bus system offers the following benefits:• Reduces labor associated with design, installation, and testing of protection and control applications using the F60 byreducing the number of individual copper terminations• Integrates seamlessly with existing F60 applications, since the IEC 61850 process bus interface module replaces thetraditional CT/VT modules• Communicates using open standard IEC 61850 messagingFor additional details on the HardFiber system, see GE publication GEK-113658: HardFiber Process Bus System Instruc-tion Manual.
