GE Multilin C60 Breaker Protection System 3-193 HARDWARE 3.2 WIRING3CONTACT INPUTSA dry contact has one side connected to terminal B3b. This is the positive 48 V DC voltage rail supplied by the power sup-ply module. The other side of the dry contact is connected to the required contact input terminal. Each contact input grouphas its own common (negative) terminal which must be connected to the DC negative terminal (B3a) of the power supplymodule. When a dry contact closes, a current of 1 to 3 mA flows through the associated circuit.A wet contact has one side connected to the positive terminal of an external DC power supply. The other side of this contactis connected to the required contact input terminal. If a wet contact is used, then the negative side of the external sourcemust be connected to the relay common (negative) terminal of each contact group. The maximum external source voltagefor this arrangement is 300 V DC.The voltage threshold at which each group of four contact inputs detects a closed contact input is programmable as17 V DC for 24 V sources, 33 V DC for 48 V sources, 84 V DC for 110 to 125 V sources, and 166 V DC for 250 V sources.Figure 3–17: DRY AND WET CONTACT INPUT CONNECTIONSWherever a tilde “~” symbol appears, substitute with the slot position of the module.There is no provision in the relay to detect a DC ground fault on 48 V DC control power external output. We recommendusing an external DC supply.GENERAL APPLICATION CONSIDERATIONSContacts outputs of protective relays, auxiliary contacts from breakers, disconnectors and other devices, are generally con-nected to contacts inputs of protective relays. In some situations, the contact outputs of some protective relays can havehigh impedance connected across it. When such a contact output is connected across a C60 contact input, it can spuri-ously operate the C60 input even when the output is open, if there is a substantial distributed capacitance (represented byC1) present in the wiring between the output and the C60 input and the debounce time setting in the C60 relay is lowenough. This false assertion of the contact input, when there is inadvertent ground present at the DC positive terminal, canbe prevented by inserting a resistor across the C60 input.The following figure shows a typical DC circuit, with battery ground detection, of contact input. The contact output has par-allel impedance across it (represented by R1).827741A5.CDR24 to 250 V(Wet)(Dry)Contact input 1Contact input 2Contact input 3SurgeContact input 4~7aCommon~7b~7c~8a~8b~8cContact input 1Contact input 2Contact input 3SurgeContact input 4~7aCommon~7b~7c~8a~8b~8cControl powerSurgeB5bFilterB8bB6bB6aB8aCritical failureB1b48 V DC outputB3bB1aB2bB3aHI+LO+Power supply moduleTerminals from type 6Bcontact input/output moduleTerminals from type 6Bcontact input/output moduleNOTE
