3-34 N60 Network Stability and Synchrophasor Measurement System GE Multilin3.3 DIRECT INPUT AND OUTPUT COMMUNICATIONS 3 HARDWARE3For the internal timing mode, the system clock is generated internally. therefore, the timing switch selection should be inter-nal timing for relay 1 and loop timed for relay 2. There must be only one timing source configured.For the looped timing mode, the system clock is derived from the received line signal. Therefore, the timing selectionshould be in loop timing mode for connections to higher order systems.The IEEE C37.94 communications module cover removal procedure is as follows:1. Remove the IEEE C37.94 module (type 2G, 2H, 76, or 77 module):The ejector/inserter clips located at the top and at the bottom of each module, must be pulled simultaneously in orderto release the module for removal. Before performing this action, control power must be removed from the relay.The original location of the module should be recorded to help ensure that the same or replacement module is insertedinto the correct slot.2. Remove the module cover screw.3. Remove the top cover by sliding it towards the rear and then lift it upwards.4. Set the timing selection switches (channel 1, channel 2) to the desired timing modes (see description above).5. Replace the top cover and the cover screw.6. Re-insert the IEEE C37.94 module. Take care to ensure that the correct module type is inserted into the correct slotposition. The ejector/inserter clips located at the top and at the bottom of each module must be in the disengaged posi-tion as the module is smoothly inserted into the slot. Once the clips have cleared the raised edge of the chassis,engage the clips simultaneously. When the clips have locked into position, the module will be fully inserted.Figure 3–41: IEEE C37.94 TIMING SELECTION SWITCH SETTING
