5-38 L60 Line Phase Comparison Relay GE Multilin5.2 PRODUCT SETUP 5 SETTINGS5For increased reliability, a dual-ring configuration (shown below) is recommended for this application.Figure 5–8: INTERLOCKING BUS PROTECTION SCHEME VIA DIRECT INPUTS/OUTPUTSIn the above application, the following settings should be applied:UR IED 1: DIRECT OUTPUT DEVICE ID: “1” UR IED 2: DIRECT OUTPUT DEVICE ID: “2”DIRECT I/O RING CONFIGURATION: “Yes” DIRECT I/O RING CONFIGURATION: “Yes”UR IED 3: DIRECT OUTPUT DEVICE ID: “3” UR IED 4: DIRECT OUTPUT DEVICE ID: “4”DIRECT I/O RING CONFIGURATION: “Yes” DIRECT I/O RING CONFIGURATION: “Yes”Message delivery time is approximately 0.2 of power system cycle (at 128 kbps) times number of ‘bridges’ between the ori-gin and destination. Dual-ring configuration effectively reduces the maximum ‘communications distance’ by a factor of two.In this configuration the following delivery times are expected (at 128 kbps) if both rings are healthy:IED 1 to IED 2: 0.2 of power system cycle; IED 1 to IED 3: 0.4 of power system cycle;IED 1 to IED 4: 0.2 of power system cycle; IED 2 to IED 3: 0.2 of power system cycle;IED 2 to IED 4: 0.4 of power system cycle; IED 3 to IED 4: 0.2 of power system cycleIf one ring is broken (say TX2/RX2) the delivery times are as follows:IED 1 to IED 2: 0.2 of power system cycle; IED 1 to IED 3: 0.4 of power system cycle;IED 1 to IED 4: 0.6 of power system cycle; IED 2 to IED 3: 0.2 of power system cycle;IED 2 to IED 4: 0.4 of power system cycle; IED 3 to IED 4: 0.2 of power system cycleA coordinating timer for this bus protection scheme could be selected to cover the worst case scenario (0.4 of power sys-tem cycle). Upon detecting a broken ring, the coordination time should be adaptively increased to 0.6 of power systemcycle. The complete application requires addressing a number of issues such as failure of both the communications rings,failure or out-of-service conditions of one of the relays, etc. Self-monitoring flags of the direct inputs/outputs feature wouldbe primarily used to address these concerns.EXAMPLE 3: PILOT-AIDED SCHEMESConsider the three-terminal line protection application shown below:Figure 5–9: THREE-TERMINAL LINE APPLICATIONA permissive pilot-aided scheme could be implemented in a two-ring configuration as shown below (IEDs 1 and 2 constitutea first ring, while IEDs 2 and 3 constitute a second ring):842716A1.CDRUR IED 1RX1TX2TX1RX2UR IED 2TX2RX2RX1TX1UR IED 4TX1RX1RX2TX2UR IED 3RX2TX1TX2RX1842713A1.CDRUR IED 1 UR IED 2UR IED 3
