5-56 B90 Low Impedance Bus Differential System GE Multilin5.2 PRODUCT SETUP 5 SETTINGS5EXAMPLE 3: PILOT-AIDED SCHEMESConsider the three-terminal line protection application shown below:Figure 5–13: 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):Figure 5–14: SINGLE-CHANNEL OPEN LOOP CONFIGURATIONIn the above application, the following settings should be applied. For UR-series IED 1:DIRECT OUTPUT DEVICE ID: “1”DIRECT I/O CH1 RING CONFIGURATION: “Yes”DIRECT I/O CH2 RING CONFIGURATION: “Yes”For UR-series IED 2:DIRECT OUTPUT DEVICE ID: “2”DIRECT I/O CH1 RING CONFIGURATION: “Yes”DIRECT I/O CH2 RING CONFIGURATION: “Yes”For UR-series IED 3:DIRECT OUTPUT DEVICE ID: “3”DIRECT I/O CH1 RING CONFIGURATION: “Yes”DIRECT I/O CH2 RING CONFIGURATION: “Yes”In this configuration the following delivery times are expected (at 128 kbps):IED 1 to IED 2: 0.2 of power system cycle;IED 1 to IED 3: 0.5 of power system cycle;IED 2 to IED 3: 0.2 of power system cycle.In the above scheme, IEDs 1 and 3 do not communicate directly. IED 2 must be configured to forward the messages asexplained in the Inputs and outputs section. A blocking pilot-aided scheme should be implemented with more security and,ideally, faster message delivery time. This could be accomplished using a dual-ring configuration as shown below.842713A1.CDRUR IED 1 UR IED 2UR IED 3842714A1.CDRUR IED 1TX1RX1UR IED 2RX2TX2RX1TX1UR IED 3RX1TX1
