GE D60 Instruction Manual

Also see for D60: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

10-8 D60 Line Distance Protection System GE Multilin10.3 PROTECTION SIGNALING SCHEMES 10 APPLICATION OF SETTINGS10For proper operation of the scheme the Zone 2 and 4 phase and ground distance elements must be enabled, configuredand set per rules of distance relaying. The Line Pickup element should be enabled, configured and set properly to detectline-end-open/weak-infeed and undervoltage conditions.If used by this scheme, the selected ground directional overcurrent function(s) must be enabled, configured, and setaccordingly.The scheme generates an output operand (HYBRID POTT TX) that is used to transmit the signal to the remote end.Choices of communications channel include Remote Inputs/Outputs and telecommunications interfaces. When used withtelecommunications facilities the output operand should be assigned to operate an output contact connected to key thetransmitter at the interface.For more application recommendation refer to the POTT scheme.The output operand from the scheme (HYBRID POTT OP) must be configured to interface with other relay functions, outputcontacts in particular, in order to make the scheme fully operational. Typically, the output operand should be programmed toinitiate a trip, breaker fail, and auto-reclose, and drive a user-programmable LED as per user application.10.3.6 DIRECTIONAL COMPARISON BLOCKINGGenerally, the scheme compares the direction to a fault at both ends of the line. Unlike the permissive schemes, theabsence of a blocking signal permits operation of the scheme. Consequently, the scheme is biased toward dependabilityand requires an “on/off” type of signaling.By default this scheme uses only a forward-looking over-reaching Zone 2 distance element to identify forward faults.Ground directional overcurrent functions available in the relay can be used in conjunction with the Zone 2 distance elementto increase the coverage for high-resistance faults.By default the scheme uses only a reverse-looking Zone 4 distance element to identify reverse faults. Ground directionalovercurrent functions available in the relay can be used in conjunction with the Zone 4 distance element for better time andsensitivity coordination.For proper operation of the scheme the Zone 2 and 4 phase and ground distance elements must be enabled, configuredand set per rules of distance relaying.If used by this scheme, the selected ground directional overcurrent function(s) must be enabled, configured and set accord-ingly.The scheme generates output operands (BLOCKING SCHEME TX INIT and BLOCKING SCHEME TX STOP) that areused control the transmission of signals to the remote end. Choices of communications channel include Remote Inputs/Outputs and telecommunications interfaces. When used with telecommunications facilities the output operand should beassigned to operate an output contact connected to key the transmitter at the interface.A blocking scheme may be preferred over a Hybrid POTT scheme, because of shorter reach settings for the Zone 2 ele-ments. This follows from the fundamental difference that all zone 2 elements are required to see an internal fault for thePOTT approach, under all system conditions, which in turn, means that the reversed Zone 4 block initiate elements mustalso have an increased reach. A blocking scheme on the other hand, can have much shorter Zone 2 reach settings ifsequential clearance can be accepted. The simple rule to ensure that all faults can be cleared, is for each terminal to havea reach setting equal to the distance to the tap plus twice the distance from the tap to the remote terminal.The Zone 2 element must have a coordinating timer BLOCK RX CO-ORD PKP DELAY, to ensure that the blocking signal isreceived for all external faults that are within the set reach of the local overreaching Zone 2.Transient blocking logic is implemented via the TRANS BLOCK timer, which continues to send a blocking signal for a settabletime TRANS BLOCK RESET DELAY, if it was being sent for at least 30 ms during the initial reverse fault set via TRANS BLOCKPICKUP DELAY.The output operand from the scheme (BLOCKING SCHEME OP) must be configured to interface with other relay functions,output contacts in particular, in order to make the scheme fully operational. Typically, the output operand should be pro-grammed to initiate a trip, breaker fail, and auto-reclose, and drive a user-programmable LED as per user application.