GE D60 Instruction Manual

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

Contents

CHAPTER 8: APPLICATION OF SETTINGS PROTECTION SIGNALING SCHEMESD60 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 8-78a permanent lock up of the transmit/receive loop. The echo co-ordination (ECHO DURATION) and lock-out (ECHO LOCKOUT)timers perform this function by ensuring that the permissive signal is echoed once for a guaranteed duration of timebefore going to a lockout for a settable period of time.Recognize that in ring bus or breaker and a half situations it can be the line disconnect or a combination of the disconnectand/or the breaker(s) status that is the indication that the terminal is open.The POTT RX PICKUP DELAY timer is included in the permissive receive path to ride through spurious receive outputs that canbe produced during external faults, when power line carrier is utilized as the communications medium.No current reversal logic is included for the overreaching phase and ground distance elements, because long reaches arenot usually required for two terminal lines. A situation can occur however, where the ground distance element has anextended reach. This situation is encountered when it is desired to account for the zero sequence inter-circuit mutualcoupling. This is not a problem for the ground distance elements in the D60 that do have a current reversal logic built intotheir design as part of the technique used to improve ground fault directionality.Unlike the distance protection elements, the ground directional overcurrent functions do not have their reach well defined,therefore the current reversal logic is incorporated for the extra signal supplementing Zone 2 in the scheme. The transientblocking approach for this POTT scheme is to recognize that a permissive signal has been received and then allow asettable time TRANS BLOCK PICKUP DELAY for the local forward looking directional element to pick up.The scheme generates an output operand (POTT TX) that is used to transmit the signal to the remote end. Choices ofcommunications channel include Remote Inputs/Outputs and telecommunications interfaces. When used withtelecommunications facilities the output operand is assigned to operate an output contact connected to key thetransmitter at the interface. Power Line Carrier (PLC) channels are not recommended for this scheme since the PLC signalcan be interrupted by a fault.For proper operation of the scheme the Zone 2 phase and ground distance elements must be enabled and configured perrules of distance relaying. The Line Pickup element needs to be enabled and configured properly to detect line-end-open/weak-infeed conditions.If used by this scheme, the selected ground directional overcurrent function(s) must be enabled and configuredaccordingly The output operand from the scheme (POTT 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 is programmedto initiate a trip, breaker fail, and auto-reclose, and to drive a user-programmable LED as per user application.8.3.5 Hybrid POTT scheme (HYB-POTT)This scheme uses an over-reaching Zone 2 distance element to compare the direction to a fault at both ends of the line.Ground directional overcurrent functions available in the relay can be used in conjunction with the Zone 2 distanceelement to key the scheme and initiate its operation. This increases the coverage for high-resistance faults.The scheme is intended for three-terminal applications and for weak-infeed conditions. As a long reach of theoverreaching distance element can be required for three-terminal applications, transient blocking logic is provided forboth distance and ground directional overcurrent elements. In order to cope with weak-infeed conditions, an echo featureis made available.By default, the scheme uses the reverse-looking Zone 4 distance element to identify reverse faults. Additionally, reverse-looking ground directional overcurrent functions can be used in conjunction with Zone 4.For proper operation of the scheme the Zone 2 and 4 phase and ground distance elements must be enabled andconfigured per rules of distance relaying. The Line Pickup element needs to be enabled and configured 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 and configuredaccordingly.The scheme generates an output operand (HYBRID POTT TX) that is used to transmit the signal to the remote end. Choicesof communications channel include Remote Inputs/Outputs and telecommunications interfaces. When used withtelecommunications facilities, assign the output operand to operate an output contact connected to key the transmitter atthe interface.For more application recommendation, see the POTT scheme.