GE C60 Instruction Manual

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CHAPTER 5: SETTINGS CONTROL ELEMENTSC60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUAL 5-2975Autoreclose pauseThe pause input offers the possibility of freezing the autoreclose cycle until the pause signal disappears. This can be donewhen a trip occurs and simultaneously or previously, some conditions are detected such as out-of step or loss of guardfrequency, or a remote transfer trip signal is received. The pause signal freezes all four dead timers. When the ‘pause’signal disappears the autoreclose cycle is resumed by continuing the shot timer it was left at when paused.This feature can be also used when a transformer is tapped from the protected line and a reclose is not wanted until thetransformer is removed from the line. In this case, the reclose scheme is "paused" until the transformer is disconnected.The AR PAUSE input forces a three-pole trip through the 3-P DEADTIME 2 path.Evolving faults1.25 cycles after the single pole dead time has been initiated, the AR FORCE 3P TRIP operand is set and later resets only whenthe scheme is reset or goes to Lockout. This approach ensures that when a fault on one phase evolves to include anotherphase during the single pole dead time of the auto-recloser the scheme forces a three-pole trip and reclose.Reclosing scheme operation for one breaker• Permanent Fault — Consider Mode 1, which calls for 1-Pole or 3-Pole Time Delay 1 for the first reclosure and 3-PoleTime Delay 2 for the second reclosure, and assume a permanent fault on the line. Also assume the scheme is in theReset state. For the first single-phase fault the AR 1-P DEAD TIME timer is started, while for the first multi-phase faultthe AR 3-P DEAD TIME 1 timer is started. If the AR 3P TD INIT signal is high, the AR 3-P DEAD TIME 2 starts for the first shot.If AR MAX NO OF SHOTS is set to “1”, upon the first reclose the shot counter is set to 1. Upon reclosing, the fault is againdetected by protection and reclose is initiated. The breaker is tripped three-pole through the AR SHOT COUNT >0 operandthat sets the AR FORCE 3P operand. Because the shot counter has reached the maximum number of shots permitted,the scheme is sent to the Lockout state.If AR MAX NO OF SHOTS is set to “2”, upon the first reclose the shot counter is set to 1. Upon reclosing, the fault is againdetected by protection and reclose is initiated. The breaker is tripped three-pole through the AR SHOT COUNT >0 operandthat sets the AR FORCE 3P operand. After the second reclose, the shot counter is set to 2. Upon reclosing, the fault isagain detected by protection, the breaker is tripped three-pole, and reclose is initiated again. Because the shotcounter has reached the maximum number of shots permitted, the scheme is sent to the lockout state.• Transient Fault — When a reclose output signal is sent to close the breaker, the reset timer is started. If the reclosuresequence is successful (there is no initiating signal and the breaker is closed), the reset timer times out, returning thescheme to the reset state with the shot counter set to "0" and making it ready for a new reclose cycle.Reclosing scheme operation for two breakers• Permanent Fault — The general method of operation is the same as that outlined for the one breaker applicationsexcept for the following description, which assumes AR BKR SEQUENCE is “1-2” (reclose Breaker 1 before Breaker 2). Thesignal output from the dead time timers passes through the breaker selection logic to initiate reclosing of Breaker 1.The Close Breaker 1 signal initiates the Transfer Timer. After the reclose of the first breaker, the fault is again detectedby the protection, the breaker is tripped three pole and the autoreclose scheme is initiated. The Initiate signal thenstops the transfer timer. After the 3-P dead time times out, the Close Breaker 1 signal closes the first breaker againand starts the transfer timer. Since the fault is permanent, the protection trips again initiating the autoreclose schemethat is sent to Lockout by the SHOT COUNT = MAX signal.• Transient Fault — When the first reclose output signal is sent to close Breaker 1, the reset timer starts. The closeBreaker 1 signal initiates the transfer timer that times out and sends the close signal to the second breaker. If thereclosure sequence is successful (both breakers closed and there is no initiating signal), the reset timer times out,returning the scheme to the reset state with the shot counter set to 0. The scheme is ready for a new reclose cycle.AR BKR1(2) reclose failIf the selected sequence is “1–2” or “2–1” and after the first or second reclose attempt the breaker fails to close, there aretwo options. If the AR BKR 1(2) FAIL OPTION is set to “Lockout,” the scheme goes to lockout state. When it is set to “Continue,”the reclose process continues with Breaker 2. At the same time the shot counter is decreased (since the closing processwas not completed).