GE L60 Instruction Manual

Also see for L60: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

5-268 L60 Line Phase Comparison System GE Multilin5.6 CONTROL ELEMENTS 5 SETTINGS5• TRANS BLOCK PICKUP DELAY: This setting defines a transient blocking mechanism embedded in the POTTscheme for coping with the exposure of a ground directional overcurrent function (if used) to current reversal condi-tions. The transient blocking mechanism applies to the ground overcurrent path only as the reach settings for the zone2 distance functions is not expected to be long for two-terminal applications, and the security of the distance functionsis not endangered by the current reversal conditions. Upon receiving the POTT RX signal, the transient blocking mech-anism allows the RX signal to be passed and aligned with the GND DIR O/C FWD indication only for a period of timedefined as TRANS BLOCK PICKUP DELAY. After that the ground directional overcurrent path will be virtually disabled for aperiod of time specified as TRANS BLOCK RESET DELAY.The TRANS BLOCK PICKUP DELAY should be long enough to give the selected ground directional overcurrent functiontime to operate, but not longer than the fastest possible operation time of the protection system that can create currentreversal conditions within the reach of the selected ground directional overcurrent function. This setting should takeinto account the POTT RX PICKUP DELAY. The POTT RX signal is shaped for aligning with the ground directional indica-tion as follows: the original RX signal is delayed by the POTT RX PICKUP DELAY, then terminated at TRANS BLOCK PICKUPDELAY after the pickup of the original POTT TX signal, and eventually, locked-out for TRANS BLOCK RESET DELAY.• TRANS BLOCK RESET DELAY: This setting defines a transient blocking mechanism embedded in the POTT schemefor coping with the exposure of a ground directional overcurrent function (if used) to current reversal conditions (seealso the TRANS BLOCK PICKUP DELAY). This delay should be selected long enough to cope with transient conditionsincluding not only current reversals but also spurious negative and zero-sequence currents occurring during breakeroperations. The breaker failure time of the surrounding protection systems within the reach of the ground directionalfunction used by the POTT scheme may be considered to make sure that the ground directional function is not jeopar-dized during delayed breaker operations.• ECHO DURATION: This setting defines the guaranteed and exact duration of the echo pulse. The duration does notdepend on the duration and shape of the received POTT RX signal. This setting enables the relay to avoid a permanentlock-up of the transmit/receive loop.• ECHO LOCKOUT: This setting defines the lockout period for the echo logic after sending the echo pulse.• LINE END OPEN PICKUP DELAY: This setting defines the pickup setting for validation of the line end open conditionsas detected by the Line Pickup logic through the LINE PICKUP LEO PKP FlexLogic operand. The validated line end opencondition is a requirement for the POTT scheme to return a received echo signal (if the echo feature is enabled). Thevalue of this setting should take into account the principle of operation and settings of the line pickup element.• POTT SEAL-IN DELAY: The output FlexLogic operand ( POTT OP ) is produced according to the POTT scheme logic. Aseal-in time delay is applied to this operand for coping with noisy communication channels. This setting specifies aminimum guaranteed duration of the POTT OP pulse.• GND DIR O/C FWD: This setting selects the FlexLogic operand (if any) of a protection element used in addition tozone 2 for identifying faults on the protected line, and thus, for keying the communication channel and initiating opera-tion of the scheme. Good directional integrity is the key requirement for an over-reaching forward-looking protectionelement used as GND DIR O/C FWD. Even though any FlexLogic operand could be used as GND DIR O/C FWD allowing theuser to combine responses of various protection elements, or to apply extra conditions through FlexLogic equations,this extra signal is primarily meant to be the output operand from either the negative-sequence directional overcurrentor neutral directional overcurrent elements. Both of these elements have separate forward and reverse output oper-ands. The forward indication should be used (NEG SEQ DIR OC1 FWD or NEUTRAL DIR OC1 FWD). For greater security andto overcome spurious directional element operation during transients, adding at least 0.5 cycles of pickup delay to theforward directional element is recommended.• POTT RX: This setting enables the user to select the FlexLogic operand that represents the receive signal ( RX ) for thescheme. Typically an input contact interfacing with a signaling system is used. Other choices include remote inputsand FlexLogic equations. The POTT transmit signal ( TX ) should be appropriately interfaced with the signaling systemby assigning the output FlexLogic™ operand ( POTT TX ) to an output contact. The remote output mechanism is anotherchoice.The output operand from the scheme ( POTT OP ) must be configured to interface with other relay functions, output con-tacts in particular, in order to make the scheme fully operational. Typically, the output operand should be programmedto initiate a trip, breaker fail, and autoreclose, and drive a user-programmable LED as per user application.