(ZMRPSB, 68) during the power swing, even after the transient impedance leavesZMRPSB (68) operating characteristic and is expected to return within a certain time dueto continuous swinging. Consider the minimum possible speed of power swinging in aparticular system.The tR1 inhibit timer delays the influence of the detected residual current on the inhibitcriteria for ZMRPSB(68). It prevents operation of the function for short transients in theresidual current measured by the IED.The tR2 inhibit timer disables the output PICKUP signal from ZMRPSB (68) function, ifthe measured impedance remains within ZMRPSB (68) operating area for a time longerthan the set tR2 value. This time delay was usually set to approximately two seconds inolder power-swing devices.6.7 Automatic switch onto fault logic, voltage and currentbased ZCVPSOF6.7.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberAutomatic switch onto fault logic,voltage and current basedZCVPSOF - -6.7.2 ApplicationAutomatic switch onto fault logic, voltage and current based function (ZCVPSOF) is acomplementary function to impedance measuring functions, but may make use ofinformation from such functions.With ZCVPSOF function, a fast trip is achieved for a fault on the whole line, when the lineis being energized. ZCVPSOF tripping is generally non-directional in order to secure atrip at fault situations where directional information can not be established, for example,due to lack of polarizing voltage when a line potential transformer is used.Automatic activation based on dead line detection can only be used when the potentialtransformer is situated on the line side of a circuit breaker.When line side potential transformers are used, the use of non-directional distance zonessecures switch onto fault tripping for close-in three-phase short circuits. Use of non-directional distance zones also gives fast fault clearance when energizing a bus from theline with a short-circuit fault on the bus.Section 6 1MRK 506 334-UUS AImpedance protection166Application manual
