protection are measured on the protected generator output terminals side (HV-side), then invertion is necessary (InvertCTCurr = Enabled), provided that theCT’s actual direction complies with ABB recommendations, as shown in Table 36.8.18 Automatic switch onto fault logic ZCVPSOF SEMOD153633-1 v38.18.1 IdentificationSEMOD155890-2 v4Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberAutomatic switch onto fault logic ZCVPSOF - -8.18.2 Application M13830-3 v6Automatic switch onto fault logic, voltage- and current-based function ZCVPSOF is acomplementary function to impedance measuring functions, but may use theinformation from such functions.With ZCVPSOF, a fast trip is achieved for a fault on the whole line when the line isbeing energized. The ZCVPSOF tripping is generally non-directional to secure a trip atfault situations where directional information cannot be established, for example, dueto lack of polarizing voltage when a line potential transformer is used.Automatic activation based on dead-line detection can only be used when the voltagetransformer is situated on the line side of a circuit breaker.When line side voltage transformers are used, the use of the nondirectional distancezones secures switch onto fault tripping for close-in three-phase short circuits. The useof the nondirectional distance zones also gives a fast fault clearance when energizing abus from the line with a short circuit fault on the bus.Other protection functions like time-delayed phase and zero-sequence overcurrentfunction can be connected to ZCVPSOF to increase the dependability in the scheme.When the voltage transformers are situated on the bus side, the automatic switch ontofault detection based on dead-line detection is not possible. In such cases the deadlinedetection is bypassed using the breaker closing status and the switch onto fault logic isactivated.Section 8 1MRK 504 163-UUS AImpedance protection488 Transformer protection RET670 2.2 ANSIApplication manual
