7.4 Loss of voltage check LOVPTUV (27)7.4.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberLoss of voltage check LOVPTUV - 277.4.2 ApplicationThe trip of the circuit breaker at a prolonged loss of voltage at all the three phases isnormally used in automatic restoration systems to facilitate the system restoration after amajor blackout. Loss of voltage check (LOVPTUV, 27) generates a TRIP signal only ifthe voltage in all the three phases is low for more than the set time. If the trip to the circuitbreaker is not required, LOVPTUV (27) is used for signallization only through an outputcontact or through the event recording function.7.4.3 Setting guidelinesLoss of voltage check (LOVPTUV, 27) is in principle independent of the protectionfunctions. It requires to be set to open the circuit breaker in order to allow a simple systemrestoration following a main voltage loss of a big part of the network and only when thevoltage is lost with breakers still closed.GlobalBaseSel: Selects the global base value group used by the function to define (IBase),(VBase) and (SBase).All settings are in primary values or per unit. Set operate level per phase to typically 70%of the global parameter VBase level. Set the time delay tTrip=5-20 seconds.7.4.4 Advanced users settingsFor advanced users the following parameters need also to be set. Set the length of the trippulse to typical tPulse=0.15 sec. Set the blocking time tBlock to block Loss of voltagecheck (LOVPTUV, 27), if some but not all voltage are low, to typical 5.0 seconds and setthe time delay for enabling the function after restoration tRestore to 3 - 40 seconds.1MRK 511 286-UUS A Section 7Voltage protection163Application manual
