Section 8 Voltage protection8.1 Two step undervoltage protection UV2PTUV (27) IP14544-1 v38.1.1 IdentificationM16876-1 v6Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberTwo step undervoltage protection UV2PTUV3U<SYMBOL-R-2U-GREATER-THANV2 EN-US278.1.2 Application M13790-3 v7Two-step undervoltage protection function (UV2PTUV ,27) is applicable in all situations, wherereliable detection of low phase voltages is necessary. It is used also as a supervision and faultdetection function for other protection functions, to increase the security of a completeprotection system.UV2PTUV (27) is applied to power system elements, such as generators, transformers, motors andpower lines in order to detect low voltage conditions. Low voltage conditions are caused byabnormal operation or fault in the power system. UV2PTUV (27) is used in combination withovercurrent protections, either as restraint or in logic "and gates" of the trip signals issued by thetwo functions. Other applications are the detection of "no voltage" condition, for example, beforethe energization of a HV line or for automatic breaker trip in case of a blackout. UV2PTUV (27) isalso used to initiate voltage correction measures, like insertion of shunt capacitor banks tocompensate for reactive load and thereby increasing the voltage. The function has a highmeasuring accuracy and setting hysteresis to allow applications to control reactive load.UV2PTUV (27) is used to disconnect apparatuses, like electric motors, which will be damaged whensubject to service under low voltage conditions. UV2PTUV (27) deals with low voltage conditions atpower system frequency, which can be caused by the following reasons:1. Malfunctioning of a voltage regulator or wrong settings under manual control (symmetricalvoltage decrease).2. Overload (symmetrical voltage decrease).3. Short circuits, often as phase-to-ground faults (unsymmetrical voltage decrease).UV2PTUV (27) prevents sensitive equipment from running under conditions that could cause theiroverheating and thus shorten their life time expectancy. In many cases, it is a useful function incircuits for local or remote automation processes in the power system.1MRK 511 358-UUS A Section 8Voltage protection201Application manual
