8.2.2 ApplicationTwo step overvoltage protection OV2PTOV (59) is applicable in all situations, wherereliable detection of high voltage is necessary. OV2PTOV (59) is used for supervision anddetection of abnormal conditions, which, in combination with other protection functions,increase the security of a complete protection system.High overvoltage conditions are caused by abnormal situations in the power system.OV2PTOV (59) is applied to power system elements, such as generators, transformers,motors and power lines in order to detect high voltage conditions. OV2PTOV (59) is usedin combination with low current signals, to identify a transmission line, open in the remoteend. In addition to that, OV2PTOV (59) is also used to initiate voltage correctionmeasures, like insertion of shunt reactors, to compensate for low load, and therebydecreasing the voltage. The function has a high measuring accuracy and hysteresis settingto allow applications to control reactive load.OV2PTOV (59) is used to disconnect apparatuses, like electric motors, which will bedamaged when subject to service under high voltage conditions. It deals with high voltageconditions at power system frequency, which can be caused by:1. Different kinds of faults, where a too high voltage appears in a certain power system,like metallic connection to a higher voltage level (broken conductor falling down toa crossing overhead line, transformer flash over fault from the high voltage windingto the low voltage winding and so on).2. Malfunctioning of a voltage regulator or wrong settings under manual control(symmetrical voltage decrease).3. Low load compared to the reactive power generation (symmetrical voltage decrease).4. Ground-faults in high impedance grounded systems causes, beside the high voltagein the neutral, high voltages in the two non-faulted phases, (unsymmetrical voltageincrease).OV2PTOV (59) prevents sensitive equipment from running under conditions that couldcause their overheating or stress of insulation material, and, thus, shorten their life timeexpectancy. In many cases, it is a useful function in circuits for local or remote automationprocesses in the power system.8.2.3 Setting guidelinesThe parameters for Two step overvoltage protection (OV2PTOV ,59) are set via the localHMI or PCM600.All the voltage conditions in the system where OV2PTOV (59) performs its functionsshould be considered. The same also applies to the associated equipment, its voltage andtime characteristic.1MRK 506 334-UUS A Section 8Voltage protection259Application manual
