1. Different kinds of faults, where a too high voltage appears in a certain powersystem, like metallic connection to a higher voltage level (broken conductorfalling down to a crossing overhead line, transformer flash over fault from the highvoltage winding to 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 voltagedecrease).4. Ground-faults in high impedance grounded systems causes, beside the highvoltage in the neutral, high voltages in the two non-faulted phases, (unsymmetricalvoltage increase).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 remoteautomation processes in the power system.8.2.3 Setting guidelines M13852-4 v10The parameters for Two step overvoltage protection (OV2PTOV ,59) are set via thelocal HMI 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 voltageand time characteristic.There are wide applications where general overvoltage functions are used. All voltagerelated settings are made as a percentage of a settable base primary voltage, which isnormally set to the nominal voltage level (phase-to-phase) of the power system or thehigh voltage equipment under consideration.The time delay for the OV2PTOV (59) can sometimes be critical and related to the sizeof the overvoltage - a power system or a high voltage component can withstand smallerovervoltages for some time, but in case of large overvoltages the related equipmentshould be disconnected more rapidly.Some applications and related setting guidelines for the voltage level are given below:The hysteresis is for overvoltage functions very important to prevent that a transientvoltage over set level is not “sealed-in” due to a high hysteresis. Typical values shouldbe ≤ 0.5%.1MRK 505 370-UUS A Section 8Voltage protectionBusbar protection REB670 2.2 ANSI 247Application manual
