8.2.3.2 Equipment protection, capacitors M13852-13 v1High voltage will deteriorate the dielectricum and the insulation. The setting has to be well abovethe highest occurring "normal" voltage and well below the highest acceptable voltage for thecapacitor.8.2.3.3 Power supply quality M13852-16 v1The setting has to be well above the highest occurring "normal" voltage and below the highestacceptable voltage, due to regulation, good practice or other agreements.8.2.3.4 High impedance grounded systems M13852-19 v5In high impedance grounded systems, ground-faults cause a voltage increase in the non-faultyphases. Two step overvoltage protection (OV2PTOV, 59) is used to detect such faults. The settingmust be above the highest occurring "normal" voltage and below the lowest occurring voltageduring faults. A metallic single-phase ground-fault causes the non-faulted phase voltages toincrease a factor of √3.8.2.3.5 The following settings can be done for the two step overvoltage protectionM13852-22 v8ConnType: Sets whether the measurement shall be phase-to-ground fundamental value, phase-to-phase fundamental value, phase-to-ground RMS value or phase-to-phase RMS value.Operation:Disabled/Enabled.VBase (given inGlobalBaseSel): Base voltage phase to phase in primary kV. This voltage is used asreference for voltage setting. OV2PTOV (59) measures selectively phase-to-ground voltages, orphase-to-phase voltage chosen by the settingConnType. The function will operate if the voltagegets lower than the set percentage ofVBase. WhenConnType is set toPhN DFT orPhN RMS thenthe IED automatically divides set value forVBase by √3. WhenConnType is set toPhPh DFT orPhPhRMS then set value forVBase is used. Therefore, always setVBase as rated primary phase-to-phase ground voltage of the protected object. If phase to neutral (PhN) measurement is selectedas setting, the operation of phase-to-earth over voltage is automatically divided by sqrt3. Thismeans operation for phase-to-ground voltage over:(%) ( ) / 3V VBase kV> ×EQUATION1713 V2 EN-US (Equation 95)and operation for phase-to-phase voltage over:Vpickup (%) VBase(kV)> ×EQUATION1992-ANSI V1 EN-US (Equation 96)The below described setting parameters are identical for the two steps (n = 1 or 2). Therefore thesetting parameters are described only once.Characteristicn: This parameter gives the type of time delay to be used. The setting can beDefinite time,Inverse Curve A,Inverse Curve B,Inverse Curve C orI/Prog. inv. curve. The choice ishighly dependent of the protection application.Section 8 1MRK 511 358-UUS AVoltage protection206Application manual
