7.3 Two step residual overvoltage protection ROV2PTOV(59N)7.3.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberTwo step residual overvoltageprotectionROV2PTOV3U0>IEC10000168 V1 EN59N7.3.2 ApplicationTwo step residual overvoltage protection ROV2PTOV (59N) is primarily used in highimpedance grounded distribution networks, mainly as a backup for the primary groundfault protection of the feeders and the transformer. To increase the security for differentground fault related functions, the residual overvoltage signal can be used as a releasesignal. The residual voltage can be measured either at the transformer neutral or from avoltage transformer open delta connection. The residual voltage can also be calculatedinternally, based on measurement of the three-phase voltages.In high impedance grounded systems the residual voltage will increase in case of any faultconnected to ground. Depending on the type of fault and fault resistance the residualvoltage will reach different values. The highest residual voltage, equal to three times thephase-to-ground voltage, is achieved for a single phase-to-ground fault. The residualvoltage increases approximately to the same level in the whole system and does notprovide any guidance in finding the faulted component. Therefore, ROV2PTOV (59N) isoften used as a backup protection or as a release signal for the feeder ground faultprotection.7.3.3 Setting guidelinesAll the voltage conditions in the system where ROV2PTOV (59N) performs its functionsshould be considered. The same also applies to the associated equipment, its voltage andtime characteristic.There is a very wide application area where general single input or residual overvoltagefunctions are used. All voltage related settings are made as a percentage of a settable basevoltage, which can be set to the primary nominal voltage (phase-phase) level of the powersystem or the high voltage equipment under consideration.Section 7 1MRK 511 286-UUS AVoltage protection158Application manual
