adding the input phase voltages. 3V0 may also be input single phase by either measuringdirectly from a voltage transformer in the neutral of a power transformer, or from asecondary broken delta connection of a transformer with a wye-grounded primary.ROV2PTOV (59N) has two steps with separate time delays. If the ground overvoltageremains above the set value for a time period corresponding to the chosen time delay, thecorresponding TRIP signal is issued.The time delay characteristic is setable for step 1 and can be either definite or inverse timedelayed. Step 2 is always definite time delayed.The voltage related settings are made in percent of the global phase-to-phase base voltagedivided by √3.7.3.7.1 Measurement principleThe residual voltage is measured continuously, and compared with the set values, Pickup1and Pickup2.To avoid oscillations of the output PICKUP signal, a hysteresis has been included.7.3.7.2 Time delay7.3.7.3 BlockingIt is possible to block two step residual overvoltage protection (ROV2PTOV, 59N)partially or completely, by binary input signals where:BLOCK: blocks all outputsBLK1: blocks all pickupand trip outputs related to step 1BLK2: blocks all pickup and trip inputs related to step 27.3.7.4 DesignThe voltage measuring elements continuously measure the residual voltage. RecursiveFourier filters filter the input voltage signal. The single input voltage is compared to theset value, and is also used for the inverse time characteristic integration. The design ofTwo step residual overvoltage protection (ROV2PTOV, 59N) is schematically describedin Figure 75.Section 7 1MRK 511 287-UUS AVoltage protection184Technical manual
