IEC05000016-2-en.vsdVoltageIDMT VoltageTimeUL1UL2UL3IEC05000016 V2 ENFigure 94: Voltage used for the inverse time characteristic integrationA TRIP requires that the overvoltage condition continues for at least the user set timedelay. This time delay is set by the parameter t1 and t2 for definite time mode (DT) andby selected voltage level dependent time curves for the inverse time mode (IDMT). Ifthe START condition, with respect to the measured voltage ceases during the delaytime, the corresponding START output is reset.9.2.7.3 BlockingIt is possible to block two step overvoltage protection (OV2PTOV) partially orcompletely, by binary input signals where:BLOCK: blocks all outputsBLKST1: blocks all start and trip outputs related to step 1BLKST2: blocks all start and trip outputs related to step 29.2.7.4 DesignThe voltage measuring elements continuously measure the three phase-to-earthvoltages or the three phase-to-phase voltages. Recursive Fourier filters or true RMSfilters of input voltage signals are used. The phase voltages are individually comparedto the set value, and the highest voltage is used for the inverse time characteristicintegration. A special logic is included to achieve the 1 out of 3, 2 out of 3 or 3 out of 3criteria to fulfill the START condition. The design of Two step overvoltage protection(OV2PTOV) is schematically described in Figure 95.Section 9 1MRK 504 135-UEN AVoltage protection214Technical manual
