TDt Vpickup VVpickup= < -<ANSIEQUATION1431 V1 EN (Equation 71)The type B curve is described as:2.0480 0.055Vpickup < -V32 0.5VpickupTDt ×= +× -<æ öç ÷è øEQUATION1608 V1 EN (Equation 72)The lowest voltage is always used for the inverse time delay integration. The details ofthe different inverse time characteristics are shown in section 21.3 "Inverse timecharacteristics".Trip signal issuing requires that the undervoltage condition continues for at least theuser set time delay. This time delay is set by the parameter t1 and t2 for definite timemode (DT) and by some special voltage level dependent time curves for the inversetime mode (TUV). If the pickup condition, with respect to the measured voltage ceasesduring the delay time, the corresponding pickup output is reset.9.1.7.3 BlockingIt is possible to block Two step undervoltage protection (UV2PTUV ,27) partially orcompletely, by binary input signals or by parameter settings, where:BLOCK: blocks all outputsBLK1: blocks all pickup and trip outputs related to step 1BLK2: blocks all pickup and trip outputs related to step 29.1.7.4 DesignThe voltage measuring elements continuously measure the three phase-to-neutralvoltages or the three phase-to-phase voltages. Recursive fourier filters or true RMSfilters of input voltage signals are used. The voltages are individually compared to theset value, and the lowest voltage is used for the inverse time characteristic integration.A special logic is included to achieve the 1 out of 3, 2 out of 3 and 3 out of 3 criteria tofulfill the PICKUP condition. The design of Two step undervoltage protectionUV2PTUV (27) is schematically shown in Figure 119.1MRK 502 043-UUS B Section 9Voltage protection255Technical Manual
