U UBase kV< ⋅(%) ( )3EQUATION1429 V2 EN (Equation 64)and operation for phase-to-phase voltage under:U (%) UBase(kV)< ×EQUATION1990 V1 EN (Equation 65)When phase-to-earth voltage measurement is selected the functionautomatically introduces division of the base value by the squareroot of three.8.1.7.1 Measurement principleDepending on the set ConnType value, UV2PTUV measures phase-to-earth or phase-to-phase voltages and compare against set values, U1< and U2<. The parametersOpMode1 and OpMode2 influence the requirements to activate the STARToutputs. Either 1 out of 3, 2 out of 3, or 3 out of 3 measured voltages have to belower than the corresponding set point to issue the corresponding START signal.To avoid oscillations of the output START signal, a hysteresis has been included.8.1.7.2 Time delayThe time delay for step 1 can be either definite time delay (DT) or inverse timedelay (IDMT). Step 2 is always definite time delay (DT). For the inverse timedelay two different modes are available; inverse curve A and inverse curve B.The type A curve is described as:kt U UU= < -æ öç ÷<è øEQUATION1431 V1 EN (Equation 66)The type B curve is described as:2.0480 0.05532 0.5kt U UU×= +< -æ ö× -ç ÷<è øEQUATION1432 V1 EN (Equation 67)Section 8 1MRK 502 034-UEN -Voltage protection220Technical Manual
