t s k AB U UU CDE = ⋅× − >> − +GUID-6E9DC0FE-7457-4317-9480-8CCC6D63AB35 V2 EN (Equation 106)t[s] operate time in secondsA the set value ofCurve parameter AB the set value ofCurve parameter BC the set value ofCurve parameter CD the set value ofCurve parameter DE the set value ofCurve parameter EU measured voltageU> the set value ofStart valuek the set value ofTime multiplier11.3.1.3 IDMT curve saturation of overvoltage protectionFor the overvoltage IDMT mode of operation, the integration of the operate timedoes not start until the voltage exceeds the value of Start value. To cope withdiscontinuity characteristics of the curve, a specific parameter for saturating theequation to a fixed value is created. The Curve Sat Relative setting is the parameterand it is given in percents compared to Start value. For example, due to the curveequation B and C, the characteristics equation output is saturated in such a way thatwhen the input voltages are in the range of Start value to Curve Sat Relative inpercent over Start value, the equation uses Start value * (1.0 + Curve Sat Relative /100 ) for the measured voltage. Although, the curve A has no discontinuities whenthe ratio U/U> exceeds the unity, Curve Sat Relative is also set for it. The CurveSat Relative setting for curves A, B and C is 2.0 percent. However, it should benoted that the user must carefully calculate the curve characteristics concerning thediscontinuities in the curve when the programmable curve equation is used. Thus,the Curve Sat Relative parameter gives another degree of freedom to move theinverse curve on the voltage ratio axis and it effectively sets the maximum operatetime for the IDMT curve because for the voltage ratio values affecting by thissetting, the operation time is fixed, that is, the definite time, depending on theparameters but no longer the voltage.11.3.2 IDMT curves for undervoltage protectionIn the inverse-time modes, the operate time depends on the momentary value of thevoltage, the lower the voltage, the faster the operate time. The operate timecalculation or integration starts immediately when the voltage goes below the setvalue of the Start value setting and the START output is activated.The OPERATE output of the component is activated when the cumulative sum ofthe integrator calculating the undervoltage situation exceeds the value set by theSection 11 1YHT530004D05 DGeneral function block features834 615 seriesTechnical Manual
