calculated with the Power1(2), Hysteresis1(2): drop-power1(2) = Power1(2) –Hysteresis1(2)For small power1 values the hysteresis1 may not be too big, because the drop-power1(2) would be too small. In such cases, the hysteresis1 greater than (0.5 ·Power1(2)) is corrected to the minimal value.If the measured power drops under the drop-power1(2) value the function will resetafter a set time DropDelay1(2). The reset means that the start signal will drop outant that the timer of the stage will reset.6.7.2.1 Low pass filteringIn order to minimize the influence of the noise signal on the measurement it ispossible to introduce the recursive, low pass filtering of the measured values for S(P, Q). This will make slower measurement response to the step changes in themeasured quantity. Filtering is performed in accordance with the followingrecursive formula:( )Old CalculatedS k S 1 k S= × + - ×EQUATION1959 V1 EN (Equation 37)WhereS is a new measured value to be used for the protection functionSold is the measured value given from the function in previous execution cycleSCalculated is the new calculated value in the present execution cyclek is settable parameter by the end user which influence the filter propertiesDefault value for parameter k is 0.00. With this value the new calculated value isimmediately given out without any filtering (that is, without any additional delay).When k is set to value bigger than 0, the filtering is enabled. A typical value for k =0.92 in case of slow operating functions.6.7.2.2 Calibration of analog inputsMeasured currents and voltages used in the Power function can be calibrated to getclass 0.5 measuring accuracy. This is achieved by amplitude and anglecompensation at 5, 30 and 100% of rated current and voltage. The compensationbelow 5% and above 100% is constant and linear in between, see example in figure93.Section 6 1MRK 505 208-UEN BCurrent protection196Technical reference manual
