BLOCKALARMDistortionmeasure-mentI_AI_BI_CDemandcalculationGUID-E5EC5FFE-7679-445B-B327-A8B1759D90C4 V1 ENFigure 409: Functional module diagramDistortion measurementThe distortion measurement module measures harmonics up to the 11th harmonic.The total demand distortion TDD is calculated from the measured harmoniccomponents with the formulaTDD IIkkNdemand= =∑ 22max_GUID-9F532219-6991-4F61-8DB6-0D6A0AA9AC29 V1 EN (Equation 97)Ik kth harmonic componentImax_demand The maximum demand current measured by CMMXUIf CMMXU is not available in the configuration or the measured maximumdemand current is less than the Initial Dmd current setting, Initial Dmd current isused for Imax_demand.Demand calculationThe demand value for TDD is calculated separately for each phase. If any of thecalculated total demand distortion values is above the set alarm limit TDD alarmlimit, the ALARM output is activated.The demand calculation window is set with the Demand interval setting. It hasseven window lengths from "1 minute" to "180 minutes". The window type can beset with the Demand window setting. The available options are "Sliding" and "Non-sliding".The activation of the BLOCK input blocks the ALARM output.10.1.5 ApplicationIn standards, the power quality is defined through the characteristics of the supplyvoltage. Transients, short-duration and long-duration voltage variations, unbalanceand waveform distortions are the key characteristics describing power quality.Power quality is, however, a customer-driven issue. It could be said that any powerSection 10 1YHT530004D05 DPower quality measurement functions766 615 seriesTechnical Manual
