Meaning
The ratio of harmonic current distortion to the maximum demand load current represents a standardized measure of power quality in industrial facilities. While total harmonic distortion compares harmonics to the instantaneous current, total demand distortion evaluates them against the peak current drawn during a long period. This metric provides a more stable and realistic assessment of a plant’s impact on the utility grid.
Assessment Standard
Industrial standards specify maximum allowable percentages of distortion to prevent damage to distribution transformers and substation equipment. Evaluating total demand distortion helps utilities determine if a specific factory is introducing harmful electrical noise into the shared network. This assessment is typically conducted over a fifteen-minute or thirty-minute demand interval.
Electrical Impact
High levels of current distortion can lead to efficiency losses and cable overheating. During the transition from pilot operations to full capacity, the total demand distortion must be measured to confirm that new machinery does not degrade power quality. Deploying large motor drives early without active filtration can push the facility past regulatory distortion limits, resulting in utility penalties and system shutdowns.
This risk emphasizes the need for early power quality audits.
Control Strategy
Installing passive filters or active compensators reduces the harmonic currents injected into the grid.
