Interference on Static Energy Meters Resulting From Droop of the Current Transformer

Abstract

Robust energy measurements for household consumption billing is important for consumer confidence. Recent studies have shown electromagnetic interference problems with static energy meters, this results in incorrect billing. The interfering current waveforms are pulsed currents with a short pulse duration, fast rising slope, and large crest factor. These kind of waveforms are largely present in modern low-voltage networks. The root-cause of the interference on static energy meters that use a Rogowski coil is known, however for meters that use a current transformer as their current sensing element this is unknown, while those meters contribute to errors up to 200%. Therefore, this article researches the root-cause of interference on static energy meters that use the current transformer principle for current sensing. It was found that the current transformer exhibits droop and the current pulses to be measured are not properly reconstructed. As a result, when the power/energy is calculated errors occur. This explains why current transformer based static energy meters are prone to electromagnetic interference.