Susceptibility of Static Energy Meters due to Amplifier Clipping Caused by a Rogowski Coil

Static energy meters installed in households, used for billing purposes of the energy consumption, have shown errors due to conducted electromagnetic interference coming from appliances in household situations. This resulted in over- and underestimations of the energy bill, and even in a perceived energy generation. The currents causing interference are known to be nonlinear pulsed currents with fast slopes. This article shows that clipping of the amplifier, following the Rogowski coil, which is used as the current sensing element, results in distorted energy measurements. Due to the pulsed nature of the current, the output of the Rogowski coil exceeds the maximum input voltage of the amplifier, resulting in clipping at the output of the amplifier. This clipped signal is then integrated in the digital chain, resulting in an offset in the perceived current. Hence, causing a higher or lower energy calculation, depending on the phase firing angle and the fastest edge of the pulse. It is found that parameters, such as the slew rate, rise and fall times, and firing angle, are correlated to the interference on static energy meters.