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Static energy meters are used for billing purposes of the energy consumption. Those that utilize a Rogowski coil as their current transducer have shown the highest susceptibility to conducted electromagnetic interference resulting in misreadings. These disturbances occur due to pulsed currents with steep slopes with higher frequency content, drawn by nonlinear household appliances. This has resulted in over- and underestimations of the energy bill, and even in a perceived energy generation. This article describes improving the robustness against conducted electromagnetic interference by using the orthogonality of power flow principle, thus focusing only on the fundamental, in contrary to the energy metering trend of increasing the measurement bandwidth. A first-order low-pass filter is implemented between the current transducer and the amplifier to reduce interference without affecting the 50 Hz signal. The results show a reduction of errors from 1632% down to below 2.5%.

Robust energy measurements for household consumption billing are 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 kinds 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.

The use of more energy efficient solutions and products contribute to the increased use of non-linear equipment, for example in households. Inherent to the switching nature of such equipment, the currents show a pulsed behavior with high peak values and fast rising slopes. Consequently, this increases the conducted emission and many electromagnetic interference problems have been reported. When analysing such problems the accurate reconstruction of a current waveform is of importance. For this, suitable current sensing elements are needed, of which the current transformer is a widely used sensing principle. However, this paper presents the susceptibility of current transformers when measuring pulsed currents that are represented by square-wave signals. As a consequence the measured current does not represent the actual current accurately.

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.

This article presents a strategy for the description of new test waveforms for static electricity meters to be included in international standards. The need of extending the existing standardization frame arises from several recent studies that have reported conducted electromagnetic interference problems of type-approved static electricity meters, resulting in significant errors in the measured electricity consumption. The proposed method is based on discrete wavelet transform and allows for a compact and parsimonious representation of test waveforms, suitable for inclusion in standards. Very few wavelet parameters are concentrating the relevant information to accurately reproduce all the characteristics that the meters need to be tested against. The same parsimonious description cannot be performed with the current practices based on Fourier transform methods since the new test signals need to be highly non-sinusoidal. The discrete wavelet transform is proposed as a more effective tool to sparsely describe the most relevant waveform features. The effect of different discrete wavelet transform decomposition settings on compactness and reconstruction accuracy is studied using suitable metrics. Finally, results from experimental validation with several different waveforms are presented to demonstrate that the error-inducing features can be preserved using only 0.1% of the original signal information.

The increased use of non-linear equipment results in conducted electromagnetic interference problems. As an example, static energy meters, used to measure the energy consumption in households, show misreadings due to pulsed currents from a speed controlled water pump or dimmed lighting equipment. To determine the existence of similar equipment in low-voltage networks, this letter surveys current waveforms drawn by equipment in the low-voltage network. These waveforms are analyzed and compared to critical waveforms from previous research that caused static energy meter interference. In this way the extent of critical situations in a real-world environment is determined. The equipment survey is performed using a multi-channel time- domain measuring method able to capture the voltage and currents synchronously. Then using a time-domain parametric model a statistical overview of parameters such as the charge, crest factor, peak value, pulse duration, and rising slope is given. The survey shows the existence of a large variety of non-linear signals, and 43% contained critical parameters related to static energy meter interference.

In 2015, the energy measurement of some static electricity meters was found to be sensitive to specific conducted electromagnetic disturbances with very fast current changes caused by highly nonlinear loads, leading to meter errors up to several hundred percent. This article describes new results on the electromagnetic compatibility (EMC) of 16 different meters from all over Europe when exposed to real-world disturbance signals. Those test signals were obtained from household appliances and onsite measurements at metered supply points all over Europe. The results show that also the interference signals recorded onsite can cause measurement errors as large as several hundred percent, even for meters that pass the present EMC standards. This unambiguously demonstrates that the present immunity testing standards do not cover the most disturbing conducted interference occurring in present daily-life situations due to the increased use of nonlinear electronics. Furthermore, to enable the adoption of potential new test waveforms in future standards for electricity meter testing, artificial test waveforms were constructed based on real-world waveforms using a piece-wise linear model. These artificial test waveforms were demonstrated to cause meter errors similar to those caused by the original real-life waveforms they are representing, showing that they are suitable candidates for use in improved standardization of electricity meter testing.

Static energy meters have shown errors beyond the standards due to conducted electromagnetic interference of pulsed currents. This was observed in several case studies and confirmed by laboratory experiments, which showed errors up to 2675%. The extent of this interference case is unknown, because there is limited information about the waveforms occurring in the real on-site scenarios. This article aims to detect critical waveforms in on-site surveyed data that have similar characteristics as the pulses that resulted in metering errors. The time-domain parameters of the laboratory experiments that show static energy meter interference are compared to the on-site waveform data using an interpolation based on an inverse weighting distance function. Using this approach, the waveform characteristics are compared, and an error is estimated. This approach was satisfactorily validated using data from validation experiments that shows a correct estimation of the actual error according to the permissible limits for energy metering for all validation indices. The performed on-site surveys show the existence of nonlinear waveforms. During the survey of three sites for ten days, 19 531 waveforms were captured, of which 14 487 indicate large nonlinearities and 379 are estimated to produce metering errors up to 925%.

This article presents a time-domain waveform model developed to characterize pulsed, nonlinear, current waveforms resulting in electromagnetic interference on static energy meters. The waveform model is calculated by fitting the sampled waveform data into a linear piece-wise function through a process that involves applying algorithms of pulse extraction, change-point detection, and redundancy elimination. The model is applied to data from laboratory experiments that have indicated critical current waveforms resulting in electromagnetic interference problems with static meters. Afterwards, the parameters of the modeled waveforms are calculated in order to correlate them to metering errors. The most relevant parameters that are correlated to significant errors are the maximum slope, crest factor, pulse duration, and charge. The waveform model provides an accurate description of the complex nonlinear waveforms through simplified analytical expressions that reproduce the significant features of the interfering waveforms. This waveform modeling approach could be used to standardize the artificial test signals that are representative of realistic devices and scenarios.

For the measurement of impulsive currents, which might occur in cases of electromagnetic interference, for example currents generated by the non-linear behavior of electronic appliances, a wide-band large dynamic range current transducer is needed. The electrical response of such a transducer is determined using conventional techniques, that use frequency sweeps of sinusoidal continuous wave signals. For non-linear and/or time invariant systems the superposition of continuous wave signals of multiple frequencies might not be equal to an impulsive current, which is representative for the actual measured signals, and is therefore of interest. In this letter the electrical response of current transducers is determined using impulsive signals, and compared to continuous wave tests. Time domain parameters such as rise time and peak amplitude are extracted, and the frequency response is analyzed using a Fourier transform. The experiments show that the impulsive test is in agreement with the continuous wave method and provides a good alternative method. A combination of impulses could cover a large bandwidth, and is a fast and cost effective approach.