Design of Cost-Effective Power Quality and EMI Sensor for Multinode Network

Multinode measurement systems are required to evaluate electromagnetic interference (EMI) propagation and power-quality (PQ) issues in microgrids or large buildings. PQ issues are a subset of electromagnetic compatibility (EMC), and identifying them can help track down problems in large networks. Commercial-off-the-shelf (COTS) sensors range from cheap smart plugs, with limited functionality and accuracy, to high-end measurement devices. For large-scale deployment and future research, a cost-effective solution is needed for distributed measurements. This letter discusses designing and evaluating a cost-effective PQ sensor that fits the gap between cheap smart plugs and high-end measurement devices. It is designed with expandability in mind while keeping the cost down. This allows the device to log other EMI parameters in the future by adding sensors without redesigning the device. An energy measurement accuracy of smaller than 1% is achieved, comparable to a class B energy meter of the EN-50470 standard. It can measure all the elementary electrical parameters so deviations to the EN-50160 can be logged in a (sub)second scale

Electromagnetic Compatible Energy Measurements using the Orthogonality of Nonfundamental Power Components

Measurement bandwidth of energy measurements are increasing to incorporate all the harmonics created by nonlinear loads and distributed generators making the measurement electronics complex and sensitive to electromagnetic interference. This article proposes to change the accuracy paradigm by focusing on fundamental active power and lower harmonics for energy metering, simplifying the electronics and making them robust against electromagnetic interference. Using the orthogonality of power flow via Parseval’s theorem, a theoretical analysis, simulations, and measurements on power calculations using the fundamental active power are presented. It is shown that a perfect power measurement is achieved with a pure 50 Hz supply voltage, regardless of the nonlinear current. Even with the highest allowed harmonic distortion of the voltage and the current as listed in the international standards EN 50160 and IEC 61000-3-2, more than 97.5% of the active power is contained in the fundamental active power. Negligible active power is contained in the higher frequency components. This error margin falls within limits for electricity meters. Filtering the current with a basic low-pass filter can prevent the erroneous measurements that have appeared with static energy meters. In other words, it has been proven that negligible energy flows in the higher frequency components

Time-Domain EMI Measurements using a Low Cost Digitizer to Optimize the Total Measurement Time for a Test Receiver

By analyzing electromagnetic interference (EMI) based on its spectral components important time-domain information is lost. Conventional super-heterodyne frequency band stepping EMI test receivers have to use long dwell times for every frequency which makes the total measurement time too long. Often dwell times are set too short, causing time-varying interference, or cyclo-stationary interference, to be detected improperly. The concept of time-varying EMI is also not incorporated in standards, which are only based on frequency domain limits. To catch these time-varying interferences the receiver has to measure for at least one repetition period. Measuring many spectral components for at least the repetition of a cyclo-stationary signal causes detrimental measurement times. Time-domain electromagnetic interference (EMI) analyzers have been proposed to reduce these long measurement times, but remain expensive. To reduce costs the utilization of time-domain EMI measurements using a low cost digitizer is examined. A PicosScope in conjunction with Digital Signal Processing (DSP) is used to create the possibility to estimate the total measurement time of a conventional EMI receiver based on the dwell times. This can be used to optimize the total measurement time needed for the test receiver, while still complying to standards, resulting in reduced measurement times otherwise needed in expensive test labs. A short-time Fast-Fourier transform (STFFT) is used to examine the interfering source in both frequency and time simultaneously. It was also shown that the conventional EMI receiver perceives certain time varying signals as continuous waves due to the spectral nature of this receiver

The Effects of Falling and Rising Edge Dimming on Static Energy Meter Errors

For a better understanding on what is causing static energy meter misreadings different current waveforms with falling and rising edges have been compared. Falling edge dimming showed higher static energy meter deviations due to the larger rate of change in the current, vert mathrm dI / mathrm dt vert, compared to the rising edge dimming. The difference in vert dI / dt vert is due to the asymmetry inherent in the semiconductors used. No specific difference in static energy meter deviation was found due to the polarity of the mathrm dI / mathrm dt. Faling edges in the first quarter of the sine wave resulted in an overestimation of the consumed power just as rising edges in the second quarter. Rising edges in the first quarter and falling edges in the second however showed an underestimation of the consumed power. The underestimation seems to compensate the overestimation when using complementary waveforms

Determining position, rotation and orientation for tethered twin nano satellite to map data from an interferometer

Nanosat projects pose a relatively cheap and flexible method to obtain knowledge of space, the universe and the technologies needed for future investigations. One of the current frontiers is low frequency radio astronomy. On Earth LOFAR is measuring these signals, however the atmosphere, ionosphere and interference make space a better place for measurements especially for frequencies below 30 MHz. TwenteSat is a nano satellite student project which aims to bring two satellites in low Earth orbit (LEO) attached to each other by a tether and together forming an interferometer. The practical, technological and measurement knowledge obtained may be used for future projects such as the OLFAR (Orbital Low Frequency ARray). TwenteSats’ satellite system will initially start as one satellite (10x10x30cm) and once in orbit change to two 10x10x10cm units connected by a tether. The interferometer will use two dipole antennas and is therefore direction sensitive. These antennas will be in line with or parallel to the tether and thereby have a donut shaped radiation sensitivity pattern with the tether in the middle of the donut. Rotation will be used to hold the nanosats apart by centrifugal force thereby also rotating the direction of the measurement. In order to map the data it is therefore necessary to know the orbit altitude, satellite system rotation and the satellite system orientation relative to Earth. To determine these parameters the usage of GPS, measurements from Earth and measurements on the nanosat itself will be discussed in general. These measurements will be conducted such that it is not necessary to know the altitude before they take place. In this paper different system level approaches to determine these variables will be discussed for a nanosat platform

From thin-air to flat-sat in 12 months: the Twentesat student project

TwenteSat aims to build a twin-satellite interferometer in space, a research satellite system in preparation of the OLFAR project. The project will be completely done by students that work on a voluntary basis. The target is to have a flat-sat of at least one of the satellites ready in a short timeframe, the reason for this is the wish to get relatively quick results as most students can’t work on the project for a long time, ideal would be 12 months A.K.A. 1 year of study. The first research on the project was done by September 2013 and most of the recruiting and acquiring finances still has to be done at this point in time. As a result of this the student team will face several problems. They have to adapt to working with a quickly changing group as the Twentesat student project experiences a generally high workforce turnover, and they need speedy access to money while still being highly unknown to the outside world. This paper analyses the group’s activities and future plans on how to achieve their goal of quickly building a flat-sat. As it is not possible to trust on the fact that students will stay involved for a long time projects will have to be divided in small tasks that students can start on quickly, won’t take too long, and can be done independently from other tasks. This will help future educational student projects to launch more successfully and with less problems

Perceived value of student participation in the field of aerospace engineering from a student's perspective

The importance of student participation in space projects is well known. New students are needed to supplement the future workforce and both experience and enthusiasm are important factors to join any industry. Students can also offer fresh perspectives to existing problems in any field of engineering. It is also argued that it is very beneficial for the students themselves. This paper will clarify the point of view from students on student participation in aerospace engineering for their own interests, both personal and professional, as well as their general opinion on space research and development. Qualitative interviews were held with several groups of (former) students: Students not (yet) engaged in a large project; Students in the concept stage of a large project and students at the end stages of a large project. Both engineering and non-engineering students are of interest for this research. A broad range of questions is asked to the participants as this is mostly explorative research. The aim of this paper is to increase student participation by means of a better understanding of student expectations and experiences. Projects better suited to student needs could be developed in the future. With this better understanding and improved projects, more student projects could be successfully launched by both universities and corporations. This should benefit both educational and corporate interests in active student involvement as more research will be done by the students and more students will be engaged and motivated in the space industry. Due to the nature of qualitative interviews students will come with ideas on how to increase student participation and make student projects more successful, so we can relay these to educational institutions and companies

Inter-satellite communication link for a space based interferometer

Radio astronomy has been moving towards lower frequencies in recent years. This trend started with Earth bound large arrays like the low frequency array called LOFAR. After that an initiative to measure even lower frequencies started like the Orbiting Low Frequency Array (OLFAR) in space using a swarm of nano-satellites. Inspired by these initiatives, the goal of the TwenteSat student project is to create a space based interferometer using two tethered nanosatellites. A crucial part of this project is the inter satellite communication which allows data to be shared and control signals to be send between the separated satellites. The possibility of wired communication is examined, as well as wireless communication. In this paper a simple low power wireless communication system is proposed, with the use of commercial off the shelf (COTS) parts

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