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Voltage transients measurements and power line communication
Abstract
Power line communication (PLC) connects energy producers with energy consumers. In the European Union stricter guidelines are under development to limit disturbances in the 2–150 kHz frequency range, because devices utilising PLC do not work. This study measured voltage transients in 22 locations and identified sources for noise. Home environments and public buildings were measured. Measurements were conducted in the frequency range of 150 kHz–500 kHz (according to EN 55011 to EN 55022) and in the lower frequency range of 3 kHz to 95 kHz. Results indicate that voltage transients are generated mostly by switching mode power supplies, pumps, rectifiers, inverters and even low quality smart meters. Several of these devices exceeded PLC standard level, 122 dBμV. Additionally we demonstrate that basic power quality recordings do not provide enough information to mitigate PLC problems occurring within microseconds and frequency specific voltage transient measurements are needed.
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The authors report the association between exposure to pulsed electromagnetic fields (PEMFs) and cancer in a nested case-control study of electric utility workers in Quebec, Canada (follow-up, 1970–1988), and France (follow-up, 1978–1989), among whom 2,679 cases of cancer were identified. Exposures were assessed through a job-exposure matrix based on about 1,000 person-weeks of measurements from exposure meters worn by workers. Exposures were considerably higher in Quebec than in France. No association was found between PEMFs and cancers previously suspected of association with magnetic fields (leukemia, other hematopoietic cancers, brain cancer, or melanoma). However, there was a clear association between cumu lative exposure to PEMFs and lung cancer, with odds ratios rising to 3.11 (95% confidence interval (Cl) 1.60–6.04) in the highest exposure group (84 cases). This association was largely confined to Quebec, where there was a monotonic exposure- response relation with an odds ratio of 6.67 (95% Cl 2.68–16.57) in the highest exposure group (32 cases). The association is substantial and was not explained by smoking or other occupational exposures. However, several factors limit the strength of the evidence for a causal relation: lack of precision in what the meters measured; little previous evidence for this association; and no elevated risk for lung cancer in the utility workers overall in comparison with the general population. Am J Epidemiol 1994; 140:805–20.
The interference of touch dimmer lamps due to PLC signals has found to be a common interference problem in Finland after the installation of smart meters that use PLC. One reason for this is the lack of equipment immunity standards for voltage frequencies below 150 kHz. This paper will study controlled discontinuous high frequency signal burst effect to two touch dimmer lamps in the laboratory environment. Both lamps were disturbed due to these signals. Based on the results it is possible that interference problems can occur even if the distance between lamp and the PLC device is close to 100 m. Paper will also show the measurement results on how one plug-in type filter improve interference situation. Results show that the amplitude of the signal burst will decrease at lamp side but filter also affects signal levels at mains side.
The authors report the association between exposure to pulsed electromagnetic fields (PEMFs) and cancer in a nested case-control study of electric utility workers in Quebec, Canada (follow-up, 1970–1988), and France (follow-up, 1978–1989), among whom 2,679 cases of cancer were identified. Exposures were assessed through a job-exposure matrix based on about 1,000 person-weeks of measurements from exposure meters worn by workers. Exposures were considerably higher in Quebec than in France. No association was found between PEMFs and cancers previously suspected of association with magnetic fields (leukemia, other hematopoietic cancers, brain cancer, or melanoma). However, there was a clear association between cumu lative exposure to PEMFs and lung cancer, with odds ratios rising to 3.11 (95% confidence interval (Cl) 1.60–6.04) in the highest exposure group (84 cases). This association was largely confined to Quebec, where there was a monotonic exposure- response relation with an odds ratio of 6.67 (95% Cl 2.68–16.57) in the highest exposure group (32 cases). The association is substantial and was not explained by smoking or other occupational exposures. However, several factors limit the strength of the evidence for a causal relation: lack of precision in what the meters measured; little previous evidence for this association; and no elevated risk for lung cancer in the utility workers overall in comparison with the general population. Am J Epidemiol 1994; 140:805–20.
Power line impedance is a very important parameter on the design of power line communications (PLC) modem architecture. Variations on the impedance of the power line affect the communications circuit performance. In order to determine impedance of the power lines, measurements were carried out in Turkey at frequencies ranging from 10 to 170 kHz, (CENELEC A,B,C,D bands). Measurements were conducted in three categories: rural, urban and the industrial power lines. Experimental results are presented in graphical form. The measured impedances were determined as 3-17 ohms, 1-17 ohms, and 1-21 ohms for rural, urban and the industrial lines, respectively. A set of the formulas between impedance and frequency are developed on the power lines using the regression analysis from the obtained empirical data. Signal attenuations on the power lines in the CENELEC band are also measured for rural, urban and industrial regions. Attenuation measurements are repeated for phase-neutral, phase-ground and the neutral-ground conductors. Signal attenuations are found to be 4-30 dB, for different power lines. To establish validity of obtained results for the design of PLC systems, the results are compared with previous investigations. The effects of some household appliances such as TV, PC, UPS, lighting and cooling systems on the impedances and the attenuations for power line communications systems are observed. Some suggestions and proposals are presented for PLC modem designers.
In recent years the grid connected photovoltaic (PV) micro-generation facilities in individual homes has increased due to the adopted governmental policies and the industry attention. The power feed-in of PV generation in rural low-voltage grid can influence the power quality and the facility operation and reliability. This paper presents the results of a power quality analysis of a real PV generation facility connected to a rural low-voltage grid. The voltage fluctuations and the voltage harmonic content are observed and a statistical analysis and discussion are performed. The main achievements of the work are the statement of the disturbances imposed to the grid and its consequences to the technical and economic viability of the PV system.
Public Utility Commissions (PUC) in several states adopted 0.5volt rms (root mean squared) or 1.0milliampere as the actionable limit for utilities to respond to complaints of uncontrolled voltage. This study clearly shows that the actionable level should be reduced to 10mV p-p (peak-to-peak), which is 140 times less than the current standard. Dairy farmer complaints that animal behavior and milk production were affected by electrical shocks below adopted standards were investigated on 12 farms in Wisconsin, Michigan, and Minnesota. Milk production per cow was determined from daily tank-weight pickup and number of cows milked. Number of transient events, transients, voltage p-p, waveform phase angle degree, sags, and sag-Vrms were measured from event recorders plugged into milk house wall outlets. Data from 1705 cows and 939 data points were analyzed by multiherd least-squares multiple regression and SAS-ANOVA statistical programs. In five herds for 517days, milk/cow/day decreased -0.0281kg/transient event as transient events increased from 0 to 122/day (P<0.02). Negative effects on milk/cow/day from event recorder measurements were significant for eight independent electrical variables. Step-potential voltage and frequency of earth currents were measured by oscilloscope from metal plates grouted into the floor of milking stalls. Milk decreased as number of 3rd, 5th, 7th, 21st, 28th, and 42nd harmonics and the sum of triplen harmonics (3rd, 9th, 15th, 21st, 27th, 33rd, and 39th) increased/day (P<0.003). Event recorder transient events were positively correlated with oscilloscope average V p-p event readings. Steps/min counted from videotapes of a dancing cow with no contact to metal in the barnyard were correlated with non-sinusoidal 8.1 to 14.6mV p-p impulses recorded by oscilloscope for 5min from EKG patches on legs. PUC standards and use of 500-Ohm resistors in test circuits underestimate effects of non-sinusoidal, higher frequency voltage/current common on rural power lines.
Unpredictable characteristics of power line communication (PLC) channels seriously affect the performance of the communication systems. Among these unpredictable characteristics, noise is considered to be the main source of errors in data transmission in PLC systems. Unlike conventional communication systems in which noise is usually modeled as additive white Gaussian noise (AWGN), its definition in PLC channels has a more complicated form. In order to design reliable PLC systems, it is essential to understand the features of noise in power line networks. Since the impulsive noise generated by electrical house appliances is one of the most significant noise types in PLC channel, it is very important to analyze these electrical devices with respect to their noise characteristics. In this paper, impulsive noise characteristics of various house appliances are analyzed over the frequency range of 30 kHz - 50 MHz.
The Geneva city utility SIG operates a large medium / low voltage distribution network with a high number of distribution transformers in place. Within the last approx. 4 years an unusual high number of transformer failed due to a premature aging. These units were all delivered between beginning of 1996 until mid 1999. Only sizes of 630 kVA and 1000 kVA were affected. Within other MV networks as well 400 kVA and 1250 kVA units failed, however a smaller number.
Many epidemiologic studies suggest a relationship between incidence of diseases like cancer and leukemia and exposure to 50/60 Hz magnetic fields. Some studies suggest a relationship between leukemia incidence in populations residing near high-voltage lines and the distance to these lines. Other epidemiologic studies suggest a relationship between leukemia incidence and exposure to 50/60 Hz magnetic fields (measured or estimated) and distance from the main system (220 or 120 V). The present work does not question these results but is intended to draw attention to a possible concurrent cause that might also increase the incidence of this disease; the presence on an electric grid of radiofrequency currents used for communications and remote control. These currents have been detected on high- and medium-voltage lines. In some cases they are even used on the main system for remote reading of electric meters. This implies that radiofrequency (RF) magnetic fields are present near the electric network in addition to the 50/60 Hz fields. This intensity of these RF fields is low but the intensity of currents induced in the human body by exposure to magnetic fields increases with frequency. Because scientific research has not yet clarified whether the risk is related to the value of magnetic induction or to the currents this kind of exposure produces in the human body, it is reasonable to suggest that the presence of the RF magnetic fields must be considered in the context of epidemiologic studies.
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Handbook of Power Signatures
- Bmi Dranetz
Dranetz-BMI. 1997. Handbook of Power Signatures. Dranetz-BMI.
Metallized Polypropylene (PP) RFI-Capacitors Class X2
- Wima
Wima. 2016. Metallized Polypropylene (PP) RFI-Capacitors Class X2.
Specification. http://www.wima.de/DE/mkpx2.htm