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This paper analyzes the path loss over the 10-kV medium-voltage power-line channels using the transmission-line theory. All discussions are supported by empirical data obtained from the field test in two substations. Our results show that the electrical equipment between the Tx and Rx affects the path loss the most. This equipment, including the distribution transformers and branches, introduces some drain loss. The other parts of the network have little impact on the path loss. In addition, the parallel compensation capacitor groups connected to the bus do not have any effect on the path loss. The equivalent impedance of any component wired into the network through a branch has been smoothed by that branch. If the impedance of the equipment is lower, smoothness favors the reduction of the drain loss caused by the corresponding equipment. The path loss is lower in phase-to-phase coupling than that in phase-to-ground coupling. In the frequency range of interest, the corresponding value is 5-15 dB. Index Terms--Medium-voltage (MV) distribution network, path loss, power-line communications.

This paper presents a statistical method to model the noise on 10-kV medium-voltage power networks. The cumulative distribution function of the Nakagami-m distribution is calculated and compared with the corresponding empirical cumulative probability distribution in time domain for both the total noise power and the noise power at certain frequencies. It shows that the Nakagami-m distribution offers an excellent fitting to the measured data. The noise spectrum is also analyzed and the exponential and Gaussian functions are used to fit the spectrum. All of the parameters of these fitting functions are random variables which follow the Nakagami-m distribution. Index Terms--Medium-voltage (MV) power line, noise statistical modeling, power system communication.

Based on the empirical data obtained from two typical 10-kV power networks, the transmission properties of the 10-kV power line channel are investigated using the transmission line model. The frequency range is over 40 kHz-l.5 MHz. Our results show: 1) the power attenuation through the channel is about 20-25 dB/km when the channel does not have a branch and 2) the channel is time dispersed. In the frequency domain, the amplitude response is frequency selective while the phase response is linear. In the time domain, the impulse response shows a delay spread. The rms delay spread and the coherence bandwidth are in correlation with the network structure, and the corresponding values are on the order of 10 [mu]s and 10 kHz. 3) The narrow fading of the channel follows Nakagami-m distribution. The channel is varying weakly with respect to time. When the data rate is up to kbps, the channel can be regarded as time invariant. Index Terms--Medium-voltage power network, power line communication, signal propagation, transmission properties.

The general method to investigate the impedance characteristics with a network analyzer is discussed. The common properties of the impedance are studied based on two-months observation of two 10-kV medium-voltage power networks. Meanwhile, the difference of the impedance measured at the headside and tailside of a feeder, the impedance characteristic impacted by the operating mode of the power system, the time variance of the impedance, and the characteristic obtained from a different coupling mode are also studied carefully. The results show that the characteristic impedance is in correlation with the power system structure and its configurations, and its value is about several tenths of ohms. The input impedance varies scarcely with the time. The capacitor group connected to the bus has no influence on the input impedance. And the input impedances in common mode and differential mode are both symmetric. The impedance value in differential-mode coupling is higher than that in common-mode coupling. Index Terms--Impedance characteristic, medium-voltage (MV) distribution network, power-line communications.

Based on the typical topology and physical properties of a 10-kV power network, this paper first proposes a linear time-variant filter with additive noise to be the general channel model which takes into account the main problems that interfere with communications. Then it discusses the corresponding measurement methods. Next, for the first time in the related research area, the electrical loop wire was applied for the measurement of amplitude and phase responses of the transfer function H(f), which provides a better way to solve the problem of obtaining the phase response if the power line is relatively long. Also, the multitones method for the narrow-band fading measurement is put forward. Finally, it is concluded that moving the calibration reference plane of the network analyzer to a proper position improves the measurements efficiency and accuracy and these methods can be referred to in the 10-kV power-line channel study. Index Terms--Channel model, measurement method, medium-voltage power-line channel.

This paper presents experimental research on the noise characteristics performed on 10-kV overhead power lines. The frequency range of interest is from 40 kHz to 2 MHz. The results show that: 1) The noise level of the 10-kV power networks depends on the power network structure, configuration, and loads. It is often higher than that of the low-voltage power networks. The noise power spectrum density usually follows the exponential distribution. However, if the power lines cross with the lines of higher voltage class power networks, the distribution is impacted by the noise from the higher voltage power network. 2) In the 10-kV power line, the noise at the power-supply side (head side) is a little higher than that at the receiving end (tail side) whereas the noise distributes uniformly. The system impedance at the busbar absorbs some noise power. 3) The noise level of phase-to-phase coupling is usually lower than or at least not greater than those of the related two single-phase-to-ground coupling, respectively. Index Terms--Medium-voltage (MV) power line, noise characteristic, power system communication.

This paper reports the measurements and the research of noise characteristics in three-phase four-wire low voltage power network channels with overhead conductor structures. The study focuses on noise classification, loads characterization, the characteristics of noise distribution along the power lines, and that from coupling across different phases. The measured frequencies range from 1 kHz to 1 MHz. Simultaneous measurements of the characteristics of noise distribution were carried out with two sets of instrument of same performance to eliminate the influence of time variance and to improve measurement accuracy. Our results show that: 1) at the frequencies of interest, the noises of power network are mainly produced by the loads. The closer to the noise source (loads), the higher level the noise is. 2) The noise level varies from different coupling phases. The noise level of phase to phase coupling is usually far less than or at least not greater than that of the related two single-phase-to-neutral coupling, respectively. 3) At lower frequencies, the power spectrum density of the power-frequency harmonic noise is much higher than that of the background noise. Index Terms--Noise measurement, power system communication, three-phase four-wire system.

Transmission properties of the power-line channels play a very important role in the reliability of signal propagations. This paper discusses the physical signal transmission property on the broadband power-line channels based on transmission-line theory, mode propagation theory and electromagnetic-field radiation theory. It also examines the carrier signal propagating through the multi-path line channel by empirical data. The correlations among the channel attenuation and frequency, length of the path, loads and branches are analyzed, respectively, and the path loss is calculated based on empirical data and linear regressive analysis. In the end, the impact of the radiation from carrier signals on the channel characteristic measurement is concluded. Index Terms--Power-line communication, signal propagation, transmission properties.