Voltage Power Lines Research Articles

Reduction of the Low Voltage Substation Constraints by Inserting Photovoltaic Systems in Underserved Areas

Background: The improvement of the voltage in power lines and the respect of the low voltage distribution transformer substations constraints (Transformer utilization rate and Voltage drop) are possible by several means: reinforcement of conductor sections, installation of new MV / LV substations (Medium Voltage (MV), Low Voltage (LV)), etc. Methods: Connection of mini-photovoltaic systems (PV) to the network, or to consumers in underserved areas, is a well-adopted solution to solve the problem of voltage drop and lighten the substation transformer, and at the same time provide clean electrical energy. PV systems can therefore contribute to this solution since they produce energy at the deficit site. Results: This paper presents the improvement of transformer substation constraints, supplying an end of low voltage electrical line, by inserting photovoltaic systems at underserved subscribers. Conclusion: This study is applied to a typical load pattern, specified to the consumers region.

Study of Wireless Sensor Network

A wireless sensor network is a group of specialized transducers with a communications infrastructure for monitoring and recording conditions at diverse locations. Commonly monitored parameters are temperature, humidity, pressure, wind direction and speed, illumination intensity, vibration intensity, sound intensity, power-line voltage, chemical concentrations, pollutant levels and vital body functions. A sensor network consists of multiple detection stations called sensor nodes, each of which is small, lightweight and portable. Every sensor node is equipped with a transducer, microcomputer, transceiver and power source. The transducer generates electrical signals based on sensed physical effects and phenomena. The microcomputer processes and stores the sensor output. The transceiver receives commands from a central computer and transmits data to that computer. The power for each sensor node is derived from a battery. Currently, WSN (Wireless Sensor Network) is the most standard services employed in commercial and industrial applications, because of its technical development in a processor, communication, and low-power usage of embedded computing devices. The WSN is built with nodes that are used to observe the surroundings like temperature, humidity, pressure, position, vibration, sound etc. These nodes can be used in various real-time applications to perform various tasks like smart detecting, a discovery of neighbor node, data processing and storage, data collection, target tracking, monitor and controlling, synchronization, node localization, and effective routing between the base station and nodes. This paper describes the concept of wireless sensor network.

Frequency Characteristics of Overhead Power Lines of Distribution Power Grids with Isolated Neutral and Their Using for Determination of Single-Phase Ground Faults

This paper show research of the dependence of the spectral composition of current and voltage depending on the place of occurrence single-phase intermittent arcing fault on overhead power lines in electrical grids with complex topology. Theoretical bases are considered of displays of higher harmonic components of voltage and current and method of their selection RSCAD. Paper show the effectiveness of pre-suppression in the information signal of the main harmonic of current (voltage) which allows with the required sensitivity to allocate a spectrum of higher harmonics in the area of up to ten kilohertz and above. This fact gives access for using high order resonant harmonics which practically do not depend on the load of substations, but are directly related to the distance to the place of single-phase ground fault. The results of field experiments are presented on modeling different variants of single-phase arc faults including when with a tree faults in existing electrical grids. It is shown that the resonant harmonics of current and voltage in overhead power lines arising from single-phase ground faults are a reliable indicator of the fact of the fault mode and a marker of the location of single-phase ground fault from the power center buses.

Analysis of influence of measuring voltage transformer ratio error on single-circuit overhead power line electric field calculation results

The paper is related to an important topic of human exposure to power frequency electric fields in the vicinity of overhead power lines. Assessment of human exposure can be based on measurements and/or calculations, while the combination of these two methods provides the most reliable results. Both measurement and calculation results have their respective uncertainties, which should be calculated as accurately as possible. Regarding calculations, both the uncertainty of calculation model and uncertainty of the input data influence the total calculation uncertainty. Power line voltage significantly influences the levels of electric field in its vicinity. Therefore, in this paper, the influence of voltage measurement error on electric field calculation results is analyzed. This error originates from ratio error of voltage measuring transformers. The influence of ratio error of measuring transformers on electric field calculation results is quantified for typical overhead power line voltage levels and geometries pertaining to transmission systems.

Suppressing <inline-formula> <tex-math notation="LaTeX">${V_{\mathrm{TH}}}$ </tex-math> </inline-formula> Variations in LTPS Thin-Film Transistors With Current Scaling Ratio Modulation for AMOLED Display

This brief suppresses threshold voltage ( ${V}_{\text {TH}}$ ) variations in low-temperature polycrystalline-silicon thin-film transistors (LTPS TFTs) with a new current scaling ratio modulation method for the application of active-matrix organic light-emitting diode displays. With a newly proposed 3T2C LTPS TFT-based pixel circuit, high-current scaling ratios at low gray levels and low ratios at high gray levels are achieved. Thus, the programming time at low gray levels can be reduced, and the driving currents of the OLED are efficiently generated over the entire data range without consuming extra power for the current source. The driving currents are also independent of the threshold voltage of the driving TFT and the power line voltage, guaranteeing the uniformity of the current. Simulation results demonstrate that the relative current error rates are below 3.7% as the threshold voltage varies ±0.5 V and below 5.3% as the threshold voltage varies ±0.5 V and the power line voltage drops by 1 V; the programming time can be as short as only $12~\mu \text{s}$ .

Noncontact AC Voltage Measurements: Error and Noise Analysis

A capacitive noncontact ac voltage measurement technique and its feasibility to measure arbitrary waveform signals are analyzed. The method provides self-calibration of the scale factor, an important feature considering the high variability that coupling capacitances present. The analysis of several errors related to the technique is performed, showing the impact of different design parameters on the final accuracy. Scaling errors due to the electronic circuit can be constrained to less than 0.5%, and can be disaffected, whereas those due to the frequency dependence of cable sheath permittivity can be up to 3% for polyvinyl chloride sheathed cables. This error is not controllable by electronic design but requires working on electrode probe. A noise model is also proposed and experimentally validated, showing that signal-to-noise ratios of up to 100 dB are achievable with common components. A functional prototype was built and tested by acquiring power-line voltage and other arbitrary signals without contact. Instantaneous voltage signals were acquired by the proposed technique and contrasted with those acquired directly. For the measurement of power-line voltage and using the self-calibration feature, the instantaneous error was lower than 7 V (2.2%) for a ±1300 V measurement range at 50 Hz. If manual correction is applied, the error can be reduced to 0.28 $\text{V}_{\text {rms}}$ (0.12%).

Autonomous Calibration of Non-Contact Power Monitors

Non-contact power monitors use electromagnetic field sensors to measure voltage and current in multiphase power lines without any ohmic contact or geometric isolation of the conductors. The complex field geometry requires these sensors to be calibrated before use. Existing work has focused on manual calibration procedures requiring a service interruption, additional loads, or other intrusive techniques. This paper introduces an autonomous calibration technique that can be used to bootstrap additional non-contact power monitors from an existing power monitor located elsewhere in the distribution network. This provides the flexibility to “zoom-in” with downstream monitors or “zoom-out” with upstream monitors and efficiently target the loads of interest. Laboratory benchmarks and installations on the U.S. Coast Guard and Naval vessels show that autonomous calibration is accurate and robust with non-contact monitors reading within 1% of commercial power meters.

Natural Timestamps in Powerline Electromagnetic Radiation

The continuous fluctuation of electric network frequency (ENF) presents a fingerprint indicative of time, which we call natural timestamp . This article studies the time accuracy of these natural timestamps obtained from powerline electromagnetic radiation (EMR), which is mainly excited by powerline voltage oscillations at the rate of the ENF. However, since the EMR signal is often weak and noisy, extracting the ENF is challenging, especially on resource-limited sensor platforms. We design an efficient EMR conditioning algorithm and evaluate the time accuracy of EMR natural timestamps on two representative classes of IoT platforms—a high-end single-board computer with a customized EMR antenna and a low-end mote with a normal conductor wire acting as EMR antenna. Extensive measurements at six sites in a city, which are away from each other for up to 24km, show that the high-end and low-end nodes achieve median time errors of about 50ms and 150ms, respectively. To demonstrate the use of the EMR natural timestamps, we discuss three applications: time recovery, runtime clock verification, and secure clock synchronization.

Comprehensive voltage and power factor control strategy for electric spring

Electric spring (ES) along with the smart load (SL) have recently been used as a smart technology for stabilising distribution networks. ESs are embedded on non-critical (NC) loads in order to protect critical loads against voltage fluctuations. Three different generations of ES have been developed in recent years. A comprehensive control scheme is proposed for the third generation of ES, through which the SL power factor and line voltage can be controlled. In order to control the power factor in steady-state condition, the radial-chordal decomposition (RCD) method, which has been previously used for the second generation, is employed in the closed-loop manner. The proposed controller has also the capability to mitigate the voltage fluctuation in over/under voltage condition. Simulation results show the superiority of this method in voltage control over RCD method. In addition, for a bunch of NC loads, the desired power factor will be reached at the point of common coupling.

The Design of Medium Size Voltage Capacitor in order to Improve the Power Factor

This article presents theory of The design of medium sized voltage capacitor in order to improve the Power Factor Value to AC motor. In present, the electrical power system has focus on improving the Power Factor significantly because it is the major key to increase or decrease the applicable expenses. The power system that has low power factor will have a lot of loss to system, especially when electrical voltage is on voltage medium. When power factor has been adjusted, the system can take more loads and electrical power loss is decreased. It also decreases voltage in power line and decreases electrical bills at the same time. This article presents the theory to analyze data from motor that needs to adjust a power factor so that it pass electricity authority standard by considering the efficiency of the motor so that the consumers do not have to pay the penalty of the Power Factor Value differences to the Electricity Authority. Furthermore, it can help decrease the bills of unstandardized electrical power which occurred in the system and enable the system to take more loads at the same time.

Analysis of power system operation at asymmetrical load

The paper presents a mathematical model of a power system (PS) consisting of a generating unit (with a synchronous generator) connected by a high voltage (transmission) power line to a bus. The state and output equations of the generator are expressed in the coordinate system d, q, 0 and with the use of phase quantities of the generator stator, the bus and the power line, which is especially useful in the analysis of asymmetrical states. A disturbance of the steady state in the form of a two-phase short-circuit in the transmission line was taken into account in the made calculations. The influence of the excitation system and angular speed control system of the generator as well as the impact of selected generator model parameters on the waveforms were investigated.

Design and evaluation of computer-based electrical power quality signal generator

Electrical power quality signal generator, capable of reproducing the power quality disturbances in accordance with European standard EN50160, is presented in this paper. Signal generator is divided in two parts: LabVIEW based virtual instrumentation software for defining the disturbance parameters and hardware electronics for signal generation (data acquisition card and power amplifier). The paper focus is on the design of power amplifier for scaling the data acquisition card output voltage level to the nominal power line voltage (230V). The signal generator can be used for generation of reference signals useful for testing the power quality measuring instruments and various algorithms for power quality disturbance detection. In such manner, this PC based signal generator can be used as suitable and cost effective alternative to the instruments for testing the power quality meters and analyzers. According to the relevant document – ISO Guide to the Expression of Uncertainty in Measurement, for detailed metrological assessment of developed signal generator, calculation and presentation of measurement uncertainty budget is performed.

Direct Sequence Spread Spectrum-Based PWM Strategy for Harmonic Reduction and Communication

Switched mode power supplies (SMPSs) are essential components in many applications, and electromagnetic interference is an important consideration in the SMPS design. Spread spectrum-based pulse width modulation (PWM) strategies have been used in SMPS designs to reduce the switching harmonics. This paper proposes a novel method to integrate a communication function into spread spectrum-based PWM strategy without extra hardware costs. Direct sequence spread spectrum (DSSS) and phase shift keying data modulation are employed to the PWM of the SMPS, so that it has reduced switching harmonics and the input and output power line voltage ripples contain data. A data demodulation algorithm has been developed for receivers, and code division multiple access (CDMA) concept is employed as a communication method for a system with multiple SMPSs. The proposed method has been implemented in both Buck and Boost converters. The experimental results validated the proposed DSSS-based PWM strategy for both harmonic reduction and communication.

P-35: New Voltage-Programmed AMOLED Pixel Circuit Employing In-Pixel Compensation Scheme for Mobility Variation

This work proposes a new active-matrix organic light-emitting diode (AMOLED) pixel circuit using an in-pixel mobility compensation technique. Moreover, the circuit can compensate for both power line voltage drop and threshold voltage variation. Thus, it is suited for backplanes utilizing p-type low-temperature polycrystalline-silicon thin-film transistors (LTPS TFTs). Simulated results demonstrate that the compensation functions are succeed at a Full HD (1920×1080) resolution with a 60 Hz frame rate. The current error rates of power line voltage drop and threshold voltage variation are all below 3%, and those of mobility variation are below 6.5%.

Secondary current distortion of inductive current transformer in conditions of dips and interruptions of voltage in the power line

The aim of this paper is to present results explaining the phenomenon of inductive current transformers (CT) additional secondary current distortion in condition of variation of their primary current rms value caused by dips and interruptions of the power line's voltage. To assess its accuracy of current transformation for such transients, harmonics spectrums’ of primary and secondary currents are compared. To ensure repeatability of measurement results with the usage of FFT algorithm, regardless of the beginning of the sampling process, the window of 16 fundamental periods consisting 4 dips/interruptions cycles is used. Additional CT's secondary current distortion caused by repeatable transients results in increased error of indirect measurement of rms values of power line's current higher harmonics and additional inaccuracy of power quality estimation.

Simulation of a Narrowband Power Line Communications System over Medium Voltage

Narrowband Power Line Communications (NB-PLCs) are investigated as an alternative option for transferring low rate smart grid (SG) data via Medium Voltage (MV) power lines. In this framework, two variants of orthogonal frequency division multiplexing are examined, namely Filtered-OFDM (F-OFDM) and Wavelet-OFDM (W-OFDM), in an attempt to determine which of them is capable of transmitting low rate SG data to greater distances over non-branched MV power lines. The reach of NB-PLC signals via MV power lines is estimated, taking into account the transfer function of the relevant PLC channels and noise mechanisms as well as the specific features of the two modulation options under consideration. Simulations show that NB-PLC transmission constitutes a technically feasible and economically affordable option for exchanging low rate data with remote SG nodes dispersed over the MV grid. Moreover, simulations show that F-OFDM allows low rate data transmission to considerably greater distances compared to W-OFDM.

Optimal Placement and Sizing of Distributed Power Sources in Microgrid for Power Loss Minimization Using Bat Motivated Optimization Algorithm

This paper recommends revealing the active power loss minimization by applying Bat Motivated Optimization Algorithm (BMOA). This loss minimization is achieved by optimal placement and sizing of Distributed Power Sources (DPS) in microgrid. The optimal size of DPS is deliberated with limitations such as bus voltage, active & reactive power generation, line flow and nil slack bus injection. DPSs are optimally located by means of the Loss Sensitivity Index (LSI). The suggested optimization technique is tested on 33-bus test system with 7 DPS. The outcomes exhibit the ability and competence of the proposed BMOA technique in evaluation with other optimization approaches.

DSP-Based Approach to Generating Computer Model of Impulse Noise Using Kernel Data Sequence

In this paper, we present a new computer model to simulate the impulse-type noise that appears in bursts on a high- voltage (HV) power line during transient and emergency situations. The computer model is designed for investigations of the effects of impulse noise on communication channels implemented over an HV power line. The simulation process relies on an authentic record of measured noise whose modified replicas we use to compose a train of short-time impulses evenly distributed in time. The recorded noise sequence is referred to as a kernel data sequence over which we apply digital-signal-processing (DSP) techniques to randomize its length and its amplitudes. Noise impulses produced by the simulator achieve and retain the sharp front ends and spectral properties of the original noise. A variable digital filter is implemented to examine the influences of impulse noise on communication channels. Performances of simulated noise have been compared with those of measured noise published in CIGRE, IEEE, and IEC documents. Comparisons demonstrate a good agreement between the characteristics of measured and simulated noise.

Active Power Filtering Using the ZDPC Method under Unbalanced and Distorted Grid Voltage Conditions

In this paper, we propose a new Zero Direct Power Control (ZDPC) technique for active compensation of harmonics and reactive power, using shunt active power filter (SAPF), based on cancellation of instantaneous active and reactive power disturbances by comparison with their zero references. To separate harmonic and fundamental components of the line voltage and current a highly selective filter (HSF) has been used. Depending on the power errors and line voltage vector position, a switching table produces the appropriate control vectors leading to the active and reactive power variation required to reach the zero power references, even under grid voltage unbalanced and distorted conditions. The experimental validation of the proposed ZDPC has been performed. The results are compared to other recent techniques to demonstrate the superiority and feasibility of the proposed strategy.

PLC-Based Street Lighting Energy-Saving Equipment and its Remote Monitoring System

PLC (programmable logic controller)-based street lighting energy-saving and remote monitoring system is designed to improve energy-saving technology and management level. The designed illumination economizer contains PLC-based controller unit and compensating transformer unit, which can realize closed-loop voltage control at the stage of voltage stabilization, and reduce the negative influence of power line voltage fluctuation upon lamp service life and visual luminance. On the basis of the illumination economizer, a GPRS-based street light remote monitoring and control system is designed with configuration software. The whole system has been operating reliably in Harbin, China for many years with an over 50% energy-saving rate, decreasing the illumination management cost and promoting the intelligent management level.