Industrial Power Distribution Systems Research Articles

The Application and Analysis on Iterative Earthing in TN-S System

Iterative earthing is a important measure in low-voltage distribution system, and necessary in industrial power distribution system or civil power supply system. This paper introduces the definition, effects and specific technical requirements of iterative earthing, and illustrates its significance through the analysis on iterative earthing of TN-S system.

Α Reliability Study of Renewable Energy Resources and their Integration with Utility Grids

Reliability analysis is considered an impressive approach for investigating the planning and design processes of industrial and commercial electrical power distribution systems. Reliability analysis is mainly concerned with the analysis of devices and systems whose individual components are prone to failure risk. The demand for renewable energy resources that work in parallel or replace traditional energy resources is significantly increasing. The current research presents the reliability analysis of the IEEE 40-bus system integrated with large-scale PV and wind systems. Reliability parameters evaluation of power distribution systems will be performed using the zone branch methodology to divide the power system layout into several sections (protected zones). The compensating capacitors will be addressed to clarify their impacts on the system reliability indices. The 40-bus system, known as the IEEE Standard 493-1997, integrated with large-scale PV and wind is simulated using ETAP software. The simulation results reveal that the integration of renewable energy resources with the utility grids can improve the reliability indices. These simulation results are consistent with similar works found in literature and some standards in the field of reliability analysis. The integration of power distribution systems with renewable energy resources improves the reliability indices of the distribution grids.

Power factor correction in power delivery systems with mutipulse nonlinear loads

THE PURPOSE. Мutipulse rectifiers are widely used as a nonlinear loads in industrial distribution systems. The advantage of mutipulse rectifiers is low harmonic emission and high power factor. However input currents of mutipulse rectifiers have a wide spectrum including characteristic and noncharacteristic harmonics. This has a negative impact on the power quality. Shunt capacitors are the simplest form of reactive power compensation in industrial power distribution systems. However power systems with nonlinear loads suffer from severe harmonic distortion due to the parallel resonance between capacitors and system inductance. Special compensating devices for reactive power compensation and correction of power system frequency response for resonances damping are necessary. METHODS. In this paper shunt compensating devices for power delivery systems with multipulse nonlinear loads are considered. Proposed devices are composed of 3-5 order parallel connected passive broadband filters. They provide power factor correction, voltage and current harmonics mitigation and resonance modes damping. A general broadband filter design procedure based on frequency and reactive power scaling of normalized filter parameters is developed. RESULTS. Characteristics of different compensating devices configurations using broadband passive filters are discussed. It is shown that broadband filtering devices enable compensation of fundamental frequency reactive power as well as mitigation of voltage harmonic level to values determined by Russian and international standards. Proposed devices have lower fundamental power losses in c omparing with known solutions. CONCLUSION. Proposed analytical design method is applicable to broadband filters of different orders.

Practical Challenges of Inverse and Definite-Time Overcurrent Protection Coordination in Modern Industrial and Commercial Power Distribution System

The characteristics of an overcurrent relay (OCR) in protection coordination are determined by adjusting the current and time delay function. This characteristic is adjusted once, fixed, and expected to overcome any disturbances in the system, which raises the risk of incorrect operation of the protection system, such as an overlapping trip or the incapability to limit the current exposure in the protected equipment. This article summarizes different efforts to overcome the modern challenges of overcurrent protection coordination (OCPC) in low or medium voltage industrial and commercial distribution systems. A brief background is introduced from a general perspective and then specifically describes in detail the problem of equipment coordination with a thorough link among mathematical concepts and fundamentals in practice. The operation challenges and ideas to avoid incorrect performance, under normal operation, are discussed. Finally, the article proposes a new optimization method based on the combination of the firefly algorithm and target remedy to overcome such challenges. The optimization considers the combination of inverse-time (ANSI 51) and definite-time (ANSI 50) function in OCR. The method is described and validated in the IEEE 242.2001 to meet the existing regulation of protection coordination. By assessing the critical cases, this article is expected to enhance the OCPC under different fault scenarios with complex coordination of time-current curves.

Review of Solid State Transfer Switch on Requirements, Standards, Topologies, Control, and Switching Mechanisms: Issues and Challenges

Large-scale industrial loads, sensitive loads, and electrical power distribution systems suffer from power quality issues such as voltage interruptions, flickering, and sags which can cause a significant financial loss. The semiconductor based solid-state transfer switch (SSTS) can utilize the dual power feeders to protect the loads against these power disturbance issues. Conventional SSTS often requires more than quarter cycles to complete the transfer process because of load dependent commutation. Numerous researchers proposed the improved SSTS with impulse commutated circuit, which can reduce the transfer time and provide better ride-through capability against voltage sags. However, the SSTS specification depends on the application types and design procedure. Recently, hybrid SSTS has been introduced by the researchers to overcome all these issues. It has been investigated that not much papers are available in literature so far to aggregate all these issues. Therefore, towards the novel contribution of research, this review critically described the requirements, standards, and specifications of SSTS; control and switching mechanisms; and application of SSTS as single or hybrid topology, to give a comprehensive idea to the future researchers about the design of SSTS for a specific application. This paper also contributes to analyzing the key issues related to the SSTS applications, which can provide an easy control strategy and reduce the transfer time significantly. Overall, this research will strengthen the efforts of the researchers and industrialists to select, develop, and design the appropriate SSTS for a particular application.

Active Reduction of Short-Circuit Current in Power Distribution Systems

In this paper, a new concept of short-circuit current (SCC) reduction for power distribution systems is presented and analyzed. Conventional fault current limiters (FCLs) are connected in series with a circuit breaker (CB) that is required to limit the short-circuit current. Instead, the proposed scheme consisted of the parallel connection of a current-controlled power converter to the same bus intended to reduce the amplitude of the short-circuit current. This power converter was controlled to absorb a percentage of the short-circuit current from the bus to reduce the amplitude of the short-circuit current. The proposed active short-circuit current reduction scheme was implemented with a cascaded H-bridge power converter and tested by simulation in a 13.2 kV industrial power distribution system for three-phase faults, showing the effectiveness of the short-circuit current attenuation in reducing the maximum current requirement in all circuit breakers connected to the same bus. The paper also presents the design characteristics of the power converter and its associated control scheme.

Voltage support in industrial distribution systems in presence of induction generator-based wind turbines and large motors

Industrial loads are usually composed of large induction motors (IM). These motors present a critical behavior under some circumstances, e.g. during starting and faults in the system. Currently, induction generator-based wind turbines are also connected to distribution systems. Essentially, these generators present the same behavior of large IM and, when directly connected to the system, their interaction can increase voltage sag levels or even lead the system to a voltage collapse. These generators, however, are usually provided with specific controls or power electronic-based equipment to comply with the voltage ride-through capability required by the grid codes. These resources, however, can be used to minimize the impact of large motors in the grid or even minimize their impact on voltage sags caused by faults in the system. In this context, this paper has the objective of analyzing the impact of different technologies used in induction generator-based wind turbines during disturbances in distribution systems in the presence of large IM. The analysis aims to clarify the potential benefit of wind turbine allocation at the demand side of an industrial power distribution system. Based on the results, an adapted control scheme, considering the control strategies currently available, is proposed for the grid side converter of the doubly fed induction generators to improve power quality.

The Impact of Distributed Generators Placements on the Reliability of Typical Industrial Power Distribution System

Electrical Distribution systems that are radially configured with one utility power source are inherently exposed to higher rates of outages and interruptions, due to failures of system components, including: transformers, breakers and switching devices. In addition, fault conditions can also be caused by weather, animals or human error. Historically in Saudi Arabia, many industrial and residential distribution networks suffered from these problems. Large-size, growing demand and cost — with the time requirements for enhancement projects — results in distributed generation (DG) — as online or backup —playing a key role in the residential, commercial and industrial sectors of the power system. In this paper, the value of DG — installed as an online power source for typical industrial distribution network in Saudi Arabia — is quantified by reliability indices that include System Average Interruption Duration Index (SAIDI), Customer Average Interruption Duration Index (CAIDI) and Energy Not Supplied (ENS). The study outcomes will provide power system engineers with the reliability benefits of DG penetration and an approach to assessing its installations, based on different factors such as size and location.

Development of an improved H-bridge cascaded static synchronous compensator in power system.

This paper presents a new configuration of H-bridge cascaded static synchronous compensator (STATCOM) based on auto disturbance rejection control and modulation wave shifting control intended for installation in industrial and utility power distribution systems. It proposes an improved controller that devotes itself not only to satisfying the requirement of dynamic reactive power compensation but also to achieving the balance of DC capacitor voltage. The new configuration is prominent in having no restriction on the number of power module. Simulation results show the proposed controller exhibits better performance in terms of response time and transient stability compared with the proportion integration controller. Two actual H-bridge cascaded STATCOMs are constructed at 10 kV, 2 MVA and 380 V, 6.5 kVA, respectively, and a series of verifications test are executed in 380 V, 6.5 kVA STATCOM experimental system. The experiment results further prove that H-bridge cascaded STATCOM with the proposed controller has excellent dynamic performance and strong robustness.

A %THD analysis of industrial power distribution systems with active power filter-case studies

Increasing use of variable speed drives in industry causes harmonic proliferation in industrial power distribution supply system. Harmonic currents generated by the variable speed drives interact with power system impedance to give rise to harmonic voltage distortion. Thus it is essential to analyze, evaluate and introduce appropriate mitigation techniques for harmonic reduction in the power system networks. In this paper, %THD harmonic load flow analysis for different industrial power system networks in the presence of harmonic loads has been carried out using DIgSILENT software. From the %THD harmonic profile of different feeders and buses of the power distribution system, it is observed that there is more %THD present at certain feeders and buses where nonlinear loads are connected. In order to reduce the %THD within the allowable limits as per IEEE standards, both passive and active filters are designed and installed in the power system networks. Simulation results are presented to validate the proposed scheme. From the results, it is observed that the reduction of %THD is more in power system networks at various buses and feeders with active power filter compared to passive filter.

Three Phase Multicarrier PWM Switched Cascaded Multilevel Inverter as Voltage Sag Compensator

This paper presents a cascaded H–bridge multilevel inverter based series active filter intended for installation on industrial and utility power distribution systems. The control strategy based on Synchronous Reference Frame theory is designed so that the voltage injected by active filter is able to mitigate the voltage sag, imbalance in the source voltage and reduce the harmonic content. The active power filter which can be used under the condition of voltage sag and unbalanced or distorted source voltages can compensate the harmonics, reactive and negative sequence currents.Simulations have been carried out on MATLAB/Simulink platform with various types of loads. The analysis and simulation results under unbalanced load and dynamic loading are presented in this paper.

Power Quality Enhancement using Shunt Active Power Filter Based on Particle Swarm Optimization

This work deals with the design, analysis and simulation of shunt active power filter SAPF, which compensate harmonic currents, and reactive power under balanced supply network. An optimal control theory for currents compensation based on particle swarm optimization is developed in this paper. The SAPF is connected in parallel with a nonlinear load which has caused current harmonics in industrial power plants and utility power distribution systems. The proposed optimal PI current controller using particle swarm algorithm determines the switching signals of the SAPF, and the algorithm based on instantaneous power (pq) theory has been used to determine the suitable current reference signals. The simulation results show that the new control method using PSO approach is not only easy to be implanted, but also very effective in reducing the unwanted harmonics and compensating reactive power. The studies carried out have been accomplished using the MATLAB Simulink Power System Toolbox.

Applying High-Resistance Neutral Grounding in Medium-Voltage Systems

The application of high-resistance neutral grounding (HRNG) to medium-voltage (MV) distribution systems is one of the least understood and often misapplied methods of system neutral grounding. An HRNG grounded system is the only intentionally grounded neutral grounding method suitable for industrial systems that allows normal operation (no voltage dips, no power surges, no shutdowns, and minimal damage) for an indefinite time period after the inception of the most common of all faults, i.e., the single-line-to-ground fault. The complexity of applying an HRNG system is due to lesser understood factors, such as the relationship between system charging current, neutral grounding resistor let-through current, and point-of-fault ground-fault current; point-of-fault arcing voltage magnitudes; escalating arcing fault phenomena; and point-of-fault energy levels, all of which are not easily determined nor easily estimated. This paper addresses the application of HRNG neutral grounding systems on MV industrial ac power distribution systems. The seemingly perfect HRNG grounding system, with ground-fault-current magnitudes often limited to 10 A or less, has a limited window of application on MV systems, such that when misapplied may actually place the electrical system backbone components at risk, as well as trip the system offline due to escalating arcing faults resulting in phase-to-phase faults. HRNG applications in MV generator protection and MV arc flash mitigation are not within the scope of this paper.

Harmonic Analysis of Reactor and Capacitor in Single-tuned Harmonic Filter Application

Industrial power distribution system includes many kinds of non-linear loads, which produce the harmonics during energy conversion transition. The single-tuned passive filter is widely used to absorb the harmonics and attenuate its undesirable effect in the distribution system. However, the passive filter might be severely stressed, and sometimes even damaged, due to the absorption of harmonics. There is voltage rise on the capacitor when the single-turned harmonic filter is applied. When the capacitor voltage rose above the allowable limit, the expected life of the capacitor will considerably deteriorate. On the other hand, the reactor can experience the spike voltage even if the voltage and current of the capacitor are within the allowable limit, and this accumulated voltage stress of the reactor causes its premature fault. In this paper, we analyzed and compared the harmonic voltage and current of the reactor and capacitor in a single-tuned harmonic filter through the EMTP software and verified them with the experimental results.

An Adaptive Multiagent Approach to Protection Relay Coordination With Distributed Generators in Industrial Power Distribution System

This paper presents new explorations into the use of agent technology applied to protection coordination of power systems. The impact of distributed generators on protection coordination is firstly discussed. Then a coordination multi-agent system is proposed with the functions of the agents described. In the proposed system, communication plays an important role to provide more information for the relay coordination besides the relay settings. Communication simulation has been carried out on the Java agent development framework (JADE) platform. The information communication process shows that adaptive coordination can be achieved.

A New Mathematic Algorithm to Analyze Power Distribution Systems With Active Compensation and Nonlinear Loads

This paper presents a new procedure to analyze power distribution systems that energize nonlinear loads. The algorithm uses the singular values of the transfer matrix that relates the output variables and the system perturbation. The algorithm is especially developed to analyze the compensation performance of shunt and series active power filters. The algorithm is proved by simulation in a multibus industrial power distribution system and programmed in Matlab.

Expanding an Industrial Load Model for Short-Term Voltage Stability Analysis

The present work proposes an extended model representing part of a huge aluminum industry load for short-term voltage stability investigations in time domain. The efforts were concentrated in the expansion of the industrial power distribution system model including explicit representation of the main transformers, capacitors, feeders and induction motors. The extended model is validated through a comparison between computer simulation results and the industry/power system utility recordings. A real sequence of events which took place in the Brazilian North Power System in the year of 2002 causing a complete industry breakdown (loss of bulk supply) was considered here for this purpose.

Control and Performance of a Transformerless Cascade PWM STATCOM With Star Configuration

This paper presents a three-phase transformerless cascade pulsewidth-modulation (PWM) static synchronous compensator (STATCOM) intended for installation on industrial and utility power distribution systems. It proposes a control algorithm that devotes itself not only to meeting the demand of reactive power but also to voltage balancing of multiple galvanically isolated and floating dc capacitors. The control algorithm based on a phase-shifted carrier modulation strategy is prominent in having no restriction on the cascade number. Experimental waveforms verify that a 200-V 10-kVA cascade PWM STATCOM with star configuration has the capability of inductive to capacitive (or capacitive to inductive) operation at the rated reactive power of 10 kVA within 20 ms while keeping the nine dc mean voltages controlled and balanced even during the transient state.

Reactive-Power Compensation for Voltage Control at Resistance Welders

Resistance welders are a source of voltage fluctuations and flicker in industrial power distribution systems. The high-reactance welding transformer that limits the welding current creates a low-power-factor (pf) load. With hundreds of welders, factories may use synchronized welding cycles that lead to annoying flicker. Other facilities use random timing to prevent flicker, but suffer deep voltage sags due to simultaneous welding operations. Severe voltage variations reduce the power delivered to the welders, causing reduced heating and poor-quality welding joints. The paper examines the design and application of a mini-static var compensator (SVC) to improve the voltage quality on the welding circuits of industrial power distribution systems. The compact range of reactive-power demands for robotic welders suggest the use of thyristor-switched capacitors (TSCs). The compensation provides the necessary voltage control for consistent welds with the added benefit of reduced load currents throughout the industrial distribution system. The compensator control is coupled with the welder controls to mitigate the random reactive-power mismatches that are often seen with other SVC welding and arc-furnace applications.

Directional ground-fault indicator for high-resistance grounded systems

Locating ground faults is a difficult and challenging problem for low-voltage power systems that are ungrounded or have high-impedance grounding. Recent work in pilot signals has renewed efforts in developing fault location methodologies. This paper presents a method for directional ground-fault indication that utilizes the fundamental frequency voltages and currents. Although the ground-fault current is small and usually less than the load currents, the fault has zero-sequence components that distinguish it from the load. Signal processing techniques are used to identify and compare the fault signals to determine the fault direction. The process takes advantage of the currents flowing from the distributed grounding capacitance. An experimental microprocessor-based directional indicator unit is tested in an industrial power distribution system. Directional indication of ground faults is applied near tap-off branch circuit connections. Promising results from field test conducted in a harmonic-noisy setting are presented. Directional indicator units simplify the search process on large networks, thus reducing the time and effort necessary to locate and remove the fault, and thereby significantly reduces the probability of a second ground fault with its destructive currents.