Feeder Circuit Research Articles

A Research Concerning a Distributed Automation Scheme for 10kV Aerial Wire with Grounding Protection

This paper puts forward a distributed automation scheme with grounding protection for 10kV aerial wire, which is based on the outgoing line and feeder circuit breaker in substation, the intelligent column circuit breaker and the intelligent load switch. Though the outgoing line and feeder circuit breaker in substation, the intelligent column circuit breaker and the load switch cooperating with each other, Which could isolate and exclude the aerial wire transient fault automatically, and isolate the permanent fault immediately. Practical application results show that the application of the scheme have reduced the hours of power failure, reduced maintenance time and improved the stability of the system.

Distribution Fault-Locating Algorithms Using Current Only

Traditional impedance-based fault-locating methods implemented in modern overcurrent protection relays require voltage and current measurements to provide reasonable fault-location estimates. Although they capture voltage and current, depending on field condition or due to equipment failure, relays may record current measurements only. Voltage measurements are thus missing or unavailable. The objective of this paper is to develop practical impedance-based fault-locating algorithms with current data (magnitude or phasors) as the only input and demonstrate the efficacy of the algorithms with simulated and actual field data. These algorithms use the circuit model of the distribution feeder and Kirchhoff's circuit laws in estimating the fault voltage at the relay location and then use impedance-based methods for fault location. Based on the analysis conducted on actual fault data, error in estimation is generally less than 0.5 mi from the actual location of the fault.

Analyzing the Impacts of Wind Generator on the Optimal Coordination of Overcurrent Relays

Wind generator and distribution systems after interconnection would change the short circuit fault characteristics of the original system and may lead to protection relay malfunctions, and review of the protection coordination. It is necessary to research the impact of existing protection strategies for distribution systems after wind generator interconnection. Linear programming methods were adopted for this study to review the coordination problems among feeder circuit breaker, lateral circuit breaker, and power fuse after radial distribution systems and wind generator interconnections.

Optimal Coordination of Automatic Line Switches for Distribution Systems

For the Taiwan Power Company (Taipower), the margins of coordination times between the lateral circuit breakers (LCB) of underground 4-way automatic line switches and the protection equipment of high voltage customers are often too small. This could lead to sympathy tripping by the feeder circuit breaker (FCB) of the distribution feeder and create difficulties in protection coordination between upstream and downstream protection equipment, identification of faults, and restoration operations. In order to solve the problem, it is necessary to reexamine the protection coordination between LCBs and high voltage customers’ protection equipment, and between LCBs and FCBs, in order to bring forth new proposals for settings and operations. This paper applies linear programming to optimize the protection coordination of protection devices, and proposes new time current curves (TCCs) for the overcurrent (CO) and low-energy overcurrent (LCO) relays used in normally open distribution systems by performing simulations in the Electrical Transient Analyzer Program (ETAP) environment. The simulation results show that the new TCCs solve the coordination problems among high voltage customer, lateral, feeder, bus-interconnection, and distribution transformer. The new proposals also satisfy the requirements of Taipower on protection coordination of the distribution feeder automation system (DFAS). Finally, the authors believe that the system configuration, operation experience, and relevant criteria mentioned in this paper may serve as valuable references for other companies or utilities when building DFAS of their own.

Excitation Method of Linear-Motor-Type Rail Brake without Using Power Sources by Dynamic Braking with Zero Electrical Output

The eddy current rail brake is a type of braking system used in railway vehicles. Because of problems such as rail heating and problems associated with ensuring that power is supplied when the feeder malfunctions, this braking system has not been used for practical applications in Japan. Therefore, we proposed the use of linear induction motor (LIM) technology in eddy current rail brake systems. The LIM rail brake driven by dynamic braking can reduce rail heating and generate the energy required for self-excitation. In this paper, we present an excitation system and control method for the LIM rail brake driven by “dynamic braking with zero electrical output”. The proposed system is based on the concept that the LIM rail brake can be energized without using excitation power sources such as a feeder circuit and that high reliability can be realized by providing an independent excitation system. We have studied this system and conducted verification tests using a prototype LIM rail brake on a roller rig. The results show that the system performance is adequate for commercializing the proposed system, in which the LIM rail brake is driven without using any excitation power source.

The Three-Phase Ground-Fault Circuit-Interrupter System—A Novel Approach to Prevent Electrocution

There are many electrocutions that occur on three-phase 480- and 600-V systems, particularly 277- or 347-V lighting branch circuits. Ground-fault circuit interrupters (GFCIs) have saved many lives on 120- and 120-240-V single-phase systems since being introduced to the National Electrical Code (NEC) in 1971. Application of GFCIs at voltages higher than 120 V has not progressed because the higher voltages-to-ground result in higher capacitive charging current of branch and feeder circuits, which in turn leads to “nuisance trips.” This paper first describes the mechanism of electrical shock, let-go threshold current, and heart ventricular fibrillation. It then describes the three-phase GFCI System (GFCIS-3Ph) that overcomes nuisance tripping by a novel approach to sensing and tripping logic. The system is most applicable for lighting branch circuits due to the historical risk of these circuits, but the GFCIS-3Ph is also appropriate to be considered as an option for all three-phase branch or feeder circuits. Application of the GFCIS-3Ph technology has the potential to almost eliminate electrocution for persons who make direct contact between an energized phase conductor and ground on three-phase systems rated below 1000 V phase-to-phase.

Estimation and management of magnetic flux density produced by underground cables in multiple‐circuit feeders

AbstractThe purpose of this paper is to estimate and reduce the magnetic flux density of multiple‐circuit underground cable feeders with randomly varying loads. The load in each phase of feeder circuits is assumed to be normally distributed. The probability distribution function of maximum magnetic flux density above the underground cable feeders is determined by using statistical approach. The optimal‐phase arrangement of feeder circuits with minimum magnetic flux density is also explored by using the genetic algorithms (GA). Copyright © 2010 John Wiley & Sons, Ltd.

Advanced feeder automation is here

Distributed intelligence, as applied to distribution feeder circuits, makes it possible to consider application of automation to solve tactical problems, such as the large retailer that requires better-than-available power reliability, is presented in this paper. The utility planner can use this new technology to not only address such tactical problems but to eliminate or reduce the need for costly system upgrades, thus providing optimal asset management. Many companies have made good use of advanced feeder automation to gain a strategic leverage in serving their customers and meeting increasingly difficult expectations on the part of the users of electric power.

Power Flow Analysis on Simplified Feeder Modeling

Three novel models to simplify distribution network analysis are presented including equivalent load model (ELM), equivalent load density model (ELDM), and discrete equivalent load density model (DELDM). The voltages and the power on/through both ends of a feeder are used to describe the load and its distribution pattern within the feeder line. Only real time field data from feeder circuit breakers in substations and sectionalizing switches along the feeder lines are needed to obtain a satisfied analysis result. The loads on the feeder are represented by one load in ELM. Six fundamental load distribution patterns are put forward in ELDM. By solving the voltage drop function and the power loss function of the feeder line, characteristic values together with the corresponding similarity parameters for the six load distribution patterns are obtained, respectively. Weighting values for the six load distribution patterns are calculated, respectively. Consequently, voltage drop and line loss can be acquired without needing the data from each distribution transformer on the feeder line. Based on above method, a discrete equivalent load density model is advanced to improve the property. Examples are also given with comparison with other approaches showing the feasibility of the proposed methods.

Arc flash calculations in systems protected by low-voltage circuit breakers

A series of previous papers has provided information regarding the arc flash hazard and methods of calculating its potential impact on persons working on or near the equipment. This paper extends that base of information by focusing on the arcing current level and duration in low-voltage circuits protected by circuit breakers (CBs). It describes a method of calculating incident energy and the flash protection boundary due to arcing occurrences in equipment protected by CBs. This method provides convenient procedures for determining these values for generic situations in which some details of the CB are not known. Further, it provides a process for determining these values in typical feeder and branch circuit applications involving common transformers and cable sizes and lengths. The values are needed to determine safe work practices and appropriate Personal Protective Equipment to comply with NFPA 70E, Standard for Electrical Safety Requirements for Employee Workplaces.

Composite reliability evaluation model for different types of distribution systems

The paper develops a set of composite distribution system reliability evaluation models that can be applied to a nonradial type system. The developed models reflect the effect of distribution substations, primary distribution systems, and the interaction between them. First, reliability assessments for five configurations of distribution substation are performed using minimal cut-set technique. Next, the interaction between distribution substation and primary distribution system is modeled according to the tripping behavior of feeder circuit breakers. Last, the contribution of reliability indices evaluated from the primary distribution system is added to the previous two effects, and then the composite load point reliability evaluation models are developed. The developed models are demonstrated on five types of distribution system modified from a reliability test system. Comparisons of reliability indices are made and discussed.

Application of evolutionary algorithms for the planning of urban distribution networks of medium voltage

Currently, an important issue in power distribution is the need to optimize medium voltage (MV) networks serving urban areas. This paper shows how an evolutionary algorithm can be used as the basis for the type of efficient algorithm such optimization demands. The search for optimal network solution will be restricted to a graph defined from the urban map, so each graph branch represents a trench. The solution space (networks) is assumed with "loop feeder circuits": networks with two electrical paths from the high voltage/medium voltage (HV/MV) substations to the customers. In the optimization process, the investment and loss load costs are considered taking into account the constraints of conductor capacities and voltage drop. The investment costs will take into account that some cables can be lying in the same trench. The process was applied for a Spanish city of 200,000 inhabitants.

Application of Evolutionary Algorithms for the Planning of Urban Distribution Networks of Medium Voltage

An important issue in power distribution nowadays is the need to optimize medium-voltage networks serving urban areas. This paper shows how an evolutionary algorithm can be used as the basis for the type of efficient algorithm such optimization demands. The search for an optimal network solution will be restricted to a graph defined from the urban map, so each graph branch represents a trench. The solution space (networks) is assumed with "loop feeder circuits": networks with two electrical paths from the hv/mv substations to the customers. In the optimization process, the investment and loss load costs are considered taking into account the constraints of conductor capacities and voltage drop. The investment costs will take into account that some cables can be lying in the same trench. The process was applied for a Spanish city of 200,000 inhabitants.

Decreasing momentary outages with specific distribution feeder improvements

This paper presents a cost-effective method of reducing momentary interruptions. Two main concepts are discussed. The first is targeting selected zones with increased maintenance to improve overall reliability of the entire feeder, and the second is overcurrent coordination for trip saving on the substation feeder circuit breaker. Trip saving is the intentional coordination of tap fuses off main feeders so that a fault on the tap will not cause a fast operation of the main breaker. Other topics discussed are the resetting of instantaneous tripping of the substation breaker, use of tap reclosers, and increasing lightning/animal protection on key parts of the feeder.

McGraw-Hill's handbook of electrical construction calculations

Procedures: basic calculations wiring methods branch circuits feeders services transformer circuits voltage drop lighting motor circuits electric heating sample calculations sizing branch-circuit conductors branch-circuit calculations makeup of feeder circuit feeder sizing neutral size in 3-phase feeders sizing parallel feeder sizing components for 3-wire, single-phase circuits currents in 3-phase circuits calculating branch-circuit and feeder components selecting feeder protection sizing grounding and bonding conductors underground service calculations size of nipples conduit fill for mixed wire sizes calculating size of pull-boxes number of wires in wireway protecting 2-wire transformer circuit transformer secondary feeder a typical transformer circuit a puzzler on wireway fill range circuits motor circuit calculations circuit for a wounded-rotor motor calculations for a motor feeder protecting motor starter coil circuit protecting contactor oil circuit.

Value-based distribution system reliability planning

Society is becoming increasingly dependent on a cost-effective reliable electric power supply. Unreliable electric power supplies can be extremely costly to electric utilities and their customers. Predictive reliability assessment combines historical outage data and mathematical models to estimate the performance of specific network and system configurations [e.g., IEEE Std. 493-1990]. This paper is concerned with the value-based assessment of proposed modifications to an existing industrial distribution system configuration to minimize the costs of interruptions to both the utility and its industrial customers. This paper presents a series of case studies of an actual industrial load area supplied by two feeder circuits originating from two alternate substations. Each case study reveals the impact on the cost of industrial load point interruptions and the frequency and duration of industrial load point interruptions when various system constraints (e.g., ideal and nonideal protection coordination schemes, substation capacity restrictions, etc.) are imposed on the distribution system. The paper discusses in some detail the variance in reliability performance indexes and their impact on the cost of load point interruptions. A basic conclusion of this paper is that expansion plans of an industrial distribution system can be optimized in terms of reliability by using an economic criterion in which the sum of both the industrial facility interruptions and the utility system costs are minimized.

Protective relay application for generators and transformer

Application of overcurrent protective devices for generators and transformers is considered to be a routine task. However, a review of the protective device selection, device settings, and protection requirements for generators and transformers, as well as their connected buses, has revealed that certain lessons can be learned in examining a few typical applications. The applications are presented in a series of case studies. The case studies are in the following categories of protection problems: (1) generator backup protection: (a) bus-connected generators with feeder circuits at generator voltage; (b) unit-connected generators with voltage restraint time-overcurrent relays (device 51V) for backup protection; (c) unit-connected generators with distance relays (device 21) for backup protection; and (2) transformer protection with high 3-phase fault currents and low-ratio current transformers: (a) original protection scheme; (b) upgraded protection scheme. Only phase-fault conditions are analysed in the following problems because the topic of ground fault protection would require an equal amount of time to discuss. Each case is presented with: (1) a brief synopsis of the problem encountered; (2) the evaluation of the problem, including the suggested solutions; and (3) the "lesson to be learned" and the trouble spots to avoid.

Mitigation of circuit breaker transient recovery voltages associated with current limiting reactors

BC Hydro and Hydro-Quebec utilize current limiting reactors on medium voltage distribution feeders to limit the magnitude of fault current. The reactors make a significant contribution to the severity of the transient recovery voltage experienced by feeder and bus circuit breakers on clearing feeder faults. Based on the conclusions of an investigation of actual circuit breaker failures while performing this duty, the mitigation of the transient recovery voltage associated with the reactors is described.

A hydroacoustic waste feed controller for tank systems

The objective of this work was to develop a commercially viable method to reduce waste feed and thus improve production efficiency and reduce discharge of solids and nutrients within tank based aquaculture systems. We developed and custom fabricated a feeding controller which uses ultrasound to detect uneaten feed and controls feeding events based upon appetite satiation as measured by the quantity of waste feed detected. During feeding, the developed device functions as a combination ultrasonic detector, feedback controller, and interval timer. The device functions as a feedback controller by ultrasonically sampling the stock tank effluent and turning off the feeder when an excessive amount of feed enters the effluent flow. After feeding has been inactivated, the ultrasonic waste feed controller operates as an interval timer and provides a user selected delay between feedings. A custom hydroacoustic probe assembly was developed to detect uneaten feed. The controller can be calibrated by adjusting the transducer signal gain to detect signals resulting from feed pellets, while reducing signals resulting from faeces. The controller has an adjustable set-point for deactivating the feeder circuit based upon the number of feed pellets detected by the transducer and a programmable delay time interval (from 5 to 160 min) to set the time between feedings. The controller also has an adjustable sampling rate for detection at different pipe velocities and an adjustable observation volume for use in standard 2, 3, 4 and 6 inch diameter effluent pipes. The cost in materials and labour to produce this waste feed controller was estimated at around $100 (U.S.).

A hydroacoustic waste feed controller for tank systems

The objective of this work was to develop a commercially viable method to reduce waste feed and thus improve production efficiency and reduce discharge of solids and nutrients within tank based aquaculture systems. We developed and custom fabricated a feeding controller which uses ultrasound to detect uneaten feed and controls feeding events based upon appetite satiation as measured by the quantity of waste feed detected. During feeding, the developed device functions as a combination ultrasonic detector, feedback controller, and interval timer. The device functions as a feedback controller by ultrasonically sampling the stock tank effluent and turning off the feeder when an excessive amount of feed enters the effluent flow. After feeding has been inactivated, the ultrasonic waste feed controller operates as an interval timer and provides a user selected delay between feedings. A custom hydroacousuc probe assembly was developed to detect uneaten feed.The controller can be calibrated by adjusting the transducer signal gain to detect signals resulting from feed pellets, white reducing signals resulting from faeces. The controller has an adjustable set-point for deactivating the feeder circuit based upon the number df feed pellets detected by the transducer and a programmable delay time interval (from 5 to 160 min) to set the time between feedings. The controller also has an adjustable sampling rate for detection at different pipe velocities and an adjustable observation volume for use in standard 2, 3, 4 and 6 inch diameter effluent pipes.The cost in materials and labour to produce this waste feed controller was estimated at around $100 (U.S.).