Experiences with medium-voltage vacuum circuit-breaker equipment in distribution systems

The characteristics of electrical noise and power harmonics from power converters and other harmonic sources, as well as the effects of such noise and harmonics on distribution system equipment and operation are described. Power system surges and their effects on converter equipment are also described. Field tests were conducted on two different distribution systems. Measurements were made of harmonic voltage and current magnitudes, capacitor-switching transients, and impulsive electromagnetic noise in the frequency range of 3 kHz to 300 kHz. Test methodology and instrumentation are described, and the measured results are presented. The implications of this high-frequency noise on power line communication systems are discussed. A computer program was developed to aid in analyzing distribution system response to harmonic sources on the system. Simulations performed for the two distribution systems tested are described, and comparisons between simulation results and measured harmonic magnitudes are presented. The project also addressed methods of controlling harmonics on distribution systems. The different methods for harmonic control, principally the filtering and/or phase cancellation of harmonics, are described.

This paper proposes a multi-objective benefit function for operation of active distribution systems considering demand response program (DRP) and energy storage system (ESS). In the active distribution system, active network management (ANM) is applied so that the distribution system equipment is controlled in real-time status based on the real-time measurements of system parameters (voltages and currents). The multi-objective optimization problem is solved using ε-constraint method, and a fuzzy satisfying approach has been employed to select the best compromise solution. Two different objective functions are considered as follows: benefit maximization of distribution company (DisCo); benefit maximization of distributed generation owner (DGO). To increase the benefits and efficient implementation of distributed generation (DG), DGO has installed battery as energy storage system (ESS) in parallel with DG unit. Consequently, DGO decides for the battery charging/discharging. DisCo has the ability to exchange energy with the upstream network and DGO. Also, DisCo focuses to study the effect of demand response program (DRP) on total benefit function and consequently its influence on the load profile has been discussed. This model is successfully applied to a 33-bus radial distribution network.

Solid-state fault current limiters (SSFCLs) offer a number of benefits when incorporated within transmission and distribution systems. SSFCLs can limit the magnitude of a fault current seen by a system using different methods, such as inserting a large impedance in the current path or controlling the voltage applied to the fault. However, these two methods can introduce a few problems when SSFCLs are used in a system along with other protection equipment such as protective relays and sensors. An experiment was designed and implemented to evaluate the behavior of the protective relays in a mimic distribution system with a SSFCL. This paper introduces the details of the experiment and the result shows that the distorted current and voltage waveforms resulting from the action of the SSFCL disturb the protective equipment.

The high voltage (HV) and medium voltage (MV) electric switchers (ES) are equipment of power transmission and distribution system (PTDS) structure, with high importance viewing the efficiency of these systems, the quality and availability of consumers' supplying service with electric energy. Consequently, the reliability of ES is an important object of study for users, producers and experts. In this paper is studied the parametrical reliability of ES and it is structured in four parts. In the first part is presenting the nature of statistical date that founds the ES analyzes of parametrical reliability. In the second part is presenting the applied mathematical model for the statistical dealing of ES state parameters. Viewing the admitted domains of ES state parameter values, is expressed the parametrical reliability of these, and it is presenting the evaluating model of selection characteristics and of identification of state parameters distribution function, performed as aleatory variables. In the third part are presenting the results, obtained by parametrical reliability analyzes, in relation with statistical parameters, for 92 ES at 110 kV, being in administration by Distribution Power and Supply branch of Oradea (DPSO). In the fourth part of the paper is presenting the structure of an expert system, used for testing of 110 kV and 20 kV ES in dynamic regime, and the obtained results synthesis. The last part presents the elaborated studies conclusions, and recommendations for the exploitation activity of ES within the framework of PTDS analyzed.

The electrical energy distribution of the power plant to customers was required the role of transformer that could increase and decrease voltage levels. Transformers was essential equipment in electricity distribution, both in transmission and distribution systems. Transformer was arranged of conductive materials and operated continuously, therefore it was need to be protected by insulation. The liquid insulation was commonly used, such as Shell Diala B which focused on this research. Although insulating oil was able to use over a long period, it might be regularly monitored because its ability to protect electrical equipment deteriorate. This paper was used laboratory research as the method. The researcher analyzed the effect of usage duration to determine its dielectric breakdown strength. It was found that the longer Shell Diala B oil is used, the more its quality declines, indicated by increased turbidity and decreased dielectric performance.

Power transformers are one of the most important equipment in power substations and distribution systems. As its price is about 55% of the whole substation price, it can be called the valuable element in the power grid. Thus, the lifetime management based on economical and technical indexes is highly essential for facilitating asset management and achieving higher reliability in the power system. This study presents the factors that can affect ageing transformers and analyzes oil test parameters. Dissolved gas analysis (DGA) is performed and some existing methods for evaluating of transformer operation based on DGA are compared. The pros and cons of each method are shown and a simple method to assess transformer condition is found. Also, three power transformers with real values and oil samples are studied for lifetime evaluation, and some possible solutions are proposed for better operation and maintenance.

This paper presents distribution system equipment models for fast distribution three‐phase unbalanced load flow calculation. Recently, the number of distributed generators introduced into distribution systems has been increasing and detailed system analysis using load flow calculation has been eagerly awaited. Moreover, since many distribution system loads are composed of single phase loads, three‐phase unbalanced load flow calculation is required for the distribution system analysis. Although the fast distribution three‐phase unbalanced load flow calculation has been developed, equipment models considering interconnection of distributed generators have not as yet been developed in Japan. This paper develops practical equipment models such as various distributed generators, voltage control equipment, and loads for fast three‐phase unbalanced load flow calculation in distribution systems. The feasibility of the developed models is verified and demonstrated on practical distribution system models with promising results. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 8–19, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10106

Distributed energy resources (DER) are quickly making their way to industry primarily as backup generation. They are effective at starting and then producing full-load power within a few seconds. The distribution system is aging and transmission system development has not kept up with the growth in load and generation. The nation's transmission system is stressed with heavy power flows over long distances, and many areas are experiencing problems in providing the power quality needed to satisfy customers. Thus, a new market for DER is beginning to emerge. DER can alleviate the burden on the distribution system by providing ancillary services while providing a cost adjustment for the DER owner. This report describes 10 types of ancillary services that distributed generation (DG) can provide to the distribution system. Of these 10 services the feasibility, control strategy, effectiveness, and cost benefits are all analyzed as in the context of a future utility-power market. In this market, services will be provided at a local level that will benefit the customer, the distribution utility, and the transmission company.

This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. The method can calculate voltage and current of distribution systems, in which distributed generators are introduced. The calculation time of the proposed method is about 40 times faster than that of the Newton-Raphson method. Moreover, an introduction effect evaluation tool for distributed generators using the proposed three phase unbalanced load flow calculation is presented. It provides various functions such as power system network diagram creation function and voltage profile chart display function. Therefore, the introduction effect evaluation of distributed generators in distribution systems can be evaluated quite easily.

DMX512 is the standard protocol used by lighting equipment in theatrical and entertainment data distribution systems. This paper describes a complete hardware and software solution for driving a high brightness 70 pixel RGB LED matrix from a computer and synchronized with environmental music, in addition to multiple running modes and possibilities achieved. Further possibilities of the developed device running as universal automation controller, are also mentioned.

This paper concerns transforming today's operations and asset management in large-scale distribution grids into efficient and reliable grid management. Particular emphasis is on dynamic monitoring and decision systems (DYMONDS) embedded into system users, distribution network and operators of distribution, sub-transmission and transmission systems, all interacting to enable electricity services within the customers' preferences for acceptable type of service and electricity tariffs. Through these interactions it becomes possible to manage higher-voltage grid congestion by either: i) direct load control (demand side management-DSM) and/or ii) DYMONDS-enabled adaptive load management (ALM). It is described how these two approaches, which appear to be similar at first sight, differ in enabling customer choice with respect to both type of service and tariff determination. Finally, the paper proposes that there is potentially a major benefit from coordinating actions of distribution, subtransmission and transmission system operators. Namely, by carefully exchanging the right information it becomes possible to implement load-transfer (LT) to relieve congestion in transmission- or sub-transmission grids by reconfiguring lower-voltage feeders in distribution grids to control the aggregate load seen at the higher voltage levels. We finally compare the economic aspects of DSM, LT and DYMONDS. A simple 60kV sub-transmission grid connected to a large distribution network in Portugal is used to illustrate these different options and the related costs and benefits.

Rapid advances in the areas of computing, sensing, and communications have enabled vehicle manufactures to provide new features for vehicles to enhance safety, pleasure, convenience, and reliability. Moreover future vehicles are expected to become a part of the Internet, either as a network node, or as a hub constructing a vehicular ad hoc network. This vehicular ad hoc network represents large dynamic distributed processing systems. These vehicles communicate with each other and with the Internet, to access services such as traffic conditions, finding nearest hospital, remote monitoring, etc. To accomplish this type of services, new methodology will be needed such as Dynamic Discovery Service. Dynamic Discovery Service is a system in which servers search through lookup services to first discover and then register the service they offer in the lookup service as a proxy.This research proposes Dynamic Discovery Service-based Jini architecture. A Dynamic Discovery Service (DDS)-based Jini system is a distributed environment where services and devices can participate to offer resources to other members of the community. To be efficient DDS-based Jini, system should be evaluated in terms of scalability, latency, bandwidth usage. This paper will examine the scalability of the lookup service mechanisms in terms of lookup latency as well as generated network traffic. Specifically, the experiments examined the lookup response time as a function of increasing number of services registered, and increasing lookup nodes, all in a static environment as well as the lookup response time in a dynamic environment.

12kV vacuum circuit breaker(VCB) is widely used in distribution system. It is important to research its state and analyze its performance changes. In this paper, several 12kV VCBs which had been in service for several years were investigated. Mechanical operate experiment was carried out on them, mechanical parameters were recorded. It was found that 7.7 percent of VCBs' closing speed was higher than upper limit, while 23 percent of VCBs' opening speed exceeded upper limit. The longer the VCB was used, the bigger the dispersion of opening or closing speed was. The experiment results showed that primary loop component faults of VCB were related to the change of mechanical parameters. Meanwhile, a model of operating mechanism in ADAMS software was built, and the opening process under normal and fault circumstance were simulated. This mode analyzed the influence of circuit components fault on separate operation. Good coincidence was achieved with experimental data.

The background of this research is an analysis of equipment disturbances that occur in distributing electrical energy. The disturbance is a blackout. Power outages cause a decrease in the continuity of service to customers and result in a lot of loss of electrical energy that is not distributed to customers. The research objectives are to find out the optimization technique of distribution network maintenance, how to reduce the value of energy not supplied (ENS), find out the losses due to ENS, and find out the total electrical energy distributed after preventive maintenance is carried out. This research uses a preventive maintenance method, which is maintenance that can prevent unexpected damage to distribution system networks and equipment. This research optimized preventive maintenance actions by reducing disturbances after preventive maintenance from 7 disturbances in February to 2 disturbances in March. Before preventive maintenance, the loss due to ENS amounted to Rp. 36,192,017.626, and the total electrical energy not distributed was 25,025.76 kWh. After preventive maintenance, there was a significant decrease in the total loss due to ENS of Rp. 953,516,447, and the amount of electrical energy not distributed was 659.28 kWh. This research can increase maintenance efficiency due to electrical energy losses by 97.36% at the time interval when this research data is managed when data collection is carried out in the field.

A Vacuum Circuit Breaker demonstrated its ability to interrupt short circuits with faster than normal rates of rise of Transient Recovery Voltage (TRV) at levels greater than those produced by most transformer secondary faults. Two recent exploratory test programs evaluated the interrupting ability of a 15kV Vacuum Circuit Breaker containing interrupters of the rotating arc type with contacts made from a Chromium-Copper powder metal mixture. The interrupting conditions covered a wide range of currents from 10% to 130% of the 28kA rated short circuit current of the tested circuit breaker and a wide range of TRV rates of rise, including : - the relatively slow rate of rise, normally used in testing and found in most indoor circuit breaker applications, - two faster rates of rise equalling and exceeding those found in a known power plant transformer secondary protection application, and - the fastest rates of rise possible in the laboratory which exceed the requirements of most transformer secondary faults. These tests showed that the interrupting performance of the tested Vacuum Circuit Breaker was unaffected by the TRV rate of rise to the fastest rates available in the test lab. Such a Vacuum Circuit Breaker can therefore be used without TRV modifying capacitors to slow down the rate of rise provided by the power system. This ability is particularly important if analysis shows that the expected TRV from a transformer secondary fault has a fast rate of rise beyond the recognized ability of an older circuit breaker to acceptably interrupt.