* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Technical inspection of remote power supply systems
Power inverter wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Stray voltage wikipedia , lookup
Standby power wikipedia , lookup
Variable-frequency drive wikipedia , lookup
Power factor wikipedia , lookup
Wireless power transfer wikipedia , lookup
Audio power wikipedia , lookup
Life-cycle greenhouse-gas emissions of energy sources wikipedia , lookup
Power over Ethernet wikipedia , lookup
Power electronics wikipedia , lookup
Electrical grid wikipedia , lookup
Buck converter wikipedia , lookup
Electric power system wikipedia , lookup
Distributed generation wikipedia , lookup
Three-phase electric power wikipedia , lookup
Electrification wikipedia , lookup
Voltage optimisation wikipedia , lookup
History of electric power transmission wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Electrical substation wikipedia , lookup
Alternating current wikipedia , lookup
Mathematical Methods in Science and Engineering Technical inspection of remote power supply systems for microgrid development Stanislav A. Eroshenko, Vladislav O. Samoylenko, Alexander O. Egorov, Pavel. V. Kolobov, Darina A. Firsova, Ekaterina M. Eroshenko considered as an alternate plan. The very system combines generators, running on fossil fuel, and/or renewable energy sources and storage systems. However, it is necessary to carry out complex technical inspection in order to choose the plan of power supply system development in the given location [3]. The methodology of technical inspection of remote customers’ power supply system is provided in the paper. Much attention is paid to the metering experiment, including data analysis and processing. The case study provides deep analysis of the results, obtained during technical inspection of remote power supply system, located in northern Ural. Abstract— the paper provides extended discussion about the procedure of remote areas’ electrical supply systems technical inspection, made in an effort to reveal energy quality and reliability problems of power supply systems. Technical inspection is carried out in order to determine prospective alternatives of existing power supply system development. The paper focuses on the possibility of distributed generation implementation for the purpose of power quality and supply reliability improvement in terms of remote territory, located in Far North region. Keywords— technical inspection, remote areas, power quality, reliability of power supply, distributed generation. I. INTRODUCTION T HE main tasks set before power grid companies are to provide end users with electric energy of required quality, to reduce long line power losses, to optimize loading of 610 kV distribution network [1], to improve consumers electricity supply reliability in case of line fault. The problem dealing with reliable supply of electric energy with required qualitative parameters is of great importance for grid companies, providing power supply for remote rural users [2]-[5]. Taking into account that 6-10 kV feeders can be considerably long (several tens of kilometers), the voltage may reach unacceptably low levels during peak load hours [3]. Moreover, the power of new consumers to be connected (remote from main 110(35) kV substation) is strictly limited owing to insufficient carrying capacity of existing grids. Consequently, there are several problems, regarding remote rural areas power supply [4], namely: 1) Impermissible voltage reduction at the consumer side. 2) Intolerably high 6-10 kV feeders’ technical power losses. 3) Low reliability due to the lack of backup systems. In order to solve above-mentioned problems the next alternatives are considered: to develop existing network infrastructure or to put into operation distributed generation unit, providing reliability and quality of power supply [5]. The construction of hybrid power supply system is frequently II. TECHNICAL INSPECTION PROCEDURE According to the methodology, provided in the paper, complex technical inspection of remote power supply systems is multistage [6]. Firstly, it is necessary to evaluate existing supply system, namely: 1) to evaluate the structure of energy consumption; 2) to analyze external power supply system; 3) to evaluate power supply system modes of operation. This stage is mostly composed of initial data gathering and analyzing. This information can be found in power utilities’ reporting documents. Generally, the initial information includes energy consumption data, electrical supply system data, distribution lines and power equipment data, the information about energy consumption structure and main electrical load units [7]. The analysis of listed above data gives the possibility to estimate energy consumption dynamics and reveal distinctive features of power supply system’s operation modes. At the next stage, it is necessary to make a set of measurements in the given power supply system, including load curves and power quality parameters identification. Special consideration must be given to the number of measuring devices and time of a single measurement interval. It is necessary to evaluate: 1) power supply center operation mode; 2) operation mode of the backbone network; 3) distribution substations’ operation modes; 4) loading conditions of the power equipment; 5) power quality parameters; 6) statistic parameters of power system operation. To determine prospective plan of power supply system This work was supported by the Ural Federal university. S.A. Eroshenko (phone: +7(312)0333335, fax: +7(343)359-16-15, e-mail: [email protected]), V.O. Samoylenko (e-mail: [email protected]), A.O. Egorov (e-mail: [email protected]), P.V.Kolobov (e-mail: [email protected]), D.A. Firsova (e-mail: [email protected]), E.M. Eroshenko (e-mail: [email protected]) are with Ural Federal University named after the first President of Russia B. N. Yeltsin, Ekaterinburg, Mira Street, 19, Russian Federation. ISBN: 978-1-61804-256-9 90 Mathematical Methods in Science and Engineering development with account of energy quality and reliability requirements, as well as to carry out investment feasibility study for distributed generation implementation, it is essential to perform permanent monitoring of power supply center (main substation) and backbone network modes of operation. Local (internal) measurements are necessary to develop recommendations for the given power supply system. At the same time the overall clear picture of power supply system mode of operation is not provided with these measurements. The measurements are to be carried out using power quality analyzing devices and are to be made in accordance with national or international standards [8-9]. For example, in Europe energy quality indices are regulated by EU 50160 “Voltage characteristics of electricity supplied by public” [8]. In this work, the experiments were conducted in conformance with national standard [9]. The voltage, phase currents and power parameters, controlled within minute intervals, included: line and phase voltages; zero-phase-sequence voltages and negative-sequence voltages; voltage unbalance ratio; voltage oscillograms, harmonic distortion; voltage nonsinusoidality ratio; phase currents; zero-phase-sequence current and negative-sequence current ; phase current unbalance; current oscillograms and harmonic distortion; current unsinusoidality ratio; active and reactive power, electric power; power factor. Additionally, the statistic parameters and dynamic changes of observed values were estimated too. parameters of the power transmission. 2. Electrical measurements of load curves and power quality parameters. №1252 160 kVA 10/0.4 kV 50 mm2 0.44 km Substation 35/10 kV Inc. cub. 10 kV 70 mm2 57 km 50 mm2 0.54 km 50 mm2 0.06 km CB-1 №135 100 kVA 10/0.4 kV 50 mm2 0.07 km №1223 170 kVA 10/0.4 kV 50 mm2 0.06 km №1232 100 kVA 10/0.4 kV №1254 250 kVA 10/0.4 kV 50 mm2 0.66 km 50 mm2 0.66 km 50 mm2 0.18 km Fig. 1 Сase study 35/10 kV network The measuring points, duration and purposes of the measurements for each point are listed in Table 1. Within the framework 10/0.4 kV №135 measurements were not carried out because of its weak influence on total load curve and close location to 10 kV sectionalizing point. TABLE 1 MEASUREMENT ALLOCATION № Measurement point Time III. THE EXPERIMENT DESCRIPTION The remote territory under consideration is supplied by 10 kV overhead distribution line (Fig. 1). The line extends from 10 kV bus section located at 35/10 kV main substation to sectioning point with the overall length of 56 km. The distribution line is made of AS-50 mm2 wire (aluminum-steel). There are six single-transformer distribution substations at the given location: №1232/100 kVA, №1254/250 kVA, №1223/170 kVA, №1244/160 kVA, №1252/160 kVA, №135/100 kVA. The total transformer power is 930 kVA, including consumer substation №135/100 kVA. Speaking about reliability, there are I-category consumers at the given territory: fire station, rural health post, kindergarten. They are to be supplied with two or more independent power sources. The great deal of electrical load is domestic. Technical inspection of electrical equipment, located at the very settlement includes: 1. Visual examination of 10 kV distribution feeder at 35/10 kV substation, 10/0.4 kV distribution substations and 0.4-10 kV internal networks of remote territory under consideration in order to control technical construction ISBN: 978-1-61804-256-9 №1244 160 kVA 10/0.4 kV 1 2 3 4 5 6 7 8 91 35/10 kV substation, 10 kV line cubicle, secondary circuit 0.1 kV 10 kV sectionalizing point, 0.22 kV relay protection circuits 10/0.4 kV substation №1254, 0.4 kV transf. bushing 10/0.4 kV substation №1223, 0.4 kV transf. bushing 10/0.4 kV substation №1232, 0.4 kV transf. bushing 10/0.4 kV substation №1244, 0.4 kV transf. bushing 10/0.4 kV substation №1252, 0.4 kV transf. bushing House, 0.22 kV inresidential network 5 days 1 day Obtained data - 10 kV bus section parameters; - load curve of «line-settlement» system; - parameter variation, curve characteristics. - 10 kV supply system “input” parameters; - 10 kV line operation parameters; - 10 kV network parameters. 1 day - load curve; - 0.4 kV network parameters 1 day - load curve; - 0.4 kV network parameters 1 day - load curve; - 0.4 kV network parameters 2 days - load curve; - 0.4 kV network parameters 2 days - load curve; - 0.4 kV network parameters 1 day - operation mode parameters “at the customers side” Mathematical Methods in Science and Engineering morning on business days. However, the weekly peak loading conditions occur in the evening on weekends. The curve of reactive power consumption is uniform with single surges, caused by electric motors starting. The daily average active power equals 109.8 kW, reactive power – 39.6 kVAr, total power – 117.0 kVA. The active power ranges within 65.9 – 183.7 kW. The line voltage profile is presented in Fig. 3. The line voltages vary from 10.23 kV to 10.81 kV. The daily average line voltage equals to 10.53 kV. The voltages are symmetrical. In general, the loads characteristics are uniform for all phases. The average asymmetry is about 10 %. It is caused by unbalanced distribution of consumers’ single-phase loads between different phases in 0.4 kV network. IV. MEASURED RESULTS A. Main substation mode The active and reactive power curves for 10 kV feeder are illustrated in the Fig. 2. The list of the consumers forming active power curve is the following: lighting load; household appliances: satellite equipment, computers; small heating devices (electric kettles, irons); big heating devices (boilers, electric ovens); induction motors: machine tools, electric saws, pumps, water-towers, fridges; cellular communication stations; distribution line losses and contact losses. The list of the consumers, forming reactive power curve is the following: power units and chargers for modern household appliances; induction motors: machine tools, electric saws, pumps, water-towers; welders; cellular communication stations and signal retransmitters; distribution line losses and transformer losses. Lighting and distributed low-rated power devices tend to predominate in the loading structure. They have active consumption characteristics and cause daily peak in the B. Backbone network operation mode In order to estimate operation mode of the backbone 10 kV network the additional measurements have been made at the end of 10 kV line in secondary circuits of 10 kV sectionalizing point. Having no access to the current transformers’ and voltage transformers’ secondary windings, the current measurements were carried out in control cabinet of sectionalizing point. The clamp meters were connected to internal circuits of two current relays in two phases. The phase voltage was measured at the terminals of the automatic breaker of control cabinet. Fig. 2 Active and reactive power flow curves at the beginning of 10 kV feeder Fig. 3 Line voltages curves at the beginning of 10 kV feeder ISBN: 978-1-61804-256-9 92 Mathematical Methods in Science and Engineering Fig. 4 Active and reactive power flow curves, measured at 10 kV feeder terminals Fig. 5 Line voltages, measured at 10 kV feeder terminals As a result, it can be stated that the line voltage, measured at 10 kV sectionalizing point, lies in the range of 9.8 – 10.4 kV, that meets voltage magnitude requirements (Fig. 4). The daily average voltage levels are 10.47 kV for distribution line sending end and 10.12 kV – for receiving end. In this way, the average voltage drop across the given 10 kV line is about 0.35 kV. The length of the line is 56 km and the loading factor of the line is nearly 0.1. The relation between measured power flows in the beginning and in the ending of the given 10 kV line (Fig. 5) arises from current and voltage transformers inaccuracy. This inaccuracy mainly occurs at the sectionalizing point where there is no energy accounting circuits provided. Current transformer’s secondary windings have 10R accuracy rating, which corresponds to 10% error. Another source of inaccuracy at the sectionalizing point is the configuration of relay protection circuits working on a.c.; such circuits contain a great number of non-linear elements. The power losses are to be subdivided on three main types, namely: series losses (load losses), shunt losses (leakage currents), contact losses, commercial losses (measurement inaccuracy, caused by current transformers low loading conditions) [10]-[12]. Load losses, which were calculated in accordance with measured data, equal to 8.6%. Leakage currents are about 1%. Moreover, it was estimated that commercial losses and contact losses are about 4.5%. In this way, the total line losses equal to 14.1%. supply system of the remote territory will be further described using measurements made at distribution substation №1254. Final conclusions, made for distribution substation №1254, are suitable for other distribution substations too. Low-rated household devices predominate in load structure of the given substation. This loads result in morning peak loads. In addition, there is motor load with approximately 12 kW active power consumption. Active and reactive power curves are given in Fig. 6. Phase voltages range from 226 V to 245 V, that exceeds voltage level standard requirements. The daily average phase voltage is 235 V. The graph illustrating phase voltages is represented in Fig. 7. The phase loads are not uniform. Phase asymmetry results in rapid deterioration of transformer isolation and worsening of electric power quality in each phase. V. CONCLUSION The paper presents methodology of electrical measurements for remote power facilities. The analysis of residential consumers operating conditions and energy quality rates is made to develop recommendations for power quality and reliability improvement. The main statistical rates of remote territory operation are provided in the Table 2. The 10 kV power supply network of the given remote settlement provides electrical energy quality in compliance with [8-9] and operates in a symmetrical three-phase mode. Taking into account the overall length of the overhead 10 kV distribution line, which equals to 56 km, the level of the power losses in the line is satisfactory. C. Internal power supply system operation mode The operation modes of 10/0.4 kV grid of internal power ISBN: 978-1-61804-256-9 93 Mathematical Methods in Science and Engineering Fig. 6 Distribution substation load curve Fig. 7 Distribution substation voltage profile It was also observed that load phase balance is inadmissible. Thus, it is recommended to reconnect a share of load to other phases. The main challenge of remote customers power supply is low reliability. In case of distribution line fault, consumers are not supplied within the repair time period. In this case, distribution generator implementation becomes the question of growing importance. Basing on the metering data the capacity of the generator, which will be installed at the remote settlement, is assessed to be 500 kVA taking into account winter peak loads. TABLE 2 POWER SUPPLY PROBLEMS Parameter Value Property Customer side voltage (0.22 kV network) Minimal, V 222,0 High Maximal, V 251,3 Inadmissible Admissible Average, V 236,3 10 kV line losses Load losses, % 8,6 Admissible leakage currents, % 1,0 Low Contact losses and commercial losses, % 4,4 Admissible Total losses, % 14,0 Admissible ACKNOWLEDGMENT The authors express their gratitude for being supported by Ural Federal University. The authors appreciate the contribution of Open Joint-Stock Company «Interregional Distributive Grid Company of Urals» dealing with assistance in measurements made at 10 kV power facilities within research and development work. Load curve uniformity Minimal α, % 18,3 Average α, % 20,7 Low Admissible REFERENCES Load current asymmetry Maximal I2 , % 58,2 Inadmissible Average I2 , % 35,6 Inadmissible [1] [2] It is important to note that the increased voltage level is observed due to low loading conditions and 10/0.4 kV transformers NLTC systems, switched to winter position. The latter represents atypical problem of remote consumers power supply. ISBN: 978-1-61804-256-9 [3] 94 Kokin, S.; Dmitriev, S.; Khalyasmaa, A., “Assessment of state of urban power supply systems' power transmission lines on the basis of indicative analysis”, Applied Mechanics and Materials 291-294,2013, pp. 2143-2148. Zomers, A., “Remote Access: Context, Challenges, and Obstacles in Rural Electrification” Power and Energy Magazine, IEEE (Volume:12 , Issue: 4), pp. 26–34. Verwers, J.L.; Sovers, J.R., “Challenges of supplying electric power to a large industrial customer in rural areas” Industry Applications, IEEE Transactions on (Volume:36 , Issue: 4 ), pp. 972 - 977. Mathematical Methods in Science and Engineering Rudnick, H. ; Mutale, J. ; Chattopadhyay, D. ; Saint, R., “Studies in Empowerment: Approaches to Rural Electrification Worldwide”, Power and Energy Magazine, IEEE (Volume:12 , Issue: 4), pp. 35 – 41. [5] Ijumba, N.M., “Application of distributed generation in optimised design and operation of rural power supply networks”, Rural Electric Power Conference, 1999., pp. C3/1 - C3/5. [6] The methodology of power inspection (energy audit) performance at enterprises and coal utilities (proved by protocol arranged at coordinating council meeting at Russian Energy Department from 29.05.2012 № 6), 2012. (in Russian) [7] Yong Li ; Jian-Jun Wang ; Tie-Liu Jiang ; Bing-Wen Zhang, “Energy Audit and Its Application in Coal-Fired Power Plant”, International Conference on Management and Service Science, 2009. MASS '09, 2022 Sept. 2009, pp. 1-4. [8] European Standard EN 50160, Voltage characteristics of electricity supplied by public distribution systems, 1999 [9] International standard GOST 13109-97 “Electric power. Electromagnetic equipment compatibility. Quality standards of electric power in common power supply systems" (introduced by State standard 28.08.1998. N 338), 1998. (in Russian) [10] Khalyasmaa, A.I.; Dmitriev, S.A.; Kokin, S.E., “Energy information model for power systems monitoring”, Advanced Materials Research 732-733, 2013, pp. 841-847. [11] Pazderin, A.V.; Samoylenko, V.O., “Localization of non-technical energy losses based on the energy flow problem solution”, Proceedings of the 6th IASTED Asian Conference on Power and Energy Systems, AsiaPES 2013, pp. 100-103. [12] Khalyasmaa, A.I.; Dmitriev, S.A., “Power equipment technical state assessment principles“. Applied Mechanics and Materials 492, 2014, pp. 531-535. [4] ISBN: 978-1-61804-256-9 95