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220KV地区变电站电气一次设计,220,KV,地区,变电站,电气,一次,设计
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Abstract This paper deals with standard and legal requirements concerning electric power quality produced by wind power plants and with conditions under which electric energy transmission in the national electric power system can take place. The electric energy quality assessment is based on the case of Kamiensk Wind Power Plant and takes into consideration the following indices: variation in supply voltage, light flickering as well as distortion and asymmetry of voltage by higher order harmonics. Following the conducted measurements, it has been observed that the parameters of electric energy quality comply with current regulations in the Common Connection Point (CCP) of the power plant electric network with the public power system 110 kV. Keywords: electric power quality, wind power plant I. INTRODUCTION Wind power plants are new electric power sources in an electric power system. They are equipped with control systems which, simultaneously, are sources of interference resulting in the introduction of harmonic currents and voltage into the system. Furthermore, they are sources sensitive to interference originating from an electric power system (overvoltage, voltage dips, asymmetry of supply voltage etc. 4, 6, 7). In order to analyse electric power quality of a selected wind power plant, production data of an existing 30 MW wind farm having 15 - 2 MW wind turbines have been used. Kamiensk Wind Power has been operating in the Polish electric power system since 15 November 2007. A target government programme included in the Ordinance of the Economy Minister of 4 May 2007 on detailed conditions of an electric power system functioning (2007 law gazette, issue 98, item 623-5),(Rozporz?dzenie Ministra Gospodarki z dnia 4 maja 2007 r. w sprawie szczeg?owych warunkw funkcjonowania systemu elektroenergetycznego. Dziennik Ustaw, 2007 r., nr 98, poz. 623 ) and concerned with renewable energy percentage at the level of 10.4% in 2014, in all likelihood, is going to result in transformation of quality standards in order to ensure quality parameters defined, among others, by sinusoidal alternating voltage of specified root-mean-square value and frequency when supply continuity is known, 3. Various interference taking place in an electric power system results in unwanted parasitic phenomena and processes occurring when devices connected to the network are operating, 1,13. II. INTEREST OF ELECTRIC POWER QUALITY Kamiensk Power Plant and its one and a half year s operation confirm an increase in sensible interest in the quality of the produced electric power. Among the reasons for this interest, there are the following, 10,11,12: ?Commercial aspects of electric power, which means that quality determines a characteristic of the offered commodity of precisely defined number parameters (energy sale ranging from wholesale prices to stock market prices, its share in the balancing market). ?In 25 EU member states benefits resulting from competition are in many cases hardly accessible for gas and electric power buyers although it has been almost 10 years since the European Parliament and the EU Council accepted a directive on common regulations concerning domestic market of electric power and it has been 8 years since a directive on domestic market of gas was accepted (and although pro-market solutions of both directives were reinforced and expanded in their new versions called market directives). ?An increase in the number and unit power of unstable, nonlinear and asymmetric receivers. A larger and larger number of technologies which are potential sources of electromagnetic disturbances, such as: 978-1-4244-5172-2/09/$26.00 2009 IEEEJan Anuszczyk Boguslaw Terlecki Institute of Electrical Power Engineering Kamiensk Wind Power Plant Technical University of Lodz Lodz, Poland Kamiensk, Poland e-mail: jan.anuszczykp.lodz.pl e-mail: Boguslaw.Terleckiewk.plAnalysis of Electric Power QualityA Case Study: Kamiensk Wind Power Plantdrives with controllable velocity, static compensators SVC, systems of electric energy transmission by direct current HVDC, etc. In general, it can be assumed that a production increase and development of its more and more diversified forms are inevitably connected with an increase in the significance of energy quality. ?A decrease in receiver resistance to electromagnetic disturbances (especially, sensitive information technology equipment miniaturization to a large extent paid for by a decrease in resistance to disturbances). ?An increase in the number of cars with electric or hybrid drives may promptly (when production of converters that are unfriendly towards a supply network increases systems of charging batteries) create a new quality of voltage distortion. ?Rising costs of failures. ?Launching energy-efficient products which, despite their undeniable advantages, are sources of numerous disturbances. ?Stricter and stricter requirements regarding the effectiveness of system operation and a simultaneous increase in technologies correcting positively the introduced disturbances, e.g. a capacitor battery for reactive power compensation. ?Electromagnetic environmental protection concerning neutralization of harmfulness of bad quality energy. III. THESTANDARDS OF ELECTRICPOWERQUALITYThe operator of a transmission system and distribution systems should provide their consumers with supply continuity and a product, i.e. electric power with specified quality parameters (defined, among others, by sinusoidal alternating voltage of a specified root-mean-square value and frequency 50 Hz). Various phenomena and processes occurring in an electric power system hinder meeting these basic requirements. Frequency changes as a result of continuous variations in power consumption. The consumption changes and reactive power generation result in various voltage values and related mains and transformer voltage drops, which makes it impossible to maintain constant and rated voltage values in receiver nodes. A lot of nonlinear receivers of energy produced by electric power systems such as electric machines and transformers also make it impossible to achieve the ideal sinusoidal course of voltage and currents. Due to all of this, the condition when a system operates without failures and disturbance is quasi-fixed. This means that frequency oscillates around a rated value of 50 Hz and deviations from this level are equal to several dozens mHz. Moreover, maintaining voltage within the acceptable range 10% of a rated value is hindered. As a result, maintaining rated parameters of electric power quality requires using systems and elements of electric power regulation. The standard concerning energy quality which is legally binding in the European Union and in Poland is document PN-EN 50160: “ Voltage characteristics of electricity supplied by public distribution systems” , 6. The standard should be regarded as a set of guidelines on what voltage quality parameters should be in order to maintain electromagnetic compatibility of a supply system and receivers. The majority of consumers use low voltage networks and accept standardized boundary values of the network parameters. Hence, values defining electric energy quality for the system in question have been made more lenient. They include: ?Supply voltage value under normal operating conditions of an electric power network, every week 95 % of a set of 10-minute mean root-mean-square values should be within the range of 10% of rated voltage and within the range from -15% to +10% of rated voltage defined in standard PN-EN 500160:2002 and it refers also to 10-minute average root-mean-square values. ?Value of quick variations in supply voltage it should not exceed 5% of rated voltage; however, in the course of a day a few variations in rated voltage which reach up to 10% and are of short duration are acceptable.?Light flicker severity it is caused by voltage fluctuations and according to the very standard 95% of the set of 2-hour indices of long-term light flicker each week ?Voltage harmonic in the terminal of electric power network voltage harmonic for the harmonic values up to the 25th inclusive should not exceed the mean values obtained throughout a week during 95% of measurements from the set of 10-minute values. ?Asymmetry of supply voltage 95 % of measurements from the set of 10-minute mean symmetric component values (obtained over a week) in a negative phase sequence should not exceed 2% of a component value with a positive phase sequence. ?Voltagesignal for transmission of information imposed on supply voltage in the course of a whole day 99% of a set of 3-second average voltages should not exceed 9% of rated voltage for the frequency of up to 500 Hz, 5% for the frequency of between 1 and 10 kHz and in a downward trend: from 9% to 5% for the frequency from 0.5 to 1 kHz and 5% to 1% for frequencies greater than 10 kHz. ?Frequency of supply voltage 95% of a set of 10-second mean values should not exceed the frequency range 49.5-50.5 Hz. Moreover, 100% of a set of 10-second mean values should not exceed the frequency 47-52 Hz. ?Voltage dips their duration is usually shorter than 1s and voltage very rarely decreases below 60% of rated voltage. Voltage dips occur in power plants due to their frequent connecting to and disconnecting from a network. ?Short power stoppages they occur from several dozens to a few hundreds times throughout a year and their duration is shorter than 1s. ?Short-time overvoltage they result from specific occurrences in a system. IV. RESULTS OF THERESERCHA. The Skope of the Reserche The scope of the research presented in this paper embraces: ?Research on electric power quality in power system 110 kV, ?Research on electric power quality in power system 30 kV, ?An analysis of using produced reactive power. Measurements were conducted on busbars 110kV and 30kV of electric power station 30/110 kV connecting the network of Kamiensk Wind Power Plant with the network of public power system, i.e. in the Common Connection Point (CCP). The parameters describing electric power quality were measured and compared to requirements of legally binding regulations, 5, 6. The measurements were conducted by means of analysers of electric energy quality, i.e. Topas 1000 (in power system 110 kV) and Memobox 800 (in power system 30 kV) manufactured by LEM. The devices are designed so as to measure and evaluate electric power quality in accordance with the requirements of the PN-EN 50160 standard.B. Selected Quality Indices According to the requirements specified in the above-mentioned regulations, energy quality is determined by means of the following parameters of supply voltage in the connection point of the system to the public power system: ?voltage variations%100cULU%LU? (1) The changes in a root-mean-square value of supply voltage in medium voltage power systems and in power systems 110 kV should be within the range from 90% to 110% of rated voltage. ?asymmetry factor%1001sU2sU2UK?(2)The acceptable value of an asymmetry factor of voltage in medium voltage power systems amounts to 2 % and in high voltage power systems to 1 %. ?relative hth harmonic %100cUhUhU? (3) ?distortion factor%1001U402h2hU%THD? (4) The acceptable value of a distortion factor in medium and low voltage power systems amounts to 8 % and to 3 % in high voltage power systems. ?long-term light flicker index 312121ii3stPltP? (5) The acceptable value of long-term light flicker index in medium and low voltage power systems is 1 and 0.8 in high voltage power systems. Acceptable values of higher order harmonics for low and medium voltage electric power systems are presented in 6. C.The Results of Research into Energy Quality in Networks 110 kVand 30 kV1) Results of Measurements of Energy Quality in a Common Connection Point of Network 110 kV The measurements were conducted by means of a Topas 1000 analyzer of electric energy from 13.09.2007 (time 0:00) to 20.09.2007 (time 0:00) by the Institute of Electrical Power Engineering, the Technical University of Lodz,2. The results of the measurements and the evaluation of particular voltage parameters are broken down in tables from I to III. TABLE I. VARIATIONS IN SUPPLYVOLTAGEVariations in supply voltage IndexMaximum value No.Value UL1UL2UL3-%1 Maximum 107.37107.54107.012 Percentile 95 % 106.22106.43105.883Acceptable value according to standards110.00TABLE II. LIGHTFLICKERINDICES(VOLTAGEFLUCTUATIONS)IndexLong-term light flicker indexNo.Value Plt,L1Plt,L2Plt,L31 Maximum 0.310.540.532 Percentile 95 % 33Acceptable value according to standards0? 0.8 TABLE III. FACTORS OF VOLTAGEDISTORTION AND ASYMMETRYIndexFactor of voltage distortion No.Value THDL1THDL2THDL3-%1Maximum 0.820.740.842 Percentile 95 % 0.70 0.62 0.68 3Acceptable value according to standards 0? 3 Selected parameters characterizing supply voltage quality in the function of time are presented in Fig. 1 and Fig. 2. Figure 1. Percentage of higher order harmonics in phase voltage UL1 in measuring time 0.00.81.01.82.013-09-070:0014-09-070:0015-09-070:0016-09-070:0017-09-070:0018-09-070:0019-09-070:0020-09-070:00t d-m-r g:mUh %THD U L1U h3 L1U h5 L1U h7 L1U h9 L1U h11 L1U h13 L1Figure 2. Variations in relative values (of percentage) of selected higher order harmonics in phase voltage UL1 Fig. 3. presents synthetic results of evaluation of parameters of supply voltage 110 kV in a common connection point (on busbars of switchgear 110 kV) which was carried out in accordance with the requirements, 4. The brown horizontal line corresponds to the boundary value given by the standard for each voltage parameter. The length of the blue bar indicates the maximum value from the set of values of a given parameter. The length of the red bar indicates the parameter value which was not exceeded by 95% of values in the evaluated set in measuring time. The graph shows that all parameters of voltage supplying the switchgear meet the requirements described in the regulations the lengths of the red bars do not exceed the boundary value determined by the horizontal line. The supply voltage quality is so good that also the maximum values of the parameters described by the blue bars are shorter than the boundary values corresponding to them. Figure 3. Evaluation of electric energy quality in network 110 kV The supply voltage quality is so good that also the maximum values of the parameters described by the blue bars are shorter than the boundary values corresponding to them. In the measuring time in supply voltage there were no events (voltage dips, increases and power stoppages) consisting in exceeding the rated value of voltage by ?10 %. Fig. 4. shows values of active power carried by higher order harmonics. The powers connected with harmonics of orders 3,5 and 7 may be of some significance too. Figure 4. Active power of higher order harmonics Active powers of other higher order harmonics are of very small values. Analyzing the flow direction of active powers of higher order harmonics, it may be observed that dominating sources of harmonic orders 5 and 7 are located in the external network whereas the wind power plant is the source of the third harmonic of negligible active power (20 W). 2) Results of Measuring Electric Power Quality in Network 30 kV The measurements were conducted by means of a Memobox 800 analyser of electric power from 13.09.2007 to 20.09.2007, 2. The overall results of measurements along 0.00.51.01.52.0Uh %2468 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40Percentile 0.95Maximal valueNumber of harmonic h-40-20020406080100Ph W246810121416182022242628303234363840Number of harmonicL1L2L3with the evaluation of particular voltage parameters are presented in tables from IV to VI. TABLE IV. SUPPLYVOLTAGEVARIATIONSSupply voltage variation IndexMaximum value No. Value UL1UL2UL3-%1 Maximum 102.96102.87102.422 Percentile 95 % 101.80101.73101.223Acceptable value according to standards 110.00TABLE V.LIGHTFLICKERINDICES(VOLTAGEFLUCTUATIONS)Index Long-term light flicker index No.Value Plt,L1Plt,L2Plt,L31 Maximum 0.280.500.532 Percentile 95 % 0.210.270.203Acceptable value according to standards 0 ? 1 TABLE VI. FACTORS OFVOLTAGEDISTORTION AND ASYMMETRYIndex Voltage distortion factor No. Value THDL1THDL2THDL3-%1 Maximum 0.280.500.532 Percentile 95 % 0.21 0.27 0.20 3Acceptable value according to standards 0 ? 8 The acceptable range of supply voltage variations in network 30 kV amounts to ?10 % of a rated value, which corresponds to the range of phase voltage variations from 15607 V to 19075 V. All the parameters of the voltage supplying switchgear 30/100 kV meet the requirements described in the regulations of standard PN-EN 50160. Every occurrence of exceeding voltage value below 15607 V is recorded as a voltage dip.Figure 5. The evaluation of electric power quality in network 30 kVThe acceptable number of voltage dips during a one-week measuring period is 100.During the measuring time 8 voltage dips were observed. The drops resulted from interference in the superior network (the public electric power system). Similarly to the results of the evaluation of voltage parameters in network 110 kV, synthetic results of voltage evaluation for electric power network 30 kV are presented in Fig. 5. (the description of the graph as in the case of Fig. 3.) ACKNOWLEDGMENTThe values of parameters characterizing electric power quality in the common connection point (CCP) of network 110 kV of Kamiensk Wind Power Plant and the public electric power system meet the requirements defined in the legally binding regulations. During the measuring time in supply voltage there were no events (voltage drops, voltage increases and power stoppages) consisting in exceeding rated value of voltage by ?10 %. However, the operation of a power plant may be affected by other interference (e.g. short circuits, connecting activities) which occur in superior public electric power systems and which result in e.g. voltage dips noticed in power plant network 30 kV or an increase in the value of sh
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