AC500KvSubstationDesigninChinaAC500千伏变电站的设计外文翻译Word格式文档下载.docx

1、1.IntroductionThe research and design of 500 kV substations in China were started in 1977,and the first substation was put into operation in 1981. From that time, because of the rapid development of electricity demand in China, design and construction of 500 kV substations have a great development.

2、Especially in recent years, due to the increase of capital investment for power system construction from the State Government, 500 kV power system has developed even faster. Till 1998 about 55 substations （500 kV） were already put into operation, in which 217 transformers were installed, and the tot

3、al capacity reached 60410 MVA. At present, there are 30 substations under construction. In addition, it has been planned to construct/extend 30 substations in accordance with the power delivery from Three Gorges Power Plant.A complete design system of AC 500 kV substation in China has been gradually

4、 established based on the past design and construction experiences and the use of new technologies. This system includes design procedure, design standards, rules and regulations, design management and so on.The essential design principles are safe and reliable ,technically advanced ,economical and

5、reasonable, and good quality.2.Size of SubstationsChina is a developing country with broad territory. The economic development is very different from one region to another. In accordance with this fact, the 500 kV substation size is different at different time and for different regions.Generally the

6、re are several classes of transformer capacity in substation according to different stages of construction:Initial stage, MVA Final stage, MVAI1 X500（750） 2 500（2 750）II1X750 3X750川 1 X750（2 X50） 4 750（1000,1500）The numbers of 500 kV and 220 kV outgoing lines from substation differ from time to time

7、. Usually there are 1-4 circuits of 500 kV lines and 6-8 circuits of 220 kV lines in the first stage of construction, and finally the number reaches 6-10 circuits of 500 kV and 12-14 circuits of 220 kV lines.Whether install or not the high voltage reactor is decided by systematical investigation in

8、overvoltage level and line length. Reactive compensation facilities at low voltage side of main transformer are also designed in accordance with the system conditions and the principle of “ compensationon the spot according to the condition of each voltage level and region . Usua”lly in first stage

9、of construction only low voltage shunt reactors are installed, reserving the possibility to install shunt capacitors. But some times, especially in recent projects, shunt reactors and capacitors may be installed simultaneously in first stage of construction.3.Electrical Design Features3.1Main Electr

10、ical ConnectionsIt is very important to select main electrical connection for safe and reliable operation and project cost control. The most popular 500 kV electrical connection is one-and-half circuit breaker connection, which are flexible, reliable, relatively and less landused. Double sectionaliz

11、ed bus with transfer bus connection also being employed in some early projects. In the 1 1/2 CB connection configuration, source and load circuits are usually arranged in pair and in series, with same title circuits arranged in different series. It is permitted to connect the same title circuits to

12、the same bus, 2 transformer groups into series separately and the other 2 groups to bus separately. 3 current transformer groups are installed in every series and single phase capacitive voltage transformers（CVT） are installed at line and transformer sides. Special calculations are required to decid

13、e if bus arresters to be installed. At initial construction stage outgoing lines and transformer groups use 1-2 breakers. For 1 1/2 Cb connection, if number of series is equal to or more than 3 at initial stage, outgoing isolating switches are not installed for the line and transformer. If there are

14、 only 2 series in the initial stage, they should be installed.In most cases double bus （single or double sectionalized bus connection） with transfer bus scheme are used in 220 kV main electrical connections. In some projects 1 1/2 CB connection is employed, but in several projects double bus without

15、 transfer facilities is also used. In case of double bus connections three phase CVT are installed on every bus section, single phase CVT being installed in line side.Single-bus connection is used at main transformer low voltage side without outgoing line circuits, only reactive compensation and aux

16、iliary power system circuits being connected. There are three cases for the general breaker at 35 kV side: not installed, reserve installation position and installed. Likewise, there are two cases for breaker in branch reactor circuits: installed at bus side or at reactor neutral point. As well, in

17、auxiliary power system circuit breakers or limiting-current reactors with fuses may be employed.Typical main electrical connection diagrams are shown in Fig.1.3.2Equipment SelectionThe short circuit current level is usually computed in accordance with the system development plan within 10-15 year af

18、ter substation commissioning. In general cases it is selected as 50 kA,50 kA,40or50 kA（31.1 kA）for 500 kV, 220 kV, 35 kV（66kV）bus-bar respectively. At present time short circuit current level for 500 kV side reaches 62 kA in some substations. The problem, that short circuit current level for 220kV s

19、ide in some substations may reach 63 kA in future, will be solved by employing control measures in the system, for example, to divide the power supply area into parts.Usually single-phase auto-transformers with forced oil and air cooling are equipped. Special system voltage regulation computation is

20、 needed for employing on-load tap-changer transformer. Because of the quality improvement of domestic made transformer, spare transformer is usually not installed in recent years. In some cases, in accordance with transformer manufacture conditions, a spare transformer is necessary for substations i

21、n the whole region. In some projects three-phase transformers are used after economical and technical comparison in transformer including its transportation conditions.500 kV circuit breakers are usually ceramic pole type or tank type. In some special cases, for example, high altitude, severe atmosp

22、heric pollution regions and limited site area, SF metal enclosed gas insulated switchgear（GIS）may also be used. Circuit breakers usually have 4-3 breaks in one phase, or 2 in recent years. 500 kV isolating switches are usually single-or double-pole horizontal swatch-and-draw type, which occupies rel

23、atively less land area. 500 kV current transformers are oil or SF insulated. 35（or66）kV shunt reactors are oil immersed type or aircrew dry type.In order to reduce switching over voltage, 500 kV insulation level and air gaps, high quality SF circuit breakers and good protection performance metal oxi

24、de arresters are employed. In case of relatively long line it may be necessary to equip closing resistors in circuit breakers according to computation study.The external insulation level of electrical equipment is selected according to the regional atmospheric pollution conditions. Usually the selec

25、ted pollution class is not lower than n ,that is, the unit leakage distanee is not less than 20 mm/kV for 500 kV and 220 kV apparatus. The external insulation level for neutral ungrounded low voltage side should be strengthened to one elass higher. The general leakage distanee is ealeulated by using

26、 maximum operating voltage.3.3Insulation CoordinationInsulation eoordination is determined in aeeordanee with the prineiples stated in China Power Industry Standard DL/T62 0- 1997“Ove rl a rg e Proteetion and Insulation Coordination for AC Eleetrieal Installations. ”Power frequeney overvoltage: 1.3U

27、xg for substation side of line breaker, 1.4Uxg for line side. Here Uxg is the maximum operating phase voltage.The eoordination faetor between nominal lightning impulse withstand voltage of eleetrieal installations and residue voltage of substation arresters under nominal diseharge eurrent is adopted

28、 as 1.4.Coordination faetor between nominal phase-to-earth switehing impulse withstand voltage of eleetrieal installation internal insulation and proteetion level of arrester under switehing overvoltage should not be less than 1.15.3.4SwitchyardUsually the following busbar types are used in 500 kV s

29、witehyard: double bundle diameter-extended soft buses, supported thiek aluminum tube buses, or suspended aluminum tube buses by V type insulator strings. The switehyard may be arranged in one, two or three outgoing line directions types. Two outgoing directions type is usually used, and breakers are

30、 arranged in three columns with medium height type. The transformers are connected in series with low frame crossing type, each bay width being 28 m. There are service paths between phases for repairing the switchgear.For 220 kV switchyard, supported or suspended aluminum tube buses are used. Circus breakers are arranged in medium height type in single or two lines, each bay width being 13 or 13.5 m. There are service paths between circuit breakers and current transformers.3.5Grounding SystemThe service life of grounding systems is th