电力英文翻译.docx

1、电力英文翻译Power Technology and Engineering Vol. 38, No. 5, 2004ENERGY SYSTEMS AND ELECTRICAL NETWORKSTECHNICAL STATE OF BASIC EQUIPMENTOF SUBSTATIONS AND OVERHEAD TRANSMISSION LINESAND MEASURES FOR RAISING THEIR RELIABILITYD. S. Savvaitov1 and L. V. Timashova1Translated from lektricheskie Stantsii, No.

2、8, August 2004A brief description of the state of basic equipment employed in 110 750-kV power networks is presented. Problems arising in operation of this equipment are outlined and recommendations on improving its reliability are made. Transformer equipment, high-voltage circuit breakers, disconne

3、ctors, measuring transformers, nonlinear overvoltage suppressors, and transmission lines are considered.Keywords: transformer equipment, high-voltage circuit breakers, disconnectors, measuring transformers, overvoltage suppressors, transmission lines, service life.The existing 110 750-kV power netwo

4、rks have been created in the Soviet Union and are now experiencing the following problems: a large volume of time-worn electric equipment at substations; poor controllability of the network and inadequate volume of devices for voltage control; low design reliability of the active transmission lines;

5、 outdated design of overhead lines; use of some outdated technologies and kinds of network equipment and control systems; low level of automation of network objects and absence of fully automated substations; inadequate performance specification and maintenance of network facilities; high operating

6、costs.A great part of the installed equipment has exhausted standardized minimum service life. It should be noted that different kinds of equipment have different load-lives. On the average, the substation equipment has been worn out by about 40%. Requirements on reliability of the base facilities a

7、re standardized only in GOST 68778 for ac circuit breakers rated for over 1000 V. The GOST 68778 State Standard also includes requirements on the mechanical life evaluated in terms of parameter N specified for every kind of circuit breaker. For overhead transmission lines N is usually equal to 1000

8、on-off cycles .However, in the actual practice overhead circuit breakers rated for 330 500 kV fail after 240 380 cycles. We can see that the reliability of the base power equipment can be evaluated only with the help of operational data. Russian transmission lines are chiefly equipped with air circu

9、it breakers. SF6 circuit breakers constitute only 4% of the total number of employed breakers. The efficiency of operation of these four percent cannot be analyzed at present due to the absence of enough data in their failures. The reliability of nonlinear overvoltage suppressors (OVS) fabricated by

10、 various domestic producers is declared in performance specifications, where their service life is limited to 25 (or 30) years with a probability of 0.98. This means that 0.8 (or 0.67) out of 1000 OVS can fail every year. These declared data have not been confirmed yet by operational experience.Tran

11、sformer equipment. Transformers, autotransformers (AT), and shunting reactors are reliable facilities at substations. The relatively high level of quality of large transformers has been ensured in the USSR by strict specialization of producers. All large transformers have been produced by the Zaporo

12、zhye Transformer Plant (ZTZ). Transformers for the Russian power industry are produced by the Moscow Electric Plant (MZ). Operational experience shows that power transformers produced in the USSR and in the Russian Federation have reliability comparable to the level of foreign producers. However, th

13、e mass and size parameters specified by GOST 1296585 and GOST 1754485 (USSR) and the losses, especially the no-load ones, are lower than in the world practice. At the present time, the fleet of power transformers rated to 110 750 kV amounts to about 30,000 pieces with a total power of 570 GV A inclu

14、ding about 25,000 pieces rated to 120 MV A. About 30% of the transformer equipment have served for over 25 years, and in 2005 about half of the transformers will serve for more that 25 years. Without allowance for the damage of terminals, hard damage of transformers produced prior to 1970 amounts to

15、 1%; for transformers produced later it amounts to about 0.2%. An analysis made in the last five years shows that the specific annual damageability of transformers is 0.45%. This kind of damage is for the most part severe and is accompanied by explosion and fire due to spark over through yellow scur

16、f on the internal surface of the bottom cover of bushings. About 23.5% of failures occur with load tap change devices (LTC). In the world practice autotransformers also fail frequentlydue to the damage of bushings and LTC. 5.36% failures occur due to inappropriate stability of windings during faults

17、, which is the most frequent for 330- and 500-kV autotransformers. Every year one-two failures occur due to defects of major insulation (including burrs on winding wires).Modern autotransformers have an efficiency exceeding 99.5% (in 500- and 750-kV AT the efficiency exceeds 99.7%) and very low dama

18、geability. The following measures are taken in order to raise the reliability of transformer equipment: use of more reliable bushings, bushings with solid insulation produced by the Khotkovo Plant in cooperation with the ABB Company, bushings produced by the “Izolyator” Plant, and imported Micafil b

19、ushings, now used seldom because of the high cost; use of more reliable LTC. Traditional supplier of LTC is the Maschinenfabrik Reinhausen Company (Germany). Less reliable but cheaper devices are produced by the Zaporozhye Transformer Plant; use of devices for measuring the oil temperature for deter

20、mining the heat load on the AT with automatic control of cooling devices instead of the now used pressure-filled thermometers that give an error exceeding 10C; use of foreign practice of measuring the temperature of windings. This makes it possible to control overloads if necessary and also indirect

21、ly control the thermal wear of the insulation (ZTZ and MZ equip domestic autotransformers and imported transformers with such devices).High-voltage 110 750-kV circuit breakers. The national (all-Russian) power network employs over 30,000 circuit breakers rated for from 110 to 750 kV of which 80.5% a

22、re 110-kV breakers, 15.2% are 220-kV breakers, 1.2% are 330-kV breakers, 3% are 500-kV breakers, and 0.1% are 750-kV breakers. Over 50% of the installed circuit breakers are tank-type oil switches rated for the voltage of 110 and 220 kV (58% are rated for 110 kV and 45% are rated for 220 kV). From t

23、he 1930s to the 1980s tank-type oil switches (MKP and U) have been produced by the Urallektroapparat Plant and then by the Urallektrotyazhmash Production Association. Live-tank circuit breakers for 110 and 220 kV constitute 24.3% of the total number of installed breakers (27% 110-Kv and 17% 220-kV).

24、 These are VMT-110 and VMT-220 circuit breakers produced by Urallektrotyazhmash (UTM), MMO-110 Bulgarian circuit breakers, and a small number circuit breakers imported from ASEA and other foreign companies. VMT-110 and VMT-220 breakers are being produced until now. In 2000 they were shipped in an am

25、ount of 285 pieces, in 2001 they were shipped in an amount of 320 pieces. The respective numbers of VMT-220 breakers are 15 and 30 pieces .The amount of air circuit breakers is equal to 18.6% of the total number of installed breakers (12% 110-kV, 35% 220-kV, and 97% 330- and 500-kV). Air breakers of

26、 the VVN, VV, VVB, VVD, and VNV series have been produced by the lektroapparat and Urallektrotyazhmash Plants.Until 1996 Russian power systems had single SF6 circuit breakers in pilot operation. In 1997 it was decided to equip newly erected and reconditioned 330- and 750-kV substations of the RAO “E

27、S Rossii” Co. with SF6 circuit breakers. The number of such breakers increased progressively and now amounts to 4%.SF6 column-type and tank-type circuit breakers are supplied by UTM (primarily 110-kV breakers with breaking current of up to 40 kA), by the Power Mechanical Plant (110- and 220-kV tank-

28、type breakers), and by foreign producers (ABB, Alstom, Siemens). A considerable part of the oil and air circuit breakers operating in the united national (all-Russian) electric network are rated for 110 and 220 kV and have exhausted the specified service life. This is 35% of the total number of brea

29、kers in operation. Ninety percent of the MKP-110 and VVN-110 breakers, 40% of the U-110 breakers, and 50% of the VVN-220 breakers have exhausted their specified service life. The damageability of circuit breakers is determined in terms of the failure flow calculated as the ratio of the total number

30、of all kinds of failure to the total service life of the breakers counted in breaker-years. For domestic high-voltage circuit breakers of the VV series rated for 110 220 kV the failure flow parameter is 0.07 0.08 per year; for the 500 750-kV switches it is 0.13 0.15 per year. According to the data o

31、f CIGRE the mean failure flow for 110-kV and higher-voltage breakers is 0.01 per year.The worst reliability is reported for the following kinds of circuit breakers: 0.100 per year for MMO-110 (Bulgaria), 0.111 per year for VVB-110, 0.134 per year for VVN-220, 0.129 per year for VVN-330, 0.242 per ye

32、ar for VVBK-500, and 0.065 per year for VV(M)-500. These switches do not meet the requirements of modern standards, including the parameters of reliability, switching and mechanical lives, repair volume, mass, and size. Domestic circuit breakers are known to be damaged for the following reasons: design drawbacks; defects due to low quality of materials; production defects; performance and maintenance failures; presence of shunting reactors and capacitor banks in circuits for which the breakers are unsuitable; operation under conditions of short-circuit currents