1、英文文献 ENERGY SYSTEMS AND ELECTRICAL NETWORKS TECHNICALSTATE OF BASIC EQUIPMENT OF SUBSTATIONS AND OVERHEAD TRANSMISSION LINES AND MEASURES FOR RAISING THEIR RELIABILITY Abstract A brief description of the state of basic equipment employed in 110 750-kV power networks is presented. Problems arising in
2、 operation of this equipment are outlined and recommendations on improving its reliability are made. Transformer equipment, high-voltage circuit breakers, disconnectors, measuring transformers, nonlinear overvoltage suppressors, and transmission lines are considered. Keywords: transformer equipment；
3、 high-voltage circuit breakers； disconnectors,；measuring transformers； overvoltage suppressors； transmission lines； service life. The existing 110 750-kV power networks have been created in the Soviet Union and are now experiencing the following problems: a large volume of time-worn electric equipme
4、nt at substations； poor controllability of the network and inadequate volume of devices for voltage control； low design reliability of the active transmission lines； outdated design of overhead lines； use of some outdated technologies and kinds of network equipment and control systems； low level of
5、automation of network objects and absence of fully automated substations； inadequate performance specification and maintenance of network facilities； high operating costs. A great part of the installed equipment has exhausted standardized minimum service life. It should be noted that different kinds
6、 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 are standardized only in GOST 68778 for ac circuit breakers rated for over 1000 V. The GOST68778State Standard also includes requiremen
7、ts 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 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
8、 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 circuit breakers. SF6 circuit breakers constitute only 4% of the total number of employed breakers. The efficiency of operation of these four
9、 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 various domestic producers is declared in performance specifications, where their service life is limited to 25 (or 30) years with a pro
10、bability 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. Transformer equipment. Transformers, autotransformers (AT), and shunting reactors are reliable facilities at substations. The relatively hig
11、h 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 Zaporozhye Transformer Plant (ZTZ). Transformers for the Russian power industry are produced by the Moscow Electric Plant (MZ). Operational ex
12、perience shows that power transformers produced in the USSR and in the Russian Federation have reliability comparable to the level of foreign producers. However, the mass and size parameters specified by GOST 1296585 and GOST 1754485 (USSR) and the losses, especially the no-load ones, are lower than
13、 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 including 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
14、 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 1%； for transformers produced later it amounts to about 0.2%. An analysis made in the last five years shows that the specific annual da
15、mageability 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 scurf on the internal surface of the bottom cover of bushings. About 23.5% of failures occur with load tap change devices (LTC). In the worl
16、d practice autotransformers also fail frequentlydue to the damage of bushings and LTC. 5.36% failures occur due to inappropriate stability of windings during faults, which is the most frequent for 330- and 500-kV autotransformers. Every year one-two failures occur due to defects of major insulation
17、(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 damageability. The following measures are taken in order to raise the reliability of transformer equipment: use of more reliable bushings,
18、bushings with solid insulation produced by the Khotkovo Plant in cooperation with the ABB Company, bushings produced by the Izolyator Plant, and imported Micafil bushings, now used seldom because of the high cost； use of more reliable LTC. Traditional supplier of LTC is the MaschinenfabrikReinhausen
19、 Company (Germany). Less reliable but cheaper devices are produced by the Zaporozhye Transformer Plant； use of devices for measuring the oil temperature for determining the heat load on the AT with automatic control of cooling devices instead of the now used pressure-filled thermometers that give an
20、 error exceeding 10C； use of foreign practice of measuring the temperature of windings. This makes it possible to control overloads if necessary and also indirectly control the thermal wear of the insulation (ZTZ and MZ equip domestic autotransformers and imported transformers with such devices). Hi
21、gh-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% are 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% o
22、f 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 the 1930s to the 1980s tank-type oil switches (MKP and U) have been produced by the Urallektroapparat Plant and then by the Urallektrotyaz
23、hmash 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). 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
