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1、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. 8, Aug
2、ust 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, disconnectors,
3、 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 networks ha
4、ve 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;1 outd
5、ated design of overhead lines; use of some outdated technologies and kinds of network equipment and control systems; low level of automation of network objects and absence of fully automated substations;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 costs
6、.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 are st
7、andardized 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 on-of
8、f 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 circuit br
9、eakers. 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 vari
10、ous 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.2Transfor
11、mer 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 Zaporozhye
12、 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, the ma
13、ss 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 including
14、 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 1%;
15、 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 scurf on
16、 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, 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 w
