Power Technology and Engineering Vol. 38, No. 5, 2004
ENERGY SYSTEMS AND ELECTRICAL NETWORKS
hasta la vistaTECHNICAL STATE OF BASIC
EQUIPMENT
OF SUBSTATIONS AND OVERHEAD
TRANSMISSION LINES
AND MEASURES FOR RAISING THEIR RELIABILITY
D. S. Savvaitov1 and L. V. Timashova1
Translated from Élektricheskie Stantsii, No. 8, August 2004
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A brief description of the state of basic equipment employed in 110 – 750-kV power networks is prented. Problems arising in 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, high-voltage circuit breakers, disconnectors, measuring transformers, overvoltage suppressors, transmission lines, rvice 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 equipment at substations;root什么意思
— poor controllability of the network and inadequate volume of devices for voltage control;
潜行深渊— low design reliability of the active transmission lines;
— outdated design of overhead lines;留学前培训
compile— u of some outdated technologies and kinds of network equipment and control systems;
— low level of automation of network objects and abnce of fully automated substations;
— inadequate performance specification and maintenance of network facilities;drl
— high operating costs.
A great part of the installed equipment has exhausted standardized minimum rvice 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 ba facilities are standardized only in GOST
687–78 for ac circuit breakers rated for over 1000 V. The GOST 687–78 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-off cycles .However, in the actual practice overhead circuit breakers rated for 330 – 500 kV fail after 240 – 380 cycles. We can e that the reliability of the ba power equipment can be evaluated only with the help of operational data. Russian transmission lines are chiefly equipped with airfollowyourheart
circuit breakers. SF6 circuit breakers constitute only 4% of the total number of employed breakers. The efficiency of operation of the four percent cannot be analyzed at prent due to the abnce 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 rvice life is li蜡笔英语怎么读crayon
mited 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. The 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 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 Zaporozh’ye Transformer Plant (ZTZ). Transformers for the Russian power industry are produced by the Moscow Electric Plant (MÉZ). 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 mass and size parameters specified by GOST 12965–85 and GOST 17544–85 (USSR) and the loss, especially the no-load ones, are lower than in the world practice. At the prent 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 rved for over 25 years, and in 2005 about half of the transformers will rve for more that 25 years. Without allowance for the damage of terminals, ha
rd 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 damageability of transformers is 0.45%. This kind of damage is for the most part vere 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 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 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 rai the reliability of transformer equipment: — u of more reliable bushings, bushings with solid insulation produced by the Khotkovo Plant in cooperation with the ABB Company, bushings produ ced by the ―Izolyator‖Plant, and imported Micafil bushings, now ud ldom becau of the high cost; — u of more reliable LTC. Traditional supplier of LTC is the Maschinenfabrik Reinhaun Company (Germany). Less reliable but cheaper devices are produced by the Zaporozh’ye Transformer Plant;—
u 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 ud pressure-filled thermometers that give an error exceeding 10°C; — u 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 MÉZ 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% 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% 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 the 1930s to the 1980s tank-type oil switches (MKP and U) have been
produced by the Uralélektroapparat Plant and then by the Uralélektrotyazhmash Production Association. Live-tank circuit breakers for 110 and 220 kV constitute 24.3% of the total number of ins
talled breakers (27% 110-Kv and 17% 220-kV). The are VMT-110 and VMT-220 circuit breakers produced by
圣诞快乐英语怎么说Uralélektrotyazhmash (UÉTM), 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 amount 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 the VVN, VV, VVB, VVD, and VNV ries have been produced by the Élektroapparat and Uralélektrotyazhmash 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 ―EÉS Rossii‖ Co. with SF6 circuit breakers. The number of such breakers incread progressively and now amounts to 4%.SF6 column-type and tank-type circuit breakers are supplied by UÉTM (primarily 110-kV breakers with breaking current of up to 40 kA), by the Power Mechanical Plant (110- and 220-kV tank-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 rvice life. This is 35% of the total number of breakers 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 rvice life. The damageability of circuit breakers is determined in terms of the failure flow calculated as the ratio of the total number of all kinds of failure to the total rvice life of the breakers counted in breaker-years. For domestic high-voltage circuit breakers of the VV ries 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 of CIGRE the mean failure flow for 110-kV and higher-voltage breakers is 0.01 per year.
