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Power Technology and Engineering Vol.38,No.5,2004 ENERGY SYSTEMS AND ELECTRICAL NETWORKS TECHNICAL 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 lektricheskie Stantsii,No.8,August 2004 A 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,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 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network and inadequate volume of devices for voltage control;low design reliability of the active transmission lines;1 outdated design of overhead lines;use of some outdated technologies and kinds of network equipment and control systems;low level of automation of network objects and absence of fully automated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 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 are 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 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 circuit 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 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.2 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 Zaporozhye Transformer Plant(ZTZ).Transformers for the Russian power industry are produced by the Moscow Electric Plant(M Z).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 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 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%;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 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 raise the reliability of transformer equipment:use of 3 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 bushings,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 determining 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 indirectly 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%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 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).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 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 4 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 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 ES 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-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 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 service 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 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 of 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 year 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:5 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 and recovery voltages exceeding the rated values.Problems with switching of reactor connections deserve special notice.According to the performance specification reactors can be switched several times a day,which requires a high mechanical strength of the circuit breaker.When a circuit breaker is switched off,overvoltages appear at its contacts.Since the GOST 68778 State Standard does not specify the mode of switching-off of reactor connections,air circuit breakers are not tested for switching-off of reactor connections.The domestic industry continues to produce oil and air circuit breakers,but there is a tendency to replace them gradually by SF6 circuit breakers.Foreign companies have stopped the production of oil and air breakers and passed to SF6 switches.According to the data of CIGRE the foreign fleet of SF6 circuit breakers amounts to 52%for 110 kV,55%for 220 kV,69%for 330 kV,66%for 500 kV,and 8%for 750 kV;the fraction of SF6 circuit breakers mounted in the last ten years is 93%.1 能源技术和工程学卷。2004年5月38日 电力系统 变电站基本设备的技术状态和架空线以及提高可靠性的措施 翻译：D.S.Savvaitov1和L.v Timashova1.lektricheskie Stantsii 2004年8月8日 本文对110-750千伏电力网络上使用的基本设备状态和在设备操作中出现的问题作了简要说明。并且提出了提高可靠性的建议 文中讨论的设备包括变压器，高压开关、分合器、互感器、非线性过电压继电器和输电线路。关键词：变压器，高压开关，分合器，互感器，过电压继电器，输电线路，产品使用期限。苏联现有的 110-750 千伏电力网络存在以下问题：-变电站存在大容量的耗电设备-电网状况不好，电压控制装置的容量不合适;-输电线路的可靠性低;-架空线的设计落后-使用的技术、电网设备和控制系统落后;-电网的自动操作水平低，缺乏足够的综合自动化的变电站 -性能说明不全面，网络设施维修不当;-高营业成本。2 现有的大部分设备已经达到了规定的产品使用期限。值得注意的是，不同的种类设备有不同的使用期限。平均来说，变电站设备的损耗已经达到了 40%。要求的基本设备的可靠性仅在 GOST 687-78 中规定断路器为超过 1000 V。GOST 687-78 确定的标准也包括设备使用期限要按照关合次数 N 规定。就架空线而言N 通常等于1000次。然而，实际在330-500千伏试验架空线上的开关在关合240-380 次以后就失灵了。我们了解到电力设备的可靠性,可以通过操作数据估计出来。俄国输电线上主要装设的是空气断路器。SF6 断路器是所有断路器总数的4%。由于缺乏足够的失灵数据，不能够分析这 4%的断路气的操作效率。国内各生产商制造的非线性过电压继电器(OVS)的可靠性在产品说明中表示的是，产品使用期限仅为 25(或 30)年，失灵概率为 0.98。这意味着每年在每 1000 个 OVS中有 0.8(或 0.67)个可能出现故障。这个数据并没有通过实际操作来验证。变压器：变压器，自耦变压器(AT)，以及分裂电抗器是变电站的可靠设备。在苏联，大容量的变压器的质量是由严格的、专业化的生产商保证。所有大容量变压器是由 Zaporozhye 变压器厂(ZTZ)生产的。俄国小型电力变压器是由莫斯科电力工厂(MZ)生产的。操作经验表明，在俄联盟和在苏联生产的电力变压器的可靠性可以与外国生产商的水平相比。然而，12965-85 和 GOST 17544-85(苏联)指定的容量和大小参数还有损失，特别是无载部分，低于世界上的平均水平。当前，在 110-750千伏总功率为570 GVA的电网中，电力变压器达到数额为30000个，包括大约 25000 个对于 120 MVA。大约 30%的变压器使用已经超过了 25 年，并且在 2005 年大约超过一半的变压器的使用超过了 25 年。终端缺陷得不到限制，在 1970 年之前生产的变压器的损耗达到了 1%;以后变压器的生产，它的损耗达到了 0.2%。在最近五年做的分析表明变压器的每年损耗为 0.45%。这种损耗一般来说是很严重的，并且伴随着爆炸和火，这是由于火花穿过了套管内部表面的杂质引起的。大约 23.5%的故障是由于调节负荷分接头装置（LTC）引起的。世界上，在自耦变压器的使用过程中由套管和 LTC 的破坏所引起的故障也经常发生。5.36%的故障是由于在故障中绕组的不稳定造成的，这种情况经常发生在 330-和 500 千伏自耦变压器中。每年 50%的故障的发生是由于主要绝缘材料的缺陷(包括在线圈上的毛刺)。所引起 3 的。目前自耦变压器的效率超过了 99.5%(在 500-750 千伏电网中效率超过了99.7%)并且极少出现故障。为了提高变压器设备的可靠性可以采取下措施：-采用更加可靠的套管，强度高的绝缘材料是由 Khotkovo 工厂和 ABB 公司合作生产的，套管是由“Izolyator”工厂生产的，并且现在很少使用价格很高的Micafil 生产的进口套管;-采用更加可靠的 LTC。传统的 LTC 供应商是 Maschinenfabrik Reinhausen Company(德国)。其可靠性很低，而更加便宜的设备是由 Zaporozh ye 变压器厂制造的;-采用可测量油温的具有自动冷却的控制装置的温度计来测量热负荷，代替每超过 10C 就会出错的压力温度计-采用国外测量线圈温度的方法。这种方法在必要时能够控制超载，并且间接地控制绝缘材料的热量穿透(ZTZ 和 MZ 装备国内自耦变压器和具有这种装置的进口变压器)。110-750 千伏高压断路器 全国(所有俄国)电力网从 110 到 750 千伏使用了超过 30,000 台的断路器，其中 80.5%是 110 千伏断路器，15.2%是 220 千伏断路器，1.2%是 330 千伏断路器，3%是 500 千伏断路器，还有 0.1%使用 750 千伏断路器在 110 和 220 千伏电网中，油型断路器的安装超过了 50%，(110 千伏为 58%，220千伏为 45%)。从 20 世纪 30 年代到 80 年代，油断路器(MKP 和 U)是由 Urallektroapparat工厂生产的，然后是由 Urallektrotyazhmash 生产协会生产的。Live-tank 型断路器在 110 和 220 千伏电网里占所有断路器的 24.3%，(110 千伏为 27%，220 千伏为 17%)。VMT-110 和 VMT-220 断路器是由 Uralelektrotyazhmashh(UTM)，MMO-110 保加利亚断路器厂生产的，只有少量的断路器是进口的。VMT-110和 VMT-220 断路器直到现在一直生产着。在 2000 年使用了 285 件，在 2001年，使用了 320 件。而 VMT-220 断路器每次的数量是 15 个和 30 个。空气断路 4 器的数量是总占所有断路器数量的 18.6%(110 千伏中为 12%，220 千伏中为35%，在 330-和 500 千伏为 97%)。VVN，VV，VVB，VVD，和 VNV 系列的空气断路器是由 lektroapparat 和 Urallektrotyazhmash工厂生产的。直到1996年俄国电力系统才开始试验使用SF6断路器。1997年才决定用SF6断路器重新架设和修复 330-和 750千伏的 RAO“ES Rossii”Co.变电站。这样，SF6 断路器的数量很快的增起来，现在共计达到所有断路器数量的 4%。SF6 柱型断路器和 tank-type型断路器是由 UTM 提供的(110千伏断路器的开断电流为 40 千安)，是由电力机械厂提供的(110-和 220千伏 tank-type型断路器)，还有由外国生产商提供的(ABB，Alstom，西门子)。在全国（全俄国）的 110KV和220KV电网中工作的大量的油和空气断路器已经达到了使用期限，这样的断路器在所有断路器中占 35%。90%的 MKP-110和 VVN-110断路器，40%U-110断路器，还有 50%的 VVN-220断路器也到达了他们的使用期限。开关的可靠性取决于各种断路器在断路器使用期限内的叫做断路器年的失灵参数。国内高压开关系列VV 在 110-220千伏电网中的失灵参数是每年 0.07-0.08;在 500-750千伏电网中，断路器的失灵参数是每年 0.13-0.15。根据这个 CIGRE数据得到 110KV和高压断路器的失灵参数是每年 0.01。可靠性最差的断路器为以下这些：MMO-110为 0.100每年(保加利亚)，VVB-110为 0.111每年，VVN-220为 0.134每年，VVN-330为 0.129每年，VVBK-500为 0.242每年，还有 VV(M)-500为 0.065每年。这些开关不符合现代标准的要求,包括可靠性，开关和机械使用期限，修理容量，质量，和大小。我们知道国内开关是由以下原因损坏的：-设计缺陷;-产生材料品质低的缺陷;-生产缺陷;-执行和维护失败;-断路器的感应器和电容器排是不合适 5-在短路电流情况下恢复电压操作超出额定值。开关的感应器的连接问题应该得到特别的重视。根据表现规格感应器一天可以被开关多次，这就需要一个高机械强度的断路器。当断路器关掉时，过电压出现于它的保护接触处。因为 GOST 687-78标准没有指定开关感应器的连接方式，空气断路器并不测试开关感应器的连接。国内产业继续生产油和空气开关，但有被 SF6断路器逐渐代替的倾向。外国公司停止了油和空气破碎机的生产并且通过了 SF6断路器。根据 CIGRE提供的数据，国外的 SF6断路器在所有断路器中的比例上升到 110千伏为 52%，220千伏为 55%，330千伏为 69%，500千伏为 66%，并且 750千伏为 8%;SF6断路器所占的比例在最近十年达到了 93%。