關鍵字： 防止； 電動隔離開關 ； 絕緣子 ； 斷裂 ； 新措施
引言 電力系統運行中，由於停送電、倒母線或檢修需要經常進行高壓電動隔離開關的倒閘操作，有時會發生隔離開關支柱絕緣子斷裂事故，嚴重危及運行操作人員的生命安全，甚至會造成大面積設備停電事故的發生，嚴重地影響了設備的供電可靠性和電網系統的穩定運行，對那些生命線用戶，將會造成不可估量的嚴重後果。此前，我公司220kV原平站、220kV義井站都發生過220kV隔離開關支柱絕緣子斷裂的事故，近期又有500kV深圳變電站220kV隔離開關支柱絕緣子斷裂和陝西330kV延安變電站110kV隔離開關支柱絕緣子斷裂等事故發生，致使電網大面積停電，給電網和用戶帶來了巨大的損失，極大地影響了社會的穩定和廣大人民民眾的生活。為此很有必要對高壓電動隔離開關支柱絕緣子斷裂的原因進行認真分析，查明斷裂的主要原因，提出防範措施和技術改進，為高壓電動隔離開關可靠運行提供保障，確保電力系統安全穩定運行。
1支柱絕緣子的特性分析t#
1.1支柱絕緣子的組成
絕緣子一般由絕緣體、金屬附屬檔案、膠合劑三部分組成。絕緣體主要起絕緣、支撐、保護作用。金屬附屬檔案一般用鑄鐵低碳鋼、鋁及合金等組成，起機械固定、連線作用，而膠合劑的作用是將絕緣體和金屬附屬檔案膠合起來。
1.2支柱絕緣子的機械性能
絕緣子在運行過程中需要承受導線以及導體的重量、覆冰重量、設備操作過程中的機械力及交流運行中短路後的電動力、風力、地震等由外界引起的負荷力。所以，其機械性能要求很高，一般要求產品在出廠時要做抗彎、抗扭試驗。
1.3支柱絕緣子的原料組成
絕緣子的坯、釉料的成分主要有二氧化矽、三氧化二鋁及少量的鹼金屬氧化物以及鹼土金屬氧化物。因此，坯料是由黏土、長石、石英以適當比例配合而成，在一般高強瓷中需要使用高鋁及其他原料，而在電瓷釉料中，還需加入一些金屬氧化物，以增加絕緣子強度。
1.4支柱絕緣子燒制過程中強度及硬度的變化
支柱絕緣子在燒制過程中，其硬度隨著溫度的逐漸增高以及燒制時間逐步增加，在小火階段，坯體的強度略有增加，在900度以後，坯體強度會不斷增加，且由於形成長石-石英玻璃及莫來石晶體，使坯體的硬度逐漸提高。
1.5支柱絕緣子的受力分析
根據支柱絕緣子機械結構及幾何分布，套用有關力學原理進行分析表明，絕緣子下瓷體法蘭附近受的剪應力最大，幾十年來，我們接觸到的以及其它地區發生的高壓隔離開關絕緣子斷裂部位都在絕緣子下瓷體法蘭附近，這一結果相互驗證說明絕緣子斷裂與受力密不可分。
2 支柱絕緣子的斷裂原因詳解
2.1製造質量存在問題
生產工藝的每一道工序都將影響產品的質量，產品完善、嚴格的檢驗制度是杜絕不合格產品出廠的主要手段。由於生產廠家利益驅使，生產工藝沒有嚴格把關，對產品沒有嚴格檢驗，沒有嚴把出廠關，造成不合格產品流向用戶。
2.2電動隔離開關安裝調試不到位
隔離開關在安裝調試時，沒有嚴格按照安裝使用說明書的有關要求進行調整，以致操作時絕緣子受力較大，有卡澀、別勁感。
2.3一次導流部分的連線引線連線不規範
隔離開關在安裝調試後，一次導流引線連線不規範，沒有留有一定的弧度，而是直線連線，由於熱脹冷縮及操作時的受力，絕緣子受垂直於軸向的水平力較大而發生斷裂。
2.4傳動部分機械卡澀
隔離開關由於長時間不進行檢修，特別是實行狀態檢修以來，基本上是4年一次，加之有些隔離開關倒閘操作很少，長期的風吹日曬、雨林冰凍，造成傳動部分氧化生鏽引起機械卡澀，操作時絕緣子受的扭力較大而發生斷裂。
2.5設備選型不當
絕緣子承受的機械負荷主要體現在接線端拉力上，沒有充分考慮到設備所處環境的實際情況，導致在惡劣氣候條件下支柱絕緣子彎曲強度低於運行要求，造成絕緣子的斷裂。
2.6隔離開關的結構設計缺陷
隔離開關機械元件抗鏽蝕能力差，運動部位潤滑脂填充不充分，在進行操作時，機構傳動卡澀、別勁，造成絕緣子承受異常彎矩或扭矩而斷裂。
2.7自然環境因素影響
氣候溫差大和惡劣的氣候條件，如熱脹冷縮引起調整好的尺寸變化、暴風驟雨引起的共振，使支柱絕緣子異常受力超過其破壞負荷所致。寒冷地區的絕緣子，由於金屬附屬檔案和膠裝水泥的應力疊加，也會導致絕緣子斷裂。
2.8絕緣子老化
絕緣子運行年限較長，有的超過二十年，在長年的運行中，逐步勞損，強度降低在受力時引起絕緣子斷裂。
綜上所述，隔離開關不論是產品質量問題，還是安裝調試不到位、導流部分連線不規範、機械卡澀，或者是設計、選型不當，以及自然環境因素影響老化等，最終斷裂都與受力有關。
New Measures to Avoid theFracture of High Voltage Post Insulator of Electric Isolating Switch
Abstract:
Thefracture of post insulator may occur during the order sheet for the electricisolating switch which operation requires continually check in the electricpower system. It can cause massive power outage regionally and can even be asevere threaten to the operators and the equipments. We made a collection ofthe accidents and analyzed the reasons from the aspects of anti-pulling force,poor quality, installation and debugging, to jam faults during transmission andmany and concluded that any kind of fractures are related to the forces that thepost insulator bear. In this sense, we propose a few new measures in the pointof electric controlled operation for the circuit.
Key words:
avoid; electric isolating switch;insulator; fracture; new measures
Foreword：
The fractureaccident occurs in the operation of the order sheet for the high voltageelectric isolating switch and arouses immeasurable consequences on the reliabilityof the power distribution device, the stability motion of the electric fenceand the supply to the users on the main lines. Not long ago, we’veunfortunately been the fracture accidents in Pingyuan, Yijing, Shengzheng, Sha’anxi,and Yanan substation at the kilovolt 110, 220, 330, 500. The aftereffect interruptedgrievously the routine lives of the users in large scale. In order to promoteand protect the high voltage post insulator of electric isolating switch andavoid the fracture, to provide a safe and stable motion, it is essential thatwe analyze these accidents and find out the reason that causes it.
1: specificityanalysis
1, 1 from of thepost insulator
The insulator is form of insulator, metal accessory and cement. Themain function of the insulator is insulation, support and protection. The metalaccessory is mainly formed of iron casting low carbon steel, aluminum andalloy. It mechanical fix and connect the parts. The cement is used to stick theinsulator and metal accessory together.
1, 2 mechanicalproperties of the post insulator
In the motion the insulator bears the weighof the wire, the conductor and the covering ice mixed with force of themechanical power during the motion, the electrodynamics and wind power afterthe short circuit in alternating motion, also load force caused by the externalword, like earthquake. Therefore the mechanical properties are highlydemanding. The insulator is exactingly tested on the flexible and torque strengthbefore leaving the factory.
1, 3 raw materialcompositions of the post insulation
Silica, aluminum oxide, a small amount of alkali metal oxide and alkali earthoxide is the component of the insulation. The billet is composed in proportionof clay, feldspar, quartz. The high tensionporcelain requires high aluminum and others. The electric porcelain needs someextra metallic oxide to strength the insulation.
1, 4 strength andhardness changes of post insulation during firing procedure
When lowheating, the adobe strength increases a little bit following the rising of temperatureand time. After passing 900 centigrade, the strength grows sharply with thehelp of feldspar-quartz glass and mullite crystal.
1, 5 force analysis of post insulation
The shear strength goes up tothe highest around the flanged porcelains according to the mechanical structure and geometric distribution of theinsulation, also with relative evidences from mechanical principles analysis. Inthe past decades years, the fracture accidents all assemble
around the flanged porcelains. That highly shows the fractures arequite possible caused by the force it bears.
2: explanation of the post insulation fracture
2, 1 poor quality
Theproducers driven by the improper benefits neglect the procedure and the qualityinspection in order to produce more. Each procedure affect the final productand that kind of poor quality account for the main responsibility for the fractureaccidents.
2, 2 incorrectly installation of the electric isolation switch
The insulation bears more forces and stucksif not installed or adjusted exactly according to the instruction.
2, 3 improper connection of the lead wire in the diversion part
The lead wire is connected in a straightinstead of remaining a certain radian, which would ends in causing fractureonce forced by thermal expansion and contraction or horizontal stress in themotion.
2, 4 mechanical jam in the transmission part
The overhaul for the isolatingswitch is neglected for long time, only goes once in four years especially afterthe condition-based maintenance is conducted. And because there is merely anorder sheet, the transmission part is oxidation of rust due to long exposure tosunlight and natural water. When operating, the insulation will beak out inresult of the torsion.
2, 5 improper selection of equipment
The mechanical loads of the insulationmainly embody in the pulling force that the terminal bears. The bending strengthof the post insulation should fit any adverse conditions that it is depositedin, otherwise it breaks.
2, 6 structure design defect of the isolation switch
The mechanical component in lowanti corrosion ability, no enough grease in the motion parts and other reasonswould all cause the torques and bending moments that commit the transmissionparts stuck and break.
2, 7 natural environment factors
Largetemperature difference and adverse climate make the abnormal strength that the insulationbears exceeding the damaging load, such as the size varies from the thermalexpansion and contraction, resonance raised by the storm, the multiplied stressby mental accessory and cementing cement would all bring the fracture.
2, 8 ageing of the insulation
The long-time running, some evenup to 20 years, of the insulation will damage the capacity that it bears the strength.And then the fracture happens.
From all above we can see whatever cause it is, the fracture is closelyrelated to the force that the insulation bears.
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