武威干式变压器：武威干式变压器的局部放电

武威干式变压器的局部放电 　　
1.概述
当外加电压在武威干式变压器绕组绝缘中产生的场强.足以使绝缘部分区域发生放电，但未达到绝缘发生贯穿性击穿的放电现象，称为局部放电。
树脂浇注和绕包绝缘的武威干式变压器的包封绕组。由于在制造过程中.不可能完全消除绝缘内部的气隙或气泡.在电场作用下.由于电场强度与绝缘材料的介电系数成反比分配.因此气隙或气泡的场强升高。当达到一定值后.就会导致气隙或气泡发生局部放电.这种放电称为内部放电;发生于绝缘表面的局部放电，称为表面局部放电。
当绕组绝缘发生局部放电时就会影响绝缘寿命。每次放电.高能量电子或加速电子的冲击.特别是长期局部放电作用都会引起多种型式的物理效应和化学变化.即带电质点掩击气泡壁上时.就可能打断绝缘的化学键而产生裂解.破坏绝缘的分子结构.造成绝缘劣化，加速绝缘损坏过程。当然实际绝缘损坏情况还与绝缘材料有关。
当发生局部放电时，能常会出现转化(如转化为冲击电流、介质损耗、超声损耗、超声波和气体压力的增加等)现象.报据这些现象就可对局部放电进行测试与监测。因此对局部放电的测试回路和测试装置等也应有基本了解。
试验研究结果表明.局部放电转化的物理和化学变化是故降诊断和寿命预测的基础。同时鉴于局部放电对于树脂绝缘的主要影响，引起了国内外制造厂家和研究单位的高度重视。并从局部放电机理、监测技术(如在线监测)和抑制干扰等多方面开展了试验研究工作。
在国家标准GB/T10228-1997《武威干式变压器技术参数和要求》中的试验方法及检验规则明确规定，对包封绕组采用树脂浇注工艺的武威干式变压器，应在例行试验中进行局部放电测量；而在JB/T56009-1998《武威干式变压器产品质量分等)中规定了包封绕组的局部放电量，10kV级为30pC,10pC和5pC；35kV级为50pC,20pC和10pC。可以看出，对武威干式变压器局部放电的严格要求，特别是对在监视状态下进行绕包绝缘的武威干式变压器而言更是严苛的考验。

Transformer partial discharge
1 Overview
When the field strength generated by the applied voltage dry-type power transformer winding insulation. Enough to make the insulation part of the regional occurrence of discharge, but did not reach the insulation penetrating breakdown discharge phenomenon, known as the partial discharge.
The cast resin and encapsulated winding around the insulation dry-type power transformers. In the manufacturing process can not completely eliminate the insulation within the air gap or air bubbles under the electric field due to the electric field strength and the insulation material is inversely proportional to the dielectric constant distribution, so the field strength of the air gap or air bubbles rise. Reaches a certain value. Lead to partial discharge air gap or air bubbles. This discharge is called internal discharge; partial discharge occurred in the insulation surface, known as surface partial discharge.
When the winding insulation partial discharge occurs will affect the insulation life. Each discharge. The impact of high energy electrons or accelerated electrons. Especially long-term partial discharge effect will lead to a variety of types of physical effects and chemical changes ie, charged particle mask to blow the bubble wall. The chemical bonds that might interrupt the insulation cracking. molecular structure. destroy insulation and cause insulation deterioration, accelerated damage to the insulation process. Of course, the actual damage to the insulation and insulating materials.
When partial discharge occurs, often transformed into the phenomenon of dielectric loss (such as into the impact of current, ultrasonic loss, ultrasonic and the increase in gas pressure, etc.) these phenomena can be reported according to the partial discharge testing and monitoring. Should have a basic understanding of the partial discharge test circuit and test devices.
The test results show that the actual occurrence of partial discharge into the physical and chemical changes down the basis of the diagnosis and life prediction. View of the partial discharge of a resin insulation, causing a high degree of attention to domestic and foreign manufacturers and research institutes. And from the mechanism of partial discharge monitoring techniques (such as online monitoring) and suppress interference aspects to carry out a pilot study.
National standards GB/T10228-97 dry type power transformers technical parameters and requirements "in the test methods and inspection rules clearly defined, encapsulated windings with resin pouring process of dry-type transformers, partial discharge in the routine test measurement; in JB/T56009-1998 dry-type power transformer product quality grading) provides for encapsulation winding partial discharge 10kV level for 30pC 10pC and 5pC; 35kV class 50pC, 20pC and 10pC. Can be seen that the stringent requirements of the partial discharge o邮 箱：1262980066@qq.comf the dry type power transformers, especially wrapped insulation dry-type power transformers in the surveillance state is a stringent test.

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