刍议高压直阻试验中如何有效判断变压器内部过热故障

本文主要提出结合高压直阻试验和色谱三比值法可以对变压器的内部过热故障进行有效的判断。相关的实例检测显示,过热故障大多存在于引线、分接开关、夹件、铁心及绕组等部件;准确的判断故障部位时,除直阻测试和油气分析外还需结合运行状态和内部结构及其它电气试验。过热性故障中其中固体绝缘的过热对绝缘危害性较大,会导致绝缘材料的劣化。及时快速的查找出变压器内部过热的故障原因,并及时排除故障,是对供电质量和供电安全的有力保证。

直阻试验在箱变检修中的应用

某油浸式变压器运行时间超10年,通过测量直流电阻发现运行中因振动而产生的机械应力等原因所造成的接线松动、导线断裂、接头开焊、接触不良、匝间短路等缺陷,对箱变的长期稳定运行具有重要意义。

励磁涌流引起主变差动保护动作的原因及防范

变压器差动保护的关键问题是励磁涌流的可靠鉴别,直接约束着变压器主变差动保护的正确动作率,文章通过研究励磁涌流引起主变差动保护。进行了原因分析,并提出了对励磁涌流相关值进行改进的防范对策,对于指导变压器合闸具有一定的指导性意义。

Study on the resistance spot welding technology of 22MnMoB hot stamping quenched steel

In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we have obtained the optimal spot welding technological parameter condition. According to the results, the relations among spot welding technological parameter, welding nugget, mechanical property and fracture mode were discussed. The effects of all the welding parameters such as welding current, welding time and electrode force on the quality of joint can be boiled down to one thing--the diameter of welding nugget. The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation. There are two typical fracture models of 22MnMoB hot stamping quenched steel sheet, i.e., interracial fracture and nugget pullout. Other than mild steel or normal high strength steel, in the shearing tensile test, hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure, welding soft zone and the porosity level of fusion zone.

对变压器差动保护误动的应用分析

直阻试验后变压器残余剩磁将影响变压器差动保护的判别,空投时会产生数值较大、二次谐波含量较低的励磁涌流,结果可能导致差动保护二次谐波闭锁失效。而采取二次谐波、波形对称多种判据混合判别的方法可以提高差动保护动作的可靠性。