﻿ 变压器铁芯接地电流测量与特征分析 Measurement and Characteristic Analysis of the Core Grounding Current of Transformer

Journal of Electrical Engineering
Vol.03 No.04(2015), Article ID:16491,8 pages
10.12677/JEE.2015.34014

Measurement and Characteristic Analysis of the Core Grounding Current of Transformer

Jiahui He1, Yongqin Wang1, Xin Tong1, Qiyi Zhou2

1State Grid Hubei Electric Power Research Institute, Wuhan Hubei

2State Grid Jingzhou Electric Power Supply Company, Jingzhou Hubei

Received: Nov. 19th, 2015; accepted: Dec. 5th, 2015; published: Dec. 9th, 2015

Copyright © 2015 by authors and Hans Publishers Inc.

ABSTRACT

In this paper, we analyze the core structure and the influence factors of the transformer. Through the study of the mechanism and circuit model of core grounding current, the harmonic component of the core is pointed out in the single-phase transformer. By selecting the typical transformer to carry out the measurement of the core, the existence of the harmonic in the core grounding current is verified, and the harmonic content is related to the structure of the transformer. At the same time, we analyze the current waveform of a transformer core with multi-point grounding transformer. Then it is proved that the installation of resistance can limit the size of the current of the core, but does not change the content of its harmonics.

Keywords:Core Grounding Current, Multi-Point Grounding Fault, Harmonic

1国网湖北省电力公司电力科学研究院，湖北 武汉

2国网荆州供电公司，湖北 荆州

1. 引言

2. 变压器铁芯接地电流理论分析

2.1. 变压器铁芯结构

1：拉带，2：接地片，3：拉带，4：夹紧螺杆，5：上夹件，6：拉螺杆，7：下夹件，8、9：垫脚，10：绑扎带

Figure 1. Structure of 3-phase 3-limb transformer core

2.2. 铁芯接地故障原因

(1) 变压器内部杂质影响。制造过程中内部残留的导电性悬浮物、油路中因轴承磨损引入的金属粉末、加工时残留的金属焊渣，这些导电悬浮物在油流作用下，往往被堆积到仪器，使铁芯与箱壁之间短接，造成多点接地[10] 。

(2) 结构件与铁芯非正常接触，如上夹件碰油箱、夹件小托板碰铁芯、穿心螺杆刚座套碰铁芯、钢垫脚与铁芯之间的绝缘破损或受潮等。

(3) 工艺不良，导致的结构变形。如铁芯本体易位变形、外部压紧件变形翘曲等因素均可能导致多点接地故障。

2.3. 铁芯接地电流理论分析

3. 典型案例分析

(a) 基波分析模型 (b) 3次谐波分析模型UA1、UB1、UC1为绕组基波等效电压，CA1、CB1、CC1为基波下等效电容；UA3、UB3、UC3为绕组3次谐波等效电压，C3为3次谐波下等效电容。I1、I3分别为铁芯接地电流基波分量、3次谐波分量

Figure 2. The equivalent circuit model of the core of three phase transformer

Figure 3. Core grounding current waveform of a 110 kV transformer

Figure 4. Core grounding current waveform of a 220 kV transformer

Figure 5. Core grounding current waveform of a 500 kV transformer

Table 1. Typical characteristics of core grounding current

Figure 6. Core grounding current waveform of a transformer with multi-point grounding fault

Figure 7. Core grounding current limiting resistor

Figure 8. Core grounding current with limiting resistor

4. 结论

(1) 变压器铁芯接地电流谐波含量客观存在，其大小与变压器本体结构有关；

(2) 对变压器铁芯接地装置加装限流电阻，能明显降低铁芯接地电流幅值，但不会改变铁芯接地电流中的谐波含量。

Measurement and Characteristic Analysis of the Core Grounding Current of Transformer[J]. 电气工程, 2015, 03(04): 107-114. http://dx.doi.org/10.12677/JEE.2015.34014

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