船舶中点接地直流供电网的绝缘检测方法研究

On insulation detection of neutral grounding DC power-supply network for ships

传统的绝缘测量方法往往不适用于特定场合下的直流供电网。针对两整流桥中点存在经电阻接地的直流供电网,文章提出了两种测量直流侧绝缘的方案,两种方案均是通过添加测量电阻,并在正负极进行投切,分别读取其电流,计算出正负母线的对地绝缘电阻。其中第一种方案通过电路分析方法,利用基尔霍夫定律给出计算式,但需要读取接地电阻上的电流;第二种则通过叠加法避免读取接地电阻上的电流,但需要在计算时代入接地电阻值。推导结果并结合PSCAD/EMTDC进行直流侧单极绝缘故障和两级同时发生绝缘故障情况的电磁仿真,表明后一种方案在测量绝缘电阻上不仅符合精度要求,而且工程应用性更好。

The traditional insulation measurement method is often unsuitable for the application of DC power- supply network under the given situation. This paper presents two DC insulation measurement methods for the DC power-supply network grounding through resistance at the two rectifier bridge midpoint. The two schemes respectively read the current and calculate the insulation resistance against the ground of the positive and negative bus by adding measurement resistance and switching on the positive and negative poles. The calculation formula for the first scheme are given by using Kirchhoff s laws based on the electric circuit analysis method. However, the current of the grounding resistance should be recorded, which can be avoided in the second scheme by using the superposition method. Instead, the grounding resistance should be substituted in the calculation. It carries out the electromagnetic simulation of the DC side single-stage and the double-stage insulation fault by using the electromagnetic simulation software PSCAD/ EMTDC. It is indicated that the second scheme can meet the accuracy requirement of the insulation resistance measurement with a better engineering application.