Research on Faint Ground Fault Detection in Power Distribution Line

在今天的配电网中，必须实现的是将供电的解释率降低到尽可能低的水平，如果可能的话，甚至为零。本研究是对这一要求的一次尝试，旨在提供一种技术，可以作为发现配电线路绝缘状态轻微恶化的有效手段。讨论了本实验室研制的磁场传感器的适用性，并讨论了提高磁场传感器探测灵敏度的几个基本问题：(1)针对低电平磁场的探测，细化了灵敏度与噪声的关系。通过三相零相电流检测对该点进行一次试验；（ii）在传感器所用磁芯的选择上，澄清了在传感器输出噪声中占据较大权重的磁芯噪声问题。开发了其测量系统，并给出了两种不同类型铁芯的具体测量结果。在此系统的基础上，给出了一种传感器核心匹配的搜索方法；（三）在传感器电路的构成上，提出了一种新型的基准电压产生电路。这有可能提高传感器电路的精度。这些都是实现传感器高检测灵敏度所需的技术。考虑到这些因素，必须对传感器进行重构。之后，通过现场测试验证60Hz电力线磁噪声的降噪程度，将提出的方法付诸实践。

What has to be achieved in the today's power distribution network is to reduce the interpretation rate of power supply to as low a level as possible, if possible to zero. This study presents a trial for such a requirement and is directed to provide a technique which can be an effective means for finding out faint deterioration in the insulation state of the distribution line. The applicability of the magnetic field sensor which has been developed in our laboratory are discussed and some fundamental problems for improving the detection sensitivity are treated : (i) with respect to such the detection of low level magnetic field, the relationship between the sensitivity and the noise is refined. One trial on this point is performed through the zero phase current detection in three phase ; (ii) on the choice of the core utilized in the sensor the problem of core noise which occupies a large weight in the noise appearing in the sensor output is clarified. Its measurement system is developed and concrete measurement result is presented on two different types of core. Based on this system, we obtain a means for searching the core fit for the sensor ; (iii) on constitution of the sensor circuit a new type of reference voltage generating circuit is presented. This has a possibility of improving the precision of the sensor circuit. These are the technology required for achieving the high detection sensitivity of the sensor. Taking into account them, the reconstitution of the sensor has to be performed. After that the proposed approach will be put into practice by certifying the degree of noise reduction of 60Hz power line magnetic noise rough the field testing.