Lightning Protection Grounding Of Secondary System And Research On Field Testing Method In Transformer Substation

Lightning protection of electric power system in our country mainly focuses on primary side,relatively speaking,secondary weak system is concerned about lightning protection.especially in the secondary system grounding.Lots of misunderstanding and error connection exists in the actual construction of the power project for the grounding of the secondary system equipment,such as the different ways for the grounding pathway and grounding point of signal and chassis.Due to the lack of mandatory standards,equipment manufacturers,design institutes and construction units are often inconsistent,bring to the construction and commissioning of difficulty,and also posing same potential threat to the safe and reliability.This paper analyzes the grounding pathways and applicable cases of the secondary system,explains some practices which are mentioned in the relevant standards,and improves some of these measures.Invasion pathway from primary side to the secondary system of lightning overvoltage interference is also researched,then mathematical model is builded to impulse voltage of low-voltage power line caused by lightning for ATP simulation and laboratory testing,in order to find measures of reducing lightning overvoltage.The mechanism of ground counterattack is explored.Due to field test is rarely performed on the characteristics of secondary system lightning protection grounding, based on impulse current, one secondary system with independent grounding grids is tested in the field, which is in a station at PZH steel. The potential rises of the neutral point of the low voltage power supply, independent grids and the main grounding grids are measured when different routes of current wave invasion into secondary system. And then potential difference between them is analyzed. The experimental results on this problem are discussed and researched, meanwhile the characteristics of secondary system grounding is introduced in this article. According to the test results, it is suggested that the station should strengthen management on operation of secondary system, and some methods of rectifiable technique are simply proposed.Through the renovation experience of Pangang blast.analyzing the practice of other plant station, adhering to the comprehensive management of layers of defense,the principle of the rise,and the overall defense,this paper summarizes a series of measures of equipotential grounding method and secondary system lightning protection for power system and communication system.