Analysis Of Power Transformer Buchholz Relay Unwanted Operation Of Protection And Improvement Measurments Of 500kV Substations

The transformer is an important device in the power grid,and its operating state plays a decisive role in the safe operation of the power system.Differential protection and Buchholz relay act as the main protection of the transformer,enabling the transformer to trip quickly when a fault occurs within the protection range.Since the Buchholz relay is greatly affected by the external environment,the correct rate of Buchholz relay action is quite low.In recent years,the statistics of China Southern Power Grid show that the correct action rate of Buchholz relay has been low,and the number of unwanted operation of protection is greater than the number of correct tripping.The artical studies the main variable severe-gas unwanted operation of protection of 500 kV substation and its improvement measures.The general contents are as follows:Firstly,the principle and scope of use of transformer electrical quantity protection and non-electrical quantity protection are introduced,and the application of Buchholz relay in non-electricity protection at our countrys and abroad is briefly discussed.Among them,gas relay is an important part of Buchholz relay,and its operation principle and time characteristics are elaborated.Secondly,qualitative analysis is carried out for the main variable severe-gas unwanted operation of protection event of 500 kV substation in the southern power grid from 2011.Combining the structural characteristics of the core transformer and the shell transformer,the short-circuit electric force is formed under the action of external faults of the two transformers.At the time of Buchholz relay,it is concluded that which type of transformer has a greater chance of Buchholz relay malfunction.Then,in order to reduce the probability of Buchholz relay unwanted operation of protection,the article proposes four protection strategies for the improvement of transformer Buchholz relay.Through the description of various protection strategies,feasibility analysis,analysis of advantages and disadvantages,combined with the operation of China Southern Power Grid,the most suitable improvement protection strategy is selected.For the on-site imple-mentation method,the article has developed a loop transformation plan based on the situation of non-electrical protection equipment of various mainstream manufacturers.In addition,due to the particularity of power operation,the author conducted a detailed analysis of the risk of on-site operations and proposed preventive measures.Finally,taking a typical line trip event as an example,by analyzing the protection action behavior,it directly proves that the transformer Buchholz relay strategy improvement is effective.