Live Detection Of Over-heated Bus Contact In GIS And State Assessment Technology

GIS,gas-insulated metal-enclosed switchgear,plays a key role in the operation of the power grid and the transportation of electricity.It is mainly used for the control,protection,monitoring and switching of the transmission line.The main advantages of GIS are:long service life,low failure rate,high reliability and small volume,etc.Therefore,it is widely used in power systems.However,due to the fact that GIS is completely sealed and has large through-current and small volume,the internal heat dissipation performance is poor.When the contacts of the GIS equipment are in poor contact,the contact overheating may occur,which may result in major faults such as short circuits and cause significant losses.At present,the main layout of GIS bus-bar has the single bus-bar structure and double bus-bar structure,and the single bus-bar structure is mainly used in China.Therefore,this paper mainly studies the method of contact overheating evaluation of single bus-bar structure.The uncertainty of GIS temperature distribution is the main technical problem of applying infrared radiation temperature measurement to the temperature measurement of GIS bus-bar contacts.To solve this problem,this paper uses the Ansys software to simulate the electromagnetic field-temperature field-fluid field coupling,by changing boundary conditions,calculates the distribution of electromagnetic field and temperature field of GIS under different working conditions,and analyzes the influence of bad contact fault on the distribution of temperature field in GIS.The result shows that load current is the main factor that leads to temperature rise of GIS bus-bar.With the increase of recombination current,the increase rate of bus-bar temperature increases.Compared to of GIS equipment operating normally,in the case of contact overheating failure,the temperature of the bus-bar contact position rises rapidly,and is much higher than that of the rest part of the bus-bar,the highest temperature on the shell appears right above the bus-bar contact position,the temperature change gradient of the metal shell of GIS above the fault point is most obvious,which provides the criterion for judging the fault according to the shell temperature gradient.Judging the contact overheating fault by the shell temperature gradient is the key technique of infrared thermal diagnosis.In order to verify the correctness of the simulation calculation,this paper builds a GIS temperature measurement experimental platform,and compares the GIS temperature field distribution under normal contact conditions and fault contact conditions.The simulation results are consistent with the overall results of GIS temperature test results,the error is small,and the simulation model is reliable.It is proposed to determine the difference of the temperature distribution gradient of the shell under the condition of over-heating of the local contact in other similar structures by the simulation calculation and take it as a criterion for judging whether the other similar structures of the GIS have the over-heating of the local contact.