The Loop-type Sensor Embedded In The Insulator Of GIS For Partial Discharge Measurement

At home and abroad,the research on partial discharge detection of gas insulated switchgear(GIS)has been studied.The high frequency(UHF)detection method has been widely studied and applied because of its good anti-jamming performance and high sensitivity.The traditional UHF sensor requires additional installation space.Its monitoring range and sensitivity are limited,and it is easy to cause the GIS seal is not strict,and the internal electric field of GIS is destroyed.Scholars on this issue made use of the inner metal shield of epoxy resin of GIS insulator to make a new loop-type sensor.However,the current study also not able to put forward a clear theory to interpret the working mechanism of the loop-type sensor,and the sensitivity of existing loop-type sensors are not better than disc-type sensors,especially for high-frequency component of partial discharge signals.In order to solve these problems,based on the size of 252 k V GIS,this paper optimized and designed new loop-type sensor.In this paper,based on the theory of GIS coaxial waveguide model,the propagation law of electromagnetic wave in GIS is studied,and the basic principle of coupling electromagnetic wave in GIS is obtained by theoretical analysis.It is found that the circular sensor is coupled with the electromagnetic wave through the detection of the terminal and the metal ring.Among them,the grounding terminals are mainly coupled with TEM mode electromagnetic wave and some high mode electromagnetic wave;the metal ring can only be coupled with high mode electromagnetic wave,and its grounding position affects the electromagnetic wave mode which can be coupled to.This paper for 252 k V GIS.In the XFDTD software to establish a mounting loop-type sensor GIS straight cavity model,different size sensor simulation results show that,the ring size is small,coupling partial discharge signals ability weaker and metal ring size reduction teenager will improve the insulator of electric field intensity inside.At last,the optimal size of the metal ring diameter is 346 mm,which has no effect on the stability of the internal strength of the insulator,and the sensor has high sensitivity.In this paper,3 kinds of different loop-type sensor structures are designed,which are the two ends of the metal ring,the structure of the metal ring,the structure of the metal ring and the structure of the metal ring.The performance of three kinds of structure type sensor is tested by simulation and experiment.The results show that compared with the other two kinds of cases,the metal ring is coupled to the local discharge signal,and compared with the simulation results,the sensitivity of this method is more obvious.In this paper,the location and number of ground terminals are changed,and the 9 kinds of loop-type sensor models are designed.Through simulation and experimental tests,the results show that the sensitivity of the number and position of the ground terminal is affected,but the impact is not big.However,when the metal ring is connected to the ground with 120 degrees from the end of the detection,it has a symmetrical structure,and the loop-type sensor has a better balance voltage and electric field.In addition,the characteristics and sensitivity of the loop-type sensor with the directly grounding through welding is better than directly grounding through the n-type connectors,and the safety and reliability of the loop-type sensor with grounding can reach the allowable range.Finally,this paper compares the loop-type sensor with other types of local discharge in 4 kinds of local discharge type.The loop-type sensor has a higher sensitivity for suspended discharge,spike discharge,free metal particles discharge and fixed metal particle discharge.Under the 4 conditions of the partial discharge,the sensitivity of the optimized loop-type sensor is higher than that of the disc-type sensor and the helical sensor.In the lower frequency band,sensitivity of the loop-type sensor is higher than other sensors up to 40 ~ 60dbm;in the higher frequency band,sensitivity of the loop-type sensor is higher than other sensors up to 0 ~ 20 dbm.And the sensitivity advantages are more obvious in suspended discharge and fixed metal particles discharge.