Research On On-Line Monitoring Technology Of Transformer Bushing

Transformer is the core equipment in substation.Bushing,as the accessories of transformer,is the bridge connecting bus and transformer of power system.Therefore,bushing is also one of the most important power equipment in substation.Once bushing fails,it will directly cause transformer outage,or even transformer failure.Therefore,it is very important to ensure the safe and stable operation of casing equipment.At present,the most widely used casing monitoring technology in China is still the traditional manual periodic maintenance method,which regularly carries out off-line detection of high and low pressure casing to determine whether the casing failure occurs.Although some faulty casing can be detected by this method,the casing with potential problems can not be detected in time.It is easy to fail before the next detection cycle after power-on operation.Moreover,the traditional off-line maintenance method needs power outage operation,which takes a long time and requires a lot of manpower and material resources.Therefore,if the on-line monitoring of the casing can be realized and the current insulation operation of the casing can be obtained in real time according to the on-line data,the safe operation of the casing can be well guaranteed,which has great practical application value.According to the operation characteristics of transformer bushing,a real-time monitoring system is designed to monitor the insulation performance of bushing.Firstly,the background and significance of transformer bushing monitoring are discussed.Combined with the current development situation at home and abroad,the off-line detection method and on-line detection principle of transformer bushing insulation performance are given.This paper introduces the concept of dielectric loss and on-line detection parameters,lists the factors affecting the accuracy of insulation performance monitoring of bushing in substation,and finally proposes a relative dielectric loss monitoring method.This method does not need the phase of bus voltage to calculate dielectric loss,so it avoids the error in the process of acquiring phase of bus voltage.Harmonic analysis method is used as phase extraction method to avoid the interference of harmonics on signal accuracy.The core processor chooses TI Kirin version DSP chip TMS320F28335 as the main control core,which can quickly and accurately digitize.In data synchronous sampling,IRIG-B code clock is selected to trigger two sampling devices synchronously.Finally,the research results are verified in the pilot substation,and the data acquisition and transmission effect is good.The on-line monitoring of insulation performance of transformer bushing is realized.The system is stable and meets the requirements of the project design.