Research On Insulation Fault Diagnosis Technology Of Dry-type Series Reactor

With the continuous development of China’s economy and the rapid improvement of the national living standard,the scale of the power grid and the voltage level of the power system are continuously rising,people’s requirements for the quality,safety and stability of power supply are getting higher and higher.In order to meet the growing demand of electric energy,dry-type series reactor,as a power equipment to limit short-circuit current,achieve reactive power compensation and stabilize power quality,has been widely used in the power system with its advantages of good linearity,strong anti-saturation ability,simple structure and high performance price ratio,and also ensures the stable operation of the power system.However,the reactor often has a longitudinal insulation fault due to the factors of operating environment,working time and process conditions,resulting in serious consequences of insulation damage,life reduction and even equipment burning.Therefore,it is important to study the mechanism and fault characteristics of reactor insulation and to find a timely and effective monitoring means.In this study,the fault mechanism of reactor is analyzed,and three basic models of longitudinal insulation fault are established for dry series reactor,such as same strand inter-turn short circuit model,different strand inter-turn short circuit model and inter-layer short circuit model.Secondly,ANSYS Maxwell finite element simulation software is used to establish a dry series reactor model,analyze its normal and fault magnetic field distribution,and simulate the changes of basic electrical parameters one by one to obtain the change rules and ranges of the parameters under three different longitudinal insulation faults;meanwhile,according to the simulation results,the change rates of the electrical parameters under different insulation faults are obtained.At the same time,according to the simulation results,the change rate of each electrical parameter under different insulation faults is obtained,and the threshold difference between them is compared and analyzed,so that the two-round monitoring method is proposed,and the power factor and equivalent resistance,which have the most prominent change rate and law of change,are used as the monitoring parameters for the first round of monitoring to determine whether the insulation fault occurs in the reactor.Finally,the means of parameter acquisition is determined and the hardware system design scheme is given.The correctness and applicability of the scheme are verified by the comparative analysis of the fault data of the actual case.The research shows that when three basic forms of longitudinal insulation faults occur in dry series reactors,namely,same-strand inter-turn short circuit,different-strand inter-turn short circuit and inter-layer short circuit,several electrical parameters show different changes with the fault location,and different parameters have different rates of change in size.Among them,the representative electrical parameters are power factor and equivalent resistance,for the same strand inter-turn short circuit,the peak rate of change occurs at the innermost end of the reactor;for the different strand inter-turn short circuit,the peak rate of change occurs at the outermost end of the reactor;for the layer short circuit,the peak rate of change occurs at the middle of the outermost layer of the reactor,and the other parameters have different patterns.Based on this,the two-round monitoring scheme proposed in this paper achieves to identify the specific fault types while monitoring the reactor for insulation faults,and obtains as much fault information as possible with limited human and material resources,saving reactor fault monitoring cost and improving system operation stability.The research content of this paper can provide some practical engineering value for further research on the means of fault monitoring of dry series reactors.