| Due to the manufacturing deviation,overcurrent,harmonics,ambient temperature and other factors,the dry-type air-core reactor is prone to overheating,which accelerates the thermal aging of the encapsulated insulation.In severe cases,a burnout event may happen because of the damaged insulation and short circuit between turns,etc.Dry-type air-core reactor features coaxial multi-encapsulations,the temperature hot-spots often exist at the inner encapsulation,therefore,it is difficult to obtain the temperature of hot-spot by infrared thermometre,which can only scan the surface temperature of outermost encapsulation.The temperature of hot-spot can best reflect the reactor's operating conditions and its service life.In order to solve the problems above,this paper studies from the following aspects:(1)A two-dimensional axisymmetric model of a dry-type air-core reactor is established in the finite element simulation software COMSOL,then the magnetic field-circuit coupling method and flow field-temperature field coupling method are applied to study the temperature field of single phase and three phase stacked reactor in rated operating condition.The rule of the reactor encapsulation temperature distribution is summarized.For single phase reactor,the axial temperature of encapsulation can be divided into three zones according to temperature gradient,and the temperature reaches highest at 95% of the height;In radial direction,the temperature of the third encapsulation which locates in the middle airway is higher than that of encapsulations which locates at two sides.For three phase laminate reactors,the temperature distribution rule of encapsulations in each phase is similar to that of single phase case.The top of reactor has the higher temperature than the bottom.(2)The influence on the temperature field of the dry-type air-core reactor under manufacturing deviation,ambient temperature changes and harmonics are analyzed respectively.Manufacturing deviation includes the number of turns deviation and airway width deviation.Decrease in number of turns will increase the encapsulation temperature.The effect of airway width deviation on the encapsulation temperature is related to the position of the encapsulation,the positive or negative polarity and the actual values of deviation.Different ambient temperature changes the heat source and the heat dissipation conditions of the reactor so that the temperature rise of the encapsulation varies.The higher is ambient temperature,the higher is temperature rise of the reactor.In addition,system harmonics may be amplified considering the reactor connects in series with capacitor banks,which results in raising the operation temperature and threatening its service life.(3)Based on the internet of things model,a set of temperature on-line monitoring system of dry-type air-core reactor is developed.The system uses M2 M structure,the temperature acquisition nodes and the acquisition terminals establish a wireless sensor networks by ZigBee.The temperature acquisition terminals send temperature data to Internet by GPRS,then a real-time temperature monitoring is operated at the cloud platform,which has both historical data query and overheating alarm function.Six sensors are installed at a reactor in a substation following tha guide of the temperature field simulation results.Then the encapsulation temperature data are analyzed during the reactor's commissioning as well as a whole day.Besides that,a comparison is made between measured and simulated data,the answer is positive.Experiments in field show that the simulation results could effectively locate the temperature weakness of a reactor in operation,which could provide a theoretical verification for the installation of the temperature sensors in the on-line monitoring system.Besides that,the self-developed on-line reactor temperature monitoring system can run stably.It can effectively improve the operation and maintenance level of dry-type air-core reactor. |
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