Design Of Over-voltage Protection Device For 35kV Dry-type Air-core Shunt Reactor

Dry-type air-core shunt reactors are widely used in power systems and are important reactive power compensation devices.Their operational stability directly affects the power supply reliability of power systems.The operating state of the system changes constantly,and it is necessary to frequently switch the dry-type air-core shunt reactor.The switching over-voltage is one of the main causes of the reactor burning accident,and it is necessary to protect the switching over-voltage.The development of over-voltage protection device for dry-type air-core shunt reactor has engineering practical significance.In this paper,based on ATP-EMTP software,a simulation model of over-voltage generation and combined protection circuit for dry-type air-core shunt reactor is established for a general-purpose 35 kV dry-type air-core reactor.The value of the protection circuit parameter is determined by simulating the protective effect.Based on the ANSYS finite element analysis software,the magnetic simulation model of the dry-type air-core shunt reactor was established.The magnetic field distribution characteristics and the eddy current loss of the metal parts inside the magnetic field were simulated and analyzed.The method of reducing the eddy current loss of the metal parts in the protection device was explored.On this basis,an over-voltage protection device was designed,and the protection effect,insulation level and temperature rise of the protection device were verified.The results show that the combined protection device limits the over-voltage by the RC device under the small cutoff value,and the over-voltage is limited by the arrester under the large cutoff value.The larger the value of the protection capacitor,the lower the cutoff over-voltage and the re-ignition over-voltage.In a certain range,the smaller the protection resistance,the better the protection effect,but the effect is not great.The axial and radial magnetic induction in the reactor are symmetric with respect to the center,the axial intermediate position is the largest,and in the radial direction,the closer to the coil position,the greater the magnetic induction.From the perspective of the electromagnetic field,the protection device is chosen to be installed near the axis of the reactor.The eddy current loss of the metal member in the protection device is proportional to the fourth power of the radius and the primary of the thickness,and the eddy current demagnetization effect causes the actual loss value to be slightly reduced.The eddy current loss of the metal part can be reduced by reducing the radius of the metal part,selecting a suitable metal material,and optimizing the shape of the part.When the cutoff value is not more than 15 A,the designed protection device limits the over-voltage to 2.2 p.u.,the power frequency flashover voltage is higher than 240 kV,the shock flashover voltage is higher than 800 kV,and the maximum temperature rise is 34°C,which is suitable for 35 kV dry-type air-core shunt reactor over-voltage protection.