For the reactor of outdoor shunt reactive power compensation device of present power system

the dry-type air-core series reactor is mostly adopted. During operation period

the influence of such factors of rector as insulation aging

excessive partial temperature rise

over-voltage

harmonics and environment leads to inter-turn insulation breakdown of reactor

surface creepage of envelope due to rainfall of coil and even arc burning due to partial discharge. For this purpose

the burning of dry type air core series reactor of 35 kV shunt capacitor bank at a 500 kV substation is introduced. Inspection at site and test after returning to the factory are performed. The burned phase and non-burned phase are analyzed from the outside to the inside of the envelope layer disintegration and the reason of the failure is deduced as follows: After nearly ten years of operation of the reactor proper

the epoxy material in the envelope layer of the reactor proper deteriorates and cracks. Moisture immerses into the envelope layer in case of rainy weather

and the insulation film of the wire in long-term operation is accelerated to age. The over-voltage due to multiple switching of the capacitor bank causes inter-turn insulation damage of the reactor and finally leads to insulation breakdown and burning of the reactor. As for the damage of reactor in this accident

the corresponding preventive and treatment measures are proposed.