The bridge arm reactor for VSC-HVDC bears the combined action of AC and DC large current in operation, while the distribution characteristics of DC and AC in the encapsulations of bridge arm reactor are completely different. DC distributes the encapsulation current according to the resistance, while AC distributes the encapsulation current mainly according to self inductance and mutual inductance. The difference of DC and AC distribution characteristics leads to the complete difference of loss and temperature rise distribution in the encapsulations. Therefore, it is necessary to carry out the calculation of encapsulation distribution current in bridge arm reactor and compare it with the temperature rise test results to demonstrate the rationality of encapsulation current and temperature rise design. Based on the relevant technical parameters of bridge arm reactor and the theoretical algorithm of encapsulation current calculation, this paper carries out the current distribution calculation of each encapsulation in bridge arm reactor under five working conditions: rated working condition, DC temperature rise current working condition, 50Hz temperature rise current working condition, 100Hz AC load current working condition and 1.2 times rated working condition. Combined with the factors of reactor heat dissipation and temperature rise, the distribution law of each encapsulation current is studied qualitatively. At the same time, the temperature field simulation results of bridge arm reactor under rated condition and 1.2 times rated condition and the temperature rise test results of bridge arm reactor under DC temperature rise current condition, 50Hz temperature rise current condition and 100Hz AC load current condition are compared and analyzed with the encapsulation current distribution results of the above five working conditions. The consistency and rationality of the design for encapsulation distributed current and temperature rise of bridge arm reactor are verified, which provides useful technical guidance for the design of encapsulation distributed current and temperature rise in bridge arm reactor.
 

bridge arm reactor, DC, AC, encapsulation current, temperature rise