Saturable reactor is the key component to protect thyristors of converter valve. During run-time the loss of saturable reactor iron core leads to temperature increment of the core. In severe cases

the saturable reactor will fail and threaten the safe operation of the converter valve. In order to reduce the core temperature of saturable reactor and ensure the reliability of UHVDC project

it is necessary to study the core cooling performance and optimize the structure of saturable reactor. Firstly

the internal structure of the shell type saturable reactor is studied

and the mechanism of iron core heat dissipation is analyzed. Then

by optimizing the internal and external structure of the saturable reactor

a new spiral saturable reactor has been designed and developed for ±1 100 kV/5 455 A UHVDC project. The heat dissipation multi-air ways are formed around the enclosure when the saturable reactor operates. Heat dissipation is optimized. Finally

based on the principle of optical fiber temperature measurement

the temperature measurement fiber is embedded on the core surface of the saturable reactor. The core temperature test of saturable reactor is carried out under the condition of long-term continuous rated load operation on the synthetic test platform. The results show that the temperature of the spiral saturable reactor core is much lower than that of the common shell saturable reactor

which meets the requirements of the operation reliability in the UHVDC project.