Configuration of Transformer Protection in UHV AC Pilot Project

The configuration and setting of transformer protection is very important to ensure the safety of power equipment.The UHV AC pilot project transformer is composed of two parts:the main transformer,the regulation and compensating transformer.The protection of transformer has its particularity because the UHV system has its special feature and the regulation of transformer is from neutral terminal on UHV autotransformers,not from the intermediate voltage line terminal.This paper introduces the system connection and transformer protection configuration of 1000 kV AC pilot project.There are individual differential protections for the regulation transformer and the compensating transformer in order to enhance the protection sensitivity during the light fault.The inrush current characteristic of main transformer,regulation transformer and compensating transformer is also discussed according to the recorded data during the system debug.Considering reliability and security of differential protection of regulation transformer and compensating transformer,three-take-two or three-take-one braking scheme is suggested.The results show that the present configuration is reliable and can guarantee the safe and stable operation of UHV pilot project.