Terminal Transformer Unit (TTU) is an important portion of Distribution Automation. But most TTU products have some disadvantages like costly price, few functions, lack of compatibility, and so on.

This paper presents the design of a monitoring terminal for distribution transformer based on C8051F020MCU, introduces the realization methods of hardware and software.

According to the current waveform and actual condition of the motor at two sides of the terminal, it is pointed out that the transformer saturation is the direct reason of causing this fault.