Design Of Distribution Transformer Monitoring Terminal (TTU) Based On ARM

In this paper, the domestic and international distribution automation technology are deeply studied.According to the functional requirements of distribution transformer monitoring system, the implementation of ARM-based distribution transformer monitoring terminal unit (TTU) are drafted, the hardware of ARM-based distribution transformer monitoring terminal unit is designed and produced, the main software functions of TTU are implemented, and the communication protocols of TTU are designed.Distribution transformer terminal unit uses dual-core CPU options, the main CPU and the secondary CPU chips are both ARM7 LPC2138. The main CPU completes the acquisition of distribution transformer capacity's parameters, the collection of external switch information, information storage, the fault conditions determine, and the connection with human-machine interface. The secondary CPU completes meter data's collection and storage. TTU uses application-specific energy measurement IC ATT7022B for data collection to improve its accuracy and speed. Distribution transformer terminal can collect status information of breaker switchs outside the Distribution Transformer, monitor their work status, alarm and ruled out of fault in real-time. The man-machine interface of TTU includes keyboard and display output. Keyboard input can be combined with the liquid crystal display to set parameters of TTU and inqure information locally. For storaging information on the site, TTU's design also includes large-capacity external memory 24LC512. It has a 512K storage capacity, and has a page read and write capabilities, which can be conducive to large amounts of data storage and retrieval. TTU uses dual communication mode of Power Line Carrier and RS-485. Because TTU is apart of the main station, so, power line carrier communication is used between TTU and main station, which make the communication can be achieved as long as the power line to the place without the other frame lines. The RS-485 communication means is used between TTU and Meter Readers in distribution transformer station area for the small distance, which has good anti-noise function and makes data transmission efficiently. TTU uses two types of communication protocols, that the protocol of 101 international by improved is used in its uplink communication with the main station and the protocol of DL / T 645 by improved is used in its downlink communications with Meter Readers.The experiments in laboratory show that the TTU achieves the desired requirements.