Research On The Measurement System Of Trace Moisture In Transformer Pressboard

The project< Research on the Measurement System of Trace Moisture in Transformer Pressboard> is one of the key problems to tackle in the electric power industry in China (No.98010211), which is also one of the worldwide problems. Since the presence of moisture in the transformer insulation can bring the transformer performance trouble by decreasing its insulate strength and shortening its service. Therefore, it is very important to monitor the moisture condition in pressboard during both manufacture and performance process of a transformer. With the feasibility that the physical characters of material can be measured through dielectrometry technique, several aspects about dielectrometry technique to detect moisture content in pressboard are researched in this thesis, and a measuring system of the trace moisture in transformer pressboard is developed.The fringing field dielectrometry sensor serves as a key factor in the moisture on-line measurement system. The figures of merit and design demands of the sensor are introduced. By designing the fringing field dielectrometry sensor, the issues about dimensions of measured materials, signal strength, penetration depth, electrodes, substrate, channel number and installation should be considered.Single chip AT89S51 of 51 series is used as the core component in sinusoidal wave signals generating system. With the help of software programmed in C51 language, it can dynamic generate sinusoidal wave signals of eleven different frequency, its peak-to-peak value is 5V and frequency scope is 0.01 ～ 1000Hz.Single chip AT89S51 is also used as the core component in data-processing and display system. With the help of software programmed in C51 language, the voltage signals can be disposed and calculated. Finally the gainsand, phase angles and moisture content can be displayed with the help of LED. This system has used host - guest double CPU structure, the two CPU communicate by COM port, so it is divided into control system and display system, the former is responsible for transform and processing data, the latter is responsible for demonstrate, the two parts is interfaced by RS-232, it is advantageous to the display system's installation.The experiment results indicate that the whole design is feasible and reliable, and the presumed functions are conducted successfully. The trace moisture in pressboard can be measured actually by using the devised capacitive sensor and relative circuit. All research...