Development Of The On-line Detecting System On Power Transformer Winding Deformation

Transformer plays a key role in power system. Its safe operation guarantees the reliability of the power grid. In recent years, the ratio of the transformer faults caused by the winding deformation directly or indirectly remains very high. Therefore it is important to find out hidden trouble of transformer in time so as to avoid outburst accident and improve safety and reliability of transformer operation. The study on methods of detecting the transformer winding deformation is of great significance.It is shown from the theoretical analysis of transformer that the short-circuit reactance of a transformer is decided by the size and the relative location of its windings. For a certain transformer, when the windings deformed and the size and the relative location varied, the value of the short-circuit reactance varied correspondingly. The extent of the variety can be used as the basic of the extent of the winding deformation. For example, by the rules of IEC and Chinese national standard, when the variety of the short-circuit reactance of a homocentric winding exceeds 2%, a certain extent of deformation can be affirmed.By measuring the voltage signal of Potential Transformer (PT) and the current signal of the Current Transformer (CT) from the primary and secondary winding of the transformer in operation, the short-circuit reactance of each phase can be calculated. Therefore the on-line monitoring of winding deformation of transformer can be realized.Based on the theory above, we developed a set of on-line detecting system on power transformer winding deformation using 51 series micro controller unit (MCU), which can perform data acquisition, displaying the result of measurement and communication with the IBM-PC. The hardware design methods of this system was introduced and much attention was paid to the main function part, including the LCD module and keypad interface circuit, the selection of AD converters and the interface circuit and the methods used to avoid the EMI on the PCB and in the shielding box.The software of the on-line detecting system consists of two important parts, one is the MCU controlling software, and the other is the IBM-PC software. The MCU controlling software is to achieve the whole measurement control, data pick-up and processing, display and communication with the IBM-PC, etc. which is compiled with the C51 language. The IBM-PC software was complied with the graphical programming language LabVIEW, and can perform communication with the MCU, digital signal processing, displaying and the database. The design method of each part of the software was presented._____________________________________________Abstract_____________________________________________Simulation experiment was performed on the transformer model using this system in the Lab. The result shows that this system is of high accuracy and reliability, which can meet the theoretical design demand.