Research And Application On Online Monitoring Device Of Transformer Bushing Based On Relative Method

Bushing is an important part of the transformer, its safety and reliability can be related to the operation situation of the whole power system, so the effective monitoring of transformer bushing become an important area for the development of modern online monitoring technology. In the transformer bushing test of the past, we can only do the periodic test, cannot be real-time monitoring of transformer bushing. At the same time, in the transformer bushing in the preventive test, the test voltage is low and insensitive response to partial failure, therefore we cannot be achieved for transformer bushing malfunction timely maintenance and repair, on-line monitoring can avoid the shortcoming of traditional test well, having a high practical and promotional value.Relative method proposed in this paper is based on the phase angle method proposed. The measurement method by measuring the dielectric loss casing to determine the sleeve of the running. Because in the power system, the possibility of simultaneous failure of the three-phase cannula is a small probability event, it is assumed that no fault phase B phase to phase bushing B leakage current signal as a reference, provisions phase bushing B dielectric loss angle(B-phase voltage signal and the angle signal leakage current) is 89.70 °, calculate the magnitude and phase angle of the three-phase current signals casing. Through the above theory as a starting point, combined with the actual operation of the field devices, the use of hardware and software methods to achieve the purpose of the online measurement.This paper is around the casing running transformer monitoring to carry out the theoretical arguments and technical implementation. From a technical and economic comprehensive consideration, the system design is based on the casing leak current signal characteristics itself, reasonable design for current sensor. From sensor monitoring leakage current, further to the current processing, filtering, isolation, as well as making signal after processing, fully meet the requirements of the A/D conversion chip, and can meet the needs of the precision of on-line monitoring system; According to the sampling frequency and precision requirement for the AD conversion module, finally chose the AD7656 electronic chip, full use of the conversion character of the AD7656, leak current signal sampling and conversion of claims. Data analysis of OMAP- L138 scheduling module choice, chose the RS- 485 bus communication bus.After completion of the system in laboratory design, we do installation and pilot application in a smart substation. Through the field measurement of casing data, compare the situation of casing running, we may say that this project developed device principle is correct, equipment functions comply with the design requirements, the field runs stability, meet all the requirements for project. On-line monitoring device with the station monitoring unit to communicate completely in accordance with IEC61850 statute, communication meet the requirements of the substation on-line monitoring device for transformer bushing equipment online monitoring can be achieved and stable running.