Study On Pressure Balanced EFPI Sensor Based On Partial Discharge Detection In Oil

In long-distance,high-power power transmission processes,high-voltage power equipment such as high-voltage power transformers,GIS,and the like are required.Due to the problems of insulation and heat dissipation,high-voltage power equipment is still using an oil-filled or gas-filled(SF6)insulation structure.However,inevitable insulation defects that occur during manufacturing,transportation,and operation will lead to deterioration of insulation and even insulation failure.Partial discharge occurs during the early stages of insulation degradation.Therefore,partial discharge detection is widely used as a method for detecting insulation defects and fault diagnosis.The blackouts and maintenance arrangements are made in advance for defective high-voltage electrical equipment to avoid the main insulation breakdown and the power outage of the power system.The optical fiber EFPI sensor based on the principle of Fabry-Perot is a non electric detection method,which can avoid the complex electromagnetic interference in the substation,have high sensitivity,good electrical insulation and low price,the sensor package can be miniaturized.However,traditional optical fiber EFPI sensors are greatly influenced by the environmental pressure and temperature due to structural design and manufacturing process deficiencies,which can easily cause the drift of static working point and the decrease of detection sensitivity.In this paper,in view of the problems existing in the actual detection of the traditional fiber EFPI sensors,the sensitivity,natural frequency and the loss characteristics of the FP cavity are analyzed.The factors affecting the sensitivity and natural frequency and the methods for improving them are studied,which lays the foundation for the optimization design of the sensor's parameter.The sensor probe with balanced structure is designed to eliminate the influence of pressure on the stability of the initial cavity.The factors that affect the temperature drift of the static working point of the sensor are analyzed,and the structure and fabrication process of the sensor are improved.Build the sensor production platform,weld pressure-balanced sensors,and design the related experiments to verify that the new sensor has very low temperature coefficient,high sensitivity,not affected by environmental pressure.Finally,the new EFPI sensor is applied to the experiment of PD detection and location detection in oil,which has achieved good detection and location effect.