Transient Surface Electric Field Measurement of the Composite Insulators Using an Integrated Optics Sensor

An integrated optics E-field sensor has been developed and used to measure the axial and radial transient surface E-field distribution of a 10-kV composite insulator under the 1.2-/50- mu s lightning electromagnetic impulse (LEMP). The experimental and simulation results showed that with a 40-mm-length internal defect inside the composite insulator, the axial E-field increased tenfold at the positions far from the defect, with little change in the time-domain waveform. However, near the defect, the radial E-field increased threefold, causing significant waveform distortion. When a 60-mm-length internal defect, the positions far from the defect, with slight changes in the time-domain waveform. Conversely, near the defect, the radial E-field increased by more than a hundredfold, resulting in severe waveform distortion. When the bird-pecking damage area of the sheds does not exceed 12% of the total shed area, the surface axial and radial E-field changed by approximately 20%, with slight variation in the time-domain waveform. When the damaged area reaches 25% of the total shed area, the maximum radial E-field increases over one time, with minimal change in the time-domain waveforms, and the change in radial E-field intensity is greater than that in the axial E-field. These results can serve as a basis for fault identification and optimization design for composite insulators under transient voltages.