Abstract
To improve the safety and antielectromagnetic interference performance of partial discharge detection in high-voltage DC cables, partial discharge of cables is used as a criterion for characterizing insulation defects. An ultrasonic detection method for the partial discharge of optical fiber detection is carried out in a long-distance high-voltage DC operating environment. By analyzing the partial discharge mechanism and ultrasonic characteristics of DC cables, a correlation model between partial discharge ultrasonic waves and discharge quantity is established. The partial discharge charge of several common insulation defects is obtained experimentally, and an ultrasonic characteristic Sagnac fiber detection system is realized. Standard ultrasonic time domain signal detection and fiber-optic sensing probe directional experiments are performed. The influence of fiber sensing probes with different lengths on the sensitivity of partial discharge signals is investigated based on the frequency distribution characteristics of partial discharges. The ultrasonic wave is measured based on a fiber-optic probe and can perform multipoint detection, and the partial discharge of the ±320 kV flexible DC transmission system was tested based on the developed optical fiber sensing system. The experimental results show that the partial discharge signal detection of 6 km long cable can be realized, and the localization accuracy is less than ±80 m. It provides a practical monitoring method for the perception of long-distance transmission equipment operating states.
Highlights
The insulation medium of DC cables and accessories suffers from high-intensity local electric fields, polarity reversal voltages and nonlinear temperature characteristics caused by space charge accumulation during power transmission[1]
The Partial discharge (PD) characteristics of a single source or multiple sources of DC XLPE cables were obtained from two different frequency bands by detecting the frequency response of the antenna [8], and the partial discharge patterns were distinguished based on image features[9]
We focused on the analysis of the mechanism of delay fiber on the sensitivity of partial discharge detection, which is an important factor affecting detection sensitivity
Summary
The insulation medium of DC cables and accessories suffers from high-intensity local electric fields, polarity reversal voltages and nonlinear temperature characteristics caused by space charge accumulation during power transmission[1]. A partial discharge detection and localization system for high voltage cable based on a long-tailed optical fiber Sagnac interferometer has been proposed and the experimental results show that the accuracy of partial discharge localization is 0.016 km [25]. These researchers carried out in-depth research on the suppression of polarization phase shift and polarization-induced signal fading by the optical fiber sensor localization detection system from the above analysis. We first analyze the mechanism of the effect of delay fiber length on the sensitivity of the partial discharge ultrasonic characteristics optical fiber sensor detection system based on Sagnac sensing technology and verify it through experiments. An experimental verification is carried out with fiber optic detection of the partial discharge ultrasonic characteristics for a DC cable in a 320 kV DC system
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