A New technology of transformer bushing state detection based on transient dielectric response

Abstract

Failure of the transformer bushing will cause the transformer to be powered down or damaged, affecting the safe operation of the power system. This paper proposes a method using system harmonics as the dielectric response excitation source and studies the transformer bushing insulation online detection technology based on transient dielectric response characteristics. The technical scheme and system structure of the online monitoring technology of transformer bushing insulation based on dielectric response characteristics are given. A calculation model of short-circuit grounding and capacitor switching of a 35kV substation was established, and the harmonic frequency content and amplitude distribution of grid disturbance were analyzed. A case of dielectric response measurement of the bushing is given. The research shows that the system will generate overvoltage in short circuit grounding, capacitor switching, etc. The system harmonic frequency is in the range of the dielectric response test frequency band (1Hz~1kHz), and the harmonic amplitude is also large, which can be used as an excitation source. The excitation source of the dielectric response test causes a change in the dielectric response of the transformer bushing and acts as a “probe” that reflects the insulation state of the bushing. The medium and high-frequency bands of the dielectric spectrum in the frequency domain are also sensitive to moisture, which can be used to diagnose the insulation state of the bushing.

Sensors in Civil Engineering: From Existing Gaps to Quantum Opportunities

“…For example, conventional voltage sensors, such as electromechanical or electronic voltage transformers, may be limited in accurately capturing small voltage fluctuations or harmonic distortions [48,50]. Some of these sensors may also have limited frequency response, preventing the detection of high-frequency transients or disturbances that can impact grid stability [51,52]. In turn, current sensors may not provide sufficient sensitivity to detect small irregularities or transient variations in current flow [53,54].…”

Intelligent monitoring of EHV transformer bushing based on multi‐parameter composite sensing technology

“…Power grid accidents caused by bushing failures are common [5][6][7][8][9][10], and chain accidents caused by ultra-high voltage bushing failures are becoming more and more serious, even causing fire, explosion, and serious harm to people and equipment [11,12]. Therefore, with the help of advanced sensing and signal processing technology, it is urgent to carry out digital intelligent online monitoring of transformer bushing status [13][14][15][16][17][18]. The insulation structure of bushing is very compact, which is different from the traditional oil-filled equipment.…”

“…Besides, the online monitoring of dielectric response test is not mature. On the basis of the existing monitoring methods, scholars have conducted beneficial exploration and proposed some new online monitoring methods for bushing state diagnosis [13,[19][20][21][22], but there are still problems such as insufficient monitoring parameters and criteria. It is urgent to develop intelligent and digital monitoring devices for transformer bushings, discovering defects in time before bushing faults, and take effective measures to avoid major accidents.…”