Gas Production Characteristics of Partial Discharge in Needle-Plate Electrodes Under Typical Vibration Conditions in a UHV Shunt Reactor

An ultrahigh voltage (UHV) shunt reactor is accompanied by continuous strong vibration during operation, and its internal partial discharge is often associated with the mechanical vibration of its electrodes. To explore the mechanism of the effect of electrode vibration on the partial discharge inside the reactor, a joint vibration-partial discharge test platform was established based on a partial discharge model of the oil-paper insulated needle board electrode. The influences of the amplitude and frequency of vibration on the partial discharge characteristics of the needle board in oil under power frequency voltage were studied. The results show that with the increases in the amplitude and frequency of vibration, the discharge process is intensified, the discharge repetition rate and the maximum discharge quantity increase, and the negative half-cycle discharge pattern exhibits “zero crossing.” The discharge intensity of the needle-plate electrodes is affected by the velocity of the oil flow velocity and field intensity; the field intensity has a more significant effect on the partial discharge. When partial discharge occurs without vibration, the characteristic gases produced by the needle-plate discharge are mainly H2 and C2 H2 and contain a small amount of CH4 and C2 H4. With the increases in the amplitude and frequency of vibration, the content of each characteristic gas increases, and vibration changes the spatial distribution of dissolved gas in the oil by driving the motion of the insulating oil around the electrode.

I. Introduction

With the rapid development of China’s economy, the construction of ultrahigh voltage (UHV) power grids is being promoted. UHV shunt reactors play a crucial role in compensating for the capacitive effects of long-distance transmission lines, optimizing reactive power distribution, and suppressing the increase of power frequency voltage. Ensuring the safe and stable operation of UHV shunt reactors is essential for the normal operation of UHV power grids [1], [2], [3], [4]. Currently, oil-immersed shunt reactors [5] are commonly applied in power grids. Operational experience has shown that insulation failure of electrical equipment is mainly caused by partial discharge-induced degradation of insulation materials [6]. Typical defects such as surface roughness and contamination during the manufacturing process of shunt reactors can lead to uneven electric fields and poor conductor contacts, which, in turn, can cause local discharges. Additionally, the magnetostrictive phenomenon [7] of ferromagnetic materials inside the reactors and Maxwell forces [8] at the interfaces of different media can induce vibration of the reactor core [9]. This is especially critical for UHV shunt reactors, as the mismatch [10] between increased capacity and volume compared to conventional reactors can result in intense vibrations, posing greater risks to insulation, making it necessary to study the generation and development mechanisms of partial discharges under vibration conditions, consider the influences of different vibration factors on discharge characteristics, select the optimal operating conditions for shunt reactors, ensure their safe and stable operation, and guarantee the normal operation of UHV transmission networks.