High-voltage switchgear is widely used in power distribution networks for interrupting and distributing power. It features a compact structure, flexible assembly, and easy installation. During long-term energized operation, the insulation materials, insulation accessories, and metal connectors within high-voltage switchgear can degrade under the combined effects of various stresses and environmental factors, leading to abnormal discharges and even insulation failure. Therefore, regular partial discharge testing to promptly detect potential insulation failures is a crucial component of distribution network operation and maintenance.
Transient earth voltage (TEV) is a highly sensitive and convenient non-invasive partial discharge detection method, widely used in equipment such as metal-clad switchgear. However, recent field experience has shown that this detection method's signal-to-noise resolution and discharge location capabilities are less than ideal, and its detection effectiveness is significantly affected by the site environment and switchgear layout. When multiple switchgear units share a common grounding system, the partial discharge TEV signal within one switchgear unit can couple to other units through the ground impedance, causing crosstalk. While ground voltage detection can effectively locate the approximate source of discharge within the switchgear unit, it is difficult to effectively determine the location of multiple switchgear units sharing the same ground. On the other hand, due to the random and intermittent nature of partial discharge (PD), traditional live inspections lack the ability to synchronize PD detection across equipment, making locating the discharge difficult.
A four-channel sensor location method can effectively locate faulty switchgear. Its advantages include not only tracing the source of the faulty switchgear but also locating the specific compartment within the switchgear where the fault occurred. However, this method requires deploying at least four TEV sensors on the same switchgear, which is costly and limits its widespread application.
Compared to the four-channel sensor location method based on signal time difference, the distributed synchronous measurement location principle requires only one TEV sensor on each switchgear. To address the current difficulties in the widespread application of TEV sensors, this paper proposes a solution for locating partial discharge in switchgear using a distributed ground pressure sensor network, based on electromagnetic-circuit coupling simulation results for single and multiple switchgears. First, based on finite-difference time-domain numerical simulation technology, this paper constructs a coupled simulation model of a switchgear field circuit. The electromagnetic wave propagation patterns and time-frequency characteristics of transient ground voltage signals under different conditions, such as those occurring at cable room support insulators and cable terminals, are analyzed, and the optimal deployment location for ground voltage detection sensors is determined. Furthermore, based on the typical layout of switchgear within a distribution room, a simulation model of side-by-side switchgear with a common ground is established. The ground voltage signal characteristics of each switchgear under the same discharge pulse electromagnetic radiation source are investigated, and a method for locating the discharge source using a distributed sensor network is proposed. To verify the effectiveness of this method, multiple distributed networked ground voltage wireless intelligent sensors were used to implement the method in a substation distribution room. The method was successfully applied, and an insulation defect was successfully located, confirming the effectiveness of the distributed sensor network positioning scheme.
