At high-voltage switchgear operation sites, maintenance personnel sometimes hear a faint "hissing" sound from inside the cabinet, or notice abnormal temperature rise on the cabinet surface, yet infrared temperature measurement finds no obvious hot spots. Such phenomena may be related to internal partial discharge. Although partial discharge energy is small, it is an early signal of insulation degradation. For procurement personnel, choosing a suitable partial discharge tester requires first clarifying the applicable boundaries of different detection technologies.
Currently, common technical approaches for partial discharge detection in high-voltage switchgear include transient earth voltage (TEV), ultrasonic (AE), ultra-high frequency (UHF), and pulse current method. The TEV method couples the electromagnetic signal generated by discharge through a sensor, and can collect data on the outer wall of the cabinet without power outage, making it suitable for inspection scenarios. The ultrasonic method is more sensitive to surface discharge and mechanical looseness defects, but is greatly affected by cabinet structure. The UHF method has strong anti-interference capability, but sensor cost and installation complexity are relatively higher. During procurement, a comprehensive judgment should be made based on the type of equipment being tested, the level of on-site interference, and the operation and maintenance mode.
For testers with TEV sensors as the core component, several key parameters should be considered during selection. First, the capacitance coverage range; some products can cover 6pF to 250μF, and can adapt to various test objects from small transformers to large switchgear. Second, signal acquisition and anti-interference capability; high-precision sensors combined with gated display circuits help identify discharge characteristics in complex electromagnetic environments. Third, the scanning time base method; display modes such as elliptical scanning can assist technical personnel in observing discharge phase distribution and improve interpretation efficiency.
Compared with UHF or pulse current method solutions, the advantage of TEV testers lies in portability and non-invasiveness. If procurement personnel are mainly engaged in daily inspections of 10kV to 35kV switchgear, the TEV solution has more advantages in operational convenience and time consumption per test. If precise localization or type identification of the discharge source is required, a combination of multiple sensors may be needed. During selection, it is not advisable to look only at a single sensitivity indicator; it is also necessary to evaluate the sensor frequency band, instrument repeatability, and on-site anti-interference design.
From the perspective of procurement decision-making, it is recommended to include the tester's range, sensor type, data storage and export method, battery life, and protection rating in the comparison list. At the same time, suppliers should be required to provide detection repeatability data under typical test objects, rather than only parameters under ideal laboratory conditions. For units that already have UHF or ultrasonic detection methods, models with multi-sensor interfaces can be given priority to balance current needs and subsequent expansion.
