In live detection of switchgear, O&M personnel commonly cross-verify using the transient earth voltage (TEV) method and the ultrasonic (AE) method. On the same cabinet, a high TEV reading with no obvious ultrasonic signal, or the reverse, does not necessarily indicate an instrument fault; rather, the two methods have different sensitivities to discharge types. TEV responds better to internal surface discharge, while the ultrasonic method is better at capturing discharge caused by external creepage or mechanical looseness. Only by understanding the frequency bands and applicable boundaries of each detection technology can data be interpreted reasonably.
A single TEV sensor solution is easy to install and suitable for general screening of switchgear, but it cannot measure apparent discharge magnitude (pC) and is difficult to distinguish discharge from interference. A single ultrasonic solution is immune to electromagnetic interference and provides intuitive localization, but has limited sensitivity to internal discharge in enclosed equipment. The pulse current method is based on the IEC 60270 standard and can measure apparent discharge magnitude with sensitivity up to 0.02 pC–0.1 pC, but it requires de-energizing the equipment to connect a coupling capacitor, making it inconvenient for routine inspection. The UHF method has strong anti-interference capability and can penetrate metal enclosures, making it suitable for internal discharge detection in GIS, but it places high requirements on sensor placement and is difficult to use directly on open-type equipment. The PD-6800 partial discharge detector integrates five detection channels—pulse current, UHF, ultrasonic, TEV, and HFCT—into one host, allowing on-site switching or combined use according to equipment type and reducing the burden of carrying multiple instruments.
The detection host supports 0–60 dB gain adjustment, a sampling rate of 100 MS/s, and a measurement range covering 1 pC–10000 pC (depending on the sensor). The pulse current channel has a linearity error of ≤±10%; the synchronization unit supports internal synchronization, external synchronization, and wired/wireless synchronization, with a phase accuracy of ≤0.1°. The data analysis software can generate PRPD/PRPS patterns and supports auxiliary discharge type identification and trend analysis. A calibration pulse generator is used for system sensitivity verification. The sensor set is selected according to the equipment under test: UHF antennas for GIS, ultrasonic probes for external detection of transformers and switchgear, TEV sensors for cabinet surface induction, and HFCT clamp-type current transformers clamped onto cable grounding wires.
The PD-6800 is suitable for live detection and online monitoring of switchgear, transformers, GIS, cables, and other equipment. When using it, O&M personnel are advised to first perform general screening with the TEV or ultrasonic method, and after abnormal signals are found, re-check with the pulse current method or UHF method. Before detection, confirm that the sensor is well coupled to the equipment surface, and periodically verify system sensitivity with the calibration pulse generator. In environments with strong electromagnetic interference, give priority to the ultrasonic method or UHF method, and record background noise for comparison. The device provides a touchscreen display, allowing patterns and measured values to be viewed directly on site.
