Let’s explore the system principles of partial discharge detectors.
发布时间：2021-11-12
Partial discharge (PD) detectors are primarily used to monitor partial discharges in electric motors under normal operating conditions. The motor’s normal operating state objectively reflects the electrical, mechanical, thermal, and environmental stresses it experiences during operation. The detection methods employed by PD detectors include the widely adopted direct method, the bridge‑balance method, and the current‑pulse method.
Its basic principle is as follows: when a partial discharge occurs in the test specimen, an instantaneous voltage change ΔU appears across the test capacitor Cx. This voltage is coupled to the measurement impedance Zm via a coupling capacitor Ck, generating a pulse current I in the circuit. By sampling, amplifying, and displaying the pulse voltage produced by this pulse current I across the measurement impedance Zm, parameters such as the apparent discharge quantity of the partial discharge can be determined. The pulse current method primarily exploits the lower-frequency components of the partial discharge signal spectrum, thereby minimizing radio‑frequency interference.
The partial discharge instrument is a pulse‑peak‑display‑type testing system, equipped with computer‑controlled functions for filtering, amplification, sampling, data storage, and display. Data acquisition is synchronized with the test voltage. It supports direct measurement, bridge‑balance methods, and can calculate the repetition rate n, the average discharge current I, and the square‑rate D, enabling the generation of various plots such as q–n, q–φ, and q–φ–t.
The complete measurement system is capable of detecting ultrasonic signals corresponding to partial discharge levels below 1000 pC. Its software provides statistical evaluation of test results and automatic fault diagnosis of partial discharges based on partial discharge data, with reports generated automatically. The virtual oscilloscope supports linear, elliptical two-dimensional, and three-dimensional graphical displays.
2024/06/29
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