Let’s take a closer look at the system principles of partial discharge detectors.

发布时间：2022-01-07

Partial discharge (PD) detectors are primarily used to monitor partial discharges in electric motors during normal operation. The motor’s normal operating conditions objectively reflect the electrical, mechanical, thermal, and environmental stresses it experiences. Common detection methods employed by PD instruments include the direct method, the bridge‑balance method, and the current‑pulse method. Their fundamental principle is as follows: when a partial discharge occurs in the test specimen, a transient voltage change ΔU appears across the test capacitor Cx; this voltage is coupled via a coupling capacitor Ck to the measurement impedance Zm, generating a pulse current I. The pulse voltage produced by this current across Zm is then sampled, amplified, and displayed, enabling the determination of parameters such as the apparent discharge quantity. The current‑pulse method relies mainly on the lower‑frequency components of the partial discharge signal spectrum, thereby minimizing radio‑frequency interference.

The partial discharge locator is a pulse‑peak‑indication‑type testing system, featuring 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 parameters such as the repetition rate n, the average discharge current I, and the square‑rate D, enabling the generation of various plots—including q–n, q–φ, and q–φ–t charts. The complete measurement system is capable of detecting ultrasonic signals corresponding to partial discharge levels below 1000 pC.

Its software features statistical evaluation of test results and an automated partial discharge fault‑identification function based on partial discharge data, with reports generated automatically. The virtual oscilloscope offers linear, elliptical two‑dimensional, and three‑dimensional display modes. This system is suitable for partial discharge testing of GIS, cables, power transformers rated 110 kV and above, instrument transformers rated 35 kV and above, bushings, surge arresters, coupling capacitors, and other power equipment.

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