One of the effective methods for on-line detection of transformer insulation is to monitor the parameters of partial discharge electric pulses. In the normal operation of the transformer, the partial discharge is small. In recent years, the partial discharge of the transformers above 110kV produced in recent years is controlled below 500pC; but in actual operation, even if there is a discharge of about 5000pC, it will still operate as usual, and the development process of its insulation defects may last for several years. weeks or even years.

During online measurement, due to the influence of on-site interference signals, it is difficult to directly measure the high-frequency parameters of partial discharge, and the running equipment should try not to change the operating wiring status of the original equipment when performing online monitoring and collecting the required signals. Therefore, it is very effective and reasonable to select the signal sampling point at the transformer core grounding lead-out line, neutral point lead-out line and high-voltage bushing end screen lead-out line.

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In any case it will not affect the normal operation of the transformer. However, when the sensor is selected at the iron core grounding point, the sensitivity requirements for the sensor and amplifier are higher than those for sampling at the end screen of the casing.

The signal detected from the sensor is suppressed by a balanced amplifier to suppress common-mode interference, such as a 75n high-frequency coaxial cable is sent to the monitoring room, the amplitude is controlled by a computer, and the pulse discrimination instrument analyzes the power frequency and high-frequency signals, and according to the setting When the fault signal exceeds the set amplitude and pulse frequency, it will automatically send out sound and light alarms.