Why do the same zinc oxide arresters show deviations between the DC reference voltage measured in the laboratory and the retest values after on-site commissioning? When configuring test instruments, selection personnel often focus on range and display mode but overlook a more fundamental issue: whether reliable electrical isolation exists between the instrument's internal voltage and current channels. This detail directly determines the credibility of leakage current measurement.
The leakage current of zinc oxide arresters is typically in the microampere to milliampere range, and the signal itself is very weak. If the instrument's voltage sampling circuit and current sampling circuit share a reference point, common-mode interference present on site may couple into the measurement channel, causing readings to drift. Poor repeatability in some test data is not due to changes in the valve disc itself but to errors introduced by the measurement chain. For personnel responsible for design and selection, the instrument's isolation structure should be evaluated together with measurement accuracy.
The DR-9300 zinc oxide arrester tester adopts a fully digital processing method. A precise mathematical model is established inside the instrument to compute the sampled data, resulting in good consistency of measurement results. In terms of electrical structure, the instrument completely isolates the voltage sensor from the current sensor. Only weak electricity is used inside the main unit, and the parts touched by test personnel carry no strong electricity, making it suitable for working conditions involving frequent on-site movement.
The instrument is used to measure the DC reference voltage and leakage current of zinc oxide arresters. The DC reference voltage reflects the conduction characteristics of the valve disc at a specified current, while the leakage current is used to assist in determining whether the valve disc has aged or its insulation has become damp. Comparing these two data items with historical records can provide a reference basis for arrester condition assessment. It should be noted that test results should be comprehensively analyzed in combination with ambient temperature, humidity, and the surface cleanliness of the test specimen, and conclusions should not be drawn directly from a single data set.
The instrument is suitable for DC parameter testing of arresters in substations, power plants, and distribution stations during pre-commissioning acceptance and routine inspection during operation, and can also be used for retesting after arrester maintenance. For design and selection personnel, it can be included in the configuration list of routine detection tools for zinc oxide arresters and used in conjunction with items such as insulation resistance testing and leakage current testing under operating voltage to form a relatively complete arrester detection scheme.
