During on-site inspections at substations, operation and maintenance personnel often encounter a specific problem: the ratio and polarity test data of voltage transformers (PTs) are unstable, and parameters must be repeatedly set when switching between different devices. This is often related to the selection of test instruments and the suitability of their functions.
For PT voltage transformer testing, selection needs to focus on three aspects. First, ratio measurement capability. The ratio range should cover 1~10000, with accuracy of Class 0.2 in the 1~1000 range and Class 0.5 in the 1000~10000 range, meeting the GB1094 requirement of 0.5% allowable deviation for power transformer ratios. Second, operational efficiency. Fully automatic operation can complete three-phase ratio, vector group, and polarity testing with one wiring setup, taking 8~35 seconds per set of data, and supports blind testing, requiring no prior knowledge of the wiring group, making it suitable for old equipment without nameplates. Third, on-site adaptability. Portable models are dual-purpose AC/DC, with built-in lithium batteries, and can test more than 100 units on a single charge; benchtop models are fully functional and suitable for laboratories and factory inspection. In terms of safety protection, they should have high-low voltage reverse connection protection, output short-circuit protection, overcurrent and overvoltage protection, and protection against mistakenly connecting the power supply to 380V. Data management needs built-in storage of 50~1000 sets, with support for USB flash drive export and Bluetooth transmission.
When selecting, benchtop fully automatic models are recommended for regular substation maintenance; portable models are preferred for multi-point inspections or outdoor work; multifunctional models are needed for railway and special transformer scenarios, supporting phase angle measurement and hexagonal vector diagrams; Class 0.1 high-precision models can be selected for manufacturer inspection.
