Current Transformer characteristic comprehensive tester, also known as CT PT Analyzer, is a multi-functional field test instrument specially designed for relay protection professional test current transformer volt-ampere characteristics, transformation ratio test and polarity discrimination. It can also be used as a transformer. Measuring instrument for polarity discrimination test. It has the characteristics of light weight, convenient operation and unique performance, and is a cost-effective product.
In fact, the accuracy of the transformer tester is not an important indicator of the instrument. In the transformer verification regulations, it is required that the test error brought by the entire circuit does not exceed 20 percent of the level of the transformer being tested. The data presented in the work must be authentic.
Common technical problems during testing:
1. Frequency selection filter performance
Transformer verification is the measurement of the fundamental wave. Since the secondary and tertiary error current waveforms of the secondary current of the standard and the tested transformer are greatly distorted and modulated by high{{0}}frequency interference, the tester must have a good frequency selection. Filter performance, separate fundamental waves, and measure. The factors that cause distortion are very complex. In the low-precision (less than 0.5) transformer test without saturation core compensation, the general distortion is about 10 percent , and the influence is not obvious. The national standard requires the harmonic attenuation of the tester to be more than 32dB, which is enough to meet use. However, this indicator is too low when testing high-precision transformers or transformers with saturated iron cores. There is no measurement in the domestic verification of this project, and the general manufacturers often do not give indicators. When purchasing a new instrument, users should compare it with the old instrument to determine whether it is credible.
2. Introduce load and match with standard transformer
The additional load brought by the tester to the tested transformer and the load brought by the tester to the standard transformer are strictly stipulated in the regulations. Domestic metrological verification does not detect these indicators, and most manufacturers do not provide indicators, but they are One of the main reasons for different unit test data is different.
3. Wire load
When the load Z is made, a resistance of {{0}}.06 ohms is reserved for the connecting wires (individually there are 0.05 ohms), so the sum of the resistances of the three wires A, B, and C in the figure is required to be 0.06 ohms in the test. The wire resistance has a great influence on the data when the current transformer is verified with a small rated load (10VA).
4. Ground wire
Because it is a power frequency measurement, the space electromagnetic field and floating potential have a greater impact on the measurement. In the test, the ground wire plays an important role. The ground wire must be properly grounded according to the regulations, which is particularly important in the test above 0.05, or when it is a high voltage. It is suggested that users should choose a complete set of equipment factory with many years of industry foundation when purchasing an instrument, rather than a single-piece production factory. The two have essential differences in the theory and experience of transformer testing. The correct selection can ensure that all the indicators of the instrument comply with the requirements of the regulations. All kinds of wiring and instrument matching are planned and designed by the manufacturer, which can avoid use errors and affect product quality.