Selecting a transformer calibrator is a rigorous technical decision that requires a deep integration of the instrument’s performance with actual needs and legal regulations. The core logic is: first, clarify the testing objective; then, follow compliance guidelines; and finally, select the appropriate tool.
Systematic selection method
The selection can follow a clear decision-making path: starting from defining core requirements, determining key performance indicators, assessing on-site operational feasibility, and finally reviewing compliance and comprehensive services.
Step 1: Anchor core requirements – clarify the testing mission
This is the starting point of the selection process, and it is necessary to precisely clarify the following dimensions:
Test object: It is necessary to clearly define whether the test object is a high-precision current transformer (CT) or voltage transformer (PT) for power metering, or an anti-saturation CT for relay protection, or both; whether it involves special types such as DC transformers or electronic transformers.
Application scenarios: The scenario directly determines the design orientation of the instrument:
Laboratory / metrology center: The core pursuit is extreme precision, high automation, and batch testing efficiency. Instruments are mostly desktop and have lower requirements for portability.
Substation on-site acceptance / preventive testing: The instrument requires high integration, robust portability, and strong battery life to quickly complete multiple tests in complex on-site environments.
Relay protection system debugging: The test focus is on the saturation characteristics of CTs. The instrument needs to have a powerful excitation (volt-ampere) characteristic test function and be able to accurately analyze the inflection point voltage and composite error.
Fault diagnosis: The instrument requires comprehensive functions. In addition to error testing, it is better to be able to conduct auxiliary diagnoses such as winding DC resistance and secondary circuit impedance.
Step 2: Determine key performance indicators – quantify technical parameters
After clarifying the requirements, they need to be converted into specific technical indicators:
Accuracy grade: As a hard requirement, the accuracy grade of the standard instrument used for laboratory verification must be at least two levels higher than that of the tested transformer; in on-site operation scenarios, 0.1 or 0.2 grade instruments are usually sufficient, but long-term stability and repeatability must be guaranteed.
Function combination:
Core essential functions: CT/PT ratio difference and phase difference testing, polarity check.
Key advanced functions: CT excitation characteristic curve testing and automatic calculation of inflection point voltage and composite error (core for evaluating the performance of protection CTs), secondary actual load measurement (ensuring the accuracy of metering and the reliability of protection actions).
Practical auxiliary functions: Winding DC resistance testing, data storage management software, etc., can significantly improve work efficiency.
Output capacity and range: The instrument’s output capacity must cover the specifications of the tested equipment. For example, when testing high ratio CTs, sufficient primary current output capacity is required (often requiring an external current booster), and when testing PT excitation curves or withstand voltage tests, sufficient high voltage output is required; at the same time, the instrument’s signal measurement range must be wide, suitable for various signals from milliamps to amps, volts to kilovolts.
Step 3: Evaluate on-site operability – focus on user experience
The instrument is ultimately operated by personnel, and in on-site scenarios, the following aspects need to be focused on:
Portability: Including weight, volume, etc., directly affecting the convenience of on-site transportation and use.
Power supply method: Whether it supports AC/DC power supply and long battery life, adapting to different on-site power supply conditions.
Human-machine interface: Outdoor visibility, whether the operation logic is friendly, determining on-site operation efficiency.
Data interaction capability: Functions such as USB and wireless transmission, affecting the efficiency of reading and storing test data.
Instruments that are powerful but operationally cumbersome and lack portability can easily become a burden in the field.
Step 4: Review compliance and comprehensive value – ensure legality and reliability
Finally, review the selection from the perspective of regulations and comprehensive value:
Compliance review: The instrument must comply with the requirements of the National Metrological Verification Regulations of the People’s Republic of China (JJG) and national standards (GB), which is the prerequisite for the equipment to have legal effect; At the same time, the instrument should be easy to send to the higher-level metrology institution for periodic verification (traceability).
Comprehensive service considerations: Attention should be paid to the completeness of technical support, technical training, maintenance network and software update services. Such services are equally important as the performance of the equipment itself.
Budget balance: On the basis of meeting technical, regulatory and operational requirements, pursue the best cost performance.
Post time: Dec-17-2025