I. Classification of Current Transformer Testing Equipment
(1) Classification by Functional Integration
Single-function tester
With a single function, it usually only tests one parameter, such as ratio, polarity or volt-ampere characteristics. The equipment structure is relatively simple, but the testing process is cumbersome, and multiple devices need to be carried for on-site operations. Typical representatives include traditional ratio testers and volt-ampere characteristic testers.
Integrated tester
It integrates multiple testing functions and can complete tests such as excitation characteristics, ratio and polarity, secondary direct resistance, and load of CT/PT. It supports one-click operation and is the current mainstream equipment type in the industry. Typical representatives include variable frequency current transformer integrated testers and current transformer comprehensive characteristic testers.
Online / Live Testing Instrument
It can conduct on-site testing without power interruption or equipment disassembly, used to evaluate the performance of operating CTs, especially suitable for low-voltage side or scenarios where power outage is inconvenient. Typical representatives include low-voltage CT online testing devices and online calibrators.
Specialized Polarity Calibration Device
It is specifically used for current transformer polarity calibration, featuring portability and wireless remote operation, which can solve the problem of low efficiency in the traditional dry battery method. A typical representative is the wireless polarity tester.
(2) Classification by Working Principle (for calibrators)
Potential comparison type: It completes voltage vector measurement with the working current as a reference.
Current comparison type: It completes current vector measurement with the working voltage as a reference.
Magnetic potential / Bridge comparison type: It achieves measurement through direct comparison.
Digital calibrator: It integrates computer and digital signal processing technology, with a high degree of automation, capable of automatically calculating ratio error and phase angle error and generating test reports.
II. Application of Current Transformer Testing Equipment
Laboratory Verification and Factory Testing
The main purpose is to verify the accuracy and precision of newly manufactured or sent-for-inspection CTs, ensuring they meet the requirements of 0.05, 0.1, 0.2, etc. precision grades. Commonly used equipment includes high-precision current transformer calibrators, standard transformers, and current transformer verification benches.
Substation On-site Handover and Preventive Testing
It is mainly used before new equipment is put into operation or during regular maintenance to test parameters such as volt-ampere characteristics, ratio and polarity, and secondary circuit load, ensuring the reliable operation of protection devices and accurate metering. Commonly used equipment is the variable frequency current transformer integrated tester.
Live Testing and Online Monitoring
It conducts error detection on operating low-voltage CTs without affecting power supply, solving the problem of inaccurate metering caused by harmonic interference and avoiding losses due to power outages. Commonly used equipment includes low-voltage CT online testing devices and online calibrators.
Infrastructure Installation and Circuit Calibration
It is suitable for new station construction or renovation scenarios, allowing for rapid calibration of current transformer polarity and the correctness of circuit wiring, preventing tripping accidents caused by reverse polarity connection. Commonly used equipment is the portable polarity calibrator.
III. Key Points for Selecting Current Transformer Testing Equipment
(1) Test Items and Integration Degree
If multiple tests need to be conducted frequently, priority should be given to integrated testers to reduce the number of wiring operations and the number of devices carried.
(2) Output Capacity (Voltage / Current)
Selection should be based on the voltage level and ratio of the CT to be tested. For the volt-ampere characteristic test of 500kV level CTs, the instrument should output 2500V to 3000V high voltage; for the primary current test of large ratio CTs, the instrument should output a current of 600A or more.
(3) Measurement Accuracy
For metering CTs: High-precision equipment should be selected, with ratio measurement accuracy reaching ±0.05% or higher, and phase measurement accuracy within ±1 minute.
For protection CTs: The accuracy requirements are relatively lower, such as ±0.2% for ratio, with more emphasis on the inflection point test of the excitation characteristic curve.
(4) Portability and Working Conditions
For on-site testing: The weight of the equipment should be a key consideration, balancing functionality and portability. Live detection: The equipment should be capable of passive non-intrusive sampling, anti-electromagnetic interference, and harmonic analysis functions.
(V) Intelligence and Data Management
Pay attention to whether the equipment supports automatic calculation of inflection points and automatic drawing of error curves; whether it supports data export and direct generation of test reports to meet the requirements of digital management.
Post time: Mar-31-2026