Instrument Transformer Testing
Accuracy and Reliability for Measurement and Protection in the Power System
Instrument Transformers (ITs), such as Current Transformers (CTs) and Voltage Transformers (VTs), play a critical role in electrical systems by conditioning primary quantities — high currents and voltages — into reduced and safe secondary values. These signals are used by devices such as protection relays, meters, power quality analyzers, and controllers, which rely on data accuracy for proper operation.
A poorly performing IT can negatively impact energy measurement, protection coordination, and fault detection, putting at risk not only the reliability of the power grid but also the operational safety of assets and personnel.
Why Test Instrument Transformers?
Due to their fundamental role, instrument transformers must undergo periodic testing during commissioning as well as during preventive and predictive maintenance routines. These tests ensure CTs and VTs continue to operate within the specified performance limits established by technical standards such as IEC 61869, IEEE C57.13, and ABNT NBR 6855.
Testing also assists in detecting incipient faults, such as changes in the turns ratio, saturation problems, or insulation deterioration, which can lead to serious measurement errors or relay malfunctions.
Conprove Solutions for Instrument Transformer Testing
To offer convenience, accuracy, and safety, Conprove provides the CE-7012, a universal tester capable of executing tests on both secondary and primary equipment, including complete tests on instrument transformers.
With the support of CTC – Conprove Test Center, Conprove’s dedicated software, users can automate test procedures, record results, generate reports, and compare collected data with reference values efficiently and traceably.
Main Tests Performed
Below are the main tests that can be performed using the CE-7012 + CTC solution:
Turns Ratio, Polarity, and Burden Test
Checks whether the ratio between primary and secondary quantities is correct and within the established tolerance. The test also validates terminal polarity and calculates the total burden applied to the transformer secondary, ensuring operation within the nominal range.
CT Saturation Curve Characterization
This test obtains the magnetization (or saturation) curve of the CT, essential to verify its suitability for the type of protection used. It can also identify magnetic core degradation or inter-turn short circuits.
Winding Resistance Measurement
Important for checking the continuity and integrity of windings, resistance measurement helps detect faulty connections, thermal variations, and internal problems that affect performance.
Dielectric Strength Test
Insulation test applying 2 kVac between terminals and ground, verifying if the instrument transformer’s insulation system remains intact and capable of withstanding electrical stresses.
Recommended Equipment
- CE-7012 – Universal multifunction tester capable of performing tests on both protection and automation equipment (secondary level) and on primary equipment such as instrument transformers. Robust, portable, and highly reliable.
- CTC – Conprove Test Center: Software platform that integrates all Conprove device features, with user-friendly interface and graphical analysis tools.
Field and Laboratory Applications
Conprove’s IT testing solutions are used in:
- Power substations
• Power plants
• Operation and control centers
• Testing and metrology labs
• Maintenance and electrical engineering companies
• Industries with internal electrical systems
Thanks to the portability of the equipment and the intelligence of the CTC software, tests can be performed in the field or on the bench, with full safety and efficiency.
