Transformer characteristic tester accurately measures the actual transformation ratio of transformers such as 600/5A



The transformer characteristic tester (also commonly referred to as the "transformer comprehensive tester" or "CT/PT characteristic tester") is the core equipment used by the relay protection specialty in power systems to conduct a comprehensive "physical examination" of current transformers (CT) and voltage transformers (PT).

Transformers play the role of "scouts" in the power grid, responsible for proportionally converting the high voltage and large current on the primary side into standard low voltage and small current on the secondary side for instrument measurement and relay protection. The core task of this tester is to verify whether the reports of these "scouts" are accurate and their responses are sensitive, ensuring that relay protection devices can act precisely when faults occur in the power grid.

⚡ Core Testing Functions (Comprehensive Physical Examination)

Modern transformer characteristic testers are highly integrated, and typically a single device can independently complete all the following core testing items without the need for external bulky auxiliary equipment such as voltage regulators and current boosters:

Voltage-Current Characteristic (Excitation Characteristic) Test: This is the most basic and important test. By automatically boosting voltage, it plots the excitation curve of the transformer and automatically calculates the knee point voltage/current. This directly reflects the saturation level of the transformer core and determines whether it is suitable for the current protection settings.

Transformation Ratio and Polarity Test: Precisely measures whether the actual transformation ratio of the transformer (such as 600/5A) matches the nameplate, and determines whether the polarity (reduced polarity or additive polarity) wiring is correct.

Error Curve and Ratio Error/Phase Displacement Test: Automatically plots the 5% or 10% error curve and precisely measures the ratio error (ratio deviation) and phase displacement (phase error), which is crucial for the accuracy assessment of metering transformers.

Secondary Winding and Burden Test: Measures the DC resistance of the secondary winding and the actual burden (VA value) of the secondary circuit to ensure there is no poor contact or overload in the secondary circuit.

Demagnetization Function: After large current surges or DC tests, residual magnetism remains in the transformer core, affecting measurement accuracy. The tester provides an automatic demagnetization function to eliminate the influence of residual magnetism.

Primary Current Injection and High Current Test: Some high-end models integrate a high current output function (e.g., 0-1000A), allowing direct primary current injection tests on CTs to verify the integrity of the entire current circuit.