The CT PT Tester is an intelligent, multi-functional instrument used in power systems for comprehensive testing of current transformers (CTs) and voltage transformers (VTs). It integrates critical test functions into a single device, significantly improving the efficiency and accuracy of testing, calibration, and maintenance for mutual inductors in both field and laboratory settings.
Core Test Functions
1.Volt-Ampere (Excitation) Characteristic Test:
Target: Primarily for current transformers (CTs).
Purpose: Measures the excitation characteristic curve of a CT, i.e., the relationship between excitation voltage and excitation current.
Significance:
Evaluates core material quality and saturation characteristics.
Calculates knee-point voltage and knee-point current-key parameters for assessing CT accuracy during fault conditions and protection relay operation.
Detects defects like inter-turn short circuits.
Provides data for relay protection settings.
Process: Automatically ramps voltage and plots the voltage-current curve.
2.Ratio (Turns Ratio) Test:
Target: CTs and VTs.
Purpose: Measures the actual transformation ratio of mutual inductors.
Significance:
Verifies nameplate ratio accuracy.
Ensures precision in metering and protection.
Identifies ratio errors caused by winding issues.
Process: Applies test current/voltage to primary windings; measures secondary values to calculate ratio (supports single-phase/three-phase methods).
3.Polarity Check:
Target: CTs and VTs.
Purpose: Determines polarity relationship (additive/subtractive) between primary and secondary windings.
Significance:
Ensures correct wiring. Incorrect polarity causes meter reversal or protection relay malfunctions, critical for system safety.
Process: Applies a transient DC/AC signal; auto-detects secondary response phase/direction to confirm polarity.
4.Additional Functions (Advanced Models):
Secondary Burden Test: Measures actual impedance of CT secondary loops.
Winding Resistance Test: Measures DC resistance of CT/VT secondary windings.
Demagnetization: Removes residual magnetism from CTs post-testing.
Phase/ Ratio Error Test: For precision metering-grade mutual inductors.