Technical Article: ZXHQ-A+ CT/PT Characteristics Tester

1. Introduction

In modern power systems, Current Transformers (CTs) and Voltage Transformers (PTs) are indispensable core components, serving as the "sensory organs" for metering, protection, and control systems. The accuracy, linearity, and operational stability of these devices directly determine the safety and reliability of power grid operation. Aging, manufacturing defects, or installation errors in CTs/PTs can lead to incorrect protection actions, metering errors, and even large-scale grid failures. Therefore, comprehensive and accurate on-site testing of CT/PT characteristics is a critical step in power equipment commissioning, maintenance, and life-cycle management. The ZXHQ-A+ CT/PT Characteristics Tester is a specialized, field-oriented solution designed to address this demand, offering a full range of testing functions for class P CTs and PTs in power grids.

2. Core Functional Capabilities

The ZXHQ-A+ tester integrates multi-dimensional testing capabilities to cover the full inspection requirements of CTs and PTs, eliminating the need for multiple standalone instruments in field operations.

2.1 Comprehensive Testing for Current Transformers (CTs)

For CTs, the device supports the following key tests:

Magnetization (Excitation) Characteristic Test: Captures the full magnetization curve to identify core saturation behavior, critical for evaluating CT performance under fault conditions.

Transformation Ratio & Polarity Verification: Ensures the CT turns ratio matches design specifications and confirms correct winding polarity, preventing protection misoperation caused by reversed connections.

5% and 10% Error Curve Analysis: Calculates the composite error under rated secondary load conditions, verifying compliance with IEC/GB standards for protection-class CTs.

Secondary Circuit & Load Testing: Checks secondary winding resistance, verifies the actual secondary load, and performs power frequency withstand tests to detect insulation defects or circuit faults.

Degaussing & Current Injection: Removes residual magnetism from CT cores to eliminate measurement drift, and supports current injection for functional verification of secondary circuits.

Automatic Knee Point Calculation: Automatically identifies the excitation knee point voltage and current, a key parameter for assessing CT saturation performance in protection applications.

2.2 Full-Range Testing for Voltage Transformers (PTs)

For PTs, the tester provides complementary testing functions tailored to voltage transformer requirements:

Excitation Characteristic & Knee Point Analysis: Evaluates core excitation behavior and knee point parameters to ensure linearity across operating voltage ranges.

Transformation Ratio, Polarity, and Resistance Testing: Verifies ratio accuracy, winding polarity, and secondary winding resistance.

Power Frequency Withstand Test: Detects insulation weaknesses in primary and secondary windings.

Degaussing & Secondary Load Testing: Eliminates residual magnetism and verifies the actual secondary load conditions of PTs.

3. Key Design & Operational Advantages

The ZXHQ-A+ is engineered for harsh field environments, with user-centric design features that streamline testing workflows:

Integrated Field Printing & Data Management: Equipped with an LCD display and built-in mini printer, the tester supports on-site printing of test reports. It also allows data export via USB flash drives for post-processing, analysis, and archiving.

Compact, Portable Form Factor: With dimensions of 400 × 200 × 260 mm and a total weight ≤ 23 kg, the device is optimized for easy transport and deployment in substation and field settings.

Wide Operating Range: The tester operates on standard AC220V±20V, 50–60Hz power supplies, and supports a wide environmental range (-10°C to +40°C, <90% RH, altitude ≤1000m), ensuring reliable performance in diverse climates.

High Precision & Stability: With a measurement error of ≤0.5% (0.2%×Reading + 0.3%×Range), the device delivers laboratory-grade accuracy in field conditions.

Broad Compatibility: The CT ratio measurement range (5–25000A/5A, up to 5000A/1A) and PT ratio range (1–500kV) cover most CT/PT specifications used in distribution, transmission, and substation applications.

4. Conclusion

The ZXHQ-A+ CT/PT Characteristics Tester addresses a critical gap in power system testing by combining comprehensive CT/PT testing capabilities, high precision, and field-ready portability into a single, user-friendly instrument. By enabling utilities and power equipment operators to perform accurate, on-site characterization of CTs and PTs, the tester plays a vital role in preventing equipment failures, reducing maintenance costs, and enhancing the overall reliability of power grids. As power systems continue to evolve with higher voltage levels and more complex protection schemes, tools like the ZXHQ-A+ will remain essential for ensuring the performance and safety of grid infrastructure.

 GDZX is a manufacturer of power detection equipment, offering a diverse range of products with comprehensive models and providing professional technical support. Contact us at +86-27-6552607 or +86-17396104357.Website: http://en.gdzxdl.com/