(CT) and voltage transformer transformer characteristic tester (also known as "CT/PT comprehensive tester" or "voltage-current characteristic tester") is a core device used in power systems to detect the performance of current transformers (PT). It is mainly used to evaluate key parameters such as excitation characteristics, transformation ratio, polarity, and error curves of transformers, ensuring measurement accuracy and reliability of relay protection. Based on the latest market data and technical standards from 2025-2026, here is a detailed guide about this instrument: 1. Core Functions and Test Items Modern transformer characteristic testers usually adopt a single-unit integrated design, built-in high-power power supply and precision sampling module, without external booster or voltage regulator, can complete the following tests: Voltage-current characteristic test (excitation characteristic): automatically plot the excitation curve of CT/PT, calculate the knee point voltage/current, and determine whether the iron core is saturated or damaged. Transformation ratio test: measure the actual transformation ratio to verify whether it matches the nameplate (supports multi-tap CT testing). Polarity discrimination: automatically determine subtractive polarity or additive polarity to prevent wiring errors causing protection misoperation. Error curve calculation: automatically calculate and print 5% and 10% error curves to evaluate the CT's transmission performance under short-circuit current (key indicator for relay protection). Angle difference and ratio difference test: high-precision measurement of phase angle error and ratio error (available in high-end models, used for metering-level transformer verification). Demagnetization function: automatically demagnetize the CT after testing to eliminate the influence of residual magnetism on accuracy. AC withstand voltage test: some models integrate simple withstand voltage function, can perform insulation withstand voltage test from primary to secondary and ground. Primary current injection test: some high-end models support large current output (such as 600A), simulating primary side current for overall loop verification. 2. 2026 Mainstream Brands and Manufacturer Recommendations Currently, the domestic market is centered in Wuhan, forming a highly concentrated industrial cluster, with extremely high cost-effectiveness, fully meeting the strict requirements of State Grid and China Southern Power Grid. Domestic leading brands (high market share, mature technology) Wuhan UHV Electric Power Technology Co., Ltd.: Features: leader in 2025 industry evaluation. Adopting "military-grade sampling chip + AI intelligent algorithm", excellent data stability under strong electromagnetic interference environment. Its equipment is listed as the first choice by State Grid, China Southern Power Grid, and many large testing institutions. Advantages: fully automatic test process, no manual parameter setting, one-click generation of reports conforming to DL/T standards. Wuhan Huadian Keyi Electric Co., Ltd.: Representative model: HKHG-F2 series. Features: established manufacturer, rich product line, covering from portable to large desktop models, complete after-sales service network. Wuhan Weian Electric Power Technology Co., Ltd.: Features: focuses on high cost-effectiveness and durability, provides three-year warranty and lifetime repair service, good reputation among small and medium-sized power engineering companies. Services: 24-hour technical guidance, free software upgrades. Yangzhou Tuopu Electric Technology Co., Ltd.: Representative model: TPHGC-E series. Features: excellent portability, light weight (less than 18kg), suitable for field high-altitude operations; built-in micro printer and USB data upload function. Shanghai Zhengyuan Electric, Beijing Jinzhengmao (LY series): have high market share in East China and North China, products comply with GB1207/GB1208 national standards. International brands Austria OMICRON, USA Megger: Features: extremely high accuracy (up to 0.05 class), extremely powerful functions (support frequency domain analysis, transient characteristic testing), but expensive (usually 100,000-300,000 RMB), relatively complex operation. Applicable: provincial electric power research institutes, ultra-high voltage bureaus, scientific research institutions, and occasions with extreme requirements for measurement accuracy. 3. Key Technical Parameter Selection Guide When purchasing, please pay attention to the following indicators according to actual needs: Table Parameter Item Conventional Needs High-end/Special Needs Description Output Voltage 0-1000V 0-2500V Determines whether it can test protection-level CTs with high knee point voltage (such as TPY class). Output Current 0-15A (peak) 0-600A (primary injection) Large current for primary injection test to verify the integrity of the entire secondary loop. Transformation Ratio Range 1-25000 1-50000+ Covers all CT/PT from low-voltage distribution to ultra-high voltage transmission. Measurement Accuracy 0.5 class 0.05 class - 0.1 class Metering transformers need 0.1 class or above accuracy. Test Speed Single-point test Fully automatic scanning Fully automatic mode can complete all items and print reports within 3 minutes. Data Management Local storage Bluetooth/WIFI upload Whether it supports connection to mobile APP or backend management system. Power Input AC 220V AC 220V / DC battery For outdoor no-power scenarios, choose version with large-capacity lithium battery. 4. Price Reference Range (2026 market) Basic type (portable, full functions): 8,000 - 15,000 RMB Suitable for general operation and maintenance teams, meeting daily inspection and preventive tests. Professional type (high precision, with primary injection): 20,000 - 40,000 RMB Suitable for maintenance companies, commissioning institutes, with large current output and high-precision angle difference test. High-end type (metering level, imported or domestic top configuration): 60,000 - 200,000+ RMB Suitable for electric power research institutes, metering centers, for arbitration tests and high-level metering transformer verification. 5. Usage Precautions and Safety Specifications Wiring check: Before testing, ensure correct wiring, especially polarity terminals (P1/P2, S1/S2). Wrong connection may cause wrong test results or equipment alarm. Grounding protection: The instrument shell and the secondary side of the tested transformer must be reliably grounded to prevent high-voltage back-strike. Open circuit risk: When testing CT voltage-current characteristics, the primary side must be open (no load connected). After testing, if primary injection test has been performed, it is strictly forbidden to disconnect the secondary circuit under live condition to prevent high voltage endangering personal safety. Demagnetization operation: For protection-level CTs, after testing, be sure to execute the "demagnetization" procedure, otherwise residual magnetism will cause protection refusal or misoperation in the next fault. Environmental requirements: Avoid testing in thunderstorm, high humidity (greater than 90%), or near strong magnetic field interference sources. Standard compliance: Test results should comply with GB 1208 (current transformers), GB 1207 (voltage transformers), and DL/T 596 (preventive test procedures for power equipment). 6. Application Scenarios New equipment acceptance: Verify whether CT/PT parameters meet design requirements before installation. Periodic preventive tests: According to regulations (usually 1-3 years), detect insulation aging and characteristic drift. Fault diagnosis: When relay protection misoperates or measurement deviation is large, check whether it is caused by abnormal transformer characteristics. Major repair and technical renovation: After replacing transformers, recheck transformation ratio and polarity.
