Selecting secondary circuit testing equipment based on site requirements hinges on clearly defining the testing objectives, system type, accuracy requirements, and operating environment. Below are selection suggestions for different application scenarios to help you accurately match equipment:
Selecting Core Equipment Based on Testing Objectives
Relay Protection Function Verification: If testing the operating logic, timing characteristics, or overall transmission of a protection device is required, a microprocessor-based relay protection tester should be used. It can simulate various fault currents and voltages and is suitable for commissioning scenarios such as transformer and line protection.
Metering Accuracy Optimization:To reduce energy metering errors, especially deviations caused by PT secondary voltage drop, a fully automatic secondary voltage drop measuring instrument should be used. This equipment supports three-phase three-wire/four-wire automatic measurement, can directly calculate the combined error, and has high anti-interference capabilities.
Instrument Transformer Performance Testing:
CT/PT Ratio and Polarity Verification: Use a dedicated ratio tester or polarity calibrator to quickly confirm the correctness of the wiring.*CT Excitation Characteristic Analysis: A CT analyzer is selected to test the volt-ampere characteristics and 10% error curve, ensuring that the protective CT does not saturate during faults.
Conductive Circuit Health Status Check: For poor contact issues in circuit breakers and disconnectors, a secondary circuit resistance tester is used. The DC voltage drop method (four-terminal method) is employed to accurately measure micro-ohm resistance, preventing overheating faults.
Optimizing Equipment Characteristics Based on Site Conditions:
High Portability Requirements (e.g., outdoor substations): Handheld, lithium-battery powered equipment is preferred. For example, the CZ3140 circuit resistance tester weighs only 1.5kg and supports operation in environments without AC power.
Strong Electromagnetic Interference (e.g., operating switchyards): Instruments with digital filtering and inter-frequency testing technology are selected to effectively suppress 50Hz power frequency interference and ensure stable readings.
Multi-Task Efficient Operation: An integrated comprehensive tester is recommended. One device can complete multiple measurements such as PT voltage drop and CT load, reducing wiring and replacement time and improving on-site efficiency.
