Correct use of secondary circuit testing equipment requires following specific operating procedures based on the equipment type to ensure accurate measurements and compliance with safety regulations. The following are the operating methods for three main types of equipment:
Current Transformer Secondary Load Tester:
Used for online measurement of the actual load of the CT/PT secondary circuit without power interruption.
Wiring and Preparation: Connect the voltage test leads (V+, V-) to the secondary terminals of the current transformer. Use a clamp meter to clamp the secondary current circuit for non-contact sampling, ensuring the clamp jaws are closed and free of obstructions.
Operating Steps: After powering on, select "CT Load" or "PT Load" mode. The instrument automatically switches ranges and samples data. After measurement, it automatically calculates parameters such as impedance (Ω) or admittance (mS).
Precautions: Incorrect clamp meter orientation may result in negative readings; in this case, reverse the clamp meter orientation. Before testing, confirm that there is no risk of open circuit (CT) or short circuit (PT) in the secondary circuit.
Secondary Voltage
Drop and Load Measurement Instrument This instrument integrates voltage drop and load testing functions, supporting wireless synchronous measurement.
Wired/Wireless Connection: The main unit connects to the PT terminal box, and the slave unit connects to the energy meter panel. Simultaneous sampling at both ends is achieved via wireless communication. If the signal is poor, a dedicated synchronous cable can be used.
Voltage Drop Measurement Operation: After startup, the instrument synchronously acquires the voltage amplitude and phase at both ends, automatically calculates the voltage drop percentage, phase difference, and composite error, and determines whether limits are exceeded according to DL/T 448 standard.
Load Measurement: Switch to load mode and combine the clamp meter sampling current to measure the actual secondary load parameters.
Safety Precautions: Grounding at both points on the secondary side of the voltage transformer is strictly prohibited to prevent short circuits. The entire test process must be performed under energized conditions and must comply with the "Electrical Safety Regulations".
