How to prevent open circuit on the secondary side of a current transformer

1. Fuses are strictly prohibited in secondary circuits. A blown fuse will directly cause an open circuit; therefore, no fuses, circuit breakers, or other protective devices that could cause an open circuit are permitted in secondary circuits.

2. Reliable anti-open-circuit measures are required during circuit switching. When switching measuring instruments or protective devices, a switching switch with short-circuit function should be used, or a connection should be made through an intermediate converter to ensure that the secondary circuit remains closed throughout the switching process, avoiding momentary open circuits.

3. Secondary windings not in use must be short-circuited and grounded. For current transformers installed but not yet in use, their secondary terminals should be reliably short-circuited and grounded in the terminal box to prevent induced high voltage and eliminate the risk of open circuits.

4. Use dedicated test terminals. Using well-designed test terminals allows for safe testing, verification, and disassembly operations without power interruption, effectively preventing open-circuit accidents caused by misoperation.

5. Ensure secure wire connections and conduct regular maintenance and inspections.

Secondary connection wires should use copper core wires with a cross-sectional area of ​​not less than 2.5mm² to ensure mechanical strength and conductivity.

Regularly check for loose, oxidized, or poorly connected terminals, especially near equipment subject to significant vibration, to prevent detachment due to thermal expansion and contraction or vibration.

6. Standardize operating procedures: Short-circuit first, then disassemble. When disassembling ammeters, energy meters, or relays during operation, terminals S1-S2 must be reliably short-circuited with a shorting clip before proceeding. Live-circuit work is strictly prohibited.

7. Strengthen personnel training and safety awareness. All maintenance personnel must master the basic principles and safe operating procedures of current transformers to prevent open-circuit accidents caused by misoperation (such as forgetting to restore wiring or not tightening the pressure plate).