Inspection and treatment methods for open-circuit and short-circuit faults on the secondary side of current transformers

Since the product can only allow a small impedance in the secondary circuit, under normal working conditions, it should be close to a short circuit state, with basically no sound. When the product fails, it is often accompanied by sounds or other manifestations. .

If the iron core screws are not tightened enough, the silicon steel sheet will loosen and the alternating magnetic flux in the iron core will change. As the alternating magnetic flux in the iron core changes, the silicon steel sheet will vibrate significantly and make a sound. If the iron core If the through screw is not tightened, the sound will continue.

When the product is in a light load or no-load state, the ends of some silicon steel sheets leaving the stack will vibrate, and they will also make sounds. This sound comes and goes and changes with the line load.

When the current on the open side of the secondary circuit is zero, the impedance will be infinite, and the secondary winding can generate high electromotive force, which can reach several thousand volts when it is at its peak. When the product is operating normally, the secondary circuit will be in a closed-circuit state, and the magnetic flux generated by the magnetic potential on the secondary side will guide and demagnetize the magnetic flux generated by the primary side.

When the secondary side is in an open circuit state, the demagnetized magnetic flux will disappear, and the magnetic flux in the iron core will increase, or even be in a saturated state. Since the magnetic flux changes over time and presents a flat-top wave, and the induced electromotive force of the secondary winding is proportional to the change in magnetic flux, once the secondary side is open-circuited, it will cause the iron core to overheat and burn out the product. .

Once an open circuit on the secondary side is found, the staff will short-circuit the test terminals of the secondary circuit on the distribution cabinet and then conduct inspection and treatment. If this method is unsuccessful, the product may have malfunctioned internally and the product should be discontinued.
If the staff finds smoke inside the current transformer, they should use a circuit breaker to cut it off to prevent the accident from expanding.