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What are the adverse effects of opening a current transformer in operation?

by:Transmart     2022-05-03

Why can't the current transformer be opened in operation? What is the principle? What are the adverse effects of opening the circuit? Most welders often hear such a sentence: 'The secondary side of the current transformer cannot be opened, and the secondary side of the voltage transformer cannot be short-circuited.' At work, everyone will definitely treat this as the 'Koran'. When disassembling the secondary line of the current transformer, first add a short turn piece or short wiring to connect the secondary side, and then carry out the surgical stitch removal or wiring work. , so that the safety of the person can be guaranteed, which is a very appropriate approach. When I dismantled the current line of the meter before, I encountered a situation where the wiring was not firm, and the terminals were cracked and charged and discharged.

Then why can't the secondary current transformer be opened? What is the principle? What adverse effects will it cause? The following is a careful analysis for everyone, I hope everyone can understand. When the current transformer is working normally, the load connected to the secondary coil is the ammeter or the electric meter current electromagnetic coil and its intelligent transmitter. The characteristic impedance of this electromagnetic coil is not large, and most of them operate in a short circuit Fault conditions. Under such conditions, the magnetic flux caused by the primary current of the current transformer and the current of the secondary coil cancel each other out, so that the relative density of the magnetic flux in the iron core is kept at a moderate level, generally within a few tenths of a Tesla car ( The unit of magnetic flux density: T), because the secondary coil resistor is not large, so the secondary coil operating voltage is also very low. Under all normal operating conditions, the magnetic fluxes of the current transformers are offset, and the relative density of the magnetic fluxes is not large. When the secondary winding of the current transformer is open, if there is no change in the primary current at this moment, the secondary circuit is broken, or the resistor is very large, then the current on the secondary side is 0, or very small, and the secondary electromagnetic coil Or the magnetic flux of the iron core is not large, and the primary magnetic flux cannot be offset. At this moment, the amount of primary current all becomes self-induced electromotive force, which makes the iron core saturated. This change is sudden, called a sudden change, and its relative density of magnetic flux is higher than that of many Tesla cars.

The adverse effects of the secondary open circuit of the current transformer After such a situation occurs, it will cause the following adverse effects:

1. The working voltage of thousands of volts is caused by the second time (this has not been certified, it is a copy of the basic theory), the high voltage will penetrate the insulation layer of the current transformer, so that all the substation equipment casings will be electrified , it will also cause the maintenance staff to get an electric shock, which is life-threatening.

2. The sudden change of the iron core to the saturation state will increase the wear and tear of the iron core of the voltage transformer, the iron core will become hot, and the voltage transformer will be destroyed.
3. The saturated iron core of the voltage transformer is in saturation state, the measurement verification is inaccurate, and the CT ratio difference and angle difference increase.
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