What is the risk of continuing to use the current transformer without heating after the secondary si

The current transformer will not generate voltage when there is voltage and no current on the primary side, and the secondary side will not produce voltage when there is a certain amount of stable current on the primary side, and the opening of the secondary side will produce a certain value of voltage, but it will not be very high. However, the primary main circuit is generally connected with the switch, when the switch turns on or off the main circuit current, the main circuit current will have a sudden change process, according to V=L*Di DT (L is the inductance of the transformer), at this time, if the secondary side is open, it will instantly excite a very high voltage, which is prone to danger. Therefore, the current transformer is not allowed to open the circuit.

The secondary side open circuit of the transformer only excites a very high voltage at the moment of a sudden change in the current, and this high-voltage pulse only occurs on the two terminals of the transformer or on the original connected to it, and will not burn the transformer.

The secondary side of the current transformer is never allowed to open the circuit, once the open circuit occurs, it will produce high voltage, resulting in equipment insulation damage or personal electric shock accidents, and the current transformer will be burned out if the fault time is too long!

The risk is relatively large, because after the secondary side of the current transformer is opened, whether the secondary side generates high voltage and whether it generates heat depends on the current of the primary side of the current transformer. When the current is small, even if the secondary side is open, the core will not be saturated, and the secondary side will not generate high voltage and will not generate heat. When the current becomes larger, the core will be saturated, and high voltage will be generated on the secondary side, which will affect the safety of people and equipment.

The saturation of the iron core causes severe heating, and even causes a fire in severe cases. Therefore, the power outage should be dealt with in time. The secondary side open circuit of the current transformer also depends on the specific role of the secondary winding, which affects the measurement, measurement accuracy or protection performance.

The secondary side of the voltage transformer can not be short-circuited, because the primary winding of the voltage transformer is connected in parallel with the circuit under test in the high-voltage power grid, the number of turns of the secondary winding is small, and the impedance is small.

The number of primary winding turns of the current transformer is very small, and the string is in the line of the current that needs to be measured, so it often has all the current of the line flowing through, and the number of turns of the secondary winding is relatively large, which is connected in series in the measuring instrument and the protection circuit, when the current transformer is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection loop is very small, and the working state of the current transformer is close to a short circuit.

Consequences of a secondary open circuit of a current transformer:1. The secondary generation of thousands of volts of voltage, high voltage may break down the insulation of the current transformer, make the entire distribution equipment shell electrified, may also make the maintenance personnel electrocuted, there is a danger to life.

2. The sudden saturation of the iron core will increase the core loss of the transformer, and the iron core will heat up and damage the transformer.

3. The transformer is saturated with iron core, the measurement is inaccurate, and the CT ratio difference and angle difference are increased.

1. Due to the sharp increase in magnetic induction intensity, the loss of the iron core increases, serious heating, and even burns out the insulation. Therefore, the secondary side of the current transformer is absolutely not allowed, which is a taboo for electrical testers.

2. When the current transformer is in normal operation, the magnetic flux potential generated by the secondary current plays a demagnetizing role in the magnetic flux potential generated by the primary current, the excitation current is very small, the total magnetic flux in the iron core is very small, and the induced electromotive force of the secondary winding does not exceed tens of volts search. If the secondary side is open, the demagnetization effect of the secondary current disappears, and the primary current completely becomes the excitation current, causing the magnetic flux in the core to increase sharply, and the core is in a highly saturated state, and the number of turns of the secondary winding is very large, according to the law of electromagnetic induction, it will generate a very high (even up to thousands of volts) voltage at both ends of the secondary winding, which may not only damage the insulation of the secondary winding, but also seriously endanger personal safety.

3. If the secondary side of the current transformer is short-circuited during operation, the impedance of the secondary coil is greatly reduced, and a large short-circuit current will occur, which will cause the secondary coil to burn out due to serious heating. Therefore, the current transformer is not allowed to be short-circuited during operation. Generally, a fuse should be used on the secondary side of the voltage transformer.

Only in the transformer of 35 thousand volts and below, there is a fuse on the high-voltage side, the purpose of which is to cut it off from the high-voltage circuit when the transformer is short-circuited, and the short-circuit resistance is small, then the quotient of voltage and resistance is large, that is, the current is large, which is very dangerous.

Hello, classmates. Because the meter or relay impedance of the secondary connection of the current transformer in operation is very small, it is basically a short-circuit state, so the magnetic density of the core of the current transformer is very low, if the secondary open circuit is the secondary current is zero, the demagnetization effect disappears, and the primary current will be used to excite, so that the iron core is seriously saturated, and the magnetic flux density can reach more than 15000 gauss. Since the number of secondary turns is many times more than the number of primary turns, the secondary induced voltage is very high, which brings great danger to equipment and staff.

Due to the sudden saturation of magnetic flux, the core will also overheat and burn out the current transformer. Therefore, the current transformer in operation is not allowed to open the circuit twice.

1. The secondary circuit of the current transformer in operation is not allowed to open the circuit. It is because once an open circuit occurs, high voltages will be generated at both ends of the open circuit, which will endanger the safety of personnel and equipment, or cause damage to the current transformer.

2. During normal operation, because the impedance of the secondary winding is very small, most of the magnetokinetic potential generated by the primary current is compensated by the magnetokinetic potential generated by the secondary current, the total magnetic flux density is not large, and the electromotive force induced by the secondary winding is not large, generally not more than tens of volts. When the secondary circuit is open, the impedance increases infinitely, the secondary current becomes zero, the secondary winding magnetodynamic potential also becomes zero, and the primary winding current does not become smaller with the secondary open circuit, and the compensation effect of the secondary winding magnetokinetic potential is lost, the primary magnetokinetic potential is very large, all used for excitation, the synthetic magnetic flux suddenly increases many, many times, so that the magnetic circuit of the iron core is highly saturated, at this time the primary current all becomes the excitation current, and a high electromotive force is generated in the secondary winding, and its peak value can reach thousands of volts or even tens of thousands of volts, Threaten personal safety or cause secondary insulation damage to instruments, protective devices and transformers.

3. Due to the high saturation of the magnetic circuit, the magnetic induction intensity increases suddenly, and the hysteresis and eddy current losses in the core rise sharply, which will cause the core to overheat and even burn the current transformer. Therefore, when it is necessary to overhaul and calibrate the secondary instrument during operation, the secondary winding or circuit of the current transformer must be short-circuited first, and then the disassembly operation must be carried out, and the fuse cannot be installed in the secondary circuit of the current transformer.

It's very simple.

Friend, can you look at what I said?

Answer: Because the load on the secondary side of the current transformer is resistantThe current coil is very small, so its secondary measurement is operated in a state close to a short circuit.

According to the magnetodynamic equilibrium agenda formula: i 1 n 1 -i 2 n 2 = i 0 n 1, it can be seen that since i 1 n 1 is mostly offset by i 2 n 2, the total magnetokinetic potential i 0 n 1 is very small, that is, the excitation current i 0 (i.e., the no-load current) is very small, and only a few percent of the primary current i1. If the secondary side is open, then i 2 = 0 , there is i 1 n 1 = i 0 n 1 , i.e. i 1 = i 0 , and i 1 is the primary circuit load current, which does not change due to the change of the secondary load of the transformer.

Therefore, at this time, the excitation current is i 1, which increases dozens of times, and the excitation potential increases dozens of times, which will produce: 1) The core is overheated, and even the transformer is burned. 2) Due to the large number of turns of the secondary winding, it will induce a dangerous high voltage, which endangers the safety of personnel and equipment.

Therefore, the secondary side of the current transformer is absolutely not allowed to open the circuit.

Because the secondary winding of the current transformer is open in the open circuit, there is no balance effect of the secondary current, the core magnetic flux will be greatly increased, and the induced electromotive force will also be greatly increased, resulting in a great increase in the secondary voltage (hundreds to thousands of volts), which can cause the danger of electric shock, and can penetrate the secondary line or secondary components.

Electrician knowledge, the secondary side of the current transformer is not allowed to open the circuit!

Voltage transformer.

Short circuits are not allowed on the secondary side. Because the impedance in the voltage transformer is very small, if the secondary circuit is short-circuited, there will be a large current, which will damage the secondary equipment and even endanger personal safety.

Voltage transformers can be equipped with fuses on the secondary side.

to protect itself from damage caused by a short circuit on the secondary side. Where possible, a fuse should also be installed on the primary side to protect the high-voltage grid from endangering the safety of the primary system due to the faulty high-voltage windings or leads of the transformer.

Current mutual inductance.

Open circuits are absolutely not allowed on the secondary side.

Because once the circuit is opened, the primary side current 11 all becomes magnetizing current, causing M and E2 to increase suddenly, causing the core to be oversaturated with magnetization, and heating up.

Severe and even burned coils; At the same time, the error increases after the magnetic circuit is oversaturated and magnetized.

When the current transformer is working normally, the secondary side is similar to a short circuit, and if it is suddenly opened, the electromotive force will be excited.

From a very small value to a very large value, the magnetic flux in the iron core.

Presenting a severely saturated flat-top wave, the secondary side winding will induce a very high spire wave when the magnetic passage is zero, and its value can reach thousands or even tens of thousands of volts, which threatens the safety of workers and the insulation performance of the instrument.

1. The secondary side current produces an unbalanced effect, resulting in a significant increase in the magnetic flux of the iron core. The induced electromotive force is proportional to the magnetic flux, resulting in a significant increase in the voltage on the secondary side, which is prone to the risk of electric shock, and even affects the insulation part of the circuit and components on the secondary side. It's broken.

At this time, the iron core will have obvious symptoms, such as discharge sound, electric sparks, noise, etc.

2. After the magnetic flux of the core increases significantly, the temperature of the core will increase significantly, causing the voltage transformer to burn out. If this happens, we will find that the transformer is smoking and has a burning smell.

3. Due to the great increase in magnetic flux, the iron core becomes saturated, so there will be a large amount of remanence, resulting in a significant decrease in the accuracy of the transformer.

4. The current on the secondary side is zero, and the power meter and ammeter are displayed as zero. The aluminum plate of the energy meter does not rotate, does not make noise, and the current relay cannot operate normally, so the protection of the primary circuit cannot be realized. and surveillance.

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When the current transformer is running, the secondary side is not allowed to open the circuit. Here's why:

1. The current transformer generates a magnetic flux 1 in the iron core with the measured current magnetic potential I1N1;

The current magnetic potential of the secondary measuring instrument i2N2 generates a magnetic flux in the iron core 2;Current transformer core combined magnetic flux: =

1+φ2；Because 1 and 2 are in opposite directions, equal in magnitude, cancel each other out, so =

0；2. If the circuit is opened twice, i2=

0, then: 1, the current transformer core magnetic flux is very strong, saturated, the core is hot, burns out the insulation, and produces leakage;

3. If the circuit is opened twice, i2=

0, then: 1, in the secondary coil N2 of the current transformer produces a high induced electric potential E, forming a high voltage at both ends of the secondary coil of the current transformer, endangering the life safety of the operator;

4. One end of the secondary coil of the current transformer is grounded, which is a protective measure to prevent the danger of high voltage;

Therefore, the fuse is not allowed to be connected to the secondary side circuit of the current transformer, and it is not allowed to remove the ammeter, relay and other equipment without bypassing during operation.

In particular, CT with a high number of turns induces a high voltage when the second open circuit is opened. For example, the theoretical open-circuit voltage peak of the 4000 1 TPY core may reach tens of thousands of volts. It may cause secondary breakdown of the connected secondary equipment or the CT itself.

A current transformer is composed of a closed core and a winding source. Its BAI original winding is connected in series in the current line that needs to be measured, and DAO often has all the current of the line flowing through, and the number of turns is less and the current is large. The number of turns of the secondary winding of the current transformer is relatively large, which is connected in series in the measuring instrument and the protection circuit, because the impedance of the series coil of the measuring instrument and the protection loop is very small, the working state of the secondary winding of the current transformer is close to short-circuit operation.

Due to the close short-circuit operation of the current transformer sub-coil, the voltage on the terminals is only a few volts, so the magnetic flux in the core is very small. Although the magnetokinetic potential of the primary coil can reach hundreds of amperes or thousands of ampere turns or more, most of it is offset by the demagnetized magnetic kinetic potential established by the short-circuited secondary coil, and only a small part is left as the excitation magnetokinetic potential of the core to establish the magnetic flux in the core. If the secondary coil is suddenly disconnected during operation, the secondary coil current is equal to zero, the magnetodynamic potential that plays the role of demagnetization disappears, and the magnetokinetic potential of the primary side remains unchanged, and the measured current on the primary side all becomes the excitation current, which will make the magnetic flux in the iron core sharp, and the iron core is seriously heated to burn out the coil insulation or make the high-voltage side short circuit to the ground, and the secondary coil open circuit will induce a very high voltage, damage the measurement loop and other secondary circuit instruments and other components, and will bring life danger to the operator.