How do the current transformers and voltage transformers of the distribution panel change with the c

Both of them work in a similar way to transformers.

In particular, the voltage transformer is actually equivalent to a transformer with a secondary side open circuit.

The current transformer is a little special, although it is the same principle as the transformer, but the voltage on the primary side will not affect the output of the secondary side, it is only related to the current on the primary side, it is more appropriate to say that it is a converter.

Especially for low-voltage current transformers, there is no terminal at all on the primary side, and it is directly passed through.

Their principle is the law of electromagnetic induction, the value of the voltage transformer generally does not fluctuate much, if there is, it is very dangerous, either your superior power supply system has a problem, or your own power supply system design is unreasonable or there are fault points.

The current transformer will change with your load, when your load size changes, the current in the loop must also change, as long as there is current, there will be a magnetic field, and the strength of this magnetic field is proportional to the size of the current, the current transformer is to capture this magnetic field, because we use sinusoidal alternating current, so this magnetic field is an alternating magnetic field, when the magnetic field is constantly changing, it will produce an induced current on the secondary side of the current transformer, and the induced current is proportional to the strength of the magnetic fieldIsn't this enough to detect the loop current?

If there is more load, the voltage drop will occur in the future, and the current will become larger, and the mutual inductance system can be measured. There will definitely be a corresponding change.

The function of the current transformer (CT) is to convert the primary current with a large value into a secondary current with a small value through a certain transformation ratio, which can be used for protection, measurement and other purposes. For example, the current transformer with a conversion ratio of 400 5 can convert the actual current of 400A into a current of 5A.

In order to ensure the safe and economical operation of the power system, the operation of the power equipment must be monitored and measured. However, the general measuring and protection device cannot be directly connected to the primary high-voltage equipment, but needs to convert the large current of the primary system into a small current proportionally and supply the measuring instrument and protection device for use.

The function of the voltage transformer is to convert the high voltage into a standard secondary voltage of 100V or lower in proportion to the ratio for protection, metering and instrumentation devices.

The difference between the two is that one is to measure the current and the other is to measure the voltage. The current transformer is connected in series in the circuit, and the number of turns of the primary winding is less than that of the secondary winding, and the secondary winding cannot be opened; The voltage transformer is connected in parallel in the circuit, and the primary winding has more turns than the secondary winding, and the secondary winding cannot be short-circuited.

The main difference is that the working state (working principle) during normal operation is very different, and the main manifestations are:

1) The current transformer can be short-circuited for the second time, but it must not be opened; The voltage transformer can be opened twice, but it must not be short-circuited.

2) For the load on the secondary side, the primary internal impedance of the voltage transformer is small or even negligible, and the voltage transformer can be regarded as a voltage source; However, the primary internal resistance of the current transformer is so large that it can be regarded as a current source with infinite internal resistance.

3) The magnetic flux density of the voltage transformer is close to the saturation value when it is working normally, and the magnetic flux density decreases when it is faulty; The magnetic flux density is very low when the current transformer is working normally, and when it is short-circuited, the magnetic flux density becomes large due to the short-circuit current on the primary side, which greatly increases the magnetic flux density, sometimes even far exceeding the saturation value.

4) Voltage transformer is a special transformer used to measure the high voltage of the power grid, which can convert the high voltage into a lower voltage according to the specified proportion, and then connect it to the instrument for measurement. For voltage transformers, no matter how many volts the primary side voltage is, and the secondary side voltage is generally specified at 100 volts, in order to supply the voltage required by the voltage coils of voltmeters, power meters, kilowatt-hour meters and relays.

5) The electrical equipment that converts large current into small current according to the specified proportion is called current transformer. The current on the secondary side of the current transformer is generally specified as 5 amps or 1 ampere to supply the current coil current of the ammeter, power meter, kilowatt hour meter and relay.

CT (Current.

copy transformer) main attack.

It is to emphasize the overcurrent, and it is to transform the large current that is inconvenient to measure into a small current that is convenient to measure, and the overcurrent should be considered when selecting the line, and the PT (voltage transformer) starring is to emphasize the voltage, which is usually used in the high-voltage distribution cabinet, and the inconvenient to use the high voltage is transformed into a convenient and practical low voltage and then used for the secondary circuit, but the principle is the electromagnetic induction principle of the transformer.

Current mutual inductance.

When measuring the large current of alternating current, in order to facilitate the measurement of the secondary instrument, it needs to be converted into a relatively unified current (China stipulates that the secondary rating of the current transformer is 5A, and the secondary rating of the current transformer is 5A), and the voltage on the line is relatively high, so it is very dangerous to measure directly. The current transformer plays the role of converter and electrical isolation, and the current transformer is the step-up (down-current) transformer. It is a sensor for secondary equipment such as measuring instruments and relay protection in the power system to obtain current information of the electrical primary circuit, the current transformer converts the high current into a low current in proportion, the current transformer is connected to the primary system on the primary side, and the secondary side is connected to the measuring instrument and relay protection.

The primary voltage of the voltage transformer is very large, if the secondary side is short-circuited, then it is equivalent to adding the primary voltage directly to the secondary book, so that the secondary side equipment runs under high voltage, causing damage to the electrical equipment

Whether it is a current transformer or a voltage transformer, the principle is the same as that of a transformer. The difference is: the secondary current of the current transformer is the secondary current that is proportional to the primary current, and its voltage is very low; The secondary voltage of the voltage transformer is the secondary voltage proportional to the primary voltage, and its current is very small.

Therefore, current transformers are used to supply a current signal proportional to the protection and measurement, while voltage transformers are used to supply a voltage signal proportional to the protection and measurement.

Voltage transformer ratio: primary side voltage ratio to upper secondary side voltage (single phase); The primary sideline voltage is higher than the upper secondary sideline voltage (three-phase).

Current transformer conversion ratio: the primary side current is higher than the secondary side current (according to single phase).

Calculation method of electricity consumption: (the current month's indication in the table, the previous month's indication) (voltage transformer ratio) (current transformer ratio).

A transformer is a special transformer specially designed for voltage and current conversion for the metering and relay protection of alternating current.

The voltage and current of the power system are high, and the measurement and control instruments cannot be directly connected to the line. The voltage must be reduced by a voltage transformer and the current by a current transformer in a certain proportion. They do the following:

1) Cooperate with the measuring instrument to measure the line voltage, current and electric energy. The voltage and current of the line are converted into a unified standard value (high voltage becomes 100 volts, high current becomes 5 amperes), which is conducive to the standardization of measurement, protection and control devices.

2) Cooperate with relay protection devices and automatic control devices to protect power systems and equipment from overvoltage, overcurrent, overload and single-phase grounding.

3) Isolate secondary devices such as relay protection devices, automatic control devices and automatic control devices from the high voltage of the line to ensure the safety of staff and secondary devices.

The transformation ratio of the current transformer is the ratio of the primary side current to the secondary side current, such as 5, etc., such as 500 5, which means that when the primary current reaches 500A, the current induced on the secondary side is 5A, and the ratio of the two types of combustion hall is the transformation ratio.

The secondary side of the current transformer is 5A. The ratio of a current transformer is the primary side current divided by the secondary side current. Because of the current transformer, our ammeter can be made to be 5A.

The current relay can also be made into 5A. A current transformer is to turn a large current into a small current. So that the measurement, protection, signal, control and other secondary fiber components can achieve unified specifications.

In high-voltage and ultra-high-voltage power systems, voltage transformers can be used to measure voltage, power, etc. In electric drag lines, current transformers can be used to measure the exchange current, the exchange of electrical power, and the degree of protection.

The transformer, also known as the instrument transformer, is a general term for current transformer and voltage transformer, which can convert high voltage into low voltage and high current into small current for measuring or protecting the system. Its function is mainly to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 1A, both refer to the rated value) in proportion to realize the standardization and miniaturization of measuring instruments, protective equipment and automatic control equipment. In addition, the transformer can be separated from the high-voltage system to ensure the safety of the human body and equipment.

The difference between voltage transformer and current transformer in terms of working principle:

The main difference is that the working state is very different during normal operation, which is manifested as:

1. The current transformer can be short-circuited for the second time, but it must not be opened; The voltage slag slag transformer can be opened twice, but it must not be short-circuited.

2. Compared with the load on the secondary side, the primary internal impedance of the voltage transformer is so small that it can be ignored, and the voltage transformer can be regarded as a voltage source; However, the primary internal resistance of the current transformer is so large that it can be regarded as a current source with infinite internal resistance.

3. The magnetic flux density of the voltage transformer is close to the saturation value when it is working normally, and the magnetic flux density decreases when it is faulty; The magnetic flux density is very low when the current transformer is working normally, and when it is short-circuited, the magnetic flux density increases greatly due to the short-circuit current on the primary side, and sometimes even far exceeds the saturation value. <>

The current signal is transmitted between the primary winding and the secondary winding finger sensitive group of the current transformer through magnetic inductive coupling. The primary winding refers to the coil used to measure the current in the current mutual cavity sensor, while the secondary winding refers to the coil used to output the current signal.

The relationship between the number of turns of the primary winding and the number of turns of the secondary winding of a current transformer is: the number of turns of the primary winding divided by the number of turns of the secondary winding is equal to the ratio of the primary current to the secondary current. This ratio is also known as the variable ratio and is usually denoted by k.

For example, if the number of turns of the primary winding of the current transformer is 1000 turns, and the number of turns of the secondary winding is 500 turns, the transformation ratio is 1000 500 = 2, which means that the secondary current is twice the primary current. In practical applications, the ratio of the current transformer needs to be selected according to the specific measurement requirements.