The current transformer model
Jul 09, 2019
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The current transformer model:
First letter: L - current transformer
The second letter: A-through-wall type; Z-pillar type; M-busbar type; D-single-turn type; V-structure inverted type; J-zero sequence
Grounding detection; W-anti-fouling; R-winding exposed
The third letter: Z—epoxy resin casting type; C—ceramic insulation; Q—gas insulating medium; W—specific for microcomputer protection
Fourth letter: B - with protection level; C - differential protection; D - D level; Q - enhanced type; J - enhanced type
Fifth number: voltage level
The working principle：
In the power generation, substation, transmission, distribution and power lines, the current varies greatly, from a few amps to tens of thousands of amps. In order to facilitate measurement, protection and control, it is necessary to convert to a relatively uniform current. In addition, the voltage on the line is generally high. Direct measurement is very dangerous. The current transformer acts as a current transformer and electrical isolation [1].
For pointer type ammeters, the secondary current of the current transformer is mostly amperometric (such as 5A, etc.). For digital instruments, the sampled signal is typically milliampere (0-5V, 4-20mA, etc.). The secondary current of the miniature current transformer is milliampere, which acts as a bridge between the large transformer and the sampling.
Micro current transformers are also known as "instrument current transformers." ("Instrument current transformer" has a meaning of multi-current ratio precision current transformer used in the laboratory, generally used to expand the meter range.)
The current transformer is similar to the transformer. It also works according to the principle of electromagnetic induction. The transformer transforms the voltage and the current transformer changes the current. The current transformer is connected to the winding of the measured current (the number of turns is N1), which is called the primary winding (or the primary winding, the primary winding); the winding of the measuring instrument (the number of turns is N2) is called the secondary winding (or the secondary winding) Winding, secondary winding).
The ratio of the current of the primary winding current I1 of the current transformer to the secondary winding I2 is called the actual current ratio K. The ratio of the current when the current transformer operates at the rated current is called the current transformer rated current ratio, expressed as Kn. Kn=I1n/I2n
For pointer type ammeters, the secondary current of the current transformer is mostly amperometric (such as 5A, etc.). For digital instruments, the sampled signal is typically milliampere (0-5V, 4-20mA, etc.). The secondary current of the miniature current transformer is milliampere, which acts as a bridge between the large transformer and the sampling.
Micro current transformers are also known as "instrument current transformers." ("Instrument current transformer" has a meaning of multi-current ratio precision current transformer used in the laboratory, generally used to expand the meter range.)
The current transformer is similar to the transformer. It also works according to the principle of electromagnetic induction. The transformer transforms the voltage and the current transformer changes the current. The current transformer is connected to the winding of the measured current (the number of turns is N1), which is called the primary winding (or the primary winding, the primary winding); the winding of the measuring instrument (the number of turns is N2) is called the secondary winding (or the secondary winding) Winding, secondary winding).
The ratio of the current of the primary winding current I1 of the current transformer to the secondary winding I2 is called the actual current ratio K. The ratio of the current when the current transformer operates at the rated current is called the current transformer rated current ratio, expressed as Kn. Kn=I1n/I2n
The function of the current transformer (CT) is to convert a large current with a large value into a secondary current with a small value for protection, measurement and other purposes. For a current transformer with a ratio of 400/5, the actual current of 400A can be converted into a current of 5A.
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