How much do you know about these 5 types of current transformers?

Current transformer has the role of current conversion and electrical isolation, is the power system measuring instruments, relay protection and other secondary equipment to obtain electrical primary circuit current information sensor. The structure of the current transformer, by the mutual insulation of the primary winding, secondary winding, iron core and frame, shell, terminals and other components. Its working principle is basically the same as the transformer, the primary winding turns N1 less, directly connected in series with the power line, the primary load current through the primary winding, the alternating magnetic flux induction generated by the proportionally reduced secondary current; the secondary winding turns N2 more, and instruments, relays, and other current coils of the secondary load in series to form a closed loop.

Positive oil-immersed current transformer 

　　At present, the domestic current transformer is mainly oil-immersed orthostatic, is a traditional form of our country, the primary line for the traditional U-shaped structure, its main insulation for the transformer oil and cable paper insulation structure, the main insulation is mainly made of cable paper wrapped and become, in order to make the internal electric field is more uniform, the insulation layer has a main screen and the end of the internal screen. As the current transformer is a U-shaped structure, the outer insulation casing is generally tower-shaped structure.

　　Advantage is that you can use insulation banding machine for insulation banding, banding equipment is generally relatively simple, low price.

　　The disadvantage is that the product is bulky, tower casing internal cavity is relatively large, the amount of oil is relatively large. 

Inverted SF6 gas-insulated current transformer 

　　Through the introduction of technology in China appeared inverted SF6 gas-insulated current transformer, the structure of the product using inverted structure, the secondary coil through the metal shielding package, placed in the upper part of the product, due to the coil is relatively heavy, generally need to pot insulator or insulated strut support, the secondary coil through the introduction of its internal a metal tube into the low-voltage side of the primary wire is generally a straight line of copper or aluminum tubes, all the cavities filled with SF6 gas.

　　The advantage is that the resistance to dynamic thermally stabilized current is strong.

　　The disadvantage is that its electric field distribution is very uneven, especially in the upper flange of the casing electric field is more concentrated, some products are equipped with shielding electrodes, the volume is larger, at the same time, because of its internal SF6 gas-filled, if the gas leakage, or impact on the atmospheric protective layer, is not conducive to environmental protection. 

Inverted oil-immersed current transformer 

　　Through the introduction of technology domestic production of inverted oil-immersed current transformer, the product for the oil-immersed cable-paper insulated current transformer, the secondary coil wrapped through the metal shielding, placed in the upper part of the product, the secondary coil of its internal a metal pipe into the low-voltage side of the secondary coil and the lead outside the metal pipe is not wrapped in cable paper and crumpled paper insulation, the primary wire is generally a straight line of copper or aluminum tubes.

　　Advantages are small size, light weight, beautiful appearance and resistance to dynamic heat stabilization of current capacity.

　　The disadvantage is that the coil part and the lead pipe part of the insulation package can not be completed at once, the coil part of the insulation package needs to be completed manually, and need to be insulated with the lead pipe part of the docking, insulation package time-consuming and laborious, long processing cycle. 

Dry type current transformer 

　　Dry current transformer is a new product, the primary line using U-shaped copper or aluminum wires, insulation for the polyester film banding, banding process between the polyester film gap filled with silicone grease to improve insulation properties, in the insulation layer outside the bonding of the silicone rubber umbrella, the formation of the current transformer's external insulation; secondary coils were set on both sides, and closed with a metal shell. The product due to the insulation layer filled with semi-liquid medium, there will be no oil leakage phenomenon. 

Electronic Current Transformer 

　　With the rapid development of optoelectronics technology, many developed countries have turned their attention to the use of optical sensing technology and electronics to develop a new type of electronic current transformer, referred to as photoelectric current transformer. Electronic current transformer refers to the output of small voltage analog signal or digital signal current transformer, its meaning in addition to include photoelectric current transformer, but also includes a variety of other current sensors using electronic testing principles. Electronic current transformer is divided into active and passive two categories.

　　The advantages of electronic current transformer is, no iron core, insulation structure is simple, small size, small quality, good linearity, good resistance to electromagnetic interference, no magnetic saturation phenomenon, high measurement accuracy, the output signal can be directly into the microcomputerized measurement and protection equipment interface.

　　Disadvantage is that the sensing head is more sensitive to temperature and vibration, in order to improve accuracy and stability, electronic signal processing part of the line will be more complex, and for active electronic current transformer, must protect the stability of the power supply.