The potential transformer (PT for short, and the voltage transformer (VT for short) is similar to the transformer. It is an instrument used to transform voltage.
However, the purpose of transformer changing voltage is to facilitate the transmission of electric energy, so the capacity is very large. Generally, the unit of calculation is kilovolt ampere or megavolt ampere;
The purpose of voltage transformation of voltage transformer is mainly to supply power to measuring instruments and relay protection devices, to measure the voltage, power and electric energy of the line, or to protect valuable equipment, motors and transformers in the line in case of line failure. Therefore, the capacity of voltage transformer is very small, generally only a few volt ampere, dozens of volt ampere, and not more than 1000 volt ampere at most.
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The basic structure of voltage transformer is very similar to that of transformer. It also has two windings, one is called primary winding and the other is called secondary winding. Both windings are installed or wound on the iron core. There is insulation between the two windings and between the winding and the iron core, so that there is electrical isolation between the two windings and between the winding and the iron core. When the voltage transformer is in operation, the primary winding N1 is connected to the line in parallel, and the secondary winding N2 is connected to the instrument or relay in parallel. Therefore, when measuring the voltage on the high-voltage line, although the primary voltage is very high, the secondary voltage is low, which can ensure the safety of operators and instruments.
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The impedance of the voltage transformer itself is very small. Once the secondary side is short circuited, the current will increase rapidly and burn the coil. Therefore, the primary side of the voltage transformer is connected with a fuse, and the secondary side is reliably grounded, so as to avoid personal and equipment accidents caused by high potential to the ground at the secondary side when the insulation of the primary and secondary sides is damaged.
Voltage transformers for measurement are generally made into single-phase double coil structure, and the primary voltage is the measured voltage (such as the line voltage of power system), which can be used in single-phase or two connected into V-V shape for three-phase. The voltage transformers used in the laboratory are often multi tapped at the primary side to meet the needs of measuring different voltages. The voltage transformer for protective grounding is also equipped with a third coil, which is called three coil voltage transformer. The three-phase third coil is connected into an open triangle, and the two leading out ends of the open triangle are connected with the voltage coil of the grounding protection relay.
During normal operation, the three-phase voltages of the power system are symmetrical, and the sum of the three-phase induced electromotive force on the third coil is zero. Once the single-phase grounding occurs, the neutral point will shift, and the zero sequence voltage will appear between the terminals of the open triangle to make the relay act, so as to protect the power system.
If zero sequence voltage appears in the coil, zero sequence magnetic flux will appear in the corresponding iron core. Therefore, the three-phase voltage transformer adopts side yoke iron core (at 10kV and below) or three single-phase voltage transformers. For this type of transformer, the accuracy of the third coil is not high, but it is required to have certain overexcitation characteristics (that is, when the primary side voltage increases, the magnetic flux density in the iron core also increases by a corresponding multiple without damage).
Voltage transformer is an indispensable electrical appliance in power transmission and power supply systems such as power plants and substations. Precision voltage transformer is a kind of instrument used to expand the measurement limit and measure voltage, power and electric energy in the electrical testing laboratory. Voltage transformers are very similar to transformers. They are used to change the voltage on the line.
Power measurement > > converts high voltage current into required current and can isolate high voltage system
Large and small voltage conversion > > convert high voltage current to measurement current
Protection of faulty electrical appliances > > self protection against grid faults
01. epoxy resin -- pouring technology > > it has the characteristics of compactness, water resistance, good leakage resistance and high strength
02. enlarged iron core steel sheet > > larger iron core capacity, more copper wires are wound to improve product performance
1. Integral pouring
Compared with the non-integrated type, the integrated pouring method has better closure, can better protect the internal line, and will not easily disintegrate .
The ability to waterproof and prevent corrosion is non-integral.
2.Shell perfusion moldingaround the wire
Machinery is related to quality stability There will be no defective products.
3.Thickness of the copper row, strong electrical conductivity
Use a thickened bronze medal touch wiring spiral Install firmly to strengthen the electrical conductivity.
Lawrence Electric Co., Ltd. is a high-tech enterprise focusing on power transmission and distribution products, providing customers with one-stop service of power transmission and distribution products.
It mainly produces and sells lightning arrester, insulator, fuse, isolation / load switch, SF6 / vacuum circuit breaker, power supply fittings, optical cable fittings, switch cabinet and other transmission and distribution products. The company has production bases and sales centers in Jiangxi, Zhejiang, Uganda, Tanzania and other places.
Our products have operated safely in the power supply systems of more than 20 countries and regions around the world for more than 10 years. They are also qualified suppliers of China State Grid and China Southern Power Grid. At present, they have gained a good reputation in the field of power system in the world.
We have received high-quality product recommendation letters from power supply companies in Kenya, Uganda, Tanzania, Zambia, Guinea, Ghana, Togo, Mozambique, Nepal, Guyana, Myanmar and other countries and regions.
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