Voltage transformer and the transformer is very similar basic structure, it also has two windings, a primary winding called a called a secondary winding. Two windings are housed in or around the core. Two windings and between windings and core have insulation that has electrical isolation between the two windings and windings and core. At runtime voltage transformer, the primary winding N1 and the line coupling, and coupling the secondary winding N2 meter or relay. Therefore, when measuring high-voltage voltage transformer on the road, despite a high voltage, but the second is a low pressure to ensure the safety of the operator and instrument. Current transformers: use transformer primary, secondary current is proportional to the characteristics thereof. It works, but also with the general transformer equivalent circuit the same, but its primary winding in series with the circuit under test, and rarely turns; secondary windings connected meter relay coil current low-impedance load, the approximate short circuit. Primary current (ie, the measured current) and secondary current depending on the circuit under test load, regardless of the current transformer secondary load. Since close to a short high voltage transformer secondary side, so the primary and secondary voltage U1 and the very small, very small excitation current I0. Fully enclosed transformer, open circuit current transformer secondary side does not allow runtime. Because once open, it has become the primary current excitation current, flux and secondary voltage much higher than normal and endanger the safety of persons and equipment. Thus voltage transformers, current transformers secondary circuit fuses must not take, do not allow it at runtime without removing the meter bypass, relays and other equipment. Current transformers wiring connected load it by running the claims. The most common wiring for the single-phase, three-phase star and incomplete star. Dry-type transformers, Huayi Electric Power (online consultation), Kunming, Xi'an, instrument transformers supplied by the power plant. Xian Huayi Electric Power Equipment Factory (www.xahy.com) is a leader in Xi'an high-voltage circuit breakers, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, and satisfy customer needs. In Huayi Electric Power leadership with the staff warmly welcome all inquiries negotiations to create Huayi electricity better future.