The voltage transformer is actually a transformer with a core. It is mainly composed of primary and secondary coils, iron core and insulation.
There are many ways to connect voltage transformers. The common ones are as follows:
(1) Using a single-phase voltage transformer to measure the wiring of a relative ground voltage or phase-to-phase voltage.
(2) Using two single mutual sensors to form incomplete star, also called V-V wiring, used to measure the voltage between the phases, but can not measure the relative ground voltage. It is widely used in the neutral point below 20KV without grounding or The arc suppression coil is grounded in the grid.
(3) Using three single-phase three-winding voltage transformers to form the wiring form of YN, yn, d0 or YN, y, d0, which is widely used in 3~220KV systems, and the secondary winding is used to measure the phase-to-phase voltage and relative ground. The voltage and the auxiliary secondary winding are connected into an open triangle for access to the AC grid insulation monitoring instrument and relay. A three-phase five-column voltage transformer is used to replace the wiring of the three single-phase three-winding voltage transformers. The form is the same as that of FIG. 3 except for the iron core, and is generally only used for the 3~15KV system.
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