All-insulated on-load voltage-regulating transformer angularly connected on 220-kilovolt high voltage side

Abstract

The invention discloses an all-insulated on-load voltage-regulating transformer angularly connected on 220-kilovolt high-voltage side. The main body comprises a high-voltage coil, voltage-regulating coils, a low-voltage coil and the like, the voltage-regulating coils in related two phases connected end to end are connected through contacts of a tap selector of an on-load voltage-regulating switch, so that the on-load voltage-regulating switch realizes the voltage-regulating function by using a two-phase switch and a single-phase switch, and the conventional structure with three single-phase switches is replaced. Meanwhile, a right amount of lightning arrester elements are connected between the head end and the tail end of each phase of the voltage-regulating coil so as to limit the potential oscillation of the voltage-regulating coil under the impact of a thunder, the insulation level of the tap selector of the on-load voltage-regulating switch is obviously reduced, and the switch is protected reliably. The invention realizes the purposes of obviously reducing the cost of the on-load voltage-regulating switch with low cost and reliably protecting the on-load voltage-regulating switch at a low cost.

Description

technical field [0001] The invention belongs to the field of transformers, and relates to a fully insulated transformer, in particular to a 220,000-volt high-voltage side delta-connected fully insulated on-load tap-changing transformer with a built-in lightning arrester. Background technique [0002] In the domestic power system, the connection method of the 220,000-volt high-voltage side is star connection, which is the most economical for high-voltage windings; both neutral points can be used, and direct grounding or impedance grounding are allowed. It can also reduce the insulation level of the neutral point (that is, graded insulation, that is, the insulation level of the winding wire end of the star connection method is higher than that of the neutral point. Taking the 220,000-volt class as an example, the insulation level of the wire end is LI950AC395, while The insulation level of the neutral point is LI400AC200); a tap can be set at the neutral point of each phase, a...

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Problems solved by technology

[0008] For this kind of 220,000-volt fully insulated on-load tap changer with delta connection on the high-voltage side, some people in China have previously proposed a method of setting the tap on the low-voltage side of the star connection for neutral point voltage regulation to avoid lightning on the high-voltage side. The direct impact of the impulse voltage on the on-load tap changer, so that a switch with a very low voltage level can be selected; but this method can only stay in theory, because in practical engineering applications, the rated capacity of this transformer is large, and it can be used It can reach more than 180MVA, and even reach 300MVA in the Middle East. If it is set to voltage regulation on the low-voltage side, the insulation level will be greatly reduced, but the current will become quite large, up to 2000-3000 amperes or even larger, and usually 1200A is three-phase The current upper limit of the integrated switch, so three single-phase switches must be used

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