High voltage dry-type current transformer and ground protection method thereof

Abstract

The invention discloses a high voltage dry-type current transformer and a ground protection method thereof, a ground wire is arranged on an end screen of a primary winding of the high voltage dry-type current transformer, a ground protection branch is further parallel-connected on the end screen of the primary winding of the high voltage dry-type current transformer, the ground protection branch is provided with a ground protector which mainly consists of a capacitor, one end of the ground protector is connected with the end screen of the primary winding, and the other end is grounded for increasing the equivalent capacitance value of the end screen of the primary winding to the ground. The capacitor type ground protector is parallel-connected between the end screen of the primary winding and a housing in the technical scheme of the invention, thereby increasing the equivalent capacitance value of the end screen to the ground, clamping the loaded floating voltage on the end screen to a smaller value which is much lower than the tolerant voltage of the end screen, further avoiding the accidents of insulation breakdown of the primary winding and greatly increasing the reliability of the user of the high voltage dry-type current transformer.

Description

technical field [0001] The invention belongs to the technical field of high-voltage power distribution, and specifically relates to a high-voltage dry-type current transformer and a matching grounding protector. Background technique [0002] The grounding protection structure of the existing high-voltage dry-type current transformer is as follows: figure 1 As shown, the grounding lead 2 of the final screen of the primary winding 1 of the high-voltage dry-type current transformer is directly connected to the grounding terminal 3 on the wiring board 4 on the casing which is at ground potential. At present, the main insulation of the primary winding of high-voltage dry-type current transformers basically adopts a multi-layer series-connected capacitive structure formed by alternately wrapping insulating layers and metal foils, and the voltage of the primary winding to ground is evenly distributed among the layers. During the operation of the equipment, the last screen of the c...

AI Technical Summary

Problems solved by technology

Since the main insulation of the primary winding of the high-voltage dry-type current transformer is formed by the series connection of multi-layer capacitors, and the last screen is connected with the outermost layer of capacitors, if the last screen is reliably grounded, it is at ground potential. When the ground wire of the last screen is missing or in poor contact, the last screen becomes insulated from the ground, and the last screen to the ground will be equivalent to a capacitor C0. The capacitance of this capacitor CO is very small, far smaller than the capacitance C1 of the primary winding. According to According to the principle of capacitive voltage division, the high voltage U loaded on the primary winding will be connected to the last screen in series to form a high-voltage floating voltage. A current path is formed between them, and the arc potential of the power generation is variable, which causes the capacitance field strength of each layer to be distorted, the partial discharge inside the product increases, and finally forms the internal insulation breakdown of the equipment, resulting in operating accidents such as line tripping. In severe cases, There may even be a major safety accident where the equipment explodes

However, in daily work, it is necessary to frequently overhaul and maintain the high-voltage dry-type current transformer, during which the dielectric loss of the end screen needs to be measured. During the measurement, the lead wire of the end screen must be separated from the ground wire terminal. The surveyor forgets to restore the lead wire of the last screen to the grounding state before switching to the grid, so this grounding method has a major safety hazard

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