RU2566469C2 - Cast current transformer - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to electrical engineering and may be used in high-voltage transformers with cast epoxy insulation. Cast current transformer comprises primary winding and secondary winding with magnet core concentric to the first one and covering it from outside. The first shield is separated from primary and secondary windings by cast epoxy insulation; it is mot grounded and free of electric connection to the windings. The second shield is placed in parallel to the first shield between them and secondary winding; it is isolated electrically from the first shield and grounded. Cast current transformer may contain N additional shields, which may be placed in parallel to the first and second shields, be electrically isolated and not grounded, where N is an integer number ≥ 1.

EFFECT: operational reliability at minimum permitted weight and dimensions and evenness of electric field distribution in interelectrode gap and outside its limits.

2 cl, 2 dwg

Description

The invention relates to electrical engineering, in particular to high-voltage apparatus engineering, and may find application in high-voltage transformers with cast epoxy insulation.

Known cast current transformer containing a primary winding and a secondary winding with a magnetic core, concentric with the primary, a screen separated from the primary and secondary windings by cast epoxy insulation, connected to the magnetic circuit and grounded [L. one].

The presence in the transformer according to [L. 1] a grounded shield located between the primary and secondary windings, allows to protect the secondary winding from high voltage, but does not allow to ensure uniformity of the electric field in the interelectrode gap and beyond.

Closest to the inventive molten current transformer is a molten current transformer containing a primary winding and a secondary winding with a magnetic core, concentric with the primary, enveloping it from the outside, a shield separated from the primary and secondary windings by cast epoxy insulation, while the shield is not grounded, has no electrical connection with the windings and is installed in such a way that the distance from it to the secondary winding with the magnetic circuit is equal to the distance from it to the primary winding, forming an equipotential surface, and its axial size is 1.3 ÷ 1.8 of the axial size of the secondary winding with the magnetic circuit [L. 2].

Described in [L. 2] cast current transformer is characterized by a uniform distribution of the electric field in the interelectrode gap and beyond, however, it has increased mass and dimensions.

The invention solves the problem of creating a high-voltage current transformer with cast insulation, characterized by high operational reliability with the minimum allowable weight and dimensions and uniform distribution of the electric field.

To solve the problem in a molded current transformer containing a primary winding and at least one secondary winding with a magnetic core, concentric with the primary winding, covering it from the outside, the first screen is separated from the primary and secondary windings by cast epoxy insulation, not grounded and not having electrical connection with the windings, it is proposed according to the present invention to introduce a second screen, place it parallel to the first screen, between it and the secondary winding, electrically isolate from the first on the screen and the ground; in this case, the molten current transformer may contain n additional screens that can be placed parallel to the first and second screens, are electrically isolated from them and between each other and are not grounded, where n is an integer ≥1.

The invention is illustrated by examples of drawings (Fig. 1 and 2), which show two options for the implementation of the inventive cast current transformer in longitudinal section.

The cast current transformer according to the first embodiment (see FIG. 1) contains cast epoxy insulation 1, a primary winding made in the form of a rod, 2 and a secondary winding 3 with a magnetic circuit 4.

The secondary winding 3 with the magnetic circuit 4 is located concentrically with respect to the primary winding 2, covers it from the outside and is separated from it by cast epoxy insulation 1.

The first screen 5, located between the primary winding 2 and the secondary winding 3 with the magnetic circuit 4, is separated from the primary winding 2 and the secondary winding 3 with the magnetic circuit 4 by cast epoxy insulation 1. It is not grounded and has no electrical connection with the windings.

The second screen 6 is placed between the secondary winding 3 with the magnetic circuit 4 and the first screen 5. In this case, it is parallel to the first screen 5, electrically isolated from the first screen 5 and grounded.

The cast transformer according to the second embodiment (see Fig. 2) contains, in addition to the listed elements, two additional screens 7 arranged parallel to the first screen 5 and the second screen 6, electrically isolated from them, as well as from each other. Additional screens 7 are not grounded. Moreover, the number of additional screens can be any integer greater than or equal to one.

The cast current transformer with two screens, the first of which is separated from the primary and secondary windings, is not grounded and has no electrical connection to the windings, and the second screen is parallel to the first and separated from it and one of the windings: primary or secondary and grounded, will provide alignment of the electric field of the transformer both between the primary winding and the secondary winding with the magnetic circuit, so inside the entire transformer and thereby increase the reliability of the transformer as a whole. The number of additional screens can be any integer greater than or equal to one.

If the additional screen 7 is placed between the primary winding 2 and the first screen 5, then it will have a larger axial size than the first screen 5. If the additional screen 7 is placed between the first screen 5 and the secondary winding 3, then the additional screen 7 will have a smaller axial dimension compared to the first screen 5.

At the same time, the presence of an ungrounded shield in addition to a grounded shield will significantly reduce the mass and dimensions of the current transformer, and therefore, reduce the consumption of active materials for the manufacture of a current transformer and thereby increase the operational reliability of a cast current transformer.

OJSC Sverdlovsk Plant of Current Transformers has developed technical documentation that implements the claimed solution and in accordance with which cast transformers are manufactured and tested.

The test results confirmed the operability of the inventive transformer, the uniform distribution of the electric field between the primary winding and the secondary winding with the magnetic circuit, and inside the entire transformer, as well as reducing the dimensions and mass of the current transformer by 25 ÷ 38%.

Literature

1. RF patent No. 2087967, IPC H01F 30/10, 27/36, 1977

2. RF patent No. 2 216809, IPC H01F 38/30, 27/36, 2003

Claims (2)

1. Cast current transformer containing a primary winding and at least one secondary winding with a magnetic core, concentric with the primary winding, enveloping it from the outside, the first screen separated from the primary and secondary windings by cast epoxy insulation, not grounded and not electrically connected to windings, characterized in that it comprises a second screen placed parallel to the first screen between it and the secondary winding, electrically isolated from the first screen and grounded. 2. A cast current transformer according to claim 1, characterized in that it contains n additional screens arranged parallel to the first and second screens, electrically isolated from them and between each other and ungrounded, where n is an integer ≥1.

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