RU2216809C2 - Cast current transformer - Google Patents

Abstract

FIELD: electrical engineering, high-voltage equipment. SUBSTANCE: invention refers to high-voltage current transformer with cast epoxy insulation. Cast current transformer includes cast epoxy insulation, primary winding and secondary winding with magnetic circuit placed concentric on primary winding, embracing it from outside to form gap with thickness h. Shield separated from primary and secondary windings with the use of insulation is located in it. Shield forms equipotential surface and is so installed that distance from secondary winding to shield is equal to distance from shield to primary winding which is bar winding and amounts to h/2. Axial dimension of shield is equal to 1.3-1.8 axial dimension l of secondary winding. EFFECT: uniform distribution of electric field in interelectrode gap and beyond its limits. 1 dwg

Description

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

 Known electrical devices (single-core power cables) containing coaxially placed electrodes separated from each other by insulation forming interelectrode gaps [1].

 In such devices, for controlling the electric field in the interelectrode spaces, multilayer insulation formed by materials with different dielectric constants is used. The interfaces between insulating materials coincide with equipotential surfaces in the interelectrode spaces.

 Closest to the claimed cast current transformer is a transformer containing a primary winding and a secondary winding with a magnetic core, a concentric primary, a screen separated from the primary and secondary windings by cast epoxy insulation, connected to the magnetic circuit and grounded [2].

 The presence of a grounded shield located in the transformer according to [2], located between the primary and secondary windings, makes it possible to protect the secondary winding from high voltage, however, it does not ensure uniformity of the electric field in the interelectrode gap and beyond.

 The invention solves the problem of creating a high-voltage current transformer with cast insulation, which ensures uniform distribution of the electric field in the interelectrode gap and beyond.

 To solve the problem in a molded current transformer containing a primary winding and a secondary winding with a magnetic core, concentric with the primary winding, covering it from the outside, a shield separated from the primary and secondary windings by cast epoxy insulation, it is proposed, according to the present invention, to make the screen ungrounded, not having electrical connection and install it in such a way that the distance from it to the secondary winding with the magnetic circuit is equal to the distance from it, and its axial size is 1.3 ÷ 1.8 axial about the size of the secondary winding with the magnetic circuit.

 The invention is illustrated by the example of the drawing, which shows the inventive cast current transformer in longitudinal section.

 Cast current transformer 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 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 does not have an electrical connection to the windings. The distance from the screen 5 to the secondary winding 3 with the magnetic circuit 4 is equal to the distance from the screen 5 to the primary winding 2, forming an equipotential surface, and the axial size of the screen 5 is 1.3 ÷ 1.8 of the axial size of the secondary winding 3 with the magnetic circuit 4.

 Making the screen ungrounded, not having an electrical connection with the windings, placing it at the same distance from the primary winding and the secondary winding with the magnetic circuit, forming an equipotential surface, and making it with an axial size of 1.3 ÷ 1.8 of the axial size of the secondary winding with the magnetic circuit , will make it possible to equalize the electric field of the transformer between the primary winding and the secondary winding with the magnetic core, so inside the entire transformer, and thereby increase the reliability of the transformer scrap.

 OJSC Sverdlovsk Plant of Current Transformers has developed technical documentation that implements the claimed solution and in accordance with which TOL 110 current transformers are manufactured and tested.

 The test results confirmed the operability of the inventive transformer, as well as the uniform distribution of the electric field between the primary winding and the secondary winding with the magnetic circuit, and inside the entire transformer.

Literature
1. G.S. Kuchinsky, V.E. Kizevetter, Yu.S. Pintal "Isolation of high voltage installations", M., Energoatomizdat, 1987, p.80-82.

 2. RF patent 2087967, IPC H 01 F 30/10, 27/36, 1997.

Claims (1)

 A molded current transformer containing a primary winding and a secondary winding with a magnetic core concentric with the primary winding, covering it from the outside, a shield separated from the primary and secondary windings by cast epoxy insulation, characterized in that the shield is not grounded, has no electrical connection with the indicated windings and is installed so 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 axial size of the secondary winding with the magnetic circuit.