Product Overview

High voltage through wall porcelain bushing is a structure that guides one or several high-voltage conductors through partitions (such as walls or boxes) and isolates the conductors from the partitions. It also includes components fixed to the partitions, such as flanges or other fastening devices.
A conductor can be a component of a sleeve, and its two (wiring) ends are connected to external leads with bolts during use. In order to facilitate installation, sometimes the conductor of the through wall sleeve is temporarily allocated by the construction unit during installation. The manufacturer only supplies insulation sleeves and end caps at both ends of the sleeve when leaving the factory. This type of sleeve is called busbar sleeve.
Indoor and outdoor indoor through wall porcelain conduit (referred to as conduit) used in three-phase AC system power stations and substations with rated voltage of 6-35kV and frequency of 15-60Hz. The installation location of the conduit should have an ambient temperature of -40 ℃~+40 ℃.

Structural features

The pure ceramic wall bushing consists of a porcelain sleeve, a conductor, a middle flange, and end accessories. The porcelain sleeve is the main insulation of the casing. The middle flange is grounded normally, the conductor passes through high voltage current normally, and the end accessories serve as a connection between the conductor and the porcelain sleeve. The flange and porcelain sleeve in the middle of the casing are mainly glued together. The glue is filled with cement glue.
For sleeves with a rated current of 600A or below, the middle flange is made of gray cast iron, and for sleeves with a rated current of 1000A or above, non-magnetic materials such as silicon aluminum alloy are used (gray cast iron can still be used for sleeves with a rated current of 7.2-12KV and 1000A), in order to reduce the hysteresis and eddy current losses of ferromagnetic materials in electromagnetic fields.
Due to the small air gap between the 24-40.5kV bushing porcelain sleeve and the conductor, corona discharge is easily generated on the surface of the conductor, and often causes gap discharge, resulting in radio interference.
To this end, the inner wall of the porcelain sleeve is coated with a semi conductive glaze and connected to the conductor through a contact spring plate, short circuiting this gap.
The outer surface of the porcelain sleeve is equipped with umbrella edges to increase the creepage distance and improve the discharge characteristics. To improve the corona and slip voltage of the 24-40.5kV bushing, the porcelain bushing is equipped with large umbrella skirts on both sides of the flange and coated with non-conductive glaze.
In the past, the inner hole of the ceramic sleeve for wall penetration and the outer circumference of the installation flange were not covered with non-conductive glaze, but were sprayed with aluminum or coated with semiconductor paint. During use, it was commonly reported that the aluminum layer or semiconductor paint peeled off, causing discharge and even serious radio interference, affecting the normal operation of television and wireless equipment. Coated with a semi conductive glaze sleeve, due to the fact that the semi conductive glaze layer is fired at a high temperature of 1200 ℃ or above, the glaze layer will not peel off and its performance is stable, overcoming the above-mentioned defects.