Insulator: types and types

This article will contain information about bushing insulators, their types and types. In detail, the design of various species, the species themselves, the scope of their application and purpose will be disassembled. They will also consider their advantages in comparison with similar devices. After reading the article, you will not only learn general information about pass-through isolators, but you will be able to decode markings and be able to distinguish one species from another.

Scope of bushing insulators

What is a bushing? This is a special device whose main function is to insulate the conductive elements from the inner or outer wall of the shell through which they pass. They are also used in the installation of switchgears in transformer substations, and also act as terminals on complete distribution systems.

Support insulators are designed to fix overhead power lines to current-carrying buses of switchgears and other electrical installations. It is worth adding that porcelain insulators of a through type, which were popular earlier, are still in use with a variety of modifications.

Insulating bushings are very convenient for connecting substation terminals, from which residential houses are powered.

Types of insulators

The bushing insulators are divided into two types. The first type is insulators, which are designed for indoor installation. They use either high-voltage or vacuum terminals from transformers of high-voltage switches. The bushing insulator of the presented kind is made of porcelain, and inside the product there is a metal rod. It is fixed with the help of flanges made of metal, joined by a porcelain cap and an adhesive sand composition.

The second view is reassigned for both outdoor and indoor installations. Such devices have intermediate ribs, which are located at a short distance from each other. These devices are designed for isolation from live parts of closed switchgears. A bushing insulator of this type is used at an operating voltage of 10, 25, 35, 110 kV, and an operating current of 630 to 11,000 A.

There are also other types of insulators, but they are designed for a specific purpose. Devices of a through type are necessary for the insulation of the conductive parts of the switchgears and for the connection of consumers by buses to overhead power lines. These products are made of materials of increased strength, so that their design is resistant to dynamic current loads.

Advantages of insulators

The bushing should have a long service life, therefore it has the following characteristics:

• High resistance to aggressive operating conditions;
• Relatively small mass;
• Resistance to ultraviolet radiation;
• High strength;
• Long service life;
• Relatively small overall dimensions.

Construction IP

Feedthrough insulators PI should have the maximum mechanical and electrical strength, so the material from which they are made can be as follows:

• polymer;
• porcelain;
• strained glass.

The isolator is designed to ensure that the breakdown voltage is higher than the overlap voltage. External insulators are constantly under the influence of external environmental factors, so their surface is ribbed. This is made specifically to improve the work of the product.

Insulators, according to their intended purpose, are divided into pass-through, supporting and suspension, and there are also types of installation for installation in buildings and structures or for outdoor installation.

Walkthrough IP-10 is most often made of porcelain. The design performance of such an insulator is determined based on the rated voltage of the current and the industrial frequency of the network. The product itself consists of a porcelain body of cylindrical shape, on the axes of which are installed ribs, tightly fastened with a cement-sand mortar.

Purpose of bushing insulators

The main purpose of bushing insulators is the insulation of current-carrying conductors that pass through walls and cover buildings or structures. Such insulators consist of dielectric porcelain. The body is made in the form of a cylinder, on the upper part of which is a current-carrying rod. At the middle level of the body there are metal flanges, which, as was said above, are intended for fixing insulators to the surface.

A bushing insulator IP at a working voltage of up to 10 kV is made of porcelain, and at an operating voltage of over 35 kV the housing of the device is manufactured as a complex insulating structure, which in turn consists of a porcelain body, cardboard plates, dielectric paper and transformer oil.

Installation of bushing insulators

During installation, the bushings of the outdoor installation are inspected for cracks and other defects, as during transportation the surface of the insulators could be damaged. Also inspect whether the surface glaze is worn, which serves for additional protection and insulation of the product.

Insulators must be placed on any metal structures for the secure attachment of products, as well as the resistance of tires or overhead power lines.

Installation of insulating passages begins with the placement of a passing plate, which is fixed to the structure or any reinforcement. Further, the insulators are closed on both sides by cast-iron caps with metal partitions having rectangular openings resembling a railway rail. Their size depends on the size of the fixed tires. Spacers are installed on the product bus terminals between the fixed tires.

Marking of bushing insulators

Marking is reassigned in order to highlight all the characteristics of the product. For example, the isolator of the pass IP-10 630 7.5 UHL1, where:

• And - an insulator;
• P - checkpoint;
• 10 - normal working voltage of the product (kV);
• 630 - normal working current of the product (A);
• 7.5 - breaking force (kN);
• UHL - the climatic condition of performance;
• 1 - accommodation category.

Breakdown voltage IP

The breakdown voltage of porcelain PIs may vary depending on the thickness of the porcelain layer. Despite this, the design of the insulators is determined by the necessary mechanical strength, design tension of the overlap and additional measures for removing the crown.

When a 10 kV bushing is used, no measures are taken to remove the corona. At rated voltages above 35 kV, measures are taken to install a crown near the stem opposite the flange, just in the place where the greatest tension in the air.

In order to prevent corona, insulators are made without an air cavity around a metal rod installed inside the insulator. During this, the PI surface is metallized with the rod. And in order to eliminate the appearance of discharges at the bottom of the IP, the surface below it is also metallized and additionally grounded.

Conclusion

Probably everyone has ever seen a transformer whose air lines are attached to a PI. These devices are also necessary for connecting wires to fixed installations, since it is impossible to attach high-voltage wires without insulators.