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Complete Knowledge of Pin Insulators (Part 1)

Pulished on Apr. 24, 2020


Structure and use

Pin insulators are the oldest type of insulators in high-voltage transmission and distribution lines. Because of its simple manufacturing, low cost, easy installation and can reduce the height of the tower (because the insulator is installed upright, the grounding part is below), it is widely used in ordinary areas with a nominal voltage of 6 to 35kV and a frequency not exceeding 100Hz, and pollution It is used for insulation and supporting wires in high-voltage overhead power lines in the region.

Porcelain pin insulators, also known as pin bottles, are composed of insulating parts and steel feet. They are rigid insulators that are rigidly mounted on the supporting structure with steel feet fixed inside the insulator. Porcelain parts and steel feet (or screw sleeves) are made of Portland cement and quartz sand adhesive not less than 42.5 grade, and the steel feet are pressed into the porcelain parts with deep grooves to prevent the steel feet from loosening; steel There is an elastic pad between the top of the foot and the porcelain. The surface of the porcelain parts is generally brown glaze or white glaze, and the steel feet are hot-dip galvanized.

Porcelain line post insulators are rigid insulators used to insulate and support conductors on transmission and distribution lines. The insulator is rigidly mounted on the support structure by a foot fixed in the insulator hole.

Insulators are divided into two types according to the structure: plastic-mounted and zinc-threaded. The glue type is that the porcelain parts are directly glued with cement and connected to the feet. The steel feet are pressed into the porcelain parts with deep grooves to prevent the steel feet from loosening. There is an elastic pad between the top of the steel feet and the porcelain pieces. Zinc sleeve thread connection type is that the inner hole of the porcelain part is firstly installed with a zinc screw sleeve through cement glue, and then the screw thread is connected to the steel foot by this screw sleeve. The zinc screw sleeve has a buffering effect and is also convenient for replacing porcelain parts. There are also mechanical connections that rely on porcelain threads.

Straight poles use pin insulators, because the insulators will not cause wind deflection, and are generally installed upright on the crossarm, so the distance between the wires and the height of the poles are smaller than those with suspension insulators, but on both sides When unbalanced tension occurs, the tower bears greater tension. Compared with porcelain crossarms, pin insulators have higher strength and can withstand larger bending loads, but they have a breakdown structure, and the withstand voltage is also lower than that of porcelain cross-arms. It can be turned to reduce the bending load of the tower.

Porcelain Line Post Insulators

Porcelain Line Post Insulators 


Insulator model

The old model high voltage pin insulators are divided into five grades of 6, 10, 15, 20 and 35kV according to the rated voltage, and are divided into iron crossarms with shorter threads and wooden crossarms with longer threads according to the installation method, according to the insulation structure Divided into ordinary type and reinforced insulation type. High voltage pin insulators are P-6T (M), P-10T (M), PQ-10T (M), P-15T (M), P-20T (M), PQ-20T (M), P-35T (M) and other models. P stands for pin type, Q stands for reinforced insulation, numbers such as 10 and 15 indicate rated voltage levels, T stands for iron crossarm straight legs, and M stands for wooden crossarm straight legs.

The rated voltage of the new model is 10kV, which is divided into three types: ordinary type, reinforced insulation type 1, and reinforced insulation type 2. The meaning of the symbol in its model is as follows:

P-ordinary pin insulator;

PQ1—Reinforced insulation type 1 (medium pollution type) pin insulator;

PQ2—Reinforced insulation type 2 (extra heavy pollution type) pin insulator;

B-All the parts above the side groove of the porcelain parts, except the burning surface, is coated with semiconductor glaze;

T-With feet, porcelain parts, and feet are directly glued together, iron ram;

L-Without feet, the porcelain pieces are connected with the feet thread;

LT-with feet, porcelain parts and foot thread connection, iron load;

The number 10 after the dash indicates the rated voltage of 10 kV; the numbers 16 and 20 after the T indicate the lower thread diameter.