I. Overview
Pin-type insulators are an older type of insulator used in high-voltage transmission and distribution lines. Due to their simple manufacturing, low cost, easy installation, and ability to reduce tower height (since they are installed vertically with the grounding part below), they are widely used in overhead power lines for three-phase power systems with nominal voltages of 6 to 35 kV and frequencies not exceeding 100 Hz in ordinary and polluted areas, serving as insulation and support for conductors.
The needle-type insulator is composed of an insulating component and a steel foot, which is a rigid insulator that rigidly mounts the insulating component to the supporting structure using a steel foot fixed within the insulator. The insulator can be made up of a single piece or multiple interconnected insulating components. The insulating component of the porcelain insulator is a porcelain piece, typically glazed in brown or white. The attachment of the porcelain piece and the foot can be separable or permanent (as in needle-type insulators with adhesive feet).
Insulators are categorized by structure into two types: glue-mounted and zinc-threaded connection. The glue-mounted type directly bonds the porcelain piece to the base with cement, featuring a deep groove on the porcelain part of the steel base to prevent loosening, with an elastic pad between the steel base top and the porcelain piece. The zinc-threaded connection type involves first cementing the porcelain inner hole with a zinc threaded sleeve, and then connecting it to the steel base using this threaded sleeve. The zinc threaded sleeve serves as a shock absorber and facilitates the replacement of the porcelain piece. There are also those that use mechanical connections relying on porcelain threads.
The old model needle-type porcelain insulators specified in the GB1000-1981 standard are divided into five grades according to rated voltage: 6, 10, 15, 20, and 35 kV. Each grade is further divided into two specifications based on the steel foot type: iron pole straight foot and wood pole straight foot.
The new model needle-type porcelain insulators specified in GB/T1000.2-1988 standard have a rated voltage of 10kV. They are categorized into three types based on applicable environmental conditions: General Type, Reinforced Insulation Type 1 (Medium Pollution), and Reinforced Insulation Type 2 (Heavy Pollution).
To reduce radio interference, edge glaze insulators with upper conductive glaze above the side slots and models containing the letter "B" are also provided.
