How are overhead line insulators
Conductors for overhead lines power transmission attached to the supports with insulators made of porcelain or tempered glass... Glass insulators are lighter than porcelain insulators and withstand shock loads better.
The advantages of glass insulators include the fact that in the event of an electrical breakdown or a destructive mechanical or thermal effect, the tempered glass of the insulator does not crack, but disintegrates. This makes it easier to find not only the location of the fault along the line, but also the damaged insulator itself in the string and thus makes it possible to abandon time-consuming preventive measurements along the lines.
Structural insulators Air lines are divided into pin and pendant.
Clip insulators are used both on lines with a voltage of up to 1 kV, and on lines with a voltage of 6 — 35 kV. Low voltage insulators are shaped (Fig. 1, a).
For high-voltage pin insulators for 6 and 10 kV (Fig. 1, b, c, d, e), "skirt" designs have been developed.Pin insulators on 35 kV lines are rarely used and only for wires with small cross-sections. Usually they are made of several glued elements (Fig. 1, e).
On the supports, the pin insulators are attached with hooks and pins. In both cases, a layer of rod (hemp) moistened with red lead, rubbed in oil, is wound on the rods of the hooks or pins provided with slots, after which an insulator is screwed onto the thread puller, which is available in porcelain.
Rice. 1… Clip insulators Air lines: a-ShFN and NS, b-ShF-10V, c-ShF10-G and ShF20-V, d-ShS10-A and ShS10-V, d-ShF35-B
In the designation of insulator types, letters and numbers mean: W — pin, F — porcelain, C — glass, H — low voltage, number — rated voltage, kV or minimum electromechanical load in kN, letters A, B, C, D — optional insulator design.
Only for overhead lines with a voltage of 35 kV with conductors of medium and large cross-section, as well as for lines with a higher voltage, only hanging insulators (oriz. 2).
Suspension insulators consist of a porcelain or glass insulating part and metal parts - caps and rods, which are connected to the insulating part by means of a cement bond.
Rice. 2… Suspended Insulators Air lines: a-PF70-V, PF160-A, PF210-A, b-PFG70-B, c-PS70-D, PS120-A, PS160-B, PS300-B, d-PSG70-A and PSG120-A.
For different environmental pollution conditions, pop insulators of various types are used, differing from each other in basic characteristics: creepage path and test voltage. Suspended insulators are assembled into strings that are supported and tensioned.Supporting garlands of insulators mounted on intermediate supports, suspended — on an anchor (Fig. 3).
Rice. 3. A garland of hanging insulators
The number of insulators in a string depends on the operating voltage of the line, the degree of atmospheric pollution, the material of the supports and the type of insulators used. So, for a line with a voltage of 35 kV — 2-3, for 110 kV — 6-7, for 220 kV — 12-14, etc.
