According to the electricity rule, which type of pole is not used in the overhead line?

Question

Question

This question was previously asked in

PGCIL NER DT (Electrical) 27 Feb 2022 Official Paper

Answer 1

The correct answer is option 4.

Types of poles used in overhead line

1.) Wooden poles

These are made of seasoned wood (sal or chir) and are suitable for lines of the moderate X-sectional area and of relatively shorter spans, say up to 50 meters.
Such supports are cheap, easily available, provide insulating properties, and, therefore, are widely used for distribution purposes in rural areas as an economic proposition.
These cannot be used for voltages higher than 20 kV.

2.) Steel poles

Steel poles are often used as a substitute for wooden poles.
They possess greater mechanical strength, and longer life and permit longer spans to be used.
Such poles are generally used for distribution purposes in the cities.

3.) RCC poles

The reinforced concrete poles have become very popular as line supports in recent years.
They have greater mechanical strength, longer life, and permit longer spans than steel poles.
Moreover, they give a good outlook, require little maintenance, and have good insulating properties.

4.) Steel towers

In practice, wooden, steel, and reinforced concrete poles are used for distribution purposes at low voltages, say up to 11 kV.
However, for long-distance transmission at higher voltage, steel towers are invariably employed.
Steel towers have greater mechanical strength, longer life, can withstand most severe climatic conditions, and permit the use of longer spans.