Page 331 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

then it is called a cross - arm (Fig 6a) and if installed on one side of the pole, then it is termed as side cross -arm
(Fig 6b) U-shaped cross - arms are specially used for three phase lines.
Channel iron cross-arms fabricated from channels of size 75 mm x 40 mm x 5.7 kg/m or size 100mm x 50 mm x
7.9 kg/m are used for H.T. lines, and those made from angle irons of size 50 mm x 50 mm x 6 mm are used for
L.T lines.

Fig 6

Joining of aluminium conductors

Objectives: At the end of this lesson you shall be able to
• state the type of joints
• explain the type and use of connectors used to joining conductors
• explain the steps to testing of O.H lines
• state the preliminary safety procedure for OH line erection.

Joining accessories in O.H lines: Normally connectors are used for joining the O.H. aluminium conductors.
Connectors maybe of several types of which few are described below.

1 Sleeved joints
2 Straight through connectors / taps
3 Vice - clamp connectors /taps with parallel grooves
4 Nut and bolt connector
Sleeved joints
Twisted joints: Oval shaped aluminium sleeves are inserted over the conductors to be joined and then twisted
as in Fig 1. Only one sleeve is sufficient for all aluminium conductors whereas two concentric sleeves are used
for ACSR conductors. One each for the aluminium and steel portions. Twisting joints are recommended for
conductors up to 15 mm diameter. Only special wrenches should be used for twisting the sleeves.
Compression joints: ACSR conductors are joined by compression joints having two sleeves as in Fig 2. The
larger sleeve is of aluminium , fitting over the entire conductor, and the smaller one is of steel fitted on the steel
portion of the wire eccentrically. Conductors to be joined are inserted into the sleeves one after the other and
compressed either by hand or by hydraulic compressors. Compression joints for all aluminium conductors consist
of aluminium sleeve only .

Straight through connectors / taps: Two types of connectors are used to join two straight through run of wires
in such locations where mass concrete foundations are to be adopted to avoid collapse of foundation in the black
cotton soil.

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CITS : Power - Electrician & Wireman - Lesson 106-116