members must be stationed along the way to establish a chain of signal communication from the head of the line back to the line truck.
Placing the Neutral Conductor
A neutral conductor should always be placed on a center crossarm pin or on a pole-top pin. Butting the neutral on a center pole pin gives the lineman a clear space around the pole to climb through; that is, it ensures that the hot wires are a considerable distance apart.
When the conductors have been hoisted in place on the crossarms and dead-ended on one end, you are ready to start "pulling in"; that is, heaving on the conductors until each has been raised to proper sag. You can do this with a tackle equipped with cable grips like those shown in figure 4-65 or individually, using a cable grip and a come-along.
A cable grip is a clamp device that grips the wire tightly when a strain is applied to the grip.
When you are pulling two or more wires at once, it is best to use the equalizer, as shown in figure 4-65. This device distributes the strain equally on all the wires.
When wires have been pulled to approximately the desired sag, a lineman goes to the center span to measure the sag. Measurement at the center of each span ensures uniformity. Three common ways of measuring sag are by dynamometer, by timing vibration, and by the use of targets.
DYNAMOMETER. - Alever-cam dynamometer is an instrument that is installed in the pulling line and that measures the strain of the pull. It is used in conjunction with a chart that gives the desired pull tension for a given conductor size, span length, and temperature. A traction dynamometer, also installed in the pulling line, provides direct readings on the face of the dial.
TIMING VIBRATION. - The timing-vibration process is done by striking the wire sharply near one of the pole supports and by timing with a stopwatch, the interval that elapses as the impulse from the blow travels to the next pole and returns. This system is not accurate when wind is swinging the line or when the line is being worked on in an adjacent span.
Figure 4-65. - Pulling wires with an equalizer.Continue Reading