Overhead Conductor Manual

[Toney Talbot]

Inwork on bare HV overhead lines and conductors, the short-circuits to ground must be placed on both side of the work area and on each of the conductors that enter the area; at least one of the short-circuit to ground devices or equipment must be visible from the work area. Exceptions:

In work on insulated HV overhead power lines, the short-circuit to ground is to be placed on the bare elements of the opening points of the installation or as close as possible to these points, on each side of the work area.

If you use a mast for overhead conductor support, it must have adequate mechanical strength, braces, or guy wires to withstand the strain caused by the conductors. Only feeder or branch circuit conductors can be attached to the feeder and/or branch circuit mast [225.17], as shown in Fig. 3.

Raceways on exterior surfaces of structures must be arranged to drain and be suitable for use in wet locations [225.22]. Underground raceways (used or unused) entering structures must be sealed in accordance with 300.5(G) to prevent moisture from contacting energized live parts [225.27].

If more than one building or other structure is on the same property, each building/structure must be served by no more than one feeder or single or multiwire branch circuit [225.30]. However, there are five exceptions to this. You can have additional supplies for:

A disconnecting means is required for all conductors that enter a building or structure [225.31]. Install it at a readily accessible location (either outside or inside) nearest the point of entrance of the conductors [225.32]. There are four exceptions to this rule:

4) For a pole or similar structure used only for the support of signs installed in accordance with Art. 600, the disconnecting means is permitted to be located elsewhere on the premises [225.32 Ex 4].

The building/structure disconnecting means can consist of no more than six switches or six circuit breakers in a single enclosure or separate enclosures for each supply grouped in one location as permitted by 225.30 [225.33].

To minimize the possibility of accidental interruption of critical power systems, the disconnecting means for a fire pump or for standby power must be located remotely away from the normal power disconnect [225.34(B)].

In a multiple-occupancy building, each occupant must have access to the disconnecting means for their occupancy [225.35]. But if building management provides electrical maintenance under continuous supervision, management can make access available only to building management [225.35 Ex].

If more than one supply feeds a building/structure, a permanent plaque or directory must be installed at each feeder disconnect location denoting all other feeders or branch circuits supplying that structure and the area served by each [225.37].

A single disconnecting means for a building/structure must have an ampere rating at least equal to the calculated load as determined by Art. 220. If the disconnecting means consists of more than one switch or circuit breaker, the combined ratings must be no less than the calculated load as determined per Art. 220 [225.39].

3. Follow all rules for the installation of disconnects. This is essential in order to provide a convenient and safe means to disconnect sources of electric power in case of fire or electrocution hazards.

The introduction of the Handheld Manual Field Probe further revolutionized phase identification. As this field probe works by proximity, it was no longer necessary to place the probe on a hotstick or long extendo stick and lift the probe up to touch a high overhead conductor.

This field probe also allows phasing at residential meters. This is an extremely valuable feature in underground neighborhoods in that it is no longer necessary to open padmount transformer cabinets to touch a live conductor. The lineman simply walks over to the meter, places the probe on the glass, and takes a phase measurement.

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