Temporary power projects usually involve running temporary power cable between a source, which is typically a generator, to a load which could be a spider box (or Beetle Box), a transformer cart, a portable panelboard or an automatic transfer switch. Choosing the right cables depends on factors including the physical environment such as temperature and precipitation, the surface area the cable will be in contact with, and the electrical properties of the load.
Temperature and precipitation can greatly affect the performance of temporary power cable. In cold weather climates such as Alaska, and the northern parts of the United States, cable can become extremely stiff and unmanageable. The main determination for the flexibility of cable in cold environments is the jacket. It recommended that a rubber (or thermoset) jacket, such as type W, is always used in cold climates as opposed to a jacket made of plastic (or thermoplastic) material. Plastic jacketed cable will become very stiff in temperatures below 40 degrees Fahrenheit (4 degrees C). In addition to temperature, water in the form of rain, snow or runoff can penetrate cable jacketing causing a short circuit which can be life threatening. Rubber jacketed cable is also recommended in environments where the cable may get wet, as rubber is a natural repellant of water.
The surface the cable is in contact with can damage the jacket of the cable and allow water, dirt or worse – people and animals, come in contact with the conductors of the cable. Rocks, concrete or even wood can be source of abrasion in temporary power applications. In these cases, we also recommend type W cable. Some temporary power applications have a much more forgiving surface area. Examples include theatres, indoor concerts, churches and sporting events. In these areas, a plastic jacketed or lighter jacketed cable such as stage cable, or SC, is perfectly acceptable. The cost of stage cable is considerably less than type W and has similar flexible properties.
Electrical Properties of the Load
Amperage and voltage are the electrical properties that determine the size of the cable and the insulation properties needed. Cable insulation is what protects people, animals and equipment from the current carried by the conductors. The higher the voltage, the thicker the insulation requirements. For example, cable carrying 15,000 volts, such as SH cable, has an insulation thickness of .21”, versus cable such as type W that has a maximum voltage rating of 2000V and has an insulation thickness of .09”. Amperage determines the size of the conductors. This higher the amperage, the larger the conductor needed. Conductor size as well as insulation thickness are the main drivers of the price of the cable. Voltage is carried in phases with single phase loads typically having a hot ( or energized) wire, a neutral wire and a ground, which means there are a total of three conductors needed to carried a single phase load. Three phase loads require 3 hot wires, a neutral and a ground. Cables that carry less than 100 amps usually have the conductors all under one jacket and insulation, called multi-conductor cable, which make it easier to move around. With amperages over 100 amps, conductors typically have their own jacket and insulation. Many companies choose to band these single conductor cables together using insulation tape placed every 18” (called banded assemblies) to keep the cables organized and together.
When it comes time to choose temporary power cable for your next project, consider these three factors. If you need help choosing, please contact one of ATI Electrical Supply’s knowledgeable sales people at firstname.lastname@example.org.