- Safety Corner | July 17, 2017
The Single-Line Diagram and Safety
The single-line diagram to the electrical professional is comparable to what a map is to a person driving across the country. If this was “back in the day,” I’d say that before I go on a journey somewhere in the car I grab my Atlas and appropriate maps. Today, I use my smartphone and my “Maps” app.
- Utility: The information shown is obtained directly from the utility and should include the voltage of the source connection, the available short-circuit current and the X/R ratio. The available short-circuit current can be represented as Short-Circuit kVA/MVA or Short-Circuit Amperes. Note who the utility is as well.
- Generators: The generator plays an important role for the reliability of the power distribution system. Information should include the voltage rating, VA rating either in kVA or MVA and sometimes could be represented instead as Watts. Sub-transient reactance and X/R ratio should also be shown at a minimum. The nameplates of generators will have all of this information and more, as required by the UL listing of the product.
Alternative energy solutions: These solutions will be connected to the system via an inverter. The key parameters of voltage ratings and output current ratings are those that should be included on the single-line diagram.
- Panelboards, switchboards and similar equipment: Assigned identifiers, voltage rating, rated equipment ampacity, available short-circuit current, shortcircuit current rating (SCCR).
- Transfer sw