Short Circuit, Coordination, and Arc Flash – Electrical Studies & Why You Need Them?

Why You Need Electrical Studies?

If you are in the electrical business, you are familiar with the typical electrical studies required to safely operate a facility (short circuit, coordination, and arc flash calculations). Furthermore, you understand the importance of knowing when to update the electrical studies. Since they’re interdependent, all three studies must be completed simultaneously.

Any employer who operates electrical equipment must have on-premises an electrical engineering calculation (stamped by a registered professional engineer) to specifically identify the hazards. Much like an elevator permit, this shows that the inherent electrical hazards have been analyzed every five years.

The National Fire Protection Association’s Standard for Electrical Safety in the Workplace® (NFPA 70E) requires employers to complete electrical studies every five years (or when significant changes happen) and post updated warning stickers on their equipment. See NFPA 70E Article 130.3 for the regulatory requirements.

Electrical Studies Low Voltage Equipment Short Circuit Summary List

Electrical Studies Overview

Short Circuit Studies

The Short Circuit study is simply an electrical calculation to determine the momentary and interrupting fault current available at each electrical equipment piece from the utility service entrance to the load.

Short Circuit Electrical Studies

This study requires an up to date and accurate single line diagram to complete (or created as part of the study effort).

The short circuit calculation creates an electrical system model with all the sources, loads, transformers, and impedances. Moreover, each piece of electrical equipment can be confirmed and appropriately rated to withstand a fault without damage to property or people.

Coordination Studies

Coordination Electrical Studies

After completing a short circuit study, the next step is to update the protective device coordination with a Coordination Study. This calculation uses software models of every manufacturer of relays, circuit breakers, fuses, transformers, and cables to plot the time versus current curve of fault current to adjust (as much as possible) the long time, short time, instantaneous, and ground fault settings.

Properly coordinated protective equipment eliminates nuisance tripping while selectively clearing electrical faults at the closest possible protective device to the fault. This electrical engineering calculation is based on the single line diagram and short circuit rating information calculated previously.

Arc Flash Studies and Stickers

The final study in this trio is the completion of the Arc Flash Study; as well as the creation of specific electric equipment stickers. Arc Flash studies are based on the specific single line diagram, Short Circuit, and Coordination study calculations. They determine the energy released in an electrical phase to phase or phase to ground fault.

This is not a shock or electrocution hazard. Instead, it is an analysis of the light, heat, and blast associated with these faults (like a giant arc welder). They can burn skin, blind unprotected eyes, and propel molten metal across the room. The completed Arc Flash study calculates the risk from these electrical faults and defines appropriate Personal Protective Equipment (PPE).

Arc Flash Example

Further, they calculate the distance around the equipment this hazard is present. Subsequently, an equipment specific label/sticker is produced and must be placed on the electrical equipment (warning employees of the hazards).

APT Can Help

As a long-time service provider, APT understands that keeping the electrical system documentation updated remains a daunting task. We’re able and willing to help, even if it is simply collecting the basic information. This allows you to bid out your short circuit, coordination, and arc flash studies as a project.

We speak the electrical engineering language and can help you operate your facility safely and cost-effectively. Please check out our datasheet or ask for help and we’ll be there for you.

Andrew E Taylor, PE CEO APT