Arc Flash Hazard Analysis

ARC FLASH HAZARD and MITIGATION:  IETC Performs IEEE 1584 and NFPA 70E-2015 Power System Studies

We have three goals in mind when performing a power system study:

  1. The primary goal is to determine the required “personal protective equipment” (PPE) per NFPA 70E-2015 for Arc Flash hazards. This is an “Arc Flash Hazard Study”.
  2. A safety-related goal is to perform a “Short Circuit Equipment Study” of the available fault current to check sufficiency of electrical AIC ratings and compliance with the National Electric code and Electrical Safety in the Workplace (NFPA 70E-2015).
  3. The third goal is to study the overcurrent protective devices (relays, circuit breakers and fuses) for coordination and equipment protection for improved reliability of the electrical system. This is a “Protective Device Coordination Study”.

IETC uses power systems software from SKM Systems Analysis Inc. SKM is the most widely accepted engineering software for this purpose.
The studies are performed to produce arc flash hazard equipment labels and energized work permits. Energized work should only be attempted as “the last alternative work practice” and a work permit is required for such work.
NFPA 70E is an OSHA recognized standard with definitions for protective clothing, tools and equipment. The clothing and equipment known as “personal protective equipment” (PPE).

PPE is to be worn to protect maintenance electricians or other qualified persons from serious or fatal burns or explosions that could occur from an accidental “arc flash” during service work on energized electrical equipment.

The Short Circuit Study portion of a arc flash hazard analysis power study is necessary to begin the Arc Flash portion of the study. It calculates the balanced and unbalanced fault currents at all busses and examines in detail the fault current associated with a fault at a single bus.

An algorithm is used to model a conventional Ohm’s law solution using superposition and complex vector analysis and contributions from induction motors.

IEEE 1584 requires a protective device coordination study as a necessary part of an arc flash hazard analysis study.

Those aspects affecting reliability and safety are “selectivity” and “protection”. Good “selectivity” is known as “coordination” and means the relay, fuse or breaker directly upstream and nearest to an abnormal short circuit or an overload opens fast enough to limit the energy to flow to the next level protective device, so that only one device will open the circuit. For example, a feeder or branch breaker will open to clear the problem without the plant main breaker opening. Adequate “protection” means that the settings of relays, fuses or breakers effectively protect the cable and equipment downstream from that device.  Contact IETC for more information – 717-252-4730.

Arc Flash Hazards displayed on warning labels