PCX Arc Flash Study

What is an Arc Flash study?

An arc flash study is a risk analysis that is performed by an electrical engineer. A correctly executed study can help improve plant safety by identifying the specific arc flash hazard at a given piece of equipment. It identifies the Arc Flash Protection Boundary, which is the closest approach allowed before PPE must be worn. Proper clothing or Personal Protective Equipment (PPE) must be worn once a worker steps inside the Arc Flash Protection Boundary. The main goal of arc flash PPE is to minimize burns to the body resulting from an arc flash incident. The only way to determine the proper PPE when working on a certain piece of electrical equipment is to have an Arc Flash Study completed. Qualified workers determine the proper PPE through the labeling from the study.

What codes and standard
dictate Arc Flash Safety?

There are four different standards that dictate practices for the prevention of arc flash incidents in the United States:

Scope of services

The following services shall be provided by PCX

1. Initial meeting and data collection

2. One-line diagram

• PCX shall generate a one-line diagram based on information from the data collection for each store.

3. Short Circuit Study

• The information will be entered into ETAP modeling software by PCX.
• A short circuit study shall be performed which gives the momentary and interrupting duties on each fault bus shown on the one-line diagram. A computer model will be used to sequentially place a bolted three-phase fault at each of the selected locations and perform accurate calculations of total fault current available at each location as well as the contribution from each adjacent bus.
• PCX will evaluate the results of the ETAP program. The short circuit program’s evaluation of protective devices within the scope of this study will be analyzed for interrupting ability by comparing their interrupting rating with the maximum interrupting duty as determined from the above calculations. Protective devices will be tabulated, showing their interrupting ratings along-side their interrupting duties for ready evaluation of their capabilities.
• The study will be run at normal operations.

4. Protection/Coordination Study

• PCX will produce a report showing the results of the study (protective device evaluation; existing vs. recommended relay settings, motor protection settings, circuit breaker settings, etc.) and any other recommendations. This information will be used in the Flash Protection Boundary Distance Calculations.

5. Arc Flash Evaluation

• PCX will use the information collected and the results of the short circuit study to provide the necessary input data required for the Arc Flash Hazard study. The specific information needed includes the calculated three-phase bolted fault currents at all system buses and all protective devices’ trip settings. Opening times can be obtained from the settings and the calculated fault currents.
• The results of the study will include the calculated Incident Energy (in cal/cm2) and the calculated Arc-Flash Boundary at key system points within the scope of the short circuit study that have arc-flash hazards.

6. Arc Flash hazard labels

• PCX will provide labels and each label will provide its Bus ID from the short circuit study, the calculated incident energy at the specified working distance, the arc-flash protection boundary, the bus voltage, the shock hazard boundaries, a description of the required combined PPE for both arc-flash hazard and shock hazard, the date of the study, and a disclaimer in regards to changes in equipment settings. As an additional service, PCX can install these labels as well as set device coordination according to the report

7. Final Report consisting of

• Report Summary
• ETAP One Line diagram
• Input data and assumptions
• Descriptions of the scenarios evaluated and identification of the scenario used to evaluate equipment ratings
• Short circuit results