Data Collection for Short Circuit and Arc Flash Study
The arc flash study must be based on accurate, up-to-date information. A single-line diagram is the preferred method of documentation of a power system. It generally represents existing conditions and equipment nameplate data for the portion of the system within the scope of the arc flash study. This may require the person performing the study, or the facility's owner to:
- Obtain any existing single-line drawings of the facility. ARCAD's short circuit calculations software program will create a simple diagram as data is entered.
- Verify and update existing single-line diagram to existing conditions.
- Verify and resolve any equipment labeling and naming issues.
- Collect system documentation including transformer, motor, generator nameplate data or data sheets, switchgear drawings, copies of previous power system studies, etc.
- Obtain wire and cable sizes, cable material, cable construction and length.
- Gather protection device information including fuse and breaker part numbers, series, ratings, trip unit settings and time-current characteristics.
- Verify nomenclature to be used for equipment and all devices in the study with the owner. This includes abbreviations, etc. This should ensure proper naming convention before creation of the drawings, reports and equipment labeling.
- Field inspections will likely be required to obtain and verify the required arc flash study information. Where possible, it is usually helpful to work with personnel familiar with the facility's power system.
- All site work should be performed in accordance with applicable facility safety requirements and applicable electrical work safety standards such as NFPA 70E Standard for Electrical Safety in the Workplace. In some cases, a partial or full system shutdown may be required to gather some information for safety reasons.
There may be other portions of the electrical power system at the facility to be studied that are not included in the scope of work. However, these portions of the system may affect the results of the system under the scope of the arc flash study. When a facility is not performing an arc flash study on its entire system, it will be necessary to obtain the available short-circuit currents and X/R ratios for sources of supply not included in the scope of the project at the terminals or buses where the project begins. It may also be necessary to obtain large motor short-circuit contribution data for large motors not included in the scope of the project at the appropriate terminals that are part of the project.