Have you ever asked one of these questions?
Is it safe to work on an energized electrical system?
Where is our power system most vulnerable?
Can our existing system support the integration of a distributed energy resource?
My distributed generation system has been operating for 5 years. Is it functioning safely?
Can I replace this piece of equipment?
If you have, it is time to model your electrical system and complete a detailed study!
What are electrical studies?
Electrical studies evaluate if power systems comply with equipment specifications and safety parameters under different operating conditions. Studies usually involve modeling extreme conditions that could stress a system to failure as well as analyzing typical conditions to optimize system design. By performing electrical studies, engineers can define safe limits and use these limits to apply the appropriate protections for equipment and personnel. These protective measures could include the application of protective devices, use of personal protective equipment or defining operational procedures.
For complex systems, computer software, such as ETAP or CDEGs, are needed to model and study how the system responds to a variety of operating conditions from baseline assumptions to extreme operating conditions. Common studies include short circuit, load flow, ampacity, coordination, protection, and arc flash hazard analysis.
The studies and associated reports become a record of the design which helps support the operation and maintenance of the system and adjacent infrastructure. Reports should be referenced prior to performing any work on the system including optimization, growth, or troubleshooting.
Electrical studies during new project design:
It is critical to involve electrical studies throughout the design process of a new electrical system. The purpose of the load flow, short circuit, protection, and coordination analyses is to ensure that new equipment will operate as expected, meet manufacturer’s specifications, and comply with applicable codes. Electrical studies supporting design can also prevent expensive mistakes such as procuring equipment that is inadequately rated for the available fault current. Once a project is built, the electrical studies should be reviewed and updated to reflect the as-built state. With the current disruption in the supply chain, it is common to expect some equipment substitutions during construction.
Electrical studies of systems in operation:
Electrical studies should be updated any time an existing power system is significantly altered. This will validate that the original equipment can accommodate new operating conditions and to identify any new electrical hazards for operators. Consider studying an existing system when you are planning to do the following:
Retrofit your power systems with the latest and greatest products on the market.
Add a backup energy storage system or distributed energy resource.
Adjust the configuration of feeder circuits.
A good practice for operation and maintenance is to update studies on a predetermined interval. The utility grid’s short circuit contribution changes with the commissioning and decommissioning of power plants across the country. Since the available short circuit current contribution from the grid is a key building block in electrical system design, it is critical that changes to the available short circuit current are accounted for and reviewed. In fact, arc flash hazard analysis’, are required by NFPA-70E to be reviewed and updated at an interval not to exceed 5 years to guarantee hazards account for these changes in the system.
The 5-year interval presents a great opportunity for owners to comply with NFPA and OSHA requirements while also performing preventative maintenance. Many of the inputs needed to complete the required arc flash hazard analysis can also be used to complete short circuit, protection, and coordination studies. By completing this set of electrical studies on a 5-year basis, an owner will ensure the reliability and dependability of their system. In addition, they will likely avoid costly time spent offline when equipment failures occur because they have a robust record of how their system operates or they have already addressed vulnerabilities found in the studies.
The easiest way to check if your existing system is due for an arc flash hazard analysis and an electrical study update is to check the date of existing arc flash labels on your equipment.
Summary
Throughout the design process, electrical studies completed by qualified engineers help ensure the safety of a power system by validating the infrastructure can tolerate all operating conditions. If problems are identified, the engineer can define safe operating practices to prevent a critical failure or make appropriate design changes to address the problem. In addition, electrical studies should be updated whenever significant electrical changes are made on a system, or at an interval not to exceed 5 years specifically, for arc flash hazard analyses. If you are seeking qualified engineers to study your new or existing power system, we would love to hear from you!