The Petroleum and Chemical Industry Committee (PCIC) recommends that Arc Flash calculations be completed in conjunction with short circuit calculations and protective device coordination to achieve the most accurate Arc Flash Hazard results. Short circuit and coordination studies verify protective devices and arc hazard ratings, calculate momentary interrupting and relay currents, establish settings for all types of protective devices, and coordinate your entire power distribution system to minimize downtime. AFA Ghana specializes in conducting these studies that provide critical information you need to ensure compliance with CSA Z462, NFPA and OSHA requirements.

The objective of a protection scheme in a power system is to minimize hazards to personnel and equipment while allowing the least disruption of power service. Coordination studies are required to select or verify the clearing characteristics of devices such as fuses, circuit breakers, and relays used in the protection scheme. These studies are also needed to determine the protective device settings that will provide selective fault isolation. In a properly coordinated system, a fault results in interruption of only the minimum amount of equipment necessary to isolate the faulted portion of the system. The power supply to loads in the remainder of the system is maintained. The goal is to achieve an optimum balance between equipment protection and selective fault isolation that is consistent with the operating requirements of the overall power system.

Short-circuit calculations are a prerequisite for a coordination study. Short-circuit results establish minimum and maximum current levels at which coordination must be achieved and which aid in setting or selecting the devices for adequate protection. When facilities are changed or upgraded, it is necessary to revisit the existing protection scheme to determine if change is needed to be made to ensure that devices are coordinated properly. A change in load or equipment could change the timing and coordination of the protective devices.

Compliance: The coordination will be performed in accordance with the recommended practices and procedures set forth in ANSI/IEEE 399 and ANSI/IEEE 242. Protective device selection and settings shall comply with requirements of NFPA 70 National Electrical Code/OESC, following the recommendations of NETA.