COORDINATION STUDIES: SHORT-CIRCUIT AND PROTECTION
How do you know if your fuses and or circuit breakers will work safely when called upon to interrupt a serious electrical fault or short-circuit?
The answer is, most people do not know for sure. The issue is if the available electrical current exceeds the capability of the protective devices in the electrical distribution system, an electrical fault can cause these devices to virtually disintegrate. Violently.
As the name so aptly suggests, a “Coordination Study” provides the required analysis of the various components connected within and are integral to the electrical system segment, or an entire electrical distribution system within a facility. The study ensures that the availability of electrical current is correctly and proportionately “coordinated” with each protective electrical device rating and setting within its electrical path so that it performs as designed…safely.
The entire coordination study process can be extremely complex and constantly variable due to the dynamic conditions of any electrical system within your facility, (which you generally have control over) and those external to your facility, (which you generally have no control over). However, the Smith & Long Engineering Services Group can systematically work through the myriad of details to be documented and calculated to capture and correct any incorrectly commissioned or incorrectly previously selected and installed components to provide you with the resultant system that is both safe and reliable.
The study starts with an existing SLD (Single Line Diagram) that first needs to be verified that is true to the “as-built” existing electrical building infrastructure. If it needs to be updated or perhaps created from scratch the Smith & Long Engineering Services Group can perform this task on your behalf. The SLD then becomes the prime document for information gathering and to begin annotating it with all pertinent data, from the LDC (Local Distribution Company) electrical feeder connection point, right down to seemingly modest loads at the furthest away sub electrical breaker panel in your facility.
In brief, the Short-Circuit Study is the analysis of an electrical system that determines the magnitude of the currents that flow during an electrical fault. Comparing these calculated values against the equipment ratings is the first step to ensuring that the power system is safely protected. Once the expected short-circuit currents are known, a Protection Coordination Study is performed to determine the optimum characteristics, ratings, and settings of the power system protective devices.
A common misnomer worthy to note on the other extreme of operations vs. catastrophic failures is with an incorrectly set up coordination of devices (or defective devices) that can take an entire plant or office building offline through a nuisance trip caused by a relatively small electrical fault sourced from somewhere in the facility. This condition generally does not translate into a personal safety issue per se, but it does potentially present an unnecessary and costly interruption of building operations nonetheless!
Contact the Smith & Long Engineering Services Group to answer your questions and to bring your facility into Short-Circuit Study and Protection Coordination Study compliance. It is important to note that while it is generally understood that these studies need to be performed when an electrical distribution system is initially designed, this is often mistakenly the last time they are performed. These studies should be routinely updated when alterations take place such as with the addition of electrical distribution systems, new equipment or due to LDC infrastructure upgrades.