Electrical substations bring efficiency, redundancy, and safety to our electrical systems for power delivery. There are different types of substation design, but they all help connect individual components or systems within the electrical grid.
Distribution substations, for example, use a transformer to step down the voltage from transmission lines so energy can flow through lower-voltage distribution lines. Collector substations take energy from wind farms, hydroelectric power plants or other renewable energy sources and step up the voltage to enable energy to flow through transmission lines. Switching substations make it possible to connect and disconnect transmission lines for planned and unplanned outages. These substations help keep service running during storms, preventative maintenance and new line construction.
Electrical Substation Equipment
Although substation design engineers create substations with a specific purpose in mind, many different types of substations overlap in their functionality and equipment. A transformer is a common piece of equipment found within a substation. Step-up transformers are used for increasing alternating voltages at low currents. Step-down transformers are used for decreasing the alternating voltages at high currents.
Substations are also generally equipped with switching, protection and control equipment. Large transformers house circuit breakers that are used to manage short circuits and overload currents. Capacitors, voltage regulators and reactors are also frequently included in power substation design.
Electrical Substation Safety
The grounding system is one of the most important power substation design features. Grounding systems help ensure the safety of anyone who may come near an electrical substation. In the event of a fault, electrical currents can be discharged into the ground. The earth does not conduct electricity, so the ground within the substation and the surrounding area is generally safe to walk on during a fault. However, conductive materials that come into contact with the ground can become electrified. Metal fences can create a significant safety threat if not included in the grounding system.
To prevent such hazards, a substation design engineer can calculate the total ground potential rise during a short circuit in the transmission system. “Touch and step potentials” as they are commonly called, are the gradient potential ground rise during a short circuit. Calculating the touch and step potentials is part of the substation design engineering process. Hazards are carefully identified and appropriately grounded to protect both utility workers and the public.
Electrical Substation Design Standards
There are numerous laws, rules, and codes that govern electrical substation design. The most important code comes from the Institute of Electrical and Electronics Engineers (IEEE). National Electrical Safety Code Standard C2-2012 creates basic provisions for the safe construction, operation and maintenance of electrical substations.
Design Concepts for Electrical Substation Safety
Electrical Safety Code Standards create hard and fast rules for electrical substation design. Within the confines of the code, substation design engineers have some leeway to improve safety through their design. A well-designed substation can reduce or minimize hazards by creating a safe environment for utility workers and the public.
Power Substation Design Clearance
Energized parts should be designed with enough clearance to reduce the risk of accidental contact. If the desired clearance cannot be achieved, live parts should be enclosed with a protective barrier.
Minimum Height in Electrical Substation Design
Ungrounded parts and other substation elements should be at least 6-8 feet from the ground. This is to ensure that a person standing on the ground cannot touch a substation element that has the potential to become energized. For example, a post insulator supporting an energized bus should have at minimum 6 feet of clearance, measuring from the bottom of the insulator. Touching the bottom of the insulator could become unsafe if the bus flashover to the ground over the insulator occurs. Giving clearance for both the bus and insulator reduces this risk.
Illumination in Electrical Substation Design
Carefully thought out illumination and lighting can help create a safe work environment. Personnel should be able to clearly see the equipment and surroundings to perform their work safely. Emergency or backup lighting sources would also improve safety.
Electrical Substation Passageway Design
All passageways, stairs, and catwalks should be wide enough for utility workers to navigate safely. Railing and handrails should be included where appropriate. Stairs should have non-slip treads as well as uniform stair height and depth. Stairs that face exposure to the elements should be designed to reduce the risk of falls from rain, snow, or ice.
Electrical Substation Exit & Evacuation Route Design
Exits should be clearly marked and free from obstructions. Where appropriate, multiple exits or escape routes should be designed to prevent personnel from being trapped in the event of a fire or other catastrophic event. Escape routes should be clearly marked. Personnel assigned to work at the substation should be educated on fire suppression safety features and/or equipment, evacuation routes, and practice drills routinely. Evacuation routes should also be pointed out to any electrical substation visitors.
Location, Aesthetic Design & Fencing Design
Although the selection of the location of a substation is largely determined by the proximity of the connecting structures and distribution area, some design decisions can be made by the substation design engineer to improve safety. In coastal areas, equipment may need to be elevated in areas prone to surges or flooding. Environmental influences such as drainage, noise, and road traffic must be taken into consideration.
In urban areas, substations are often disguised as homes or other buildings. Often this is done for aesthetic reasons, but it can have added benefits. Cleverly designed facades can reduce curiosity from the passing public. This can help keep the area secure, protecting intruders from the risk of injury and the equipment from vandalism or damage.
Fencing is also important for substations located on open land. Metallic fencing must be grounded. Fence design should aim to keep out people and animals. Gates should have sturdy locking mechanisms.
Substation design engineers have many considerations during the substation design process. They must create a structure that is cost-effective and reliable. But most importantly, they must build a substation that is safe. Engineers must juggle electrical substation design standards, performance requirements, and many of the design concepts we’ve laid out here. A quality design will exceed these constraints and make substation design a wise investment of time and resources.
Power Delivery Solutions from Matrix NAC
At Matrix NAC, we are known for our expertise in power delivery. Our long-standing partnerships with both public and private utility companies help us provide powerful solutions across North America. Matrix NAC is considered an industry leader in substations, power, and industrial electrical work. Guided by our core values, we are committed to safety, quality, and stewardship. Start a conversation with one of our experts today, and see why we are considered the contractor of choice to so many of our clients.