Commercial Power System

Commercial Power System

Commercial Power System

Commercial Power System includes all the equipment used to supply backup power for commercial facilities. This system also provides redundancy to prevent significant losses resulting from power quality problems.

Once electricity leaves the substation, it moves through a transformer to adjust it for building use. It then travels through wires to an electric closet in the facility, typically located in a basement or utility room.

How It Works

Electric power systems differ widely, both in terms of their design and how they operate. This section gives an overview of some key components that are common to most power systems.

Power plants produce electricity in three-phase alternating current (AC), which transfers far more efficiently over long distances than direct current (DC). From there, it moves to the local distribution system via high-voltage wires, with regulator banks along the way to prevent both overvoltage and undervoltage conditions.

Once it gets to a small town or suburban area, the voltage must be “stepped down” so that the fuses in homes and businesses can handle it. This is normally done in a substation, as shown here. The wires leading away from the substation are usually labelled as “live” and “neutral”. The live wire is passed through the main isolating switch in a fuse box, then split to feed different circuits. Fuse boxes are now typically replaced with miniature circuit breakers which can be reset by occupants, and which can respond much more quickly to certain types of fault.

Depending on the type of commercial equipment and building regulations, there may be a requirement for a backup power system to keep vital services running in the event Commercial Power System of an outage. These systems are available as either rotary or static units.


For large buildings, incoming high voltage electricity will pass through a meter and then be transmitted to transformers that feed power safely and efficiently into the building’s different electrical closets serving zones or floors of the facility. The electrical closets will contain a variety of linear and nonlinear equipment in varying power ratings. Nonlinear equipment creates harmonics on the power lines, which can degrade equipment performance and cause voltage fluctuations in the system. Performing a power quality survey can help identify the problem areas and target mitigation techniques.

The electric current passes through a transformer that increases the voltage for transmission and distribution, then through switchgear to be distributed throughout the facility. Depending on the load demand, the switchgear may be equipped with various types of circuit breakers, including fused or unfused switches, differential trip devices and automated transfer switches.

Back up power is vital for commercial facilities, not only to maintain productivity but to meet regulatory and safety requirements. Whether you need a legally required emergency backup system or simply an onsite generator, our team will design an optimum solution. Ideally, the back up power system should be designed with redundancy to ensure that your critical systems will stay functional during a power loss. Performing a load study helps to determine which systems should get top priority and ensure that the equipment is sized correctly.


A commercial power system utilizes transformers to raise or lower voltage levels. These electrical regulators work with AC (alternating current) and are able to step the voltage up or down without changing the frequency. The core of a transformer is constructed from laminations of thin metal sheets to minimize the path for eddy current that would otherwise disrupt the magnetic field. The windings are insulated from the core, and from each other. The insulation must be durable and withstand high temperatures.

Pole-mounted or pad-mounted transformers convert the high ‘primary distribution’ or ‘utilization’ voltage from the overhead or underground lines to the lower’secondary distribution’ voltage Commercial Power System inside the building. They may be single-phase or three-phase units. They are connected to the main distribution line by means of three ‘hot’ wires or, in the case of single-phase units, a single ‘hot’ and a neutral.

The secondary distribution of the power within a building can be as simple or complex as needed, depending on the use of the facility. For example, a power closet can have another transformer that drops the 480 volts to the 120 volts required for lighting and convenience outlets. These transformers are often dry-type with a NEMA 2 enclosure.

Larger buildings or sites with multiple tenants often have a shared power infrastructure that allows different customers to share the same transformer and power supply. When this is the case, harmonics generated by one customer can affect other tenants. This requires careful consideration when sizing the transformers for these larger systems, as overly large units can degrade equipment and produce additional losses over time.

Circuit Breakers

Electrical circuit breakers are a critical safety mechanism used to protect commercial power systems against overloads and short circuits. These devices interrupt current by opening and closing the power circuit. During normal operation, a CB opens to interrupt an overcurrent while closing to stop the flow of electricity when a fault occurs.

While the details of how a medium voltage circuit breaker works vary depending on its amperage, voltage class and application, there are several things that remain consistent across all types of CBs. These include the presence of contactors, arc extinguishers and the trip unit. The contacts, which allow current to pass through when the breaker is closed, are located within an arc interruption chamber. In air-insulated and miniature circuit breakers, this chamber is filled with mineral oil, while in SF6 high voltage ones it’s filled with sulfur hexafluoride gas.

When a fault occurs, a signal is sent to the trip unit, which then releases the latch and opens the operating mechanism to interrupt the current. The time delay between this signal and the actual breaking of the arc depends on the size of the load and the sensitivity of the trip unit.

Unlike fuses, which must be replaced when they heat up, modern smart electrical circuit breakers can often be reset or reactivated. Some of them can also be integrated into a home, office or industrial power automation system, which can help you better manage your energy usage.

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