All electrical systems & equipment require a power source (or sources) and distribute these sources to power downstream equipment, this is called power distribution. Electrical power distribution needs to be distributed in a safe and efficient manner. Electrical switchgear is an essential element of this distribution. Modern metal-clad switchgear has changed with new tech. But, many traits remain the same. The following is a summary of industry common applications and an attempt to explain what is included in the solutions. Switchgear is essentially a large metal box that houses items
like circuit breakers or fuses to protect the equipment it is distributing power to. Much like the circuit breaker box on the side of your house that send power safely into you home, the circuit break if it senses an issue it will trip before allowing electricity to continue to pass o that individual circuit. As a comparison the circuit breaker panel on the side of your house could be compared to a small car that can carry a few people, switchgear would be compared to a heavy duty large copper bus system that can carry dozens of people. Now lets dive a little deeper into Switchgear.
Components of Switchgear
As stated in the opening paragraph, Switchgear distributes power to smaller loads. The main power source could com various different sources. It has enough capacity to power the total need. A user of that power, often, is tasked with safely distributing this power once the service entrance from a utility is established. The most common way to make such a point is a metal enclosure, made in a factory. It includes at least the following:
Metal enclosure called a switchgear enclosure
Typical paint colors such as industry standard ANSI Gray paint. This also serves as a corrosion protectant.
Bus Bars to carry the power source
Non-metallic barriers and insulators to keep the bus bar away from the metal enclosure
Main breaker, Main Fused Disconnect, or Main non-fused disconnect
Protection devices such as breakers or fuses
Protection Relays these are common on low voltage switchgear but medium and high Voltage switchgear they are an requirement for each breaker.
Hardware there are specific types of fasteners and bolts used in switchgear systems that are teste and approved by the manufacture. Its important to note you cannot just use any standard hardware when making replacements
Control devices such as pilot lights for indication, switches or push buttons to control the protection devices to do various operations such as Open / or Close/
Switchgear often includes components. They allow unsupervised and automated protection from failures in the electrical distribution system.
Instrument transformers are electrical devices that sense power. They reduce voltage and current to safe levels. These levels are normally 120VAC and 5A. Relays and meters interpret these signals to show the state of the power.
Circuit protectors are extra power sensors. They may or may not work with the instrument transformers. Their job is to stop the electrical system from damage to its insulation. This damage can be from short-circuits (phase to phase) or phase to ground. Examples are circuit breakers, current interrupting fuses, and load-break switches (manual and electrically operated).
Protective relays interpret the power system operation. They often use the outputs of the instrument transformers. Based on those inputs, they send signals to alarm personnel or operate the circuit isolators. This isolates faults or overloads safely.
Metering – allows for monitoring the power system operation. Control power transformer(s) allow for efficient power delivery. They provide power to the devices for operating the switchgear.
Power transformers – unit substations, typically dry-type fan cooled. Using switchgear to hold many of these components has three benefits. It is efficient to make and install. It protects against outside factors that can harm electrical systems. And it guards people and property from the dangers of high voltage.
What do the terms and mean when referring to switchgear?
When you see a push button labeled “open” or “close” on the outside of switchgear or on the front of a breaker, it controls the contacts inside the breaker.
Pressing “open” disconnects the contacts, turning off or restricting the power flow through the breaker. Pressing “close” reconnects the contacts, allowing power to flow through the breaker to its downstream source. Think of this power flow like water running through a hose connected to a valve with push buttons: pressing “open” turns the valve, allowing water to flow, while pressing “close” shuts the valve, stopping the water flow.
As mentioned earlier, fuses can serve as protection devices, but they cannot be opened or closed like a breaker. If a fuse blows, it means the circuit is interrupted, and power will no longer flow through it. Fuses contain a strip of thin metal that melts or blows out when it reaches a certain temperature, stopping the power flow. To control a fuse in a piece of switchgear, a separate disconnect is needed in front of it. For low voltage, this would be a non-fused switch or knife switch to perform the open and close functions. For medium voltage, a load break switch or a larger equivalent is required, similar in function but scaled up.
Enclosure Integrity and Composition
Switchgear enclosures are designed with varying levels of protection against external contaminants, suitable for both indoor and outdoor applications. They must accommodate power conductors, as well as external communication or control circuit connections. Modular designs allow users to route these systems efficiently while maintaining enclosure integrity, optimizing cooling, and maximizing space. Switchgear enclosures can be connected to transformer enclosures or motor control centers (MCCs), including large motor control cabinets for variable speed drives or soft starters, and panel boards.
Exterior surfaces can be made from powder-coated steel, stainless steel, or aluminum. The structural strength of the enclosure depends on the thickness of the material and the fastening methods used for its supports and sheathing. Enclosure integrity provides inherent protection, which can be further enhanced with an arc-resistant design. This classification ensures that any internal arc flash is contained, preventing harm to personnel and equipment. High Voltage Switchgear Manufacturers
Electrical Rating: Voltage
Switchgear enclosures are designed with varying levels of protection against external contaminants, suitable for both indoor and outdoor applications. They must accommodate power conductors, as well as external communication or control circuit connections. Modular designs allow users to route these systems efficiently while maintaining enclosure integrity, optimizing cooling, and maximizing space. Switchgear enclosures can be connected to transformer enclosures or motor control centers (MCCs), including large motor control cabinets for variable speed drives or soft starters, and panel boards.
Exterior surfaces can be made from powder-coated steel, stainless steel, or aluminum. The structural strength of the enclosure depends on the thickness of the material and the fastening methods used for its supports and sheathing. Enclosure integrity provides inherent protection, which can be further enhanced with an arc-resistant design. This classification ensures that any internal arc flash is contained, preventing harm to personnel and equipment.