In the design of power distribution systems, there is ambiguity regarding the use of switchgear vs switchboard vs panelboard. The application of each of them requires the deployment of a common node to supply power for onward distribution to other parts of a facility, while offering protection to the circuits downstream.
Despite these similarities, each of them has unique characteristics that make one more suitable for an application than others. In this article, we review the attributes of switchgear, switchboards, and panelboard, as well as compare them vs. each other.
Switchgear
As per Article 48 of NEC, switchgear is an assembly completely enclosed on all sides and top with sheet metal (except for ventilating openings and inspection windows) and containing primary power circuit switching, interrupting devices, or both, with buses and connections.
Typically, doors, removable covers, or a combination of both, provide access to the interior of the assembly. In comparison to switchboards and panelboards, switchgear has a larger capacity – with a voltage rating of up to 38 kV and a current rating of up to 6,000A. Generally, their design follows ANSI C37.20.1, UL 1558, and NEMA SG-5.
Components of a Switchgear
The components of switchgear are set up to deliver automatic safety and can be classified into three categories.
- Power Switch Components: These include components that break the power in a circuit such as fuses, circuit breakers, insulators, etc.
- Power Control Components: These are components that control power like transformers and control panels.
- Draw-out Breakers: The use of draw-out breakers makes switchgear effective in isolating various parts of the power distribution system. As a result, only select sections can be shut down for maintenance.
Types of Switchgear
Different types of switchgear provide different functionality, depending on voltage and enclosure requirements.
- Metal-clad Switchgear: This is one of the most popular types where all electrical components involving incoming bus, outgoing bus, metering equipment, and main circuit breaker are contained in separate metal partitions. Thereby providing additional security, strength, and comfort for maintenance. In the industry, they are the go-to option for medium voltage (1 to 75 kV AC) applications.
- Metal-enclosed Switchgear: On the outside, this type of switchgear appears to be the same as the metal-clad because they both have metal enclosures. But, the devices on metal-enclosed switchgear are not compartmentalized. They are ideal for systems with smaller loads and lower fault currents.
- Pad-mounted Switchgear: These are suitable for outdoor and underground applications due to its low profile and sturdy construction. Usually, it serves ratings between 5 to 38 kV.
- Vault/Subsurface Switchgear: This type of switchgear is ideal for systems rated 15 to 38 kV that require the switch and accessories be operable from inside a vault or below-grade location. These locations could be dry or subject to water ingress. Also, this system can allow the user to operate the switch from above ground manually, or by using relays. In addition, it uses vacuum interrupters for load protection and fault isolation.
Switchboard
A switchboard is an assembly of components that reroute electricity from one or more sources to several smaller regions of usage. Because it is an assembly, it is easily modified and usually has overcurrent protection. Voltages handled by switchboard systems are 600 V or less, with currents of 1,600 A or higher. Thus, operates at power levels less than switchgear. Switchboards adhere to NEMA PB-2 and UL 891, and are accessible from the front and the rear.
Components of a Switchboard
A switchboard is a single vertical structure that contains:
- Panels or Frames: These metal frames hold equipment such as indicators, switches, and other power-delivering and controlling devices.
- Monitoring and Control Devices: These include frequency gauges and synchroscopes that can control devices through multiple power sources.
- Bus bars: These receive power and distribute it to multiple circuits.
Types of Switchboard
Various types of switchboards in the industry include:
- General Purpose Switchboards: These are switchboards that consist of surge protection, fused switches, molded case circuit breakers, and insulated case circuit breakers. They can serve in a wide variety of applications.
- Draw-out Molded Case Switchboards: These are similar to the general-purpose switchboards but can supply a draw-out function for feeder breakers. Thus, making them ideal for crucial applications where system interruption during maintenance is not desirable, like in data centers and healthcare.
- Fusible Switchboards: These serve in commercial and industrial applications to safeguard and switch feeder and branch circuits. On these switchboards, each panelboard forms a switching contact arrangement with an immediate trip element.
- Commercial Metering Switchboards: This type of switchboard offers a blend of circuit breakers, surge protection, and meter sockets in an enclosure. Typically, the metering is either of bulb-type watt-hour or electronic tenant, depending on the demands of the utility.
Panelboard
The NEC defines a panelboard as: “A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front”.
They are ideal for residential, commercial, and small industrial facilities operating between 120 and 600V or higher, depending on the location. Also, they can be designed to accommodate single-phase or three-phase power. Components on a panelboard include the main breaker, respective circuit breakers, and bus bars. Various types of panelboards include:
- Lighting panelboards
- Power/Distribution panelboards
Difference Between Switchgear vs Switchboard vs Panelboard
Although they all play similar roles in electrical distribution systems, there are several differences between a switchgear vs switchboard vs panelboard.
Criteria | Switchgears | Switchboards | Panelboards |
Voltage | Effective in low, middle, and high voltage applications ranging from 1 to 350 kV AC. | Generally serve in systems of 600 V or less. | Ideal for systems of 600 V or less, with lower amperage than both switchboard and switchgear. |
Safety Features | Equipped with automatic safety features with manual operation as an option during emergencies. | Do not have automatic safety components, but display the amount of power going to each circuit. | Have neither automatic safety components nor display components. |
Accessibility | Most types provide access only from the front, but some versions also have rear access. | Devices are mounted and access is provided at both the front and the rear. | Provides access for maintenance only from the front. |
Applications | Typically for large commercial and industrial facilities. | Also serves for commercial and industrial facilities, but at a smaller scale. | Ideal for residential and small-scale commercial facilities. |
Short Circuit Resistance | Its compartmentalized configuration of breakers enables it to withstand a short circuit condition for up to 30 cycles. | Less robust, so able to withstand short circuit conditions for up to 3 cycles. | Similarly, can withstand short circuit conditions for up to 3 cycles. |
Cost | The most expensive of the lot, largely because of its capacity and customized design. | Less expensive than switchgear but more expensive than panelboard. | Mass produced, so it is less expensive. |