top of page

Low Voltage Switchgear: An Introduction

What is Low Voltage Switchgear?

Low voltage switchgear is a critical safety feature in electrical distribution systems, with “low voltage” denoting a rating below 1000V and a current below 6000 amps. This type of switchgear is commonly used for equipment such as pumps, motors, compressors, and lighting. Low voltage switchgear serves several safety and protective purposes within an electrical system, including:


  • Electrical Protection: A core function of low voltage switchgear is to protect against the thermal and mechanical stresses of short circuits. By separating defective, excess currents from the rest of the system, the switchgear protects human operators from electric shock and machine components, like electric motors, from damage.

  • Isolation of Circuits and Equipment: During maintenance or repairs, it is vital to isolate certain circuits and de-energize equipment. This is done using switchgear.

  • Equipment Control: Low voltage switchgear allows operators to control equipment for functional purposes and in emergencies.


At its most basic level, low-voltage switchgear interrupts and isolates a faulty, excessive current whenever the relay detects it. At the same time, it switches the load to still functioning circuits or backup power, ensuring a continuous power supply.


Low voltage switchgear on a pallet

What Components are Used in Low Voltage Switchgear?


Low voltage switchgear is usually designed around three segregated sections:


  • Breaker compartment: Up to four power circuit breakers are contained within each of these compartments, each separate from the others.

  • Bus compartment: This is segregated from the breaker compartment by solid barriers and from other bus compartments by insulated barriers.

  • Cable compartment: Situated at the rear of the switchgear section, it has hinged doors and removable covers, allowing operators or maintenance crews to access landing lugs to terminate line and load cables. 

Several different components are used in low voltage switchgear, which may vary depending on the needs of your electrical distribution or downstream equipment. Different electrical codes or regulations, such as the NEC/NFPA 70 or UL 891, outline the different rated requirements and testing procedures for low-voltage switchgear components.


These components include:


  • Circuit Breakers: Circuit breakers are the primary protection mechanism in low voltage switchgear. They interrupt the current by creating a gap in the circuit, such as an air, vacuum, SF, or oil gap. The function is achieved through an electronic, hydraulic, or thermal-magnetic mechanism. In low voltage switchgear, these will commonly be miniature circuit breakers (MCB) and molded-case circuit breakers (MCCB).

  • Protective Relays: The relays sense the short circuit or current overload and trigger the circuit breaker mechanism.

  • Disconnect Switches: Also known as isolators, these are manually operated switches that shift current from one circuit to another to isolate and de-energize a particular circuit.

  • Fuses: Fuses are protective devices designed to burn out or melt when subjected to excessive current, thus protecting against sudden current overload.

  • Bus Bars: Bus bars are copper, brass, or aluminum bars that ground or conduct electricity, including between switchgear components and external connections.

  • Transformers: These step-down voltage within an electrical system.

  • Monitoring Components: These give operators or control rooms readouts on the conditions of the system and include volt meters, amp meters, and power factor meters.

  • Enclosure: Depending on requirements and conditions, low voltage switchgear can be housed in metal-clad, enclosed, or open-type enclosures. The enclosure protects the components from dust, moisture, grease, and physical damage.

Benefits of Low Voltage Switchgear


The main benefits of low voltage switchgear are in its protective function, resulting in:


  • Improved Safety: Arc flash and equipment electrification present significant risks to the health of employees in your facility. Switchgear reduces that risk and protects operators, diminishing the potential for work absences, stoppages, and litigation.

  • Reduced Equipment Downtime: Short circuits can damage equipment by burning out motors, monitoring equipment, or causing fire. This requires the shutdown of the machine for repairs, keeping it out of service and making it unproductive. The protective function of low voltage switchgear prevents this and ensures continuous operation by switching loads to an operational energy source.

  • Control: Even outside of sudden emergency responses, switchgear allows operators to manage circuits and loads. This allows quicker identification and responses to issues, as well as the safe powering down or isolation of equipment for maintenance or inspection.

There are additional benefits to low voltage switchgear due to additional components, such as:


  • Monitoring: Devices can deliver wide-ranging capabilities in terms of load and usage monitoring, demand tracking, and cost allocation.

  • Security features: Such as lockout-tagout, safety interlocks, and padlocking.

  • Thermal scanning: Infrared devices can detect thermal fluctuations in cables and components.

  • Safety features: Shutters can protect operators from contact with live conductors, while improved instrument panels inform them of conditions quicker.


low voltage switchgear

Conclusion


Low voltage switchgear serves a vital function in an electrical distribution system, particularly when serving equipment such as pumps, motors, and compressors. The switchgear is housed in an enclosure that protects it from environmental conditions. The low voltage switchgear detects abnormal conditions, such as short circuits, through a relay. It then isolates the circuit through a circuit breaker, often operating in tandem with fuses. This reduces the chance of downstream equipment damage or operator injury through equipment electrification, arc flash, or fire.


Operators can also use low voltage switchgear to purposefully power down equipment or isolate circuits for inspections and maintenance. Additional equipment and components can improve safety, allow better monitoring of conditions, and provide feedback on energy usage.


At Enercon, we have been designing, building, and installing low voltage switchgear for clients for decades. We can work to your unique specs or deliver general designs to supply you with switchgear that improves safety, reduces operator risk and equipment downtime, and meets regulatory requirements. To discuss your low voltage switchgear requirements, contact us here.

Related Posts

See All

Comments


bottom of page