Electrical system insights

• Switchgear, transformers and uninterruptible power supplies (UPS) are key components of electrical infrastructure, each fulfilling a distinct role to ensure reliable and safe power distribution across various sectors, from commercial and industrial to residential and health care.
• Switchgear controls and protects electrical flow, transformers manage voltage levels and UPS systems provide emergency backup power during outages, collectively forming the backbone of modern electrical systems.

In the field of electrical engineering and electrical infrastructure, the seamless operation of critical electrical systems relies heavily on the integration of robust components such as switchgear, transformers and uninterruptible power supplies (UPS). These indispensable elements play crucial roles in ensuring the reliability, efficiency and safety of electrical systems across various sectors, including mission critical, industrial, commercial and residential facilities.

Electrical switchgear performs as the foundation of electrical distribution, facilitating the control and protection of power flow, while transformers provide voltage transitions and distribution, bridging the gap between different voltage levels. Complementing these components, UPS provide vital backup power during outages or fluctuations, safeguarding against downtime and data loss.

Together, these vital pieces of electrical equipment form the backbone of modern electrical infrastructure, underpinning the functionality and resilience of critical operations in an ever-evolving technological landscape.

Switchgear in electrical systems

Electrical switchgear is the foundation of electrical distribution within commercial facilities. Switchgear is composed of electrical devices, such as circuit breakers, switches, fuses, relays and protective equipment, used to control, protect and isolate electrical equipment and circuits in power distribution and transmission systems. Switchgear plays a critical role in ensuring the safe, reliable and efficient operation of electrical networks by allowing operators to control the flow of electricity, protect against overloads and faults and isolate faulty equipment.

The construction of electrical switchgear involves several key components and processes to create a reliable and efficient system for controlling and protecting electrical power distribution. The main components of switchgear construction can give us a better understanding of their role in electrical distribution. Switchgear is typically housed in an enclosure or cabinet, which protects the internal components from environmental factors such as dust, moisture and physical damage.

Switchgear enclosure ratings include but are not limited to National Electrical Manufacturers Association (NEMA) 1, 3, 3R and 3Xall offering various types of protection including protection from rain, snow, dirt, dust water and so on. These enclosures may be made of metal, such as steel or aluminum or nonmetallic materials including but not limited to acrylonitrile butadiene styrene or polyvinyl chloride plastic or fiberglass.

Inside the switchgear are busbars. Busbars are conductive bars or strips made of copper or aluminum that carry electrical current within the switchgear assembly. These can be both horizontally mounted and vertically mounted within the board. Horizonal busbars connect the vertical sections of the switchgear together where vertical busbars distribute electricity to the branch circuits within a single vertical section. Depending on the number of feeder breakers within the switchgear these may come in multiple vertical sections.

Figure 1: An example of an electrical switchgear and its construction. These enclosures come in various ratings, such as NEMA 3R. The enclosure rating depends on where the switchgear is located. The left vertical shows the incoming power section with the main breaker to de-energize the downstream circuits for maintenance purposes. The right vertical illustrates the downstream branch circuits being served by the switch gear, which can include but is not limited to transformers, branch panels equipment, etc. Courtesy: Certus

The busbars inside the gear will be bolted together for electrical continuity. They provide a low-resistance path for electricity to flow between the various components of the switchgear, such as circuit breakers or fused switches, otherwise referred to as the overcurrent protective devices (OCPD). OCPDs are automatic switches that are responsible for interrupting the flow of electrical current in a circuit when abnormal conditions occur, such as overloads or short circuits. They are a critical component of switchgear, providing protection for electrical equipment and wiring from damage caused by excessive currents.

Protective relays are devices that monitor electrical parameters, such as voltage, current and frequency and initiate protective functions in response to abnormal conditions. They can be used to trip circuit breakers, control the operation of switches or initiate alarm signals when predetermined thresholds are exceeded.

Control panels are integrated into switchgear assemblies to provide a centralized location for monitoring and controlling electrical systems. They may include instruments, meters and control devices for monitoring electrical parameters, as well as annunciators and alarms for indicating system status and alarms.

Wiring and connections within switchgear assemblies must be carefully installed and maintained to ensure proper operation and reliability. Wiring methods and practices must comply with applicable NFPA 70: National Electrical Code (NEC) codes and standards to prevent electrical hazards and ensure safe operation. Safety features such as interlocks, barriers and warning labels are incorporated into switchgear assemblies to protect personnel and offer maximum maintenance safety. These features help prevent accidental contact with live parts and provide a clear indication of hazardous conditions.

For commercial projects, switchgear is the backbone of a facility and designers must have a firm understanding of national and local codes to provide safe and effective designs. Designers must abide by NEC and any local code amendments and adhere to best design practices to produce a design that emphasizes safety and minimizes hazards.

NEC Article 100 provides definitions for various terms used throughout the NEC, including definitions related to switchgear, but not limited to switchgear assembly and switchgear compartments. NEC Article 110 covers general requirements for electrical installations. This article addresses aspects such as installation and use of electrical equipment, working space requirements and access for maintenance.

NEC Article 240 provides requirements for overcurrent protection devices, such as fuses and circuit breakers, which are commonly used in switchgear assemblies to protect electrical circuits and equipment from overcurrents. NEC Article 250 covers requirements for grounding and bonding of electrical systems, including switchgear installations. This article addresses aspects such as grounding electrode systems, equipment bonding and grounding of metal enclosures to ensure electrical safety and system reliability.

NEC Article 408 provides requirements for switchboards and panelboards, which are types of switchgear assemblies used to control and distribute electrical power within buildings and facilities. This article covers aspects such as construction, installation, wiring methods and access for maintenance. NEC section 517.17 covers provisions for additional ground fault protection on switchgear serving patient care areas, which include general care areas, critical care areas as well as wet procedure locations.

Electrical transformers

A transformer is an electrical device that is used to reduce or increase voltage through electromagnetic induction. It consists of two or more coils of insulated wire wound around a magnetic core, generally made of laminated iron or steel. Transformers play a crucial role in electrical power distribution and transmission systems by changing the voltage levels of alternating current electricity while maintaining the frequency. This allows designers to provide branch circuits for important electrical components such as receptacle branch circuits, lighting branch circuits, motor branch circuits, branch circuits for control circuits, as well as branch circuits serving pieces of equipment.

Figure 2: Visual representation of busbars within electrical switchgear. The busbars run horizontally from each switchgear section and are bolted together to maintain continuity between each section. The alternating current is carried across the busbars, which supply current to the downstream branch circuits. Typically, these busbars are made from materials such as copper and aluminum. Courtesy: Certus

Transformers are composed of various major components that make up their overall construction. Taking a deeper dive into the major components can help better understand their role in electrical distribution systems as well as a further in-depth conceptual understanding.

The first major component is the primary coil. The primary coil is also known as the input winding. The input winding is connected from the source of electrical energy such as a branch panel, distribution board, switchgear, etc. When the alternating current flows through the primary coil of the transformer it creates a change in magnetic flux within the transformer’s magnetic core. The magnetic core then provides a path for the magnetic flux generated by the current flowing through the primary coil. The transformer’s magnetic core is generally composed of laminated iron or steel to minimize energy losses due to eddy currents and hysteresis.

The next major component is the secondary coil. The changing magnetic flux created by the primary coil in the magnetic core generates a voltage in the secondary coil, also known as the output winding. The induced voltage in the secondary coil depends on the turn ratio between the primary and secondary windings. The turn ratio between the primary and secondary windings determines the voltage transformation ratio of the transformer.

A step-up transformer increases the voltage level from the primary to the secondary coil, while a step-down transformer decreases the voltage level. This voltage transformation enables efficient power transmission and distribution across different voltage levels.

During the design phase of a project, designers partake in multiple considerations for the an economical and code-compliant electrical room design. Particularly for transformers, designers may take the approach of suspending the equipment to the structure of the building, pad mounting or stacking them within the room while keeping NEC in mind for each instance. A better understanding of NEC that apply to transformers helps build a concrete understanding for proper and safe electrical design.

Taking code-compliant design into consideration is paramount for electrical safety and maintenance. NEC Article 240 discusses requirements for overcurrent protection devices, such as fuses and circuit breakers, which are used to protect electrical transformers and associated wiring from excessive currents. It specifies the sizing, location and installation of overcurrent protection devices for transformers.

NEC Article 110 includes requirements for equipment clearances which is key to proper room design. NEC Article 450 provides detailed requirements for the installation, wiring and protection of transformers, including their location, ventilation and clearances. It covers various types of transformers, such as dry-type, liquid-filled and autotransformers and addresses specific installation considerations for transformer vaults and enclosures.

When dealing with the design of a health care facility, NEC Article 517 goes in-depth on the additional requirements needed to meet health care standards. For transformers installed in health care facilities, Article 517 provides provisions related to patient safety, electrical grounding and emergency power systems. It addresses the installation of transformers in patient care areas, critical care spaces and medical equipment rooms.

Article 700 delves into emergency systems. Article 700 can be applied to any mission critical facility such as health care facilities, data centers, commercial facilities, etc. Article 700 provides the foundation for emergency power systems, including generators, transfer switches and batteries, which may be connected to electrical transformers to provide backup power during outages. This article specifies the installation and operation of emergency power systems to ensure their reliability and functionality during emergencies.

Next is Article 450, Section 450.9, which involves transformer ventilation. This section provides requirements for the ventilation of transformer vaults and enclosures to prevent the accumulation of heat and gases generated during transformer operation. It specifies minimum ventilation requirements based on the transformer’s kilovolt-ampere rating and the type of cooling system used.

Lastly, NEC Article 110 lays the groundwork for general requirements for electrical installations. Article 110 addresses aspects such as wiring methods and equipment labeling to ensure the safety and reliability of electrical systems.

What is a UPS?

A UPS is a piece of electrical equipment that provides emergency backup power to connected equipment in the event of a power outage or disturbance. UPS systems are commonly used to protect electronic equipment, such as computers, servers, networking devices, telecommunications equipment and critical industrial processes, from power interruptions, voltage fluctuations and electrical disturbances.

A UPS works by converting incoming alternating current (ac) power from the main supply into direct current (dc) power, storing it in a battery and then converting it back to ac power when needed to power connected devices.

The construction of a UPS involves integrating several essential components to ensure a reliable backup power supply during normal power outages or disturbances. An UPS comprises a rectifier or charger responsible for converting alternating current from the main supply into direct current to charge a battery bank. This battery bank serves as the primary energy storage unit, storing electrical energy to be used during power interruptions.

Figure 3: Completed electrophysiology lab in Dallas showing the final construction such as the light fixtures, lab equipment, light booms, monitor arms, etc. Courtesy: Certus

An inverter then converts the stored dc power back into ac power to supply connected equipment. The system also includes a static bypass switch for seamless power transfer in case of UPS maintenance or if the system incurs a failure, as well as a transfer switch to manage transitions between power sources.

A monitoring and control system oversees UPS operation, continuously monitoring parameters such as voltage input, voltage output and battery status, ensuring optimal performance. The components of a UPS are carefully engineered to guarantee uninterruptible power supply for various critical applications, including data centers, health care facilities and telecommunications infrastructure.

Each component of a UPS has a different role:

Battery bank: The internal batteries store the electrical energy in the form of dc. Batteries are typically sized based on how long the UPS can provide backup power during a normal power outage. Battery technology can be several different types including valve-regulated lead-acid, lithium ion and nickel zinc. The size of the battery cabinet is largely dependent on how long the required run time is desired.

Inverter: The inverter converts the stored dc power to ac power.

Monitoring and control system: The monitoring system and control system oversees the entire operation of the UPS components. This constantly monitors input voltage, output voltage and the battery status. If a utility outage occurs, the transfer switch will switch from utility power to battery backup power.

Rectifier and charger: The rectifier and charger take incoming ac power and converts it into dc power.

Static bypass switch: This provides a path for normal power to bypass the UPS system and supply electricity directly to the equipment it is serving.

Transfer switch: The transfer switch switches power from normal power to UPS power.

Employing practical electrical design

Some practical uses of a UPS system in a facility include:

• Hospitals, clinics and health care facilities to provide backup power for medical equipment, patient care systems and critical life support systems. They help maintain patient safety and ensure continuity of care in the case of power disruptions.

• Telecommunications infrastructure relies on UPS systems to maintain uninterruptible power for communication equipment, including telecommunication rooms, switching centers and data transmission facilities. UPS systems help prevent service interruptions and downtime in telecommunications networks.

• Police stations, fire departments and emergency response centers rely on UPS systems to ensure continuous power supply for communication systems, dispatching equipment and emergency response coordination. UPS systems support critical operations during emergencies and natural disasters.

• Industrial facilities incorporate UPS systems to provide backup power for control systems, process automation equipment and manufacturing machinery. They help prevent production disruptions and equipment damage caused by power fluctuations or outages.

• Banks, stock exchanges and other financial institutions use UPS systems to safeguard critical electronic transactions, data processing systems and communication networks. UPS systems ensure continuous operation and data integrity in financial services environments.

• UPS systems are essential in data centers to provide backup power for servers, networking equipment and other critical information technology infrastructure. They ensure uninterrupted operation and prevent data loss or corruption during power outages.

UPSs play a crucial role in numerous applications, necessitating adherence to several NEC articles to ensure their safe and compliant installation. NEC Article 645 outlines the use of UPS systems in information technology equipment settings, while Article 517 provides guidelines for UPS installation in health care facilities, ensuring patient safety and system reliability.

Additionally, UPS systems integrated into emergency power systems fall under the guidelines of Article 700, ensuring their proper operation during power outages. Legally required standby power systems, which may include UPS components, are subject to regulations outlined in Article 701, ensuring the reliability of systems crucial for safety or security.

Moreover, Article 708 addresses the installation of critical operations power systems, including UPS systems, in facilities requiring continuous and reliable power supply. Compliance with these NEC articles ensures the safe and effective deployment of UPS systems across various industries and applications.

UPS, switchgear and transformers are indispensable components in modern electrical distribution systems, each playing a vital role in ensuring the reliability, safety and efficiency of power supply. UPS systems provide critical backup power, safeguarding against disruptions and protecting sensitive equipment in the event of outages or disturbances.

Switchgear acts as the heart of electrical distribution, enabling precise control, protection and isolation of electrical circuits, ensuring smooth and reliable power distribution. Transformers facilitate voltage transformation, optimizing power transmission and distribution while minimizing energy losses.

Together, these components form a robust infrastructure that underpins the functioning of various industries, critical facilities and infrastructure networks, ensuring uninterrupted power supply and supporting the seamless operation of modern society.

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