The Electrical Distribution System

Summary

This educational video script offers an in-depth virtual tour of an electrical distribution system in a building. It starts with the utility company supplying high voltage, which is stepped down by transformers to meet various electrical demands. The script explains the function of components like oil transformers, switchgear, bus ducts, and motor control centers. It also touches on emergency power systems with automatic transfer switches and battery banks, ensuring uninterrupted power supply in critical facilities.

Takeaways

• 🏢 The electrical distribution system is crucial for delivering power throughout a building, starting from the utility company's supply.
• ⚡ Transformers play a key role in stepping down high voltages from the utility to safer, usable levels within buildings.
• 🔌 Oil-filled transformers are used for stepping down voltages and are typically located outside due to fire risk.
• 🛠 Switchgear is the starting point of the electrical distribution system inside a facility, containing switches and breakers for managing power flow.
• 🔵 The function of a bus bar is to distribute voltage within the switchgear, similar to how wires in conduit distribute power.
• 🔄 Draw out breakers in switchgear allow for easy maintenance and are designed for specific circuit amp ratings.
• 🏗 Bus ducts are used for larger amp ratings and contain bus bars within a metal enclosure, facilitating power distribution.
• 🏥 Automatic transfer switches ensure continuity of power by switching to an emergency generator in case of utility power interruptions.
• 🔋 Battery banks provide temporary power in critical facilities until the generator supplies the correct voltage after a power failure.
• 🔧 Motor control centers (MCCs) distribute power to electric motors used in various machinery and equipment within a facility.
• 💻 Power distribution units (PDUs) in data centers and computer rooms provide clean power to computer servers and network equipment.

Q & A

What is the purpose of the electrical distribution system described in the script?

The electrical distribution system described in the script is designed to distribute electrical power throughout a building by stepping down voltage from the utility company and distributing it to various components and systems within the facility.

What is the primary function of a transformer?

A transformer's primary function is to step down high voltage from the utility company to a lower, safer voltage suitable for use within a building.

Why are the incoming wires carrying 4,160 volts smaller than the wires carrying 480 volts?

The incoming wires carrying 4,160 volts are smaller than those carrying 480 volts because, as voltage is lowered, the amperage increases, which generates more heat and requires larger wires to handle the higher current.

What role does the oil in an oil transformer play?

The oil in an oil transformer is used for cooling the core. It is filled with non-conductive oil, typically mineral oil, which helps dissipate heat through the conduction process.

Why are oil transformers often located outside the facility?

Oil transformers are often located outside the facility due to the high fire risk they pose. They are placed on a concrete pad to help contain any potential fire.

What is switchgear and where is it typically located?

Switchgear is the beginning of the electrical distribution system inside a facility. It is typically located in an electrical room and is made up of several sections containing switches and/or breakers.

What is the purpose of a draw-out breaker in switchgear?

A draw-out breaker in switchgear is a large disconnect switch with a designated amp rating for a specific circuit. It allows for easy removal for maintenance and repair.

What is the difference between a distribution switchboard, a distribution panel, and a branch circuit breaker panel?

The difference between a distribution switchboard, a distribution panel, and a branch circuit breaker panel lies in their amperage ratings. A distribution switchboard has an amp rating between 1,201 and 1,999, a distribution panel has a rating of 401 to 1,200, and a branch circuit breaker panel has a rating equal to or less than 400 amps.

How does a dry transformer differ from an oil transformer?

A dry transformer differs from an oil transformer in that it uses air for cooling instead of oil. It is generally used to step down 600 volts or less.

What is the role of an automatic transfer switch in an electrical distribution system?

An automatic transfer switch monitors the incoming power from the utility. If there is an interruption, it sends a signal to start an emergency generator and switches over to emergency power once the generator reaches the desired voltage level.

What is the purpose of a battery bank in an electrical distribution system?

A battery bank in an electrical distribution system provides power until the generator is able to supply the correct voltage in case of a power interruption, ensuring uninterrupted power supply in critical facilities like data centers and hospitals.