Topic 3: Electrical Systems in Buildings

Electrical System

Network of conductors and equipment designed to carry, distribute, and convert electrical power safely from the point of delivery or generation to the various loads around the building that consume the electrical energy

Earthing (or grounding) systems and bonding

Electric wiring

Industrial installations

Lighting controls

Light sources, Lamps, Lighting design

Telecommunication installations

Basics of Electricity Distribution

Lighting

Providing illumination both inside and outside of the buildings.

Exhaust fans

Providing ventilation both inside and outside of the buildings.

Lighting

Exhaust fans

Use of portable and non-portable electrical machines

Basics of electrical installations

100 kV

Transmission lines, transformers, substations, and other equipment have voltages ________ and above.

AC Distribution System

DC Distribution System

Types of Electric Power Distribution Systems

According to the nature of the supply

Overhead system

Underground system

Types of Electric Power Distribution Systems

According to a type of construction

Single-Phase Power Supply

The power is distributed using only two wires called Phase and neutral. Since AC Power takes the shape of a sinusoidal wave, the voltage peaks at 900 during the positive cycle and again at 2700 during the negative cycle.

Designed for household supplies and residential homes

Voltage is 230V and the frequency is 60Hz in the Philippines

Three-Phase Power Supply

Consists of three power wires (or the three phases). Additionally, depending on the type of the circuit (which there are two types: Star and Delta), and can be with 4th wire as neutral wire. Each AC Power Signal is 1200 out of phase with each other.

Three-phase electric power

Type of alternating current that is commonly used in power generation, transmission, and distribution. Thick wires on tall transmission towers carry high-voltage electricity from power plants to local communities.

Three-phase electric power

It is a type of polyphase system that uses three wires (or four if a neutral return wire is used) and is the most common method used by electrical grids around the world to transfer power.

Home Electrical Systems

Includes incoming power lines, an electric meter, a service panel, subpanels, household wiring, electrical boxes, receptacles (outlets), switches, and, of course, the appliances, lights, and equipment that put the power to work

Consistency

Protection

2 main functions of protection devices

Protective Device

A device used to protect equipment, machinery, components and devices, in electrical and electronic circuit, against short circuit, over current and earth fault

Fuse Wire or Fuse

MCB – Miniature circuit breaker

ELCB – Earth Leakage Circuit Breaker

ELCB & MCB

Earthing or Grounding

Ground-Fault Circuit Interrupter (GFCI)

Types of Protective Devices

Fuse

Device that protects electrical systems against potentially dangerous power surges and excessive temperatures

Cannot be reset, it must be replaced

Fuse Box

Metal box that contains screw-in fuses and cartridge fuses.

Cartridge fuses normally manufactured in the range of 2A. to 100A

Miniature Circuit Breaker (MCB)

An electrical switch used to guard a circuit against short circuits or overloads, which can be operated automatically or manually to restart normal operation.

Molded Case Circuit Breaker (MCCB)

An electrical protection device used when load currents exceed MCB limits (available from 100A up to 100 kA), providing overload and short-circuit protection for heavier domestic and industrial applications.

Residual Current Device

A safety device that notices a problem in your home power supply and then turns OFF in 10-15 milliseconds to stop electric shock.

High-sensitivity residual current devices

(up to 30 mA), which are used in kitchens, bathrooms, workshops, studios, etc. – where the risk of fire caused by a faulty installation or appliance is quite high

Medium-sensitivity residual current devices

(from 30 to 500 mA), which are ideal for protecting general-purpose circuits in residential buildings or on construction sites

Low-sensitivity residual current devices

(from 500 mA up), which are used for circuits with high leak current and as main circuit breakers for the entire home electrical installation.

High-sensitivity residual current devices

Medium-sensitivity residual current devices

Low-sensitivity residual current devices

Types of Residual Current Device

Earth Leakage Circuit Breaker

A safety device used to identify small stray voltages on metal enclosures and stop the damage to protect humans and animals from electric shock.

Ground Fault Circuit Interrupter

Help prevent electrocution

Generally installed where electrical circuits may accidentally come into contact with water

Grounding

Integral part of any properly operating electrical system and protects the occupants by providing a safe pathway for unwanted electricity that might otherwise create a hazard.

System ground

A special circuit designed to protect the entire distribution system of a residence (Level of Grounding)

Equipment ground

Essentially a circuit designed to protect individual components of an electrical system (Level of Grounding)

Electrode Grounding

A grounding method using a long metal rod (electrode) driven into the earth to make direct contact, providing a flow path to the earth with less than 25Ω of resistance

Water Pipe Grounding

Uses the underground metal pipe that supplies a residence with water and is typically the best electrical ground for a residential electrical system

Equipment Grounding

Safely grounds any devices or appliances attached to an electrical system or plugged into receptacles inside a home

Main purpose is to protect individual electrical devices

Grounding Wire

Primarily in place to protect the outlet and surrounding area in case of an overload or power surge

Diesel Generator

The most widely used alternative source of power in facilities, providing continuous backup power during utility interruptions to maintain daily activities and business operations.