Electrical system design is the design of

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

systems. This can be as simple as a flashlight cell connected through two

wire Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is c ...

s to a light bulb or as involved as the

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program ...

. Electrical systems are groups of electrical components connected to carry out some operation. Often the systems are combined with other systems. They might be subsystems of larger systems and have subsystems of their own. For example, a subway

rapid transit Rapid transit or mass rapid transit (MRT), also known as heavy rail or metro, is a type of high-capacity public transport generally found in urban areas. A rapid transit system that primarily or traditionally runs below the surface may be ...

electrical system is composed of the wayside electrical power supply, wayside control system, and the electrical systems of each transit car. Each transit car’s electrical system is a subsystem of the subway system. Inside of each transit car there are also subsystems, such as the car climate control system.

Design

The following would be appropriate for the design of a moderate to large electrical system. # A

specification A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard. There are different types of technical or engineering specificati ...

document is written. It probably would have been written by the customer. The specification document states in plain language and numerical detail what the customer expects. If it is well written, it will be used as a reference throughout the electrical system design. # A

functional specification A functional specification (also, ''functional spec'', ''specs'', ''functional specifications document (FSD)'', ''functional requirements specification'') in systems engineering and software development is a document that specifies the functions ...

(design) document that goes into more technical details may be created. It uses the specification document as its basis. Here calculations may be used or referenced to support design decisions. # Functional diagrams may be made. These use block diagrams indicating information and electrical power flow from component to component. They are similar to the

functional flow block diagram A functional flow block diagram (FFBD) is a multi-tier, time-sequenced, step-by-step flow diagram of a system’s functional flow. The term "functional" in this context is different from its use in functional programming or in mathematics, where p ...

s used with computer programs. #

Schematic A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the ...

diagrams showing the electrical interconnections between the components are made. They may not show all the conductors and termination points. Except for

one-line diagram In power engineering, a single-line diagram (SLD), also sometimes called one-line diagram, is a simplest symbolic representation of an electric power system. A single line in the diagram typically corresponds to more than one physical conductor: ...

s, this should show all the circuit nodes. One-line diagrams represent the three or four conductors of three-phase power circuits with one line. #

Wiring diagram A wiring diagram is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified shapes, and the power and signal connections between the devices. A wiring diagram usually gi ...

s are sometimes made. These show and name the termination points and names of each conductor. In some systems, enough information can be put onto the schematics so that wiring diagrams are not needed. # Physically smaller systems that are built many times may use a

cable harness A cable harness, also known as a wire harness, wiring harness, cable assembly, wiring assembly or wiring loom, is an assembly of electrical cables or wires which transmit signals or electrical power. The cables are bound together by a durable mat ...

. A full-sized to-scale wiring diagram can be made of a cable harness. This wiring diagram can then be laid on a peg board and used to guide the construction of more cable harnesses. Harnesses can be inserted into their equipment as an assembly. Cable harnesses that are reused many times, like automobile wiring harnesses, are created with automated machinery. # A wire list is made in

spreadsheet A spreadsheet is a computer application for computation, organization, analysis and storage of data in tabular form. Spreadsheets were developed as computerized analogs of paper accounting worksheets. The program operates on data entered in c ...

or list format. It shows the electrical assembly people what wires are to be connected and to where. When it is printed out on paper, it is easy for the assembly people to check off conductors as they are connected. The wire list contains at a minimum each wire name, terminal name, and wire model number or gage. It may also contain the wire termination device model numbers, voltage classes, conductor class (high-voltage, medium voltage, or control wiring), etc.

References

* Bosela, Ayanda Voyi, Theodore R.(2002). Electrical Systems Design, Prentice Hall, , 542 pages. {{Design Electrical engineering Systems engineering Technical communication Electrical wiring Electrical standards