ELECTRICAL CABLES AND WIRES TYPES, SIZES, INSTALLATIONS AND PRACTICAL APPLICATION IN LIFE
ELECTRICAL CABLES AND WIRES TYPES, SIZES, INSTALLATIONS AND PRACTICAL APPLICATION IN LIFE
An electrical cable is an assembly of one or more wires running side by side or bundled, which is used to carry electric current.
Electrical cables and wires are the same but quite different. A wire is made of a single electrical conductor while a cable is a group or bundle of multiple wires inside a common sheathing. Both of them are used for carrying electrical current.
An electric cable has the purpose of transporting electrical energy from one point to another. Depending on their final application, cables can have different configurations, always basing their design on national and international regulations.
In this modern days, due to the advancement in technology, almost everything is powered by electricity. Be it indoor or outdoor, we need supply of smooth, uninterrupted electricity which is achieved by using suitable type of wires and cables. Not only the electrical sector uses cables and wires for power transmission and distribution to our house and industries, the Telecom sector also relies on various types of cables for uninterrupted data transmission. This uninterrupted power distribution can only be achieved by the use of quality cables and wires.
ELECTRIC CABLE VOLTAGE
An electric cable is measured in volts and, depending on these, they are categorized into one group or another:
- Low voltage cables (up to 750 V):
In a variety of applications, and with thermoplastic and thermoset coatings. They are designed and built according to harmonized standards.
- Low Voltage cables (up to 1,000 V): (also called (0,6/1 kV)
The cables in this section are used for industrial power installations in various fields (general industry, public installations, infrastructures, etc.). They are designed according to international standards (UNE, IEC, BS, UL).
- Medium Voltage cables: from 1 kV to 36 kV.
They are used to distribute electricity from electrical substations to transformer stations.
- High Voltage cables: (from 36 kV).
They are used to transport electricity from the generating plants to the electrical substations.
TYPES OF ELECTRIC CABLE BY THEIR USE
Low voltage cables
- Cables for electric panels:
Flexible cables for wiring electric cabinets. These electric cables are especially suitable for domestic use, for installation in public places and for internal wiring of electrical cabinets, switch boxes and small electrical appliances.
- Power cables:
Energy cables for industrial facilities and public places. It is common to find power cables in applications for power transmission in all types of low voltage connections, for industrial use and for variable frequency drive (VFD).
- Armoured cables:
Cables with aluminium or steel reinforcement for installations with risk of mechanical aggression. It is also common to find armoured cables in places where rodents are present, as well as in installations in premises with a risk of fire and explosion (ATEX).
- Rubber cables:
The use of extra flexible rubber cables is very varied. We can find rubber cables in fixed industrial installations as well as in mobile service. Welding cables should have a rubber sheath, which allows high currents to be transmitted between the welding generator and the electrode.
- Halogen-free cables:
High Security Halogen Free (LSZH) Cables with low smoke and corrosive gas emission in case of fire are suitable for use in wiring of electrical panels and public places, installations of all kinds in public places, individual derivations, emergency circuits, public distribution networks and also for mobile service.
- Fire resistant cables:
These cables are specially designed to transmit electrical energy in the extreme conditions that occur during a prolonged fire, guaranteeing supply to emergency equipment such as signalling, smoke extractors, acoustic alarms, water pumps, etc. Their use is recommended in emergency circuits in places with public concurrence.
- Control cables:
Control cables for fixed or mobile installations should be extremely flexible, as they are mainly designed for small household appliances, for the interconnection of machine parts used for manufacturing, for signalling and control systems, for the connection of motors or frequency converters, for signal transmission where the voltage induced by an external electromagnetic field may affect the transmitted signal or for power supply connections to avoid generating electromagnetic fields.
- Instrumentation cables:
These are flexible and shielded cables for the transmission of signals between equipment in industrial installations. Especially suitable for optimum data transmission in environments with a high level of electromagnetic interference.
- Solar cables:
These cables are particularly suitable for connecting photovoltaic panels, and from the panels to the DC to AC inverter. Thanks to the design of their materials and their cover, which is especially resistant to solar radiation and extreme temperatures, they can be installed outdoors with full guarantees.
- Special cables:
There is a wide variety of electric cables for special installations such as: temporary light garland installations at trade fairs; connections for overhead cranes, hoists and lifts; applications in submerged pumps and drinking water areas such as aquariums, purification systems, drinking water fountains or in swimming pools for lighting, purification and cleaning systems.
- Aluminium cables:
Aluminium cables for power transmission are suitable for fixed installation indoors, outdoors and/or underground.
Medium Voltage Cables
Medium Voltage Cable type RHZ1 with XLPE insulation, halogen free and non flame and/or fire. They are cables perfectly adapted for the transportation and distribution of energy in Medium Voltage networks.
Medium Voltage cable with HEPR insulation, halogen-free and not flame- and/or fire-propagating Ideal for the transportation and distribution of energy in Medium Voltage networks.
Medium Voltage cable with XLPE insulation, according to American standard. For transportation and distribution of energy in Medium Voltage networks.
Copper and aluminium medium voltage cable for special applications. Especially recommended for installations where there is a risk of presence of oils and chemical agents of the hydrocarbon type or their derivatives.
OTHER TYPES OF ELECTRIC CABLES AND THEIR APPLICATIONS
- Non-Metallic Sheathed Cable:
These cables are also known as non-metallic building wire or NM cables. They feature a flexible plastic jacket with two to four wires (TECK cables are covered with thermoplastic insulation) and a bare wire for grounding. Special varieties of this cable are used for underground or outdoor use, but NM-B and NM-C non-metallic sheathed cables are the most common form of indoor residential cabling.
- Underground Feeder Cable :
These cables are quite similar to NM cables, but instead of each wire being individually wrapped in thermoplastic, wires are grouped together and embedded in the flexible material. Available in a variety of gauge sizes, UF cables are often used for outdoor lighting and in-ground applications. Their high water-resistance makes them ideal for damp areas like gardens as well as open-to-air lamps, pumps, etc.
- Metallic Sheathed Cable :
Also known as armored or BX cables, metal-sheathed cables are often used to supply mains electricity or for large appliances. They feature three plain stranded copper wires (one wire for the current, one grounding wire and one neutral wire) that are insulated with cross-linked polyethylene, PVC bedding and a black PVC sheathing. BX cables with steel wire sheathing are often used for outdoor applications and high-stress installations.
- Multi-Conductor Cable :
This is a cable type that is commonly used in homes, since it is simple to use and well-insulated. Multi-conductor or multi-core (MC) cables feature more than one conductor, each of which is insulated individually. In addition, an outer insulation layer is added for extra security. Different varieties are used in industries, like the audio multicore ‘snake cable’ used in the music industry.
- Coaxial Cable :
A coaxial (sometimes heliax) cable features a tubular insulating layer that protects an inner conductor which is further surrounded by a tubular conducting shield, and might also feature an outer sheath for extra insulation called ‘coaxial’ since the two inner shields share the same geometric axis. These cables are normally used for carrying television signals and connecting video equipment.
- Unshielded Twisted Pair Cable :
Like the name suggests, this type consists of two wires that are twisted together. The individual wires are not insulated, which makes this cable perfect for signal transmission and video applications. Since they are more affordable than coaxial or optical fiber cables, UTP cables are often used in telephones, security cameras and data networks. For indoor use, UTP cables with copper wires or solid copper cores are a popular choice, since they are flexible and can be easily bent for in-wall installation.
- Ribbon Cable :
Ribbon cables are often used in computers and peripherals, with various conducting wires that run parallel to each other on a flat plane, leading to a visual resemblance to flat ribbons. These cables are quite flexible and can only handle low voltage applications.
- Direct-Buried Cable :
Also known as DBCs, these cables are specially-designed coaxial or bundled fiber-optic cables, which do not require any added sheathing, insulation or piping before being buried underground. They feature a heavy metal core with many layers of banded metal sheathing, heavy rubber coverings, shock-absorbing gel and waterproof wrapped thread-fortified tape. High tolerance to temperature changes, moisture and other environmental factors makes them a popular choice for transmission or communication requirements.
- Twin-Lead Cable :
These are flat two-wire cables that are used for transmission between an antenna and receiver, like TV and radio.
- Twinaxial Cable :
This is a variant of coaxial cables, which features two inner conductors instead of one and is used for very-short-range high-speed signals.
- Paired Cable :
With two individually insulated conductors, this cable is normally used in DC or low-frequency AC applications.
- Twisted Pair :
This cable is similar to paired cables, but the inner insulated wires are twisted or intertwined.
Cable Color Code
Color coding of cable insulation is done to determine active, neutral and earth conductors. The NEC has not prescribed any color for phase/active conductors. Different countries/regions have different cable color coding, and it is essential to know what is applicable in your region. However, active conductors cannot be green/yellow, green, yellow, light blue or black..
Cable size is the gauge of individual wires within the cable, such as 14, 12, 10 etc. Again, the bigger the number, the smaller the size. The number of wires follows the wire-gauge on a cable. So, 10/3 would indicate the presence of 3 wires of 10-gauge within the cable. Ground wire, if present, is not indicated by this number, and is represented by the letter ‘G’.
Components of an electrical cable
An electric cable consists of:
- Electric conductor: which channels the flow of electricity
- Insulation: it covers and contains the electric flow in the conductor.
- Auxiliary elements: that protect the cable and guarantee its longevity.
- Outer sheath: it covers all the mentioned materials protecting them from the outside.
Types of electric conductors
Bare wire conductor: single wire in solid state, not flexible and without coating.
- Aluminum electrical conductors: in some cases, aluminum conductors are also used, despite the fact that this metal is 60% worse conductor than copper.
- Copper electrical conductors: the most commonly used material.
- Flexible copper wire conductor: it is a set of fine wires covered by an insulating material. They are flexible and malleable.
- Single-core cable: a cable with a single conductor.
- Multi-core cable: a cable that has several conductors.
Types of insulation for electric cables
The insulation consists of placing an insulating coating on the conductor to prevent current leakage. They are classified into two large groups: thermoplastic and thermoset.
- Thermoplastic insulation
They are most common in the manufacture of electrical cables are:
- PVC:Polyvinyl chloride
- Z1: Polyolefins
- PE: Linear polyethylene
- PU: Polyurethane
- Thermosetting insulation
The most common are:
- EPR: Ethylene Propylene
- XLPE: Crosslinked Polyethylene
- EVA: Ethyl Vinyl Acetate
- SI: Silicone
- PCP: Neoprene
- SBR: Natural Rubber
Types of metal protections for electrical cables
In some cases, the cables may have metal shields.
- Screens: These are electrical metal protections applied to isolate the signals that pass through the interior of the cable from possible external interference.
- Armours: These are mechanical protections that protect the cable from possible external aggressions: animals, blows, etc.
Some factors that will affect your choice of electrical wiring include color, label information and applications. The information printed on the electrical wire covering is all that you need to choose the correct wire for your home. Here’s some detailed information on the various features of electrical wire, which will help you choose the correct composition:
- Size of Wires – Each application requires a certain wire siz
e for installation, and the right size for a specific application is determined by the wire gauge. Sizing of wire is done by the American wire gauge system. Common wire sizes are 10, 12 and 14 – a higher number means a smaller wire size, and affects the amount of power it can carry. For example, a low-voltage lamp cord with 10 Amps will require 18-gauge wire, while service panels or subpanels with 100 Amps will require 2-gauge wire.
- Wire Lettering – The letters THHN, THWN, THW and XHHN represent the main insulation types of individual wires. These letters depict the following NEC requirements:.
T – Thermoplastic insulation
H – Heat resistance
HH – High heat resistance (up to 194°F)
W – Suitable for wet locations
N – Nylon coating, resistant to damage by oil or gas
X – Synthetic polymer that is flame-resistant
- Types of Electrical Wire
There are mainly 5 types of wire:
- Triplex Wires :
Triplex wires are usually used in single-phase service drop conductors, between the power pole and weather heads. They are composed of two insulated aluminum wires wrapped with a third bare wire which is used as a common neutral. The neutral is usually of a smaller gauge and grounded at both the electric meter and the transformer.
- Main Feeder Wires :
Main power feeder wires are the wires that connect the service weather head to the house. They’re made with stranded or solid THHN wire and the cable installed is 25% more than the load required.
- Panel Feed Wires :
Panel feed cables are generally black insulated THHN wire. These are used to power the main junction box and the circuit breaker panels. Just like main power feeder wires, the cables should be rated for 25% more than the actual load.
- Non-Metallic Sheathed Wires:
Non-metallic sheath wire, or Romex, is used in most homes and has 2-3 conductors, each with plastic insulation, and a bare ground wire. The individual wires are covered with another layer of non-metallic sheathing. Since it’s relatively cheaper and available in ratings for 15, 20 and 20 amps, this type is preferred for in-house wiring.
- Single Strand Wires :
Single strand wire also uses THHN wire, though there are other variants. Each wire is separate and multiple wires can be drawn together through a pipe easily. Single strand wires are the most popular choice for layouts that use pipes to contain wires.
- Color Codes
Different color wires serve different purposes, like:
Black : Hot wire, for switches or outlets.
Red : Hot wire, for switch legs. Also for connecting wire between 2 haand Yellow : Hot wires, pulled in conduit. Blue for 3-4 way switch application, and yellow for switch legs to control fan, lights etc.
White : Always neutral.
Green and Bare Copper : Only for grounding.
- Wire Gauge, Ampacity and Wattage Load
To determine the correct wire, it is important to understand what ampacity and wattage a wire can carry per gauge. Wire gauge is the size of the wire, ampacity is how much electricity can flow through the wire and wattage is the load a wire can take, which is always mentioned on the appliances.
Safety is very important, and if your installation of wires and cables is not proper, it could lead to accidents. Before you start any electrical project that includes wiring and cabling, you need to obtain permission from your local building inspector. Once the job is done, get the installation inspected for compliance with local codes and regulations.