Service Drop
Encyclopedia
In an electric power distribution grid, a service drop is an overhead electrical line running from a utility pole
, to a customer's building or other premises. It is the point where electric utilities
provide power to their customers. The customer connection to an underground distribution system is usually called a "service lateral". Conductors of a service drop or lateral are owned and maintained by the utility company.
At the customer's premises, the wires usually enter the building through a weatherhead
that protects against entry of rain and snow, and drop down though conduit
to an electric meter which measures and records the power used for billing purposes, then enters the main service panel. The utility's portion of the system ends, and the customer's wiring begins, at the output socket of the electric meter. The service panel will contain a "main" fuse
or circuit breaker
, which controls all of the electrical current entering the building at once, and a number of smaller fuses/breakers, which protect individual branch circuits. There is always a main shutoff switch to turn off all power; when circuit breakers are used this is provided by the main circuit breaker.
system is used. A service drop is made up of two 120 volt lines and a neutral line
. When these lines are insulated and twisted together, they are referred to as a triplex cable which may contain a messenger cable in the middle of the neutral conductor to provide strength for long spans. The neutral line from the pole is connected to an earth ground near the service panel; often a conductive rod driven into the earth. The service drop provides the building with two 120 volt lines of opposite phase
, so 240 volts can be obtained by connecting a load between the two 120 volt conductors, while 120 volt loads are connected between either of the two 120 volt lines and the neutral line. 240 volt circuits are used for high-power devices, such as air conditioners, clothes dryer
s, oven
s and boiler
s, while 120 volt circuits are used for lighter loads such as lighting and ordinary small appliance outlets.
. In the USA, common services are 120Y/208 (three 120V circults 120 degrees out of phase, with 208V line to line), 240V three phase, and 480V three phase. 600V three phase is common in Canada, and 380-415V or 690V three phase is found in many other countries. Generally, higher voltages are used for heavy industrial loads, and lower voltages for commercial applications.
Utility pole
A utility pole is a pole used to support overhead power lines and various other public utilities, such as cable, fibre optic cable, and related equipment such as transformers and street lights. It can be referred to as a telephone pole, power pole, hydro pole, telegraph pole, or telegraph post,...
, to a customer's building or other premises. It is the point where electric utilities
Electric utility
An electric utility is a company that engages in the generation, transmission, and distribution of electricity for sale generally in a regulated market. The electrical utility industry is a major provider of energy in most countries. It is indispensable to factories, commercial establishments,...
provide power to their customers. The customer connection to an underground distribution system is usually called a "service lateral". Conductors of a service drop or lateral are owned and maintained by the utility company.
At the customer's premises, the wires usually enter the building through a weatherhead
Weatherhead
A weatherhead, also called a weathercap, service head or service entrance cap, is a weatherproof entry point for above-ground electrical wiring or telephone lines into a home or business. It is used at a service drop, where overhead wires from a utility pole supplying power or telephone service...
that protects against entry of rain and snow, and drop down though conduit
Electrical conduit
An electrical conduit is an electrical piping system used for protection and routing of electrical wiring. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Flexible conduit is available for special purposes....
to an electric meter which measures and records the power used for billing purposes, then enters the main service panel. The utility's portion of the system ends, and the customer's wiring begins, at the output socket of the electric meter. The service panel will contain a "main" fuse
Fuse (electrical)
In electronics and electrical engineering, a fuse is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit...
or circuit breaker
Circuit breaker
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...
, which controls all of the electrical current entering the building at once, and a number of smaller fuses/breakers, which protect individual branch circuits. There is always a main shutoff switch to turn off all power; when circuit breakers are used this is provided by the main circuit breaker.
North American
In North America and countries that use their system, the 120/240V split phaseSplit phase
A split-phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial applications. It is the AC equivalent of the original Edison 3-wire direct current system...
system is used. A service drop is made up of two 120 volt lines and a neutral line
Ground and neutral
Since the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding of equipment and structures...
. When these lines are insulated and twisted together, they are referred to as a triplex cable which may contain a messenger cable in the middle of the neutral conductor to provide strength for long spans. The neutral line from the pole is connected to an earth ground near the service panel; often a conductive rod driven into the earth. The service drop provides the building with two 120 volt lines of opposite phase
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
, so 240 volts can be obtained by connecting a load between the two 120 volt conductors, while 120 volt loads are connected between either of the two 120 volt lines and the neutral line. 240 volt circuits are used for high-power devices, such as air conditioners, clothes dryer
Clothes dryer
A clothes dryer or tumble dryer is a household appliance that is used to remove moisture from a load of clothing and other textiles, generally shortly after they are cleaned in a washing machine....
s, oven
Oven
An oven is a thermally insulated chamber used for the heating, baking or drying of a substance. It is most commonly used for cooking. Kilns, and furnaces are special-purpose ovens...
s and boiler
Boiler
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...
s, while 120 volt circuits are used for lighter loads such as lighting and ordinary small appliance outlets.
European
In European countries, the three phase 220Y380, 230Y400 or 240Y415 system is used, with "harmonization" towards 230Y400. The service drop consists of three phase wires and a neutral wire which is grounded. Each phase wire provides 220/230/240 volts to loads connected between it and the neutral. Each of the phase wires carries 50 Hz alternating current which is 120° out of phase with the other two.Commercial and industrial
Commercial and industrial service drops can be much bigger, and are usually three phaseThree-phase electric power
Three-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by grids worldwide to transfer power. It is also used to power large motors and other heavy loads...
. In the USA, common services are 120Y/208 (three 120V circults 120 degrees out of phase, with 208V line to line), 240V three phase, and 480V three phase. 600V three phase is common in Canada, and 380-415V or 690V three phase is found in many other countries. Generally, higher voltages are used for heavy industrial loads, and lower voltages for commercial applications.