Concept
In electric power distribution, 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 usually owned and maintained by the utility company, but some industrial drops are installed and owned by the customer. 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 through 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 electric current entering the building at once, and a number of smaller fuses/breakers, which protect individual branch circuits. There is always provision for all power to be cut off by operating either a single switch or small number of switches (maximum of six in the United States, for example); when circuit breakers are used this is provided by the main circuit breaker. In North America , the 120/240 V split phase system is used for residential service drops. A pole-mounted single phase distribution transformer usually provides power for one or two residences. The secondary winding of the transformer provides 240 volts between its ends and is center tapped. The service drop is made up of a neutral line connected to the transformer's center tap and two lines connected to the ends of the winding which provide 120V with respect to the neutral line. When these lines are insulated and twisted together, they are referred to as a triplex cable which may contain a supporting messenger cable in the middle of the neutral conductor to provide strength for long spans.
