DISTRIBUTION LINES: ELECTRICAL DISTRIBUTION SYSTEM
A major part of an electrical power system that contributes the most losses in the entire network is usually found in its distribution system. Distribution system or commonly referred to as distribution lines is the part after voltage transformation at the distribution substation is completed.
Distribution line’s purpose is to transmit power through conductors to different parts of the utility’s franchise area. These lines typically use medium voltage to circulate power needed by the consumers. Distribution lines is said to be the final stage before satisfying the consumers or end users and when power is delivered to them.
Unlike transmission line’s simplicity in operation, distribution lines are far more complicated network of conductors. Distribution network popularly configured in 3-phase, receives electricity from the transmission lines where the voltage is converted first in the substation transformers. As mentioned a while ago, typical voltage used in distribution system is in the medium voltage level (not more than 50kV).
Similar to transmission lines, the choice of distribution voltage is in the utilities discretion primary depending on the economic factors and choice of equipments. The choice of voltage is said to be the deciding factor on what type of distribution transformers to be used, insulators to be installed, and structure designs to be followed.
Also, the voltage level will determine the kilowatt capacity of the distribution lines to carry. Following the power formula, 3 x V x I x power factor, the higher the voltage with given constant wire ampacity will yield higher power that the conductor can carry.
Typical construction of distribution lines is consisting mainly of poles, insulators, connectors and wires. Also, widely used set up for distribution lines is an overhead type similar to that of a transmission line system. However, in some countries especially those with highly urbanized areas uses underground distribution system by using power cables and cabinet substations.
The networks of these distribution lines are typically categorized into two, Radial system and interconnected system. Radial system starts in the substations and traverses to consumers’ area as their supply with no connection to other supplies. This set-up can usually be found in rural areas where a utility needs to supply isolated service points.
Interconnected system on the other hand, consists of multiple interconnections between two or more supplies. This set up can be found in urban areas where loads are usually concentrated. The connections between supplies are identified by switches which are normally open and can be controlled remotely or by a lineman. Reliability and flexibility are the two main factors why a utility seems to be bias in this kind of configuration.
Distribution lines not only serves as a medium in disseminating power to customers but also houses different types of power quality devices like line capacitors and line voltage regulators. These devices are directly connected to distribution lines all for the purpose of insuring a quality power for the consumers to enjoy.
Distribution line loss study will be later discussed in the succeeding articles.