Power Generation and Distribution Thomas K P Assistant professor EEE RSET

Distribution System Distribution system is that part of power system which distributes power to the consumers for utilization. The transmission and distribution systems are similar to human circulatory system. The transmission system may be compared with arteries in human body and distribution system with capillaries. In general part of power system which distributes electrical power for local use is known as distribution system. Distribution system is the electrical system between the substation and the consumer meters ;consists feeders ,distributors and service mains.

Distribution System Feeder: A feeder is a conductor which connects the substation to the area where power to be distributed. Generally ,no tappings are taken from the feeder. So that the current in it remain the same throughout. The main consideration in the design of a feeder is the current carrying capacity. Distributor: A distributor is a conductor from which tappings are taken for supply to the consumers. Service mains: A service mains is generally a small cable which connects the distributor to the consumers terminals.

Classification of Distribution System A distribution system may be classified according to Nature of current : DC and AC distribution system Types of construction: Overhead and underground system Scheme of connection: Radial ,ring main and inter-connected system

A C Distribution System AC distribution is divided in to Primary distribution system Secondary distribution system DC distribution is divided in to 2 wire DC system 3 wire DC system

Methods of obtaining 3 wire DC system Two generator method 3-wire DC generator Balancer set

Overhead versus Underground system Public safety Initial cost Flexibility Faults Appearance Fault location and repair Current carrying capacity and voltage drop Useful life Maintenance cost Interference with communication circuits

Connection schemes of distribution system Radial System: In this ,separate feeders radiate from a single substation and feed the distributors at one end only. The radial system is employed only when power is generated at low voltage and the substation is located at the centre of the load. Advantages: Simplest and lowest initial cost. Disadvantages: The end of the distributor nearest to the feeding point will be heavily loaded, Less reliable and the consumers at the distant end of the distribution would be subjected to serious voltage fluctuation

Connection schemes of distribution system Ring main system: The primaries of distribution transformers from a loop. The loop circuit starts from the substation bus-bars, makes a loop through the area to be served, and return to the substation. Advantages: There are voltage fluctuation at consumers terminals and the system is very reliable.

Connection schemes of distribution system Interconnected system: When the feeder ring is energised by two or more than two generating stations or substations, it is called inter-connected system. Advantages : it increase the service reliability and efficiency.

Requirement of a Distribution system Proper voltage Availability of power on demand Reliability

Design consideration in Distribution system Good voltage regulation of a distribution network is probably the most important factor responsible for delivering good service to the consumers. Feeders: A feeder design from the point of view of its current carrying capacity while the voltage drop consideration is relatively unimportant. Distributors : A distributor is designed from the point of view of the voltage drop in it.

Types of DC Distributors The DC distributors are classified based on the way they are fed by the feeders. Distributor fed at one end Distributor fed at both ends Distributor fed at the centre Ring Distributor