Ever since the advent of the modernization of the world which is propelled by critical inquiry, the world largely has taken a new turn into what the new future which is now the present should look like. It has then never stopped spiraling. Part of those beautiful things that is brought up to the human is electricity.
This out of many others has created the ease necessary for general growth and development immediately electricity began getting distributed from one house to the other through a reliable distribution system after Nikola Tesla innovation that finally made electricity open to all. The aim here is to throw to you some of the basic types of electrical distribution system.
The part of the power system that distributes electric power for local use is called as distribution system. A distribution system is the electrical system between the substation fed by transmission system and the consumer’s meters. A typical distribution system is shown in the figure. There are certain components of the electrical distribution system which you will need to know here. These are:
- Distribution Sub-Station: A distribution sub-station is the electrical system which transfers power from transmission system to the distribution system of an area.
- Feeders: A feeder is a conductor which connects the distribution sub-station to the area where power is to be distributed. The current in a feeder remains the same throughout its length because no tapings are taken from it. The main consideration in the design of a feeder being its current carrying capacity.
- Distribution Transformers: The distribution transformer is a step-down transformer in which primary and secondary are delta and star connected respectively. It is also termed as service transformer. The output voltage of distribution transformer is 440 V in 3-phase system whereas 230 V in 1-phase system in India.
- Distributor: A distributor is a conductor from which tapings are taken for supply to the consumers. Due to the taping is done at various places in a distributor, the current being not same throughout its length. The main design consideration of a distributor is the voltage drop across its length because the statutory limit of voltage variations is ± 6 % of rated voltage at the consumer’s terminals.
- Service Mains: Service Mains is a small cable which connects the distributor to the consumer’s meter.
Basic Types of Electrical Distribution System
Electricity has two major types since the popular discovery by Benjamin Franklin who is credited for discovering it in the 1700s with his kite experiment, in which he flew a kite with a metal key tied to it during a thunderstorm. The first type is introduced by Thomas Edison, then subsequently we have the other one by Nikola Tesla. These are the AC and the DC. It is in support of this backdrop that we will be sharing the basic types of electrical distribution system.
1. Primary Distribution System
Primary distribution systems consist of feeders that deliver power from distribution substations to distribution transformers. A feeder usually begins with a feeder breaker at the distribution substation. Many feeders leave substation in a concrete ducts and are routed to a nearby pole. At this point, underground cable transitions to an overhead three-phase main trunk.
The primary distribution system is the part of AC distribution system which operates at voltages slightly higher than general utilization. The voltage used for primary distribution depends upon the amount power to be transferred and distance of substation required to be fed. The commonly used primary distribution voltages are 11 kV, 6.6 kV and 3.3 kV. The primary distribution is done by 3-phase 3-wire system because of economic considerations.
The main trunk is routed around the feeder service territory and may be connected to other feeders through normally-open tie points. Underground main trunks are possible-even common in urban areas, but cost much more than overhead construction.
Lateral taps off of the main trunk are used to cover most of a feeder’s service territory. These taps are typically single phase, but may also be two phases or three phases.
2. Secondary Distribution System
The secondary distribution system includes those ranges of voltage at which consumer utilizes the electrical energy. In India, the secondary distribution employs 440V (3-phase) & 230V (1-phase), 3-phase 4-wire system. A low-voltage network or secondary network is a part of electric power distribution which carries electric energy from distribution transformers to electricity meters of end customers.
Secondary networks are operated at a low voltage level, which is typically equal to the mains voltage of electric appliances. Most modern secondary networks are operated at AC rated voltage of 100–120 or 230–240 volts, at the frequency of 50 or 60 hertz.
Operating voltage, required number of phases (three-phase or single-phase) and required reliability dictate topology and configuration of the network.
Electric power distribution systems are designed to serve their customers with reliable and high-quality power. The most common distribution system consists of simple radial circuits (feeders) that can be overhead, underground, or a combination. Typically, a rural primary feeder supplies up to 50 distribution transformers, spread over a wide region but the figure significantly varies depending on configuration. They are sited on pole tops, cellars or designated small plots.
From these transformers, low voltage or secondary network branches off to the customer connections at customer premises, equipped with electricity meters.
Necessities for a Perfect Distribution System
Here are things that are considered efficient for the proper distribution of electricity:
- Availability of Power: The electric power must be available to the consumers in any amount that they may require from time to time.
- Proper Voltage: The voltage variations at consumer’s terminals should be as low as possible. The statutory limit of voltage variations is ± 6 % (India) of the rated voltage at consumer’s terminals.
- Reliability: The modern industry is almost dependent on electric power for its operation. This calls for reliable service as much possible.
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