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Production, Transmission and Distribution of Energy
Transcript of Production, Transmission and Distribution of Energy
Earth has a potential (voltage) of 0 V. End of session 1 The neutral has a number of purposes;
It enables us to have a variety of single-phase supplies.
It ties down the neutral to a known voltage because it is connected to earth (0 V).
It allows a neutral current to flow.
This is important in single and unbalanced three-phase supplies. Neutral Wire This form of supply is useful because;
It allows an even spread of loads across a number of consumers. If one of the phases became overloaded it would be called an unbalanced supply.
It allows businesses to make use of more efficient machines because they can have a three-phase supply. The voltage between any two phases is 400 V.
A 400 V supply between any two phases is called a 400 V single-phase supply.
A 400 V supply between all three phases is called a 400 V three-phase supply.
The voltage between any phase and neutral or earth is 230 V.
This form of supply is called a 230 V single-phase supply.
If you multiply 230 V by you will get 400 V. Voltage Differences The output from the step down transformer is called a three-phase four wire system. When:
The primary is connected in delta.
The secondary is connected in star.
The centre point of the output star winding is connected to earth Three-phase four wire system The supply into the transformer has the coils arranged, so that the outgoing leg of one coil is connected to the incoming leg of the next.
This is called a delta connection, there are only three wires.
The output from the transformer has four wires. The coils are connected in star, where each outgoing leg is connected to a common point, which is then connect to earth. Delta and Star Connections Each set of windings creates an emf which is set 1200 apart Electromotive Force (emf) Transmission lines are not usually buried, but carried on pylons because;
Increased costs from burying cables
Using pylons eliminates the need for insulation The grid voltage varies from 230 V to 400 000 V (400 kV). Transmission System The national grid company buys power from power stations and then sells it on.
On the right is a diagram of what happens to the power once it is generated. The national grid is a system
which links all the power stations to all of the consumers. The National Grid Gas is heated up and driven through the turbines to produce the electricity
They are popular for two reasons:
They can be built smaller
They can be run up to full power much quicker than coal Gas The water passes through the turbines in the same way as an hydroelectric power station.
The difference being, the water is stored in a lake further down the mountain, when there is less demand the water is pumped back to the top. Pumped Storage Generation Hydroelectric power plants are found in areas of high rainfall they are placed beside rivers or within dams.
The water is fed through turbines that turn generators that produce electricity. Hydroelectric Power Session 1
Production , transmission and distribution of energy Outcome 4
Describe the basic principle of operation of polyphase systems
Aims and objectives of this session
Gain a further understanding of how energy is produced, transmitted and distributed. They are given labels L1, L2 and L3.
To comply with European harmonisation the phases are now coloured brown, black and grey.. Alternator power generator Power generators have three coils, each produces a voltage.
These voltages are called lines or phases. Power Generation Coal, oil and nuclear energy all heat water up until it is high pressure steam Block diagram of electrical power production This steam then drives turbines, which drive generators, that produce the electricity
Turbines are the mechanical way of converting steam into rotational energy
Generators convert rotational energy into electrical energy Producing Power Production , transmission and distribution of energy