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Tutorial: Mechanic - electrician
Basics of electrical engineering
the 2nd. year
Three-phase current, electrification system
Prepared by: Škarka Miloš
Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002
je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.
It is a mutually connected complex of devices enabling
transfer of electric energy from a source to an
appliance while carrying out certain parameters like
performance, distance, highest possible transfer
efficiency, lowest possible voltage loss, supply
enassurance, frequency stability, shape of the curve
(sine curve)
Facilities for transfer, transformation and
distribution to a consumer
Measuring, controlling and security systems
Individual appliances
Power plants
Secure – it mustn‘t be the cause of fire or security
Reliable – it has to ensure transfer of performance on
the certain distance
Parameters (f, U, shape of the curve, assured supply)
Economical – in optics of investment costs,
maintenance costs
It must have the lowest possible performance losses
400 (200) kV
Distribution point
110 kV
400 (200) kV
Transfer system
Distribution system
Transformation to vvn radically lowers losses in lines
Transfer losses – appear at any electric energy transfer and their amount is
directly proportional to the impedance of the transfer line and squared
passing through current.
It is valid: Pz = ZI2, where Pz is the loss performance, Z is the impedance of
line and I is passing current.
 Power plants- serve as transformers of any kind of energy into electric energy
 Electric stations – buildings and facilities in nodes of the electrification system. They enable transformation,
distribution with the same voltage to different directions
 Electric networks – complex of mutually connected electric stations and lines for transfer and distribution of
electric energy.
According to purpose we divide them:
 Transfer ( superior) for long-distance transfers with voltage 220kV and 400kV.
 Distributional – for distribution from the transfer system to customers. Voltage is 110kV, 35kV, 22kV. 110 kV
networks are sometimes called primary. Sometimes they serve for bringing of the performance to the system from
power plants with lower performance (hydro plants).
 Industrial – networks with voltage 22kV, 10kV, 6kV and 0,4kV.
 Local – bring energy directly to consumption place, their voltage is 0,4kV.
They are basic elements of the network, connect two its points and
consist of complex of conductors, insulation and construction parts for
mechanical attachment.
pylons 110, 220kV
pylons 400kV
Basic division:
outdoor - bare (on pylons with isolators) Outdoor lines is nearly completely made of bare conductors attached on the
pylon construction via isolators made of porcelain, ceramic, glass or special plastic. In specific cases the
insulated conductors can be used on outdoor lines.
cabel- in the ground, on bridges, on pylons.
Conductors for distribution of electric energy
The purpose of the conductor is to create precisely determined path for electric current. To accomplish the task, the
conductor has to be attached separately from the environment.
Conductor material has to be:
- very well conductive
- hard enough
- economical
Electrification system
Main parts of the electrification system
Difference between distribution and transfer network
What voltage does each network operate on?
Types of eletric lines
Significance of the transformation for the transfer
Calculate losses in the line: Z=12Ω, I =10A
If we increase the voltage two times, what is the loss decrease?
Is there any other possibility to decrease line losses?
základy elektrotechniky 2, L.VOŽENÍLEK- F.