Tutorial: Mechanic - electrician Topic: 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 threat

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

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.

G

G

Substation400 (200) kV

Substation400 (200) kV

Transfer system Distribution system

Výroba

6-25kV

Distribution point

220-400kV110 kV

110kV

22-35kV

22-35kV

6kV

0,4kV

0,4kV

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.

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

pylons 400kV pylons 110, 220kV

They are basic elements of the network, connect two its points and consist of complex of conductors, insulation and construction parts for mechanical attachment.

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?

G

G

www.wikipedia.cz www.ceps.cz základy elektrotechniky 2, L.VOŽENÍLEK- F.

STIBŮREK www.cez.cz