Anglicky v odborných předmětech "Support of teaching technical subjects in English“

1. Anglicky v odborných předmětech"Support of teaching technical subjects in English“ 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.

2. Electrification system It is a mutually connected complex of devices enabling transfer of electric energy from a source to anappliance 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)

3. What does the electrification system consist of? • Facilities for transfer, transformation and distribution to a consumer • Measuring, controlling and security systems • Individual appliances • Power plants

4. Demands on the electrification system • Secure – it mustn‘t be the cause of fire or security threat • Reliable – it has to ensure transfer ofperformance on the certain distance • Parameters (f, U, shape of the curve, assured supply) • Economical – in optics of investment costs, maintenance costs • It must have thelowest possible performance losses

5. Block scheme of the electrification system 6kV Substation 400 (200) kV Distribution point 22-35kV 0,4kV G 110 kV Výroba 6-25kV 220-400kV Substation 400 (200) kV 0,4kV 110kV 22-35kV G Distribution system Transfer 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.

6. Division and parts of the transfer system • 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.

7. Electric Lines They are basic elements of the network, connect two its points and consist of complex of conductors, insulation and construction parts for mechanical attachment. 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 110, 220kV pylons 400kV

8. Describe and explain • 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

9. Describe the picture G G 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?

10. Literature • www.wikipedia.cz • www.ceps.cz • základy elektrotechniky 2, L.VOŽENÍLEK- F. STIBŮREK • www.cez.cz