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Anglicky v odborných předmětech "Support of teaching technical subjects in English“. Tutorial: Mechanic - electrician Topic: Fundamentals of electrical engineering the 2nd. year , RCD Prepared by : Škarka Miloš.
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Anglicky v odborných předmětech"Support of teaching technical subjects in English“ Tutorial: Mechanic - electrician Topic: Fundamentals of electrical engineering the 2nd. year, RCD 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.
RCD (Residual current device) Residual current device is an electrical device used for increased protection against injury caused by an electric current. It can‘t be used for basic protection – by automatic disconnection. Working wires are conducted through RCD, protective conductor mustn't be conducted through this device. It is used in environments with higher danger of injuries caused by an electric current. It‘s main parameters are: • Nominal current • Residual (differential) current • Selectivity
Principle of RCD (Residual current device) In normal conditions the vector sum of currents in working conductors equals null. In the secondary winding of the transformer no voltage is induced. In case of a current leak from the phase conductor to the ground, the voltage emerges in the secondary transformer winding, the current gets through the coil of the electro magnet and a malfunction is quickly disconnected from the rest of the electric network.
Two-pole and four-pole RCDs Test buttons For one-phase circuits For three-phase circuits
RCD Design (1) Input power terminals(2) Output load terminals(3) Reset button(4) Contacts (the second one is for relay)(5) Relay equipment (6) Differential transformer (7) Control valve(8) Test button(9) Test conductor (orange)
RCD connection in TNC-S network One-phase appliance With null Without null
RCDs in TT, IT network IT Network TT Network L1 L1
Describe and explain • Principle of RCD • Which conductors have to be conducted through RCD? • What is a residual current? • When do you have to use RCD? • Draw the connection of RCD in TN network
Describe and explain What do numbers in picture 1 connote? Picture 1
Literature • http://www.jtlelektro.cz • www.wikipedia.cz