Student groups 5А5В Made by: Kustov Mikhail Overcurrent protection devices

3 Contents Introduction Fuse Circuit breaker Thermal relay Conclusion

2 Introduction Each transformer substation and each overhead line, each cable line and distribution in-house network, each of the power consumers have protection devices that provide smooth and reliable operation. Devices protect electrical equipment and electric networks of a very large group and includes such devices as fusible links (fuses), circuit breakers, a variety of relays (current, heat, voltage, etc.).

4 Fuse Fuses protect the circuit from current overloads and short circuits. Divided into one-time fuses-fuses with replaceable inserts. They are used both in industry and in everyday life. Ease of operation, simplicity of construction and ease of replacement provided the fuse to a very large extent.

5 Circuit breakers play the same role as fuses. Only in comparison with them have a more complex structure. But it is much more convenient to use automatic switches. In the event of, for example, a short circuit in the network as a consequence of aging insulation, the circuit breaker will disconnect from the power damaged area. Thus he is easily restored Circuit breaker

6 Thermal relay-the most common type of protection of motors, heaters, any power devices against overload currents. The principle of its operation is based on the possibility of an electric current to heat the conductor through which it flows. The main part of the thermal switch is a bimetallic plate. Which bends upon heating and thereby breaks contact. The heating of the plate occurs when the current exceeds its permissible value. Thermal relay

14 Conclusion All existing operated or newly constructed electric networks shall be provided with necessary and sufficient means of protection, first of all, from electric shock of the people working with these networks, sites of chains and electric equipment from currents of overload, currents of short circuit, peak currents. These currents can cause damage to both the networks and appliances, working in these networks.

15 Thank you for listening.