Protection techniques play a fundamental role in guaranteeing the integrity and safe operation of any electrical energy system. The first protection systems were based on electromechanical devices employing movable parts and in a later period of development, solid-state based devices with discrete components were introduced. Although both types of devices are still widely used in on-operation protection systems, they are currently being replaced by microprocessor-based relays, knows generally as digital or numerical relays. The latter protection technology has permitted that many new techniques be implemented. With the development of digital technology, more and more protection functions for any given apparatus (line, transformer, generator, etc.) have been implemented within one protective device to achieve a certain degree of integration. The benefits of numerical relays are accurate tripping, less tolerance, display of fault parameters on screen and faults events and counter storage. The relays used in power system protection are of different types and De Lorenzo, to highlight the main industrial components used in practice, has designed the following digital relays such as differential transformer relay, distance relay, feeder manager relay, generator differential relay, inverse time overcurrent relay and earth-fault relay. All of them have RS485 interface for communication MODBUS, which gives the possibility to be integrated with the SCADA software, thus to set and monitor all the main parameters under control. They are dedicated to high schools and first years of university.
In electrical power supply systems, currents and voltages are constantly measured and monitored to ensure that they remain within certain limits. In general, the current and voltage values are so high that they cannot be measured directly.
Special transformers have to be used to reduce these values to a level that can be measured safely and economically. These values are needed in order to provide information on the health of the system, to calculate the amount of power supplied to a customer and to rapidly switch off sections of a network in case of a fault event to avoid its propagation that could result in the collapse of the entire power supply system.au dans le cas d’une défaillance afin d’éviter sa diffusion vu qu’elle pourrait entraîner dans l’effondrement de toute le système d’alimentation de courant.
Dedicated protection relays are used for monitoring each section of the power system (generators, transformers and transmission lines), to recognize a damaged system component for a specific fault event (under/over voltage, under/over frequency, over-current, earth-fault, reverse power, etc.), and to disconnect it quickly and reliably, protecting humans and the other healthy parts of the system while maintaining the power distribution.