In our age of high technology, people are surrounded on all sides by a huge number of devices and devices that work with electricity. And the larger their number, the higher the likelihood of electric shock to a person. To avoid this, the RCD was invented. What it is and what it is for, we will describe in detail in this article.
Destination
The residual current device (RCD) is designed to differentially protect a person from electric shock when touching the housing of electrical equipment (household appliances), which, if the insulation is broken, turned out to be energized.
When RCD trips
Let's continue the story about the RCD. What is it and how does it work? An electric current begins to flow through a person who touches the housing of an electrical appliance under voltage. When it reaches a value of 30 mA, the RCD turns off. As a result, the voltage is automatically disconnected from the damaged equipment. Whereina person does not feel anything, since painful sensations occur at much higher currents (from 50 mA). Lethal for humans is a current of 100 mA.
What RCDs consist of
The residual current device includes a current transformer, an actuator (relay and breaking lever system), a self-test circuit. More advanced devices contain in their design a system of electromagnetic and inversely dependent on the magnitude of the cut-off current (protection against short-circuit currents and overload).
The principle of operation of the RCD
What is this? How is this device powered? Now let's talk about all this in as much detail as possible. The RCD is based on the principle of operation of a current transformer (CT). Phase and working neutral conductors pass through the current transformer. With normally operating equipment (with intact insulation), the magnitudes of the currents flowing through them are equal in magnitude, but reverse in direction. As a result, they induce magnetic fluxes in the CT winding, equal in magnitude, but reverse in direction, which completely cancel each other (there is no voltage at the ends of the CT secondary winding). If the insulation of the equipment is broken, part of the phase conductor current flows to the ground through the grounding conductor (if the instrument case is grounded) or through a person who has touched this electrical appliance. As a result of this, the amount of current flowing through the zero working conductor becomes less than the current flowing through the phase conductor. This leads to the fact that the magnetic fluxes inwindings of the transformer become different in size. As a result, voltage appears at the ends of the CT winding. Through the relay connected to them, current begins to flow. When a difference of 30 mA is reached, a relay is activated, which activates a system of breaking levers. Equipment shutting down.
Turn on the RCD
It is done only after identifying and eliminating the malfunction of the electrical equipment that led to the operation of the device by pressing the cocking levers.
Conclusion
In this article, we introduced you to RCD in sufficient detail: what it is, how it works and what it is used for. We hope you find this information useful.
