The differential machine is a combined power line protection device that combines a classic machine and an RCD (photo below).
This overview will help the user understand the design features of this device, as well as familiarize himself with the existing schemes for connecting it to the home electrical network.
Differential automaton functions
One should start acquaintance with this complex device with its purpose and functions performed by it.
They are as follows:
- reliable protection of a person from dangerous electric shock by detecting leaks through his body;
- instant disconnection of the damaged section of the power grid, in which a short circuit has occurred or an overload is in effect;
- ensuring the safety of expensive equipment connected to the network.
Thus, the device considered here guarantees reliable protection against all dangerous manifestations of electric current that occur in the lines.
How the machine works and works
Protection of the electrical network against overload and short circuit is provided by a separate automatic module (automatic machine), which includes a shunt release and a thermal relay. To protect a person from electric shock, the complex device provides a differential protection unit that reacts to leaks in the controlled circuit.
To do this, he constantly compares the values of currents flowing in and out of it. The situation when there is a difference between them is regarded as potentially dangerous for living organisms and equipment connected on the load side. When it occurs, the differential module, by means of a built-in amplifier and an electromagnetic relay, instantly disconnects the hazardous area from the mains.
Rules and methods of connection
The inclusion of a difavtomat in an electrical circuit is no different from connecting an RCD to it and is therefore performed according to the same rules, namely:
- phase and neutral wires are connected to one such device, which relate only to this protected line (photo below);
- combining neutral wires from other devices on a common busbar (from a linear machine, for example) is undesirable;
- if this requirement is violated, then when a leakage current appears, the triggered device will disconnect the entire supply network.
Two possible ways of connecting a difavtomat follow from the listed rules, one of which is beneficial from the point of view of economy (when zero buses are combined). In the second case, the differential device protects only the dedicated line and, when a leak is detected, only disconnects it. This option is somewhat more expensive, but it allows you to selectively control the state of the circuits.
There is another method of switching on, in which a two-level protection of the supply line is organized. In this case, the selectivity of the protective action is ensured due to the operation of the series-connected difavtomats, designed for different leakage currents (photo below).