On any modern facility using the services of suppliers of electricity, it should be provided protection from dangerous potential 220/380 volts.
According to current standards (SAE, in particular) for these purposes in homes and buildings are arranged special design called grounding devices (memory), or simply grounding. Their main purpose - to protect the person using household appliances and power grid itself from possible electric shock (photo below).
The operating principle of the ground
To understand the essence of the action of the grounding device is enough to remember that electric current always flows through the path of least resistance.
In connection with this easy to imagine a situation where metal casing or electrical accident are under high voltage (due to damage to the insulation, for example). In this case, the only sure way to protect the working person with them is to organize the chain drip dangerous current into the ground.
This feature provides immersed into the ground the grounding circuit, which is associated with the elements of the protected electrical enclosure. If any dangerous current is decreased for a person to minuscule quantities, because most of it flows into the ground merely by parallel chain (pictured below).
Note: The amount of current flowing through the human body, is largely determined by the isolation of his feet from the ground.
When quality protection (with rubber shoes, in particular), the current through the human body even decrease, approaching zero. That is why the novice and experienced electricians prefer to work with the equipment while standing on the rubber mat (ie, at a good insulator feet from the ground).
ground organization
It is important to know that to organize the effective grounding (earthing circuit to make a qualitative) have failed to do in all cases.
To this end, in the vicinity of the protected power line to which instruments or equipment should be placed dirt earth. Build a memory the easiest way is in a private house on a plot next to which there is always space to accommodate its members.
It is quite another - a city apartment house, where the organization Remote protective circuit seems an impossible task. In this case, usually cost alternative protection means (RCD installation, in particular).
Classic ground loop or simply earthing switch consists of the following mandatory elements:
- Driven into a depth of about 2-3 meters metal bars (rebar segments) arranged in a pre-dug trench in the shape of an equilateral triangle.
- Connecting them to weld steel bridge (photo below).
- The copper or steel outlet connecting the whole structure to the main earthing bus, located in the control cabinet houses.
Additional Information: Plane location triangular contour is recessed into the ground about 50-60 cm.
After the end of excavation and installation work is filled with the resulting design is simple folded before the earth.
Checking function of grounding loop
When the grounding circuit connected to the electrical shield, with a multimeter need to check the value of the voltage between the phase contact and the earthing bar. It should be approximately the same as that between the phase and neutral conductors. This demonstrates that the ground is functioning properly.
Ground bus, intravascular into the house, decided to paint in black light. Flexible copper wire used to connect the bus electrical grounding in switchboard has insulation repetitive colored yellow and green stripes.
conclusions
To be clear about why you need to ground - it is important to understand its basic function, which consists in the organization of parallel chains to drain current.
In this case touches the damage to the instrument or equipment the person is protected from the effects of dangerous currents. It is also important to know that for the efficient operation of its grounding resistance of the system is periodically checked for compliance with the permissible level (see PUE).