Interruption of the neutral conductor (or "burning-off the ground") - a very common phenomenon, familiar to most service personnel grids. This damage can occur not only in the three-phase line, but also on the input in the riser or in an apartment.
In the latter two cases, it appears as a broken PEN conductor for common ground system and N conductors - for its separate options. To understand the essence of burning-off of zero, first try to understand the causes of this phenomenon.
Causes of failure
When forming part of the load current 380 volts of electricity is connected to a separate group of consumers of each phase (residential houses or apartments). Like last windings of the transformer station connected on a "star" and distributed in phases as evenly as possible. In this case, the vector compensated current components, and their total value in the neutral conductor is close to zero.
Any deviation from the normal distribution is skewed phases and a zero conductor appearance in the resultant parasitic currents.
Important! Since the number of households that are connected to each of the phases is constantly changing - without phase asymmetry nutrition impossible to do.
As a result, the neutral conductor is always current flows in the direction of the neutral biasing one of the phases (see photo below).
When the significant largest phase skew section of the neutral conductor may not be enough to withstand the resulting increased current. When the conductor is heated, it gradually leads to its subsequent erosion and failure.
Zero causes breakage in single-phase networks may include:
- Poor contact, as well as damage to the combined conductor PEN retraction from the transformer substation (pictured below).
- The same thing, but what happened in the linear branch in the residential building.
- Dropouts reliable connection cable at the place of entry into the dispenser.
- Violation contact in the wiring of premises (apartments).
First, these faults appear as a short-term loss of light or turn off the device, but gradually all consumers do not work at all.
At break ground in three-phase effects can be very dangerous for the connected equipment, and especially - for the person. Due to the considerable phase unbalance on separate wiring lines become effective voltage close to 380 volts.
On the other phase branches, on the contrary, they are reduced to almost zero. This stress distribution pattern in the first place is dangerous for the connected electrical appliances which are likely to simply "be burned up."
Important! At the same time there is a risk of overheating the aluminum wiring, which is fraught with serious consequences themselves (up to the fire).
Furthermore, if the object is connected to the system TN-C (combined with PE and N buses) - strand breakage general lead to the loss of protective function s. In this case, in the absence of re-grounding the consumer will be totally unprotected.
He did not help, and set in the apartment special equipment (RCD), because without "zero" This device can not work.
Furthermore, in a situation with a broken neutral hazardous voltage as the potential of 220 volts across the load falls permanently connected to the second terminal.
As a result, in the working outlets there is another phase, which is extremely dangerous in the absence of a full-fledged ground. In case of accidental damage to insulation in the washing machine, for example, will have nowhere to drain current, as "zero" torn (see photo).
For a user standing on a concrete floor and touched the body of the unit with the phase trapped him, this situation is extremely dangerous, because the entire fault current will flow through his body.