The 400V electrical network has 中��?does not earth, the earth, the neutral axis repetition earths three ways.

Every use leakage protector 400V power supply system, 中��?is must earth, obviously is for establish the electrical network earth information channel. But does not permit the neutral axis repetition earth, because has the possibility to cause like this to leak the protector to appear the divergence to resist to move flows with the string moves by mistake. Obviously, so long as planned carries on the earth monitoring to the electrical network, cannot use the neutral axis repetition to earth the way. But in fact, along with the time growth, the electrical network aging, the earth fault increases, the neutral axis unavoidably appears the repetition earth, moreover was very difficultly discovered, like this may create leaks the protector to malfunction with the work is chaotic, this is a contradiction which is unable to solve.

The net insulation monitor is suitable to the neutral axis is not direct (through total monitor) earths the way, simultaneously has implemented the monitoring to the neutral axis earth, then has solved 400V electrical network n, a, b, the c four earths monitorings question. And promptly removes through the monitoring 接地�? maintains the electrical network to insulate to the place, achieves the monitor function goal.

The 400V electrical network 中��?does not earth, the earth, the neutral axis repetition earth, according to the standard all is the permission, in the concrete implementation also is respectively selects it to need, respectively selects its is good. These three ways respectively have the good and bad points, which better? Only can from need the angle to look that, has met the use need is good. For example, supposes some electrical network to have to use the leakage protector, then the electrical network 中��?must earth, moreover only can 中��?as soon as accept after checking. Because only can satisfy the use leakage protector like this the request. Again for example, supposes some electrical network some current collector to have the special request, the electrical network neutral axis must duplicate the reliable earth, then cost Gao Yezhi has again this.

Through the investigation, every mine pit uses electricity does not permit the neutral axis earth, not the special request ordinary electrical network also mostly uses the neutral axis not to earth the way. What reason? The analysis believed, because the electrical network and the place are does not pass, occasionally appears the earth not to be able immediately the looping-in, therefore such electrical network loses slightly, creates receives an electric shock the casualties and the leakage fire possibility also small, is safer.

Some people thought 中��?the earth system cannot create 中��?the displacement, affects the voltage quality the stability. Truly has this possibility, but this merely is compares with the neutral axis repetition earth system says, the neutral axis repetition earth system truly stabilizes some. But with 中��?as soon as accepts after checking the place system to compare, cannot have the too big difference. 中��?(line) the earth system actually has the following question to be worth paying attention:
1, because 中��?(line) already earthed, could all cause the electrical network phase line to install the strut year to year to withstand the phase voltage, possibly produced divulges, penetrates, creates the phase line earth the possibility to increase.
2, because 中��?(line) already earthed, once had the phase line earth (to contain receives an electric shock) can produce immediately under the phase voltage function very in a big way leaks the electric current, therefore created receives an electric shock the casualties, the leakage fire possibility in a big way, created the loss was also bigger.
3, because 中��?(line) already earthed, when occurred the phase line touched the place, is equal to zero short-circuits, could create stepping down of voltage, affected the voltage quality.
4, because 中��?already earthed, very was difficult to the neutral axis repetition earth monitoring to realize, the neutral axis once appeared the repetition earth, leaked the protector on possibly to appear the divergence to resist to move with the string flows moves the question by mistake, caused it stall or the disturbance normally uses electricity. But duplicates 接地�?is very difficult to find.

Obviously, the electrical network 中��?(line) earthed itself already constituted the electrical network accident hidden danger. The fact proved, so long as according to the standard wiring, three-phase tallies approximately balances, the neutral axis earth system is not may answer the purpose.

Very obvious, 中��?(line) the earth system does not have the following merit:

1, because the electrical network does not earth, the electrical network installed the strut to avoid year to year withstanding the electrical network voltage, greatly reduced the electrical network to install the strut to penetrate, formed 接地�?the probability because of year to year the bearing pressure.

2, because the normal time electrical network does not earth, when the electrical network phase line occasionally has the earth, cannot form in a big way divulges the electric current. Therefore uses electricity loses slightly, creates receives an electric shock the casualties, the leakage fire possibility is also small.

3, because the normal time electrical network does not earth, when the electrical network occasionally appears the earth, this information is very easily monitored, like this for implemented the net insulation monitoring to smooth the way. [ Makes commentary ]
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