TN Grounding Mode of Three-Phase Five Wire System

TT grounding method:

The first letter T indicates that the neutral point of the power supply is grounded, and the second T is the grounding of the metal casing of the equipment. This method is generally used in high-voltage systems, and should not be used when there are large-capacity electrical appliances in low-voltage systems.

TN-S grounding method:

The letter S represents that N is separated from PE, the metal shell of the equipment is connected to PE, and the neutral point of the equipment is connected to N.

The advantage is that there is no current in PE, so the metal casing of the equipment has zero potential to ground. Mainly used for data processing, precision detection, power supply system of high-rise buildings.

TN-C grounding method:

The letter C means that N and PE are combined into PEN, which is actually a four-wire power supply method. Both the equipment neutral point and the metal casing are connected to N. Since three-phase unbalanced current and harmonic current flow when N is normal, the metal casing of the equipment normally has a certain voltage to the ground, which is usually used in general power supply places.

TN-C-S grounding method:

Part of N and PE are separated, which is a four-wire half-system power supply mode. It is used in places with poor environment.

The standard wire colors of the three-phase five-wire system in China are: A wire is yellow, B wire is green, C wire is red, N wire is blue, and PE wire is yellow-green.

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