Three-phase five-wire system connection method for distribution box
The three-phase five-wire system includes three phase wires (A, B, and C wires), a neutral wire (N wire); and a ground wire (PE wire). The neutral line (N line) is the neutral line. When the three-phase load is symmetrical, the vector sum of the current flowing into the neutral line of the three-phase line is zero, but for a single phase, the current is not zero. When the three-phase load is asymmetrical, the current vector sum of the neutral line is not zero, and a voltage to the ground will be generated.
The color of the standard three-phase five-wire system is: A line yellow, B line green, C line red, N line light blue, PE line yellow green.
The three-phase five-wire system is divided into TT grounding mode and TN grounding mode, and TN is specifically divided into TN-S, TN-C, and TN-C-S three modes.
The three-phase five-wire system is divided into TT grounding mode and TN grounding mode, and TN is specifically divided into TN-S, TN-C, and TN-C-S three modes.
TT grounding method:
The first letter T means 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 commonly used in high-voltage systems. It is not suitable for low-voltage systems with large-capacity electrical appliances.
TN-S grounding method:
The letter S represents that N is separated from PE, the metal casing 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 potential of the metal casing of the equipment to the ground is zero. Mainly used for data processing, precision detection, and power supply system for high-rise buildings.
TN-C grounding method:
The letter C means that N and PE merge to form PEN, which is actually a four-wire power supply mode. Both the neutral point of the device and the metal shell are connected to N. Since the 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 is separated from PE, which is a four-wire half-system power supply mode. Used in places with poor environment.
When N and PE are separated, they are not allowed to merge.
China stipulates that the voltage between the phase lines of civil power supply lines (ie, the line voltage) is 380V, and the voltage between the phase line and the ground or neutral line (ie, the phase voltage) is 220V. The incoming line generally adopts a single-phase two-wire system, that is, any one of the three phase lines and the neutral line (as the neutral line). In case of high-power electrical appliances, you need to set up a grounding wire by yourself.
The color of the standard three-phase five-wire system is: A line yellow, B line green, C line red, N line light blue, PE line yellow green.
The three-phase five-wire system includes three phase wires (A, B, and C wires), a neutral wire (N wire); and a ground wire (PE wire). The neutral line (N line) is the neutral line. When the three-phase load is symmetrical, the vector sum of the current flowing into the neutral line of the three-phase line is zero, but for a single phase, the current is not zero. When the three-phase load is asymmetrical, the current vector sum of the neutral line is not zero, and a voltage to the ground will be generated.
