Principle of system leakage detection
Most technicians are very familiar with the GFCI sensor for ground fault current detection.The detection principle is as follows:
Having said that, briefly review the type of leakage current type.
1) AC type leakage protector:
The AC type leakage protector is designed for the power frequency sinusoidal leakage current, and can reliably protect the sinusoidal leakage current that is suddenly applied and slowly rising.
2) Type A leakage protector:
In addition to the reliable protection of the sinusoidal leakage signal, the A-type leakage protector can also reliably protect the leakage signal containing the pulsating DC component.
3) Type B leakage protector:
B type leakage protector can reliably protect sinusoidal AC signal, pulsating DC signal and smooth signal
3. Application of leakage current protection in electric vehicle charging piles
1. There are 4 modes of electric vehicle charging piles:
1) Mode 1:
• Charging is not controlled
• Power interface: ordinary power socket
• Charging interface: dedicated charging interface
•In≤8A;Un:AC 230,400V
•The conductor on the power supply side provides phase, neutral and ground protection
In a three-phase system, a chip-type RCMU (leakage current monitoring unit) is placed on the bus. The most important thing is that all three buses pass through the middle hole of the RCMU randomly. The illustrated system does not have a neutral line and is a three-phase three-wire AC system. If it is a three-phase four-wire system, if the current does not run on the center line, the center line does not have to pass through the RCMU. Assuming a 10A load connected to a 480/277vac system, the RCMU will measure it simultaneously. According to Kirchhoff's law, the incoming and outgoing currents will cancel each other out. The current vector sum of the three busbars should be zero. It can be seen from the figure that without considering the direction: 10A-5A-4A = 1A, that is, the leakage current value on the system line is 1A. RCMU's chip-based design principle is different from passive transformers in that it can detect different leakage components and belongs to Type-B RCMU.
1) AC type leakage protector:
The AC type leakage protector is designed for the power frequency sinusoidal leakage current, and can reliably protect the sinusoidal leakage current that is suddenly applied and slowly rising.
2) Type A leakage protector:
In addition to the reliable protection of the sinusoidal leakage signal, the A-type leakage protector can also reliably protect the leakage signal containing the pulsating DC component.
3) Type B leakage protector:
B type leakage protector can reliably protect sinusoidal AC signal, pulsating DC signal and smooth signal
3. Application of leakage current protection in electric vehicle charging piles
1) Mode 1:
• Charging is not controlled
• Power interface: ordinary power socket
• Charging interface: dedicated charging interface
•In≤8A;Un:AC 230,400V
•The conductor on the power supply side provides phase, neutral and ground protection
Electrical safety depends on the safety protection of the power supply grid, and the safety is poor, and it is eliminated in the GB/T 18487.1-2 standard
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