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In electrical design, grounding system design occupies an important position. Regardless of the type of power distribution system, grounding system design is always included in the design because it relates to the safety of the power supply and distribution system. With the different requirements for power supply quality, each Different equipment functions, grounding system requirements are also different. For different power supply and distribution needs, identify the appropriate power supply mode to provide safe and reliable power supply. The TT grounding method refers to a protection system that directly grounds the metal housing of an electrical device, which is called a protective grounding system, also called a TT system. The first symbol T indicates that the neutral point of the power system is directly grounded; the second symbol T indicates that the conductive part of the load device that is not exposed to the live body is directly connected to the ground, and is not related to how the system is grounded. When the metal shell of the electrical equipment is charged (the phase wire touches the shell or the equipment insulation is damaged and leaks), the grounding protection can greatly reduce the risk of electric shock. However, low-voltage circuit breakers (automatic switches) do not necessarily trip, causing the earth-leakage voltage of the leakage device to be higher than the safe voltage, which is a dangerous voltage. TN mode power supply system This type of power supply system is a protection system that connects the metal housing of the electrical equipment with the working neutral wire. It is called the zero protection system and it is represented by TN. When the device is energized in the enclosure, the zero-crossing protection system can increase the leakage current to short-circuit current. This current is very large, several times that of the TT system. It is actually a single-phase short-circuit fault, and the fuse of the fuse will blow, and the low voltage The release of the circuit breaker will immediately trip and trip, making the faulty device powered off and safer.
During normal operation, there is no current on the dedicated protection line, but there is unbalanced current on the working zero line. The PE line has no voltage to the ground, so the zero protection of the metal shell of the electrical equipment is connected to the special protection line PE, which is safe and reliable. The greater the voltage deviation of the device shell from ground. Therefore, it is required that the load unbalance current cannot be too large, and that the PE line should be grounded repeatedly. In any case, the leakage protector cannot be entered because the action of the leakage protector at the end of the line will cause the front leakage protector to trip and cause a large-scale power failure. When the three-phase load is unbalanced and there is a dedicated power transformer on the construction site, the TN-S power supply system must be used. In some power supply and distribution projects, the construction department requested that the TT system neutral line should be grounded repeatedly. The impact of the lightning protection components is closely related to the test method. It is one of the basic standards for the technical parameters of lightning protection components. The lightning protection of electronic systems and electronic equipment focuses on the induction of lightning. The methods and measures for lightning protection are the installation of SPD equipment at the junction of each lightning protection zone in accordance with the current lightning protection regulations.
During normal operation, there is no current on the dedicated protection line, but there is unbalanced current on the working zero line. The PE line has no voltage to the ground, so the zero protection of the metal shell of the electrical equipment is connected to the special protection line PE, which is safe and reliable. The greater the voltage deviation of the device shell from ground. Therefore, it is required that the load unbalance current cannot be too large, and that the PE line should be grounded repeatedly. In any case, the leakage protector cannot be entered because the action of the leakage protector at the end of the line will cause the front leakage protector to trip and cause a large-scale power failure. When the three-phase load is unbalanced and there is a dedicated power transformer on the construction site, the TN-S power supply system must be used. In some power supply and distribution projects, the construction department requested that the TT system neutral line should be grounded repeatedly. The impact of the lightning protection components is closely related to the test method. It is one of the basic standards for the technical parameters of lightning protection components. The lightning protection of electronic systems and electronic equipment focuses on the induction of lightning. The methods and measures for lightning protection are the installation of SPD equipment at the junction of each lightning protection zone in accordance with the current lightning protection regulations.
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