How to ensure the power supply safety of landscape lights?

What are the basic power supply systems?

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u003cbru003eThe basic power supply system used in construction engineering power supply includes three-phase three-wire system, three-phase four-wire system, etc., but the connotation of these terms is not very strict. The International Electrotechnical Commission (IEC) has made uniform regulations on this, which are called TT system, TN system and IT system. Among them, the TN system can be divided into three categories according to the different ways of connecting the exposed conductive parts of the electrical equipment to the system: namely TN-C system, TN-S system, TN-CS system.

u003cbru003e IT system: The neutral point of the power transformer is not grounded (or grounded through high impedance), and the electrical equipment housing uses protective grounding.

u003cbru003e TT system: The neutral point of the power transformer is grounded, and the enclosure of electrical equipment is grounded.

u003cbru003e TN system: It is called protection connection zero. When the fault makes the metal shell of the electrical equipment live, the phase line and the neutral line are short-circuited, the loop resistance is small, the current is large, and the fuse can be quickly blown or the protection device can act to cut off the power supply.

u003cbru003eWhat is the scope of application of different power supply systems?

u003cbru003e When the power supply distance of the IT system is not very long, the reliability and safety of the power supply are high, and it is generally used in places where power outages are not allowed, or places that require strict continuous power supply, such as electric power steelmaking, large hospitals Operating room, underground mine, etc.

u003cbru003e TT system does not rely on equipotential bonding to eliminate electrical accidents caused by fault voltage conducted by PE wires elsewhere, so TT system is mainly used in some outdoor installations that are difficult to equipotential bonding, such as street lamp installations, agricultural electricity Wait for the occasion.

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u003cbru003e TN-C system: 1. General industrial plants and places where the three-phase load is relatively balanced, the third harmonic current in the circuit is not large, and there are professional maintenance and management. 2. It is not suitable for electronic equipment sensitive to low pressure and explosive dangerous environment.

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u003cbru003e TN-C-S system: is a widely used power distribution system, suitable for industrial and civil buildings.

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u003cbru003e TN-S system: 1. Places where single-phase loads are concentrated 2. Places that require explosion protection. 3. Places without precision electronics and data processing equipment. 4. Places with many third harmonic current equipment.

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u003cbru003eWhich power supply system is more advantageous for landscape lights?

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u003cbru003e Now that there are more and more landscape lighting projects, the safety of electricity consumption cannot be ignored. According to the third point of Article 10.9.3 of the 'Civil Building Electrical Design Code JGJ 16-2008': 'The indoor landscape lighting should be in line with the building The grounding pattern of the power distribution system is the same. The facilities installed within 20m from the exterior wall of the building in the outdoor landscape lighting should be consistent with the grounding form of the indoor system, and the TT grounding form should be adopted for those more than 20m from the exterior wall of the building.'

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u003cbru003e It is understood that the TT system is basically adopted for street lamps, and each lamp has an independent ground. The distance between landscape lighting and buildings is basically greater than 20m. It is not realistic to use single lamp grounding. Now most landscape lighting grounding systems use TN-C-S systems. Is the TN-C-S system suitable? The following analysis is for your discussion.

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u003cbru003e Outdoor landscape lighting is generally far away from the substation. The power supply is generally led by the TN-C system (four-wire). The PEN line is repeatedly grounded in the distribution box. If the PE line is drawn out for protection, the power supply system is It becomes a TN-CS system, and sometimes the drawing review fails. The landscape lamp adopts the TT system. It is unrealistic for each lamp to have an independent grounding pole. Only the grounding bus bar is used to connect the grounding of all lamps together. The simplest way to connect the grounding busbar is to use a five-core cable and PE wire as the ground connection line. It can be seen here that the biggest difference between the TT system and the TN-C-S system is whether the ground wire is repeatedly grounded with the power supply line, followed by the difference in ground resistance.

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u003cbru003eConclusion

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u003cbru003e Regardless of whether the TN-CS system or the TT system is used, a leakage protection switch should be installed in the front of the power supply circuit. When the lamp leakage occurs, the reliable grounding of the lamp can avoid personal injury. At the same time, the leakage protection switch acts to quickly cut off the power supply. , Protecting personal safety. Therefore, good grounding and leakage protection are essential safety measures for landscape lighting.