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Diversified grounding protection ensures street lamp network security

With the development of urban streetlights, most of the past cement poles have been replaced with metal poles. The grounding protection problem is particularly prominent. In addition, the streetlight cable is mainly laid in the ground, with many contacts and is very susceptible to operation. Chemical erosion and damage of external forces, short circuit and leakage faults occur, which requires us to have a perfect grounding protection device to ensure the normal operation of the street lamp network. In response to this need, the Bureau has set up a QC team for street lighting network protection, using a variety of grounding protection measures to ensure the safe operation of the street lamp network.

street lamp

First, connect all metal poles.

The family knows that the grounding is divided into working grounding, protective grounding and lightning protection grounding according to its function. The grounding of the metal pole is both a protective grounding and lightning protection grounding. According to the regulations, “the grounding resistance of the low-voltage power equipment grounding device should not exceed”, but it is actually difficult to achieve this standard. To this end, we have considered the grounding protection of metal poles from the design stage. We have placed a single wire to connect all the metal poles together. As a grounding pole, the grounding resistance of the pole can be greatly reduced. Claim.

Second, install a leakage protector at the bottom of the metal pole.

For this measure, the peers have been controversial until now. We believe that in the street lamp 380V/220V power supply system, when a certain fire line in the lamp post is charged due to insulation damage, the body resistance and the lamp post grounding resistance are in parallel. Once the human body touches the lamp post, the leakage current exceeds 50 mAh, this is very dangerous. Because the electric current flowing through the human body is small when the electric shock accident occurs, the line protection device cannot operate under such a small leakage current. Therefore, relying solely on the basic grounding cannot be absolutely guaranteed to be safe, and it must be in the metal lamp post power supply. Install a leakage protector at the line position.

Third, install a fuse in the lamp.

Due to the large number of electrical components in the luminaire, in order to avoid the entire line tripping caused by electrical faults inside a luminaire and to expand the fault range, a 6A quick-fuse insurance should be installed in each luminaire. Fast-blow insurance can not only be used as over-current protection for lamps, but also as backup protection when the leakage protector does not operate.

Fourth, Install the “Street Light Automatic Control Box” on the low voltage side of the street light transformer.

The street light automatic control box has overcurrent and overvoltage protection functions and features high current grounding protection. When the cable line has a ground fault, as long as the ground current is greater than 8A, the street light automatic control box can quickly cut off the power supply, thus ensuring personal and equipment safety (4 health? A = 32V, less than the safe voltage 36V). Here, it is necessary to note that cable ground faults often occur. Before the grounding protection device is installed, the grounding fault of the buried cable is generally difficult to detect. The long-standing ground current will not only consume a lot of power, but also be dangerous. The hidden danger of the accident, I hope to attract everyone's attention.

In short, the metal poles are connected together as a grounding pole, which greatly reduces the grounding resistance of the pole, which provides a basic guarantee for the reliable operation of the grounding protection device; the installation of a leakage switch at the incoming line of the metal pole ensures personal safety; Install a quick-blow fuse in each luminaire to avoid the expansion of the fault range; install a “street light automatic control box” on the low-voltage side of the street light transformer to protect the street light line. At present, our Jingzhou Street Light Administration has jurisdiction over 125 streetlights, 12,000 street lights and 400km low-voltage lines. Since the establishment of the Jingzhou Street Light Administration in 1996, there has never been an electric shock accident, which proves that our street lamp network grounding protection The measures are still perfect.

Of course, the problem of street lamp grounding protection needs to be paid attention to by leaders and departments at all levels, from design, pipeline pre-burial, foundation watering, grounding resistance shaking, pole, foundation connection, lamp installation, power wiring, project completion acceptance, etc. The links are carefully checked to fundamentally prevent the occurrence of electric shock accidents.

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