The design scheme for lightning protection grounding of high pole lights is essential as these lights are installed outdoors and are of considerable height. The threat of lightning strikes on high pole lights is significant. A direct lightning strike can damage both the luminaire and the pole, leading to considerable losses. The energy contained in a direct strike is immense, with voltage levels that can reach 5000 kv, causing extensive destruction. Based on years of practical research on high pole lights, it is noted that LED power supply voltages generally fall within the range of 12v or 24v, which are considered safe voltages. However, appropriate lightning protection grounding measures are necessary. The main reasons for lightning strikes affecting LED high pole lights include the following.
Lightning currents generate powerful electromagnetic waves, inducing extremely high pulse voltages in power and signal lines. The heat generated by lightning passing through electrical equipment can lead to fire or explosion incidents. Frequent discharges between thunderclouds create intense electromagnetic waves causing common-mode and differential-mode interference, affecting the operation of electrical equipment.
Currently, the external materials of most LED high pole lights are conductive, essentially making them a form of lightning rod. Therefore, if no conductor taller than the pole is present nearby during a lightning strike, the pole itself can guide the lightning and disperse it into the ground through grounding devices, preventing equipment damage and personal safety incidents. The LED high pole light poles are made of steel and hot-dip galvanized, allowing the pole itself to act as a down conductor. Since the exterior is coated with powder for insulation, it retains a level of insulating capability while ensuring the conductivity of the grounding line.
Overvoltage from high pole light switches occurs due to the opening or closing of inductive and capacitive loads within the power supply system, or a short circuit in the power lines, leading to high-voltage pulses in the power lines. The pulse voltage can reach 3 to 5 times the normal voltage, potentially damaging equipment severely. The destructive effects are comparable to those of lightning strikes.
The grounding device is constructed using hot-dip galvanized angle steel of 50*50*T5 dimensions, with a length of 1875px. One end of the angle steel is cut to a sharp point to facilitate deep burial underground, while the other end is welded to hot-dip galvanized flat steel with a width of 50mm, maintaining a welding width that is double the width of the flat steel. Corrosion protection measures are applied at the welding joint. The completed grounding device should be vertically buried at least 1m below the ground surface during the foundation construction of the high pole light. After the pole is erected, the flat iron is welded to the flange of the high pole light with a welding width that is double that of the flat iron. Once the installation of the high pole light is complete, a grounding resistance tester should be used to verify that the lightning protection grounding meets the required standards.
