Protection Target: Prevent transformers from being directly struck by lightning, which could cause insulation breakdown or even equipment burnout.
Implementation Method: Install
lightning rods or lightning conductors near the transformer.
Core Principle: Lightning rods/conductors use their height advantage to attract lightning, guiding the lightning current through the down conductor to the grounding body and into the ground, avoiding direct lightning strikes on the transformer itself.
Protection Target: Suppress lightning intrusion waves (lightning overvoltage propagating along power lines) from entering the transformer and damaging its internal insulation.
Implementation Method: Install
valve-type arresters at the transformer’s inlet and outlet terminals (usually in parallel with the transformer).
Core Principle: When a lightning intrusion wave causes the system voltage to exceed the arrester’s action voltage, the valve-type arrester quickly conducts, shunting the high-amplitude lightning current to the ground, and limiting the overvoltage to a level that the transformer can withstand. After the overvoltage disappears, the arrester automatically recovers to an insulating state.
Protection Target: Ensure that the lightning current from lightning rods and arresters is safely and quickly discharged to the ground, avoiding backflow or residual voltage harm.
Implementation Method: Connect the grounding terminals of lightning rods and valve-type arresters to the
transformer’s working grounding body.
Core Principle: The transformer’s working grounding body is a low-resistance grounding system. Sharing this grounding body for lightning protection not only simplifies the grounding layout but also ensures that the lightning current has a low-resistance path to the ground, preventing the grounding potential from rising too high and causing insulation breakdown between equipment.
Protection Target: Prevent lightning from causing flashover on overhead line insulators near the distribution room, and avoid lightning current intruding into the distribution room along the insulator iron feet.
Implementation Method: Connect the
iron feet of insulators on the incoming and outgoing overhead lines of the distribution room to the substation’s working grounding body.
Core Principle: When lightning strikes the overhead line or induces overvoltage, the insulator iron feet connected to the grounding body can quickly discharge the accumulated charge to the ground, reducing the probability of insulator surface flashover. This also blocks the path of lightning current intruding into the distribution room through the insulator iron feet, protecting internal equipment.
It is worth noting that the effectiveness of all the above measures depends on a reliable grounding system. The working grounding body must maintain a low grounding resistance (usually required to be ≤ 10Ω, depending on the specific standard) to ensure the rapid dissipation of lightning current.
