Detailed Explanation of Tiered Surge Protection for Distribution Boxes

In lightning protection, the surge protection device in distribution boxes plays a crucial role. According to the principle of graded lightning protection, and based on the likelihood of a building being struck by lightning, it is necessary to deploy surge protector against lightning in stages to ensure the safety of the power system and electrical equipment.

Level 1 Protection: Main Distribution Box Surge Protection

Scope of Application

The main distribution box at the power supply system's entry point.

Purpose

Absorb high-energy surge currents and protect downstream circuits and equipment.

Installation Recommendations

• Connect the three-phase wires A/B/C to the corresponding terminals of the surge protector.

  
  

• The yellow-green ground wire should be connected to the distribution box's dedicated surge protection grounding terminal (note: not the power ground or protective earth).

  
  

Technical Requirements

• Level 1 SPD box surge discharge current ≥ 12.5kA.

  
  

• Maximum discharge capacity: ≥ 100kA per phase.

  
  

• Voltage protection level: ≤ 2500V.

  
  

The Level 1 surge protection device is designed to withstand high-current surges from direct lightning strikes or induced lightning. It diverts most surge current to the earth. This device mainly protects the basic safety of the power system and provides a medium level of voltage limitation, but cannot fully protect sensitive equipment within the system.

Level 2 Protection: Distribution Equipment Surge Protection

Scope of Application

Distribution boxes supplying power to important or sensitive equipment.

Purpose

Further absorb the residual surge energy after Level 1 protection and enhance the ability to suppress transient overvoltages.

Installation Recommendations

• Install the Level 2 surge protection device in the distribution equipment to focus on protecting sensitive equipment.

  
  

Technical Requirements

• Maximum discharge capacity: ≥ 40kA per phase.

  
  

• Voltage protection level: ≤ 2000V.

  
  

Level 2 protection mainly focuses on suppressing transient overvoltages and effectively absorbs the residual surge energy after Level 1 protection. This level of protection is usually sufficient for the normal operation of most electrical devices.

Level 3 Protection: Terminal Equipment Surge Protection

Scope of Application

Within the electrical equipment or at the terminal power supply.

Purpose

Completely eliminate the effects of micro transient overvoltages and protect precision electronic equipment.

Installation Recommendations

• Install the Level 3 surge protection device inside the equipment or at the equipment's power supply input, especially for critical or sensitive electronic devices.

  
  

Technical Requirements

• Maximum discharge capacity: 20kA per phase or lower.

  
  

• Voltage protection level: ≤ 1800V.

  
  

Level 3 protection is the final barrier of the system, capable of fully eliminating any transient overvoltage that may occur, ensuring the long-term stable operation of sensitive equipment.