*Question E4E14:
What is the purpose of a single point ground panel?*  

*Correct Answer is  D: Ensure all lightning protectors activate at the same time*  

### AI Response: (may contain errors)  

A single point ground panel is used to ensure that all lightning protectors activate at the same time. This is crucial for protecting equipment from lightning strikes or other electrical surges.

### Explanation:

1. **Correct Answer (D): Ensure all lightning protectors activate at the same time**
   - A single point ground panel provides a common grounding point for all equipment and lightning protectors. By having a single grounding point, it ensures that all protectors are at the same electrical potential. This synchronization is essential for the simultaneous activation of all lightning protectors, which helps to prevent damage from voltage differences during a surge.

2. **Why the Other Choices are Incorrect:**
   - **Choice A: Remove AC power in case of a short-circuit**
     - A single point ground panel does not function to remove AC power. Instead, circuit breakers or fuses are used to disconnect power in the event of a short-circuit.
   
   - **Choice B: Prevent common-mode transients in multi-wire systems**
     - While grounding can help reduce common-mode transients, the primary purpose of a single point ground panel is not specifically to address this issue. Other techniques, such as using twisted pair cables and proper shielding, are more directly related to preventing common-mode transients.
   
   - **Choice C: Eliminate air gaps between protected and non-protected circuits**
     - A single point ground panel does not eliminate air gaps. It is concerned with providing a common grounding point rather than physically bridging gaps between circuits.

### Key Concept:
- **Single Point Grounding**: This technique minimizes potential differences between different parts of the system during a surge, ensuring that all protective devices operate in unison. This is critical for effective surge protection.