Distinguish between the limited approach boundary and the restricted approach boundary.

• A. Limited boundary is for unqualified persons with a safe approach to live parts; restricted boundary is for qualified persons with proper training and PPE to approach more closely.
• B. The restricted boundary is always larger than the limited boundary.
• C. Limited boundary refers to a voltage threshold, restricted boundary to a current threshold.
• D. There is no difference between the two boundaries.

Answer: (C)

The main idea here is that these boundaries are defined by different electrical hazard criteria. One boundary is determined by the voltage present, while the other is determined by the current that could flow through a person if contact or a fault occurred.

Limited approach boundary is set by a voltage threshold. It marks the distance from exposed energized parts within which a shock hazard can exist due to the voltage difference. This boundary helps determine how close someone can get to live parts without the appropriate protection and procedures, focusing on the potential for shock from the voltage itself.

Restricted approach boundary, on the other hand, is defined by a current threshold. It represents how close a person can approach where the current that could flow through the body under fault conditions would be hazardous. This boundary emphasizes the likelihood and severity of injury from current flow, and access is restricted to qualified persons who have received the proper training and are equipped with the required PPE and procedures.

So, the key distinction is that one boundary is anchored to voltage levels and the shock hazard they can produce, while the other is anchored to the current that could pass through the body under fault conditions. This difference in what each boundary is based on explains why they are treated as separate concepts in safety guidelines.