Oklahoma Electrical Practice Exam

How many surge arresters are required for a 4 wire WYE-connected grounded system in an area with frequent thunderstorms?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 3

In a 4 wire WYE-connected grounded system, the requirement for surge arresters is based on protecting each phase of the system from transients, such as those caused by thunderstorms. A WYE-connected system typically includes three phases and a neutral wire. For effective protection, it is advisable to install a surge arrester on each of the three phases, as this helps to shield the system from voltage surges that may occur on any of the phase conductors, such as during a thunderstorm when electrical surges are common. Additionally, while the neutral wire is typically considered grounded and might not require a separate surge arrester, having protection on all phases ensures that any differential surge in voltage between the phases is effectively managed. This helps in preventing equipment damage and maintaining system integrity during voltage spikes. Thus, installing surge arresters on all three phases aligns with best practices for safeguarding electrical systems in environments prone to severe weather, making three arresters the optimal solution for this situation.