ABYC Marine Electrical Practice Exam

Where should overcurrent protection be installed in relation to a transformer?

1. Secondary side

2. Primary side

3. Ground side

4. Neutral side

The correct answer is: Primary side

Overcurrent protection for a transformer is ideally installed on the primary side to safeguard the transformer and the supply circuit against excess current. This placement serves multiple important purposes. Firstly, installing overcurrent protection on the primary side ensures that any fault conditions, such as a short circuit or overload, are addressed before they can affect the transformer itself. It prevents potentially damaging high currents from reaching the transformer, helping to maintain its operational integrity and longevity. Secondly, primary-side protection aligns with the concept of protecting the entire electrical system feeding the transformer. If overcurrent occurs in the supply circuit, the protection device will trip, de-energizing the transformer and any connected loads before significant damage can occur. Furthermore, it is easier and more effective to protect the power supply system at its source, rather than downstream where the transformer is. In contrast, placing overcurrent protection on the secondary side may leave the transformer itself vulnerable to damage from events in the supply line. Ground side and neutral side configurations do not provide the same level of protection since the primary objective is to monitor and disconnect power before it impacts the connected transformer or loads.