Which protection devices are commonly used by transformers?

The correct answer focuses on grounding devices, which play a crucial role in the protection of transformers. Grounding helps to mitigate the risk of electrical faults, such as short circuits or insulation failures, by providing a safe path for fault currents to flow into the ground. This helps to prevent damage to the transformer and maintains safety for users and equipment.

Grounding devices are essential for ensuring that any excess voltage is safely dissipated, thus protecting the transformer from damage that could be caused by lightning strikes, power surges, or other electrical abnormalities. They are an integral part of any electrical installation where transformers are used, ensuring both the equipment and the surrounding environment are safeguarded.

Other options like fuses and circuit breakers are also important protective devices, but they are not as directly related to the function of grounding. Surge protectors are designed to protect from voltage spikes, while resistors typically do not serve as protective devices in the sense of safeguarding transformers.