Which device would you use to protect against a sudden increase in electrical voltage?

A surge protector is specifically designed to protect electrical devices from sudden increases in voltage, commonly known as voltage spikes or surges. These surges can occur due to various reasons, including lightning strikes, power outages, or sudden fluctuations in power supply. When a voltage spike occurs, the surge protector diverts excess voltage away from the devices it is protecting, ensuring they remain safe from potential damage.

In contrast, other devices listed have different primary functions. A current transformer is used for measuring current and providing electrical isolation but does not protect against voltage surges. A voltage regulator maintains a steady output voltage level, which is more about stabilizing voltage rather than protecting against excess voltage. Similarly, a capacitor bank is used for power factor correction and energy storage, but it does not specifically provide protection against voltage spikes. Therefore, the surge protector is the clear choice for safeguarding against sudden increases in electrical voltage.