A surge protector limits the voltage supplied to the electrical devices to a certain threshold by short-circuiting current to ground or absorbing the spike when a transient occurs, thus avoiding damage to the devices connected to it. These devices typically offer multiple AC outlets for complete home surge protection. What is a Surge Protection Device (SPD)? Types and Working Principle Electricity helps run various devices such as computers, lights, refrigerators and air conditioners. However, with every advantage, there are some drawbacks too, and in this case, power surges are a menace. Founded in 1923, the family-owned company now employs around 14,000 people worldwide.