What is an expulsion arrester characterized by?

An expulsion arrester is characterized by having vented ports, which is a distinct feature of this type of device. The vented ports are crucial because they allow gases to escape when the arrester operates, particularly during a fault condition. This attribute helps to prevent the buildup of pressure that could lead to failure or damage to surrounding equipment.

The function of these vented ports is to expel the ionized gases produced when the arrester is conducting excessive voltage, helping to safely redirect or dissipate the energy associated with voltage surges. This design is particularly important in maintaining system safety and reliability, ensuring that the arrester can effectively protect the electrical system from overvoltage conditions.

While other characteristics like low cost and simplicity may be relevant to the design and implementation of other types of arresters, they are not defining features of expulsion arresters specifically. Similarly, reliance on external power does not apply, as expulsion arresters operate based on their internal mechanisms rather than external power sources.