2036-09-SM

Gas Discharge Tube Arresters (GDTs) are surge protective devices which are designed to protect electrical and electronic equipment from the devastating effects of overvoltage. GDTs are usually the last line of defense for these systems, providing fast response to transient overvoltage events and significantly mitigating their intensity.

GDTs vary in their applications and how they work. In general, they are divided into two categories based on their specific function-stationary GDTs and portable GDTs. Stationary GDTs are connected directly to the electrical equipment they are protecting. This includes power substations, communications systems, and radar systems, among others. They are designed to constantly monitor the voltage of the system and activate when a transient voltage event occur. Portable GDTs are more often used in lightning protection apparatus and networks, providing protection from isolated lightning strikes.

Under normal operating conditions, GDTs remain in an off state. This is achieved by keeping the voltage between the two electrodes below the GDTs normal breakdown voltage. In the event of a transient overvoltage event, the voltage rises to a level higher than the GDTs normal breakdown voltage, causing a current to flow between the two electrodes. This current flow determines the speed and magnitude of the response of the GDT and thus determines the effectiveness of its protection of the system.

The most common type of working principle used by GDTs is referred to as “breakdown voltage switching,” which is also known as “triggering voltage switching.” This type of working principle is characterized by a very rapid response to the overvoltage condition, leading to a rapid interruption of the current flow and thus a very effective protection of the system.

Another working principle used by GDTs is referred to as “clamping voltage switching.” This principle allows the GDT to operate at a lower voltage, where the current flow is only partially interrupted. This allows for a slower but still effective response to the overvoltage event.

Finally, there is the “thyristor-controlled voltage switching” principle, which is characterized by an even slower response to a transient overvoltage event. This type of GDT has a special component, a thyristor, which controls the flow of current to the GDT. This enables the GDT to delay its response to the overvoltage condition, allowing for a more controlled response time.

In conclusion, GDTs are an essential part of any electrical system, providing protection from the potentially devastating effects of an overvoltage event. It is important for engineers and technicians to understand the different types of GDTs and the different types of working principles they employ, in order to ensure that their system is adequately protected from the threat of overvoltage.