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Gas Discharge Tube Arresters (GDT)

Gas discharge tube arresters, often referred to as GDTs or surge arresters, are an effective and economical way of protecting sensitive devices from random transient disturbances caused by lightning and other sources. Gas discharge tube arresters are the primary form of electrical surge protection used for electronic systems, particularly for outdoor applications.

A GDT arrester is a passive device consisting of a positive temperature coefficient (PTC) resistor with one or more gas-filled tubes coupled to it. When an inundating voltage is applied to the GDT, a spark may jump across the gap between the electrodes of the tube if the voltage is high enough. The spark ignites the gas mixture contained within the tube, creating a hot plasma, which then dissipates the energy of the surge or surge wave.

The actual working principle of the GDT is twofold. First, it is designed to respond only to voltages of particular magnitudes and above. Any surge voltage that is lower than the specified breakover voltage of the GDT will not cause breakdown of the gas. This places a significant limitation on the capability of the GDT to operate in areas with partially exposed power lines, since the voltage differences caused by them are often too low to cause a breakdown.

Secondly, the working principle of the GDT is based upon a low-voltage negative-resistance characteristic. This means that as the voltage increases, the current will decrease until a certain voltage (breakdown voltage) is reached; only at this point will the current increase steeply, dissipating the energy of the surge and clamping the GDT’s output voltage. It is this characteristic that allows the GDT to effectively protect against lightning strikes (or other high-voltage events) without interfering with daily operation. This feature also allows for a more precise voltage protection, since it limits the response to only those voltages of sufficient magnitude to cause damage.

In addition, GDTs are often matched to the line of protection in order to provide the best combination for the application. Different varieties of GDTs are available for various voltage classes, current levels, operating frequencies, surge lengths and pulse shapes. Other considerations include the surge arrestor’s ambient temperature ratings, environmental reliability, quality control, mounting and maintenance requirements.

Finally, GDTs are highly economical devices compared to other surge arrestors on the market. GDTs also provide a self-resetting and self-clearing capability, reducing the need for manual resetting or physical examination. Furthermore, the breakdown is an electrically clean process, thus the arresters are free from harmful back-arc and spark jumping, making them suitable for all classes of high isolation systems.

GDTs typically have a lifetime of up to 100 years or more when used in accordance with the manufacturer’s specifications. This makes them an ideal choice for applications requiring long-term protection from random transient disturbances.

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