2036-23-B3LF

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Gas Discharge Tube Arresters (GDT)

The 2036-23-B3LF application field and working principle of Gas Discharge Tube Arresters (GDT) is an important topic in the protection of electric power systems. This type of arrester is used in a wide variety of applications, such as Voltage-limiting, Short-circuit protection, High Speed Short-circuit protection, High Current and Voltage Protection and Surge protection. Specifically, GDTs are used for the protection of primary and secondary facilities against lightning and other overvoltage transients. The GDT protects the systems from the damaging effects of overvoltage by utilizing the gas discharge principle that leads to a very rapid breakdown of the gas inside the tube, and consequently a large impedance decrease.

The working principle of the GDT rests on the arrangement of two electrodes to which a constant voltage is applied. In case of overvoltage or transients, the applied voltage exceeds the breakdown voltage of the filled gas and leads to the generation of a spark. This spark transfers energy into the environment thus causing a current between the two electrodes leading to current flow through the discharge tube. The voltage across the tube is significantly reduced and the surge is absorbed by the discharge tube.

In order to further understand the working principle of a GDT it is important to take into consideration the breakdown characteristics of the gas; these characteristics depend on the type and pressure of the gas inside the tube, the shape and diameter of the tubes, and the type of electrodes used. At the time a spark appears, and depending on the set of parameters described earlier, the output voltage can differ enormously; this voltage is also referred to as the “gaseous withstand voltage”. Once the spark is developed, the path resistance is extremely low and the current can be very large. During this process, energy is released in the form of heat, the generated electrode oxide has a much higher resistance, and this serves as an isolator between the atmospheric voltage and the electrode. This holds until the overvoltage is fully absorbs and the oxide is broken down. In case of an unidirectional spark, the current in the tube is rapidly reduced to a minimum at the moment when the oxide is fully formed.

Reducing the protection voltage of the GDT is also an important factor to consider when working with GDTs. The voltage reduction is caused by the faster charging of the capacitance. The capacitive effect is a function of the applied voltage, and the speed of the breakdown of the oxide. This results in an altered charging of the capacitance, thus leading to a reduction of the voltage. The amount of voltage reduction depends on the applied voltage, the capacitance, the current, and the time. These parameters are important in order to determine the amount of voltage reduction and level of protection.

In conclusion, the working principle of a GDT is based on the gas breakdown phenomenon. A voltage exceeding the breakdown voltage leads to the occurrence of a spark inside the tube, leading to a large current flow. This current reduces the overvoltage, thus protecting the system and facilities from potential damages. The voltage reduction is due to the capacitive effect, and the effect is a function of the applied voltage, the capacitance, the current, and the time. This provides an insight on the working principle of a GDT, and how it is used in a wide variety of applications to protect electric power systems from overvoltages.

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