What is a Gas Discharge Tube Arresters (GDT) and why do they important?

Gas Discharge Tube Arresters (GDT) are crucial components in electronic circuits, providing protection against over-voltage conditions. These devices are widely used in various industries to safeguard sensitive electronic equipment from transient surges and spikes. In this article, we are going to explore the essential aspects of GDTs, including their classifications, structure, characteristics, and the widely applications they serve.

What is a gas discharge tube arrester?

A Gas Discharge Tube Arrester is a protective device used to protect electronic circuits from high-voltage surges. Due to the most of packaging of GDTs used is ceramic, so it is called “ceramic discharge tube” as well in some fields.

It operates by creating a controlled electrical discharge in a gas-filled tube, which effectively diverts the excess voltage away from the protected equipment. Because the electrode insulation resistance of the discharge tube is very large and the parasitic capacitance is very small, the lightning protection of the high-frequency signal line has a clear advantage.

What’s the working principle of gas discharge tube arrester?

The working principle of gas discharge tube arrester is based on gas discharge phenomenon. When the voltage exceeds a certain threshold, the gas medium inside the gas discharge tube will ionize and discharge, quickly releasing the overvoltage to the ground, thereby protecting the device from high voltage damage. Here we introduced the different state when the GDT parts in and what it will works.

Normal working state

Under the normal operating conditions, the voltage in the gas discharge tube is lower than its breakdown voltage. At this time, the gas medium is in an insulating state and does not conduct electricity. The equipment can operate normally, and the gas discharge tube will not affect the normal operation of the circuit.

Overvoltage state

When external factors (such as lightning strikes, switching operations, or other causes) cause an overvoltage in the power system or electronic equipment, the voltage in the gas discharge tube rises rapidly. Once the voltage exceeds the breakdown voltage of the gas discharge tube, the gas medium will be ionized, forming a conductive channel and starting to discharge.

1. Ionization and discharge

The gas medium in the gas discharge tube is ionized under the action of high voltage, and a large number of free electrons and ions are formed. These free electrons and ions move rapidly under the action of an electric field, forming an electric current. In this case, the resistance in the gas discharge tube is greatly reduced, and the overvoltage is quickly released to the ground through the gas discharge tube to avoid damage to the device.

2. Overvoltage release

During the discharge process, the gas discharge tube quickly introduces the overvoltage to the ground, reducing the voltage at both ends of the device to a safe range. The discharge current of the gas discharge tube is usually large, which can release a lot of energy in a short time to ensure the safety of the equipment.

3. Restore insulation

When the overvoltage disappears, the voltage in the gas discharge tube returns to the normal level, and the gas medium returns to the insulation state. At this time, the conductive channel of the gas discharge tube disappears, the resistance returns to the high resistance state, and it is no longer conductive. The device can continue to operate normally, and the gas discharge tube returns to standby, ready for the next overvoltage.

Classifications of gas discharge tube arresters

Gas discharge tube arrester according to its structure and working principle, can be divided into the following types:

1. Unipolar GDT

The unipolar gas discharge tube arrester is composed of a discharge electrode and a ground electrode. When the overvoltage appears, the gas medium between the discharge electrode and the ground electrode will break down and discharge, and the overvoltage will be introduced to the ground.

2. Bipolar gas GDT

The bipolar gas discharge tube arrester is composed of two discharge electrodes. When the overvoltage exceeds a specific threshold, the gas medium between the two electrodes will discharge, limiting the overvoltage to a safe range.

3. Three-pole GDT

The three-electrode gas discharge tube arrester has three electrodes and is commonly used for more complex power system protection. When an overvoltage occurs, the gas medium between the three electrodes will discharge according to the voltage situation, providing more comprehensive protection.

4. Surface Mount GDT

This kind of gad discharge tube is specially designed for compact and high-density circuit boards, these GDTs are mounted directly onto the surface of the PCB, making them ideal for modern electronic devices.

(surface mount GDT)

What is the structure of a gas discharge tube arrester?

The structure of the gas discharge tube arrester is usually composed of the following parts:

1. Electrode

The electrode is the core component of the gas discharge tube arrester and is usually made of a metal material with good electrical conductivity, such as copper, aluminum or alloy. The shape and arrangement of electrodes will affect the performance and discharge characteristics of gas discharge tube.

2. Gas medium

Gas medium is the key part of discharge in gas discharge tube arrester. Commonly used gas media include neon, hydrogen and argon, which are easy to ionize under high voltage and form a discharge channel.

3. Insulators/housing

The insulator is used to isolate the electrode and the gas medium to ensure that the gas discharge tube has good insulation performance under normal working conditions. Common insulating materials include ceramics, glass and polymers.

What are characteristics of a gas discharge tube arrester?

The primary function of a Gas Discharge Tube Arrester is to protect electronic devices from transient over-voltage conditions. When a voltage spike exceeds the normal operating voltage of the protected circuit, the gas inside the tube ionizes, creating a conductive path. Additionally, it has other functions when used in electronics, for example:

1. Quick response

The gas discharge tube arrester has a very fast response speed, and when the overvoltage appears, the discharge process can be completed in a very short time (usually in the nanosecond level), effectively protecting the equipment from damage.

2. High energy absorption capacity

The gas discharge tube arrester can absorb and release a large amount of overvoltage energy, ensuring that the equipment can still operate safely under high energy impact.

3. Low residual pressure

The gas discharge tube arrester will limit the overvoltage to a lower residual voltage level during the discharge process, further improving the safety of the equipment.

4. Long life

The gas discharge tube arrester has a long service life and can maintain good performance and stability in long-term use.

Where a can gas discharge tube arrester be used?

Gas Discharge Tube Arresters are versatile devices used in a variety of applications, including:

1. Telecommunications - protect telephone lines, modems, and other communication equipment from lightning-induced surges and electrostatic discharge.

2. Power Supply Systems - they are used in power supply circuits to

safeguard transformers, generators, and other critical components from voltage spikes.

3. Data Transmission - protect data lines and sensitive electronic equipment in data centers and networking installations.

4. Consumer Electronics - be employed in household electronic devices such as televisions, computers, and gaming consoles to prevent damage from power surges.

5. Industrial Equipment - used in industrial automation systems, protecting

sensors, controllers, and other machinery from electrical disturbances.

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