Why Gas Discharge Tube Can’t be used between Live and Neutral

Gas Discharge Tube (GDT) has two plates of metals which is separated by inertia gas and then sealed in a porcelain cylinder.

What is difference between type 1, type 2 and type 3 surge protective devices?

Type 1 Surge Protective Device (SPD)s are intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures, and are intended to be installed without an external overcurrent protective device.

Surge Protective Devices (SPD)

Surge Protective Devices (SPD) are used to protect the electrical installation, which consists of the consumer unit, wiring and accessories, from electrical power surges known as transient overvoltage.