GAS TUBE SURGE ARRESTORS FOR 500V SOLAR SYSTEMS

OVERVIEW

The Insurance Institute for Business & Home Safety found that an estimated $26B dollars annually is lost due to non-lightning power surges. Additionally, the are an estimated 25 million lighting strikes in the US each year that cause between $650M to $1B in losses according to the Insurance Institute, State Farm . Solar equipment due to their high incidents of exposure must be protected from threats due to lighting, power surges and power induction.

How Gas Tubes Operate

Gas Discharge Tube (GDT) Surge Arrestors operate on the principle of arc discharge. Operating as a voltage-dependent switch, an arc is formed within nanoseconds inside the hermetically sealed discharge chamber once a voltage exceeds the GDTs spark-over voltage. During its on-state, the gas tube essentially forms a short circuit allowing the entire surge current to flow and instantaneously eliminating the overvoltage transient. Upon dissipation of the overvoltage event, the GDT device extinguishes, and the internal resistance returns to its high impedance off-state. GDT devices reliably limit over voltages to permissible levels, can handle large surge currents and are invisible to the system being protected due to low capacitance and very high insulation resistance.

Solar System Protection

GDT are an ideal solution for overvoltage protection of solar systems due to their small size, high current capacity, high insulation resistance and low capacitance. Boost converter and inverter board level circuity and sensitive components should be safe guarded against damage caused by surge events.

Gas Tube Protecting Solar System

Selecting the appropriate Gas Tube

Key considerations for selection of a GDT for Solar equipment include location, system voltages, package types and surge ratings. Solar systems typically operate in a range from 500Vdc to 1500Vdc. When selecting a GDT, the minimum DC breakdown of the GDT must be considered. A 600V GDT with a -15%/+20% tolerance has a minimum DC breakdown voltage of 510V which is above the maximum voltage for a 500Vdc solar system. For Solar systems, an 8mm gas tube is recommended due to robust surge ratings available up to 20kA.

Recommended GDT

Part Number	Circuit	DC Sparkover Voltage	In	Package
BHS 600/-15+20	500Vdc	600-15%+20%	10kA

References