Research into gas arrester follow current selfextinguishing characteristcs

Gas discharge overvoltage arresters are applied in overvoltage protection of class I, where besides voltage surges also significantly high current pulses are expected. Gas discharge arresters are found in protection of TN systems as well as in equipotential bonding between N-PE conductors in TT systems. A spark-gap electrode system is enclosed in special gas mixture in the presence of discharge activation agent. At breakdown voltage, which is defined by electrode gap and gas mixture, the electrical conductivity is changed from normaly non-conductive to the conductive state. The conductive state is established by spark discharge followed by intermediate glow discharge and final arc-discharge phase. The conductive state lasts untill discharge current falls below the order of magnitude 1A or voltage in spark gap below 10 V. So in the L-N circuits, where the supply voltage exists in the normal circuit conditions the undesirable short circuit is maintained further by overvoltage arrester even after voltage transient has been already cleared. Due to the existence of power supply voltage in L-N system a considerably high follow-on current can be maintained, which should be broken by other means of interruption. A prospective current in the range up to few kA is expected, which is far above self-interrupting ability of simple spark-gap gas discharge arrester having breaking capacitiy limited to up to approximately 10 A. In order to avoid the neccessitiy of back-up circuit breaker an increase of self-interrupting capacity of gas discharge surge arrester is required up to the value of 1 kA. This task will be achieved by methods of current limiting as applied for low-voltage circuit breakers. For the research purpose the construction of various experimental models of gas discharge protective device with incorporated components for arc quenching are planned, which will be manufactured by methods of vacuum degassing and incapsulation by high-temprature brazing in determined gas. They will be subjected to tests of breaking capacity of follow-on current initiated by high voltage pulse.