... communication, if one or more modules of SPD is invalid. LYD5-100 SPD is suit-able for the IT, TT, TN-C ... from lightning impulse and other transient over voltage, it is applicable in class I lightning proof system where there has higher danger ... conditions of IEC61643-1:1998-02 standard, Class I surge protective device, it is category B surge protective device.Working principle1.Fast ...