SPD protecteds the devics by discharging current to the ground. One time strike will not damage SPD unless SPD is chosen incorrectly.

Power supply SPD is equipped with disconnector. If SPD fails, it will indicate through the indication window. SPD disconnector will not trip when it discharges lightning current. It is used to avoid fire hazadous caused by continuous fault current flowing through SPD when SPD is degradaed.

For signal SPD, The risk of fire is small, so it is not required to set a disconnector. Normally, special lightning protection testing devices need to be used for off-line tests. Nowadays, with the technology development, the status indication function of signal SPD is becoming popular, so it’s also possible to judge by status indication.