SPD Specific Disconnector (SSD),  SPD-specific backup protection device for low-voltage power distribution systems, is capable of withstanding the expected surge current at the location where the SSD is installed, and can break the current passing through SPD due to failure. It also has the characteristic of operating with small operating current. It is also known as SPD Backup Protector or SCB.

Normally, SPD backup protection uses Fuses or Circuit Breakers. However, since the surge current resistance capacity and rated current value of fuses and circuit breakers are positively correlated, this means that in order to pass the surge test, their rated current values need to be relatively large. For example, passing the 20kA(In) and 40kA(Imax) tests, a typical gL/gG fuse requires 125A, while a typical circuit breaker requires 63A-100A. The 125A fuse will have an action current of up to 625A within 5 seconds, which meets the same surge test requirements of a typical circuit breaker, which is approximately this value as well. This characteristic leads to blind spots when using ordinary fuses and circuit breakers for SPD backup protection. A typical situation is that the capacity of the power distribution system is relatively small. When a short circuit occurs, the fuse of the SPD does not act, causing the SPD to catch fire rapidly. Most SPD fires are caused by this mismatch and the failure of the backup protection to act.

The characteristic of SSD is that it can undergo surge testing matching with SPD. Meanwhile, it can be activated with a relatively small operating current, typically around 3A, which ensures the activation of protection before the SPD catches fire. SSD has higher surge tolerance, smaller starting current characteristics, and is small in size, highly sensitive, and also has strong breaking capacity.

The PTG SSD can fully correspond and match the PTG SPD, thus achieving an extremely effective protective effect. The design of the PTG SSD adopts a single-chip free assembly structure, making it more flexible for pairing use.