An add on device assembly for surge arresters used in substation, distribution and transmission applications that provides a means to electrically and mechanically disconnect a surge arrester at the end of life, such that it leaves a physical dimension between electrodes that is able to withstand normal system voltage and at the same time continue to provide surge protection until the arrester is replaced. The assembly contains a spring locking assembly that will lock a line spacing buss in an open position post isolator operation. The resultant gap is set to provide sufficient air insulation for system voltage and at the same sufficient surge protection for the system Basic Insulation Level.