Abstract: An electrical surge suppressor includes a capacitive component incorporated inside a housing and immersed in, or filled with, oil; a linear resistive component; and a non-linear resistive component connected or connectable in parallel with the linear resistive component. The surge suppressor has a monitoring circuit configured to measure at least one operating characteristic of the linear and/or non-linear resistive and capacitive components and an auxiliary power supply integrated within the capacitive component to provide an auxiliary supply voltage to the monitoring circuit.