The invention provides a protection system for a fluid compartment of variable volume. The protection system comprises a detection means for detecting when the volume of the fluid compartment is outside a predetermined acceptable limit. The protection system also comprises a valve arrangement mountable on at least one port that is in selective fluid communication with the fluid compartment. The protection system further comprises an actuator, wherein the detection means is coupled to the valve arrangement via the actuator. When the detection means detects that the volume of the fluid compartment is outside the predetermined limit, the actuator causes the valve arrangement to change state and alters the volume of the fluid compartment. The protection system can be used with a compensator to protect a movable part of the compensator from damage.