Monitoring system for monitoring the state of an electric cable system, wherein the electric cable system comprises: - a first cable section (2a, 3a, 4a) comprising a first conductor (12a, 13a, 14a) and a first sheath (22a, 23a, 24a); wherein the monitoring system comprises: - a first current sensor (112, 113, 114) for measuring a signal representative of the current (Is; Is1) through the sheath (22a, 23a, 24a); - a signal processing unit connected to the first current sensor (112, 113, 114) for processing of the signal representative of the current (Is; Is) through the sheath (22a, 23a, 24a); wherein the signal processing unit is configured to: - determining a parameter representative of the state of the first sheath (22a, 23a, 24a) of the first cable section (2a, 3a, 4a) of the electric cable system based on the signal from the current sensor (112, 113, 114), said monitoring system further comprising: - a communication unit providing communication between the signal processing unit and a central control system and being characterized in that the parameter representative of the state of the first sheath (22a, 23a, 24a) is a current difference (ΔI) between the current (Is) through the sheath (22a, 23a, 24a) and an expected current value (Ie). - a first cable section (2a, 3a, 4a) comprising a first conductor (12a, 13a, 14a) and a first sheath (22a, 23a, 24a); wherein the monitoring system comprises: - a first current sensor (112, 113, 114) for measuring a signal representative of the current (Is; Is1) through the sheath (22a, 23a, 24a); - a signal processing unit connected to the first current sensor (112, 113, 114) for processing of the signal representative of the current (Is; Is) through the sheath (22a, 23a, 24a); - a first current sensor (112, 113, 114) for measuring a signal representative of the current (Is; Is1) through the sheath (22a, 23a, 24a); - a signal processing unit connected to the first current sensor (112, 113, 114) for processing of the signal representative of the current (Is; Is) through the sheath (22a, 23a, 24a); wherein the signal processing unit is configured to: - determining a parameter representative of the state of the first sheath (22a, 23a, 24a) of the first cable section (2a, 3a, 4a) of the electric cable system based on the signal from the current sensor (112, 113, 114), - determining a parameter representative of the state of the first sheath (22a, 23a, 24a) of the first cable section (2a, 3a, 4a) of the electric cable system based on the signal from the current sensor (112, 113, 114), said monitoring system further comprising: - a communication unit providing communication between the signal processing unit and a central control system and being characterized in that the parameter representative of the state of the first sheath (22a, 23a, 24a) is a current difference (ΔI) between the current (Is) through the sheath (22a, 23a, 24a) and an expected current value (Ie). - a communication unit providing communication between the signal processing unit and a central control system and being characterized in that the parameter representative of the state of the first sheath (22a, 23a, 24a) is a current difference (ΔI) between the current (Is) through the sheath (22a, 23a, 24a) and an expected current value (Ie).