A thermal-mechanical fatigue assessment system comprising: an electrical conductor, the electrical conductor being a fuse element of an electrical fuse having a cold resistance and a non-linear resistance when connected to an energized electrical power system; an arc quenching medium that surrounds the fuse element and includes quartz silica sand and sodium silicate binder to create a mechanical and thermal conduction bond between the sodium silicate binder and the electrical conductor; and a controller (304, 306) operable to estimate a service life of the electrical conductor based on the cold resistance of the electrical conductor and temperatures of the electrical conductor over time; characterized in that the controller is configured to estimate temperatures of the electrical conductor over time by deducing the current in the electrical conductor and the ambient temperature of the electrical fuse, estimating a first temperature differential between the electrical conductor and the arc quenching medium, estimating a second temperature differential between the arc quenching medium and the ambient temperature of the electrical fuse, and adding the first temperature differential, the second temperature differential and the ambient temperature together to estimate the temperatures of the electrical conductor over time; and the controller is configured to determine at least one of a B5 service life of the electrical conductor, a B50 service life of the electrical conductor, and a B95 service life of the electrical conductor and thus the electrical fuse based on the cold resistance of the electrical conductor and the estimation of the temperatures of the electrical conductor over time wherein the B5 service life represents a service life that the fuse element has a 95% probability of reaching, wherein the B50 service life represents a service life that the fuse element has a 50% probability of reaching and wherein the B95 service life represents a service life that the fuse element has a 5% probability of reaching. an electrical conductor, the electrical conductor being a fuse element of an electrical fuse having a cold resistance and a non-linear resistance when connected to an energized electrical power system; an arc quenching medium that surrounds the fuse element and includes quartz silica sand and sodium silicate binder to create a mechanical and thermal conduction bond between the sodium silicate binder and the electrical conductor; and a controller (304, 306) operable to estimate a service life of the electrical conductor based on the cold resistance of the electrical conductor and temperatures of the electrical conductor over time; characterized in that the controller is configured to estimate temperatures of the electrical conductor over time by deducing the current in the electrical conductor and the ambient temperature of the electrical fuse, estimating a first temperature differential between the electrical conductor and the arc quenching medium, estimating a second temperature differential between the arc quenching medium and the ambient temperature of the electrical fuse, and adding the first temperature differential, the second temperature differential and the ambient temperature together to estimate the temperatures of the electrical conductor over time; and the controller is configured to determine at least one of a B5 service life of the electrical conductor, a B50 service life of the electrical conductor, and a B95 service life of the electrical conductor and thus the electrical fuse based on the cold resistance of the electrical conductor and the estimation of the temperatures of the electrical conductor over time wherein the B5 service life represents a service life that the fuse element has a 95% probability of reaching, wherein the B50 service life represents a service life that the fuse element has a 50% probability of reaching and wherein the B95 service life represents a service life that the fuse element has a 5% probability of reaching.