A method of operating an isolation valve can include continuously transmitting a signal to a detector section, and a control system operating an actuator in response to the detector section detecting cessation of the signal transmission. A well system can include an isolation valve which selectively permits and prevents fluid communication between sections of a wellbore, a remotely positioned signal transmitter, and the isolation valve including a control system which operates an actuator in response to detection of a signal by a detector section. Another well system can include an isolation valve interconnected in a tubular string, and the tubular string being cemented in a wellbore, with cement being disposed in an annulus formed radially between the isolation valve and the wellbore.