An electrical protection system protects a high-voltage DC electrical installation and comprises at least one sensor of first type configured to perform measurements of a non-electrical physical quantity, at least one sensor of second type configured to perform measurements of an electrical physical quantity, and a control unit connected to said at least one sensor of first type and to said at least one sensor of second type. The control unit commands a circuit breaker of the high-voltage DC electrical installation to open when, in a sliding time window, an abnormal non-electrical phenomenon is detected by virtue of the measurements of said at least one sensor of first type and when, furthermore, an abnormal electrical phenomenon is detected by virtue of the measurements of said at least one sensor of second type.