The invention relates to a substation and a transmission line fault protection method and device and detection method and device. The installation proximal end is protected on the opposite side of theline according to the remote fault of the fault line and the opposite side quickly operates at the distance of I section. Then the measured impedance of each sampling period of each line is calculated and then the fault line is judged according to different changes of the measured impedance of the fault line and the non-fault line after the quick operation of the opposite side at the distance section I, and finally the fault is removed. Therefore, the fault protection method can shorten the fault removal time and solve the problem that the remote fault removal time is too long when the line loses the main protection. Moreover, the fault protection method can reliably and accurately identify the fault line and remove the fault according to the measured impedance so as to improve the reliability of fault detection and fault removal.