Protecting method of current change rate with self-adaptive output time-delay characteristic

The invention discloses a protecting method of metro direct current supply system of a current change rate with a self-adaptive output time-delay characteristic, which comprises the steps of: sampling a feed line current to obtain a current instantaneous value; filtering a high-frequency component through a digital filter algorithm; converting the filtered current sampling value into a practical current value, figuring out the current change rate; when the current change rate exceeds the starting set value, starting protection, timing by starting a T1 delay element; after the protection is started, if the current change rate is lower than the return constant value before protective trip, returning the protection; after T1 delay is reached, judging whether current increment exceeds a current increment constant value; and carrying out integral operation on the current increment when the current increment firstly exceeds the increment constant value, and outputting protecting actions when the integral value exceeds the integral constant value. When fault characteristics are remarkable, the trip is carried out rapidly, when the fault characteristics are not remarkable, judging is carried out for long, and then the trip is output, thus false operations of the protection at the edge of an action region are effectively prevented, and protection reliability is greatly improved.