The invention relates to a method and a device for monitoring short-circuit capacity on line, in particular to the method and the device for monitoring the short-circuit capacity on line based on dynamic
transfer impedance. The method comprises the following steps of: (A), replacing the conventional form of a single power supply of an equivalent target of a power
system with a form of a multi-power supply to a single load node; (B), computing a pure network
admittance matrix of a
system according to the
power grid topology information, and converting the pure network
admittance matrix into an order increasing form in an X-
Y coordinate; (C), aiming at power supply nodes and a load node, amending the network
admittance matrix; (D), computing the dynamic
transfer impedance from each power supply node to the load node; and (E), computing the internal
electric potential of each power supply node according to the measured values of a power angle,
terminal voltage, terminal current and the like of a motor in the running process of the
system, thus computing the short-circuit
capacity value of the nodes. As the method and the device are based on the dynamic
transfer impedance, the change of the short-circuit capacity of the nodes can be traced quickly and precisely without any
hypothesis or approximation, and the method and the device have promotional and applicable value.