Current source converter differential protection method and relay protection device

A relay protection device, wherein the device comprises:

• a sampling unit, a rectifier unit, a first acquisition unit, a second acquisition unit and a differential protection unit;
• wherein the sampling unit is configured to sample secondary side currents of current transformers on two sides of a protected current source converter, to obtain incomer-side three-phase currents iNa, iNb and iNc, and outgoer-side three-phase currents iMa, iMb and iMc;
• the rectifier unit is configured to rectify the incomer-side three-phase currents and the outgoer-side three-phase currents, to obtain an incomer-side input current iN and an outgoer-side output current iM which are equivalent;
• the first acquisition unit is configured to convert the incomer-side input current and the outgoer-side output current according to a current ratio of the current transformers on the two sides, to acquire a transient differential current idiff and a transient restraint current ires;
• the second acquisition unit is configured to acquire a differential current idiff and a restraint current Ires according to the transient differential current and the transient restraint current;
• and
• the differential protection unit is configured to achieve differential protection according to the differential current idiff and the restraint current Ires.