Patent ID: 8649131

Claim:
A method for supervising a secondary circuit of an instrument transformer in a power system, the instrument transformer being connected to a power system component, wherein the method comprises: detecting, by a protection Intelligent Electronic Device (IED), which is connected to the secondary circuit of the instrument transformer and protects the power system component, disturbances in a signal from the instrument transformer; and determining whether a failure occurs in the secondary circuit of the instrument transformer, according to both a disturbance detection result from the protection IED and another disturbance detection result from at least one of other protection IEDs, the other protection IEDs comprising protection IEDs which are connected to other secondary circuits of the instrument transformer or to secondary circuits of another instrument transformer connected to the power system component, and protection IEDs which are connected to other instrument transformers connected to other power system components connected to a same busbar as the power system component is connected to; and wherein the determining whether the failure occurs in the secondary circuit of the instrument transformer comprises; if a disturbance is detected by the protection IED and a message indicating detection of a corresponding disturbance is not received by the protection IED from any of the other protection IEDs in a preset delay, determining, by the protection IED, that the failure occurs in the secondary circuit of the another instrument transformer.