A method for operating an Intelligent Electronic Device (IED) in a power swing condition, wherein the IED is associated with a terminal of a power transmission line, the method comprising: receiving voltage measurements for each phase of the terminal of the power transmission line, wherein the voltage measurements are sampled to obtain a plurality of samples, each of the plurality of samples corresponding to a sampling instant which is a time instant at which a sample is captured; determining a plurality of root mean square (RMS) values for the measurements in each phase based on the voltage measurements of the corresponding phase, wherein each of the plurality of RMS values is associated with a respective sampling instant, amongst the plurality of sampling instants, and is calculated using a predefined number of samples, the predefined number of samples including the sample captured at the respective sampling instant and samples captured at preceding sampling instants; determining a plurality of delta quantities for each phase, wherein each of the plurality of delta quantities is associated with the respective sampling instant, and is calculated as a difference between an RMS value associated with the respective sampling instant and an RMS value associated with a sampling instant preceding the predefined number of samples; detecting whether a delta quantity, amongst the plurality of delta quantities, is greater than a predefined threshold, based on continuous monitoring of the plurality of delta quantities; detecting a peak delta quantity, in response to determining that the delta quantity is greater than the predefined threshold; determining a time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity, amongst the plurality of delta quantities; detecting a disturbance condition based on a comparison of the time interval with a threshold time; and blocking fault detection at the IED, in response to detecting that the disturbance condition is a power swing. receiving voltage measurements for each phase of the terminal of the power transmission line, wherein the voltage measurements are sampled to obtain a plurality of samples, each of the plurality of samples corresponding to a sampling instant which is a time instant at which a sample is captured; determining a plurality of root mean square (RMS) values for the measurements in each phase based on the voltage measurements of the corresponding phase, wherein each of the plurality of RMS values is associated with a respective sampling instant, amongst the plurality of sampling instants, and is calculated using a predefined number of samples, the predefined number of samples including the sample captured at the respective sampling instant and samples captured at preceding sampling instants; determining a plurality of delta quantities for each phase, wherein each of the plurality of delta quantities is associated with the respective sampling instant, and is calculated as a difference between an RMS value associated with the respective sampling instant and an RMS value associated with a sampling instant preceding the predefined number of samples; detecting whether a delta quantity, amongst the plurality of delta quantities, is greater than a predefined threshold, based on continuous monitoring of the plurality of delta quantities; detecting a peak delta quantity, in response to determining that the delta quantity is greater than the predefined threshold; determining a time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity, amongst the plurality of delta quantities; detecting a disturbance condition based on a comparison of the time interval with a threshold time; and blocking fault detection at the IED, in response to detecting that the disturbance condition is a power swing. <EOS>