Frequency measurement for load shedding and accurate magnitude calculation

An intelligent electronic device (IED), comprising:

• input circuitry configured to receive an input signal indicating an electrical characteristic of a power system;
• and
• processing circuitry configured to:
• determine an estimated accuracy of a rate of change of phase by comparing an estimated phase angle of the power system with a measured phase angle;
• and
• selecting an estimated frequency of the power system from among a first estimated frequency determined from the rate of change of phase of the power system and a second estimated frequency determined from zero crossings of the power system, wherein the selection between the first estimated frequency and the second estimated frequency is based on the estimated accuracy.

A non-transitory, computer readable medium comprising instructions that, when executed by processing circuitry, are configured to cause the processing circuitry to perform operations comprising:

• obtaining electrical measurements of an input signal of a power system;
• determining a first estimated frequency of the power system using a rate of change of phase;
• and
• determining a second estimated frequency of the power system using zero crossings;
• wherein selection of the first estimated frequency and the second estimated frequency is based at least in part on an estimated accuracy of the rate of change of phase.