Pilot transient protection method and system based on oscillation frequency, and device

A pilot transient protection system based on an oscillation frequency, comprising:

• a preliminary fault determining module, configured to:
• detect, by protection devices mounted on two sides of a line, a sudden change in current, and determine whether a fault occurs, wherein the sudden change in current is a change of a differential current at two adjacent sampling points;
• a time window length calculation module, configured to:
• when it is determined that the fault occurs, determine a time window length according to a system structure of the line, wherein the system structure of the line comprises a system side impedance, a line parameter, and a topological structure of the line;
• a high-frequency and low-frequency energy calculation module, configured to:
• decompose, by using a frequency analysis method, a differential current signal in the line within the time window length into a high-frequency band signal and a low-frequency band signal, to calculate high-frequency energy and low-frequency energy;
• and
• an internal fault determining module, configured to:
• determine that an internal fault occurs when the low-frequency energy is larger than an action threshold and a ratio of the low-frequency energy to the high-frequency energy is larger than a ratio threshold, and allow the protection device to trip.