Abstract <p>One approach to detecting cyber threats at a digital substation is examined by developing and investigating a basic algorithm for ensuring the information security of the process bus using fundamental laws of electrical engineering (Kirchhoff’s laws, Ohm’s law, the principle of superposition, detection of current imbalance) in combination with the patterns and operational rules of the computing networks of a digital substation that employ the seven-layer ISO/OSI model. A method is proposed for detecting cyber threats at a digital substation related to the falsification (spoofing) of current and voltage measurements, as well as unauthorized interference with the substation’s digital bus or with measurement sensors and devices for processing currents and voltages.</p>