Subsynchronous oscillation relay

A method of detecting and reacting to a subsynchronous oscillation event in an electrical energy generation system, comprising:

• providing a subsynchronous oscillation relay, the subsynchronous oscillation relay comprising:
• protection logic circuitry provided with filtering functionality through which a subsynchronous oscillation component is extractable from a fundamental frequency component of a monitored signal from an electrical energy generation system, and
• programming, including a protection algorithm that uses quantities of both the subsynchronous oscillation component and the fundamental frequency component of the monitored signal as an operational quantity;
• using the subsynchronous oscillation relay to monitor each phase of the monitored signal from the electrical energy generation system;
• causing the protection algorithm of the subsynchronous oscillation relay to calculate the ratio of the magnitude of the subsynchronous oscillation component to the magnitude of the fundamental frequency component;
• comparing the calculated ratio to a provided threshold setting;
• and
• when the calculated ratio exceeds the threshold setting, determining that a subsynchronous oscillation event is occurring, and causing the subsynchronous oscillation relay to output a signal that initiates a protection protocol.

A subsynchronous oscillation relay for detecting and reacting to subsynchronous control interaction (SSCI) events, comprising:

• a housing for substantially enclosing various electronic components of the relay;
• a power supply;
• a controller with a microprocessor;
• protection logic circuitry for each phase of a monitored signal from an electrical energy generation system, the protection logic circuitry including a bandpass filter that is operable within a predetermined frequency range to extract a subsynchronous oscillation component from a fundamental frequency component of the monitored signal;
• and
• programming, including a protection algorithm that:
• uses quantities of both the subsynchronous oscillation component and the fundamental frequency component of the monitored signal as an operational quantity,
• includes a fundamental frequency component minimum pickup threshold value,
• includes a subsynchronous oscillation minimum pickup threshold value, and
• includes a selectable time delay before which the relay will react to a detected SSCI event;
• wherein, upon detection of a SSCI event, the controller is adapted to initiate a protection protocol selected from the group consisting of bypassing a capacitor bank of a series-compensated transmission line to which the relay is connected, disconnecting an associated wind turbine from an associated transmission grid, and a combination thereof.