Ground fault protection
AssigneeABB Schweiz AG
InventorAndreas CALLSEN
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Abstract
A robust ground-fault protection system is disclosed which can possess a reduced sensitivity to system noise. In a ground-fault protection system for an electrical machine such as a generator, an injection signal with an injection frequency fi is applied to the electrical machine in order to generate a periodic bias voltage on a conductor of the electrical machine, and a response signal thereto is evaluated. The injection frequency can be adapted such that a flexible approach respective of a most recent value of a system quantity of the electrical machine, can provide increased stability and reliability of the ground-fault protection system.
Claims18
A method of adapting a ground-fault protection system for an electrical machine, wherein the system injects an injection signal ui— with an injection frequency fi into a conductor of the electrical machine and evaluates a response signal uRE thereto to identify a ground-fault in the electrical machine, the method comprising:
- measuring a system quantity of the electrical machine indicative of system noise;
- and
- adapting the injection frequency according to the system quantity.
A ground-fault protection system for an electrical machine, comprising:
- a signal generator for injecting a frequency signal ui with an injection frequency fi into a conductor of the electrical machine;
- and
- an earth fault protection relay for evaluating a response signal uRE thereto, to identify a ground-fault in the electrical machine,
- wherein the signal generator is communicatively connected to the protection relay via a communication link, and configured for receiving a value of the injection frequency fi adapted to a measured system quantity of the electrical machine indicative of system noise.
Dependencies are inferred from the claim text.