| CPC H02H 7/268 (2013.01) [H02J 3/36 (2013.01); H02H 3/16 (2013.01); H02H 7/261 (2013.01)] | 12 Claims |
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12. A method of detecting a fault in a bipole power transmission scheme including a first converter station positioned remote from a second converter station and first and second transmission conduits interconnecting the first and second converter stations to permit the transmission of power between the first and second converter stations,
the first converter station having first and second power converters, the first power converter including a first DC terminal connected with the first transmission conduit, at least one AC terminal connected with a first AC network, and a second DC terminal interconnected with a third DC terminal of the second power converter by a first interconnection defining a first neutral area, the second power converter additionally including a fourth DC terminal connected with the second transmission conduit and at least one AC terminal connected with a second AC network, and
the second converter station having third and fourth power converters, the third power converter including a fifth DC terminal connected with the first transmission conduit, at least one AC terminal connected with a third AC network, and a sixth DC terminal interconnected with a seventh DC terminal of the fourth power converter by a second interconnection defining a second neutral area, the fourth power converter additionally including an eighth DC terminal connected with the second transmission conduit and at least one AC terminal connected with a fourth AC network,
the bipole power transmission scheme further including a fault detector comprising:
a first grounding circuit connected in use between the first neutral area and ground and switchable into and out of operation;
at least one of a first current sensor configured in use to measure the flow of current between the first neutral area and ground and a first voltage measurer configured in use to measure the voltage difference between the first neutral area and ground;
a second grounding circuit connected in use between the second neutral area and ground and switchable into and out of operation;
at least one of a second current sensor configured in use to measure the flow of current between the second neutral area and ground and a second voltage measurer configured in use to measure the voltage difference between the second neutral area and ground; and
the said method detecting a ground fault in one or other of the first and second neutral areas by carrying out the following steps:
configuring the first grounding circuit to be in operation and the second grounding circuit to be out of operation;
checking for at least one of a first erroneous current flow in the first neutral area using the first current sensor and a first erroneous voltage in the second neutral area using the second voltage measurer;
recognising a ground fault in the second neutral area if a first erroneous current flow is identified or if a first erroneous voltage is identified;
configuring the first grounding circuit to be out of operation and the second grounding circuit to be in operation;
checking for at least one of a second erroneous current flow in the second neutral area using the second current sensor and a second erroneous voltage in the first neutral area using the first voltage measurer; and
recognising a ground fault in the first neutral area if a second erroneous current flow is identified or if a second erroneous voltage is identified.
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