Fault location in DC networks

Abstract

This application relates to methods and apparatus for fault protection in a DC power transmission network or grid (200) that aid in determining the location of a fault in the network. The method involves, in the event of a fault, controlling at least one current limiting element (201; 202) of the network so as limit a fault current flowing to below a first current level which is within the expected current operating range of the network in normal operation, i.e. a safe level. The current limiting element (201) may be part of a suitable voltage source converter (101) or a DC breaker (202) capable of current limiting. The fault current is then controlled to maintain a non-zero level of fault current flow. The characteristics of the fault current flow at different parts of the network are then determined by fault current detection modules (203a-d). The location of the fault is then determined, by the fault current modules (203a-d) or a control system (205), based on the determined characteristics of the fault current flow at different parts of the network. The characteristic may include the direction or polarity of current flow. In some embodiments the current limiting elements may impose an AC modulation on the fault current which differs across the network and the characteristics of fault current may include the presence or absence of such modulation.

Description

technical field [0001] The present invention relates to methods and devices for identifying and / or locating faults in DC (direct current) grids or networks used to transmit electric power, in particular to fault location and isolation in high voltage DC (HVDC) power supply grids Methods and Apparatus. Background technique [0002] DC power transmission is employed in a number of different applications. HVDC is especially useful for long-distance power transmission and / or interconnecting alternating current (AC) networks operating at different frequencies. Thereby the first station can transmit electrical energy to the second station via a DC transmission line, for example an overhead line or a submarine or buried cable. The first station may generate DC power by converting from received AC input power. The second station then typically provides the conversion from DC back to AC. Each of the first and second stations may thus typically include a voltage source converter (...

AI Technical Summary

Problems solved by technology

This fast operation can be beneficial in reducing the possibility of any damage caused by high fault currents, but this creates challenges for the control and protection systems of DC networks to be able to locate fault locations in the network

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