# US 10,310,003 B2 · Fault location in DC networks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,310,003 B2 - Document ID: US10310003B2 - Status: Granted - Kind: B2 - Application number: 15/120,109 - Filed: 2015-02-18 - Published: 2017-03-16 - Granted: 2019-06-04 - Earliest claimed: 2014-02-19 - Assignees: General Electric Technology GmbH - Applicants: General Electric technology GmbH - Inventors: Colin Davidson; David Reginald Trainer; Carl Barker; Oleg Bagleybter - Web page: https://patentgrep.com/patent/US10310003B2 ## CPC - G01R 31/086: {in power transmission or distribution networks, i.e. with interconnected conductors} - H02H 7/268: {for DC systems} - H02H 9/02: responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)} - H02H 3/305: {involving current comparison} - H02H 7/261: {involving signal transmission between at least two stations (transmission of signals in general H02H1/0061)} - H02H 7/30: Staggered disconnection - Y04S 10/52: Outage or fault management, e.g. fault detection or location - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS ## Abstract This application relates to methods and apparatus for fault protection in a DC power transmission network or grid 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 of the network so as to 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 fault current is then controlled to maintain a non-zero level of fault current flow and the characteristics of the fault current flow at different parts of the network are determined by fault current detection modules. The location of the fault is then determined based on the determined characteristics. ## Claims ### Claim 1 A method of fault location in a DC power transmission network comprising: in the event of a fault, controlling at least one current limiting element of the network to: limit a fault current flowing through the network to less than a first current level, wherein the first current level is within an expected current operating range of the network in normal operation; and maintain the fault current flowing through the network at a non-zero level; determining a plurality of fault currents, wherein each of the plurality of fault currents is the fault current at a different part of the network; and determining a location of the fault based on comparing at least two of the plurality of fault currents to one another. ### Claim 2 (depends on 1) The method of claim 1, wherein determining the plurality of fault currents comprises determining a polarity or direction of each of the plurality of fault currents. ### Claim 3 (depends on 2) The method of claim 2, wherein determining the location of the fault comprises determining a part of the network where the polarity or direction of one of the plurality of fault currents changes with respect to the polarity or direction of another of the plurality of fault currents. ### Claim 4 (depends on 1) The method of claim 1, wherein determining the location of the fault comprises determining a differential between at least two of the plurality of fault currents. ### Claim 5 (depends on 1) The method of claim 1, wherein the non-zero level of fault current is maintained for a first time window. ### Claim 6 (depends on 5) The method of claim 5, wherein, at the end of the first time window, the at least one current limiting element is controlled to reduce the fault current in the network to zero. ### Claim 7 (depends on 1) The method of claim 1, comprising, following the determination of the location of the fault, opening at least one circuit breaker to disconnect a part of the network comprising the fault from the rest of the network. ### Claim 8 (depends on 1) The method of claim 1, wherein the at least one current limiting element comprises a voltage source converter. ### Claim 9 (depends on 1) The method of claim 1, wherein the at least one current limiting element comprises a DC breaker operable in a current limiting mode. ### Claim 10 A current limiting apparatus for a DC power transmission network comprising: a current limiting element that can be selectively connected and disconnected to the network, wherein, in a current limiting mode of operation, the current limiting element is selectively connected to the network to limit a current through the apparatus; a controller for controlling the current limiting element, the controller being configured to: in the event of a fault, activate the current limiting mode of operation so as to selectively connect the current limiting element to the network and limit a fault current through the current limiting apparatus to less than a first current level; maintain the fault current at a non-zero level; and selectively connect and disconnect the current limiting element to apply a predetermined modulation to the fault current. ### Claim 11 A method of fault location in a DC power transmission network comprising: in the event of a fault, controlling a plurality of current limiting elements at first different parts of the network to: limit a fault current flowing through the network to less than a first current level, wherein the first current level is within an expected current operating range of the network in normal operation; maintain the fault current flowing through the network at a non-zero level; and applying a plurality of modulations to the fault current at second different parts of the network, wherein each of the plurality of modulations has a different characteristic frequency of a plurality of characteristic frequencies and each of the plurality of characteristic frequencies is associated with an associated one of the second different parts of the network; determining a plurality of fault currents, wherein each of the plurality of fault currents is the fault current at an associated one of third different parts of the network; and determining a location of the fault based on characteristic frequencies found in the plurality of fault currents. ### Claim 12 (depends on 11) The method of claim 11, comprising controlling, the plurality of current limiting elements to apply the plurality of modulations to the fault current. ### Claim 13 (depends on 11) The method of claim 11, wherein determining a location of the fault based on characteristic frequencies found in the plurality of fault currents comprises monitoring for a presence or absence of the plurality of characteristic frequencies. ### Claim 14 (depends on 11) The method of claim 11, wherein the first different parts of the network are the same as the second different parts of the network.