# US 10,768,243 B2 · Method and detection device for detecting a high-impedance ground fault in an electrical energy supply network with a grounded neutral point > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,768,243 B2 - Document ID: US10768243B2 - Status: Granted - Kind: B2 - Application number: 16/161,348 - Filed: 2018-10-16 - Published: 2019-05-02 - Granted: 2020-09-08 - Earliest claimed: 2017-10-27 - Assignees: Siemens Aktiengesellschaft - Applicants: Siemens Aktiengesellschaft - Inventors: Heiko Englert; Andreas Jurisch - Web page: https://patentgrep.com/patent/US10768243B2 ## CPC - G01R 31/52: Testing for short-circuits, leakage current or ground faults - G01R 31/085: {in power transmission or distribution lines, e.g. overhead} - G01R 31/086: {in power transmission or distribution networks, i.e. with interconnected conductors} - H02H 3/17: by means of an auxiliary voltage injected into the installation to be protected {(using summation current transformers H02H3/33)} - H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)} - H02H 3/16: responsive to fault current to earth, frame or mass (with balanced or differential arrangement H02H3/26 {; monitoring earth connection H02H5/105}) - 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) ## Abstract A method detects a high-impedance ground fault in an electrical energy supply network with a grounded neutral point. A test signal is fed via a detection device into the energy supply network, the test signal has a frequency which differs from the network frequency of the energy supply network. To enable a reliable detection, with low equipment costs, of high-impedance ground faults in energy supply networks with a grounded neutral point, a three-phase test signal is fed into the phase conductors of the energy supply network as the test signal. A measuring signal which indicates the residual voltage of the test signal is generated with the detection device. The residual voltage is compared with a threshold value using a test device of the detection device, and the presence of a high-impedance ground fault is detected if the residual voltage exceeds the threshold value. ## Claims ### Claim 1 A method for detecting a high-impedance fault having a presence of a fault current in a three-phase electrical energy supply network with a grounded neutral point, which comprises the steps of: feeding a test signal, via a detection device, into the three-phase electrical energy supply network, the test signal having a frequency differing from a network frequency of the three-phase electrical energy supply network, the test signal being a three-phase test signal injected into phase conductors of the three-phase electrical energy supply network; generating a measuring signal indicating a residual voltage, the residual voltage is vector sum of the voltages to ground of the several phrase wires of an electrical supply circuit, of the test signal induced in three-phases of the three-phase electrical energy supply network via the detection device; comparing the residual voltage with a threshold value using a testing device of the detection device; and detecting a presence of the high-impedance fault if the residual voltage exceeds the threshold value. ### Claim 2 (depends on 1) The method according to claim 1, which further comprises forming the three-phase test signal such that a symmetrical three-phase network with an isolated neutral point is simulated with a signal-generating device of the detection device. ### Claim 3 (depends on 1) The method according to claim 1, which further comprises selecting the frequency of the test signal within a range in which transformers present in the three-phase electrical energy supply network have a high impedance. ### Claim 4 (depends on 1) The method according to claim 1, which further comprises injecting the test signal by means of a coupling device into the three-phase electrical energy supply network, the coupling device is configured as a capacitive coupling, as an analog amplifier or as an inverter. ### Claim 5 (depends on 1) The method according to claim 1, which further comprises determining the residual voltage of the test signal with the detection device in relation to a ground potential of the three-phase electrical energy supply network. ### Claim 6 (depends on 1) The method according to claim 1, which further comprises performing, via the testing device, a separation of the measuring signal from signals having the network frequency of the three-phase electrical energy supply network. ### Claim 7 (depends on 1) The method according to claim 1, which further comprises comparing either an absolute amplitude of the residual voltage or a deviation of the residual voltage from a stationary value of the residual voltage with the threshold value. ### Claim 8 (depends on 1) The method according to claim 1, which further comprises forming the test signal in a form of a sinusoidal wave, a pulsed signal or a pseudo-random binary signal. ### Claim 9 A detection device assembly for detecting a high-impedance fault having a presence of a fault current in a three-phase electrical energy supply network with a grounded neutral point, the detection device assembly comprising: a detection device configured to: connect to phase conductors of the three-phase electrical energy supply network; inject a test signal into the three-phase electrical energy supply network, the test signal having a frequency which differs from a network frequency of the three-phase electrical energy supply network, said detection device configured to inject the test signal as a three-phrase test signal into phase conductors of the three-phase electrical energy supply network; and generate a measuring signal which indicates a residual voltage, the residual voltage is vector sum of the voltages to ground of the several phrase wires of an electrical supply circuit, of the test signal induced in three-phases of the three-phase electrical energy supply network; said detection device having a testing device configured to compare the residual voltage with a threshold value; and said testing device is configured to detect a presence of a high-impedance ground fault if the residual voltage exceeds the threshold value.