# US 12,763,573 B2 · Joint fault detection and communication for DC power lines > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,763,573 B2 - Document ID: US12763573B2 - Status: Granted - Kind: B2 - Application number: 18/764,522 - Filed: 2024-07-05 - Published: 2026-01-08 - Granted: 2026-10-13 - Earliest claimed: 2024-07-05 - Assignees: Cence Power Inc. - Applicants: Cence Power Inc. - Inventors: Milad Johnny; Bolis Ibrahim; Sagar Jaiswal; Willy Liu - Web page: https://patentgrep.com/patent/US12763573B2 ## CPC - H02H 7/268: {for DC systems} - H04B 3/46: Monitoring; Testing - H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT} - 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) - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A fault detection system for detecting a fault condition in a direct current (DC) system. The system may include a DC power transmitter to energize a cable and a DC power receiver connected to the cable. A signal generator at the receiver employs orthogonal frequency division multiplexing (OFDM) and combines symbols for messaging or data communications with redundant symbols dedicated to fault detection. At a signal receiver, the transmitted OFDM signal is used to measure changes in the channel transfer function by monitoring changes in a parameter of the received redundant symbols. The redundant symbols need not be decoded to detect a greater-than-threshold change in the transfer function that is indicative of a fault on the cable. ## Claims ### Claim 1 A fault detection system for detecting a fault condition, the system comprising: a power transmitter to energize a transmission line with high voltage DC power; and a power receiver to couple the transmission line to a load, wherein the power receiver includes a signal generator coupled to the transmission line to generate and propagate a high frequency signal on the transmission line using multiple subbands and orthogonal frequency division multiplexing to encode a bitstream that includes a set of message symbols and a set of redundant symbols, and wherein the set of redundant symbols are transmitted on one or more of the multiple subbands, and wherein the power transmitter includes, a signal receiver coupled to the transmission line to receive the high frequency signal, to extract a set of propagated redundant symbols, and to measure, using the set of propagated redundant symbols, a parameter proportional to a channel frequency response of the transmission line, a fault detection circuit to output a fault signal based on a change in the parameter that exceeds a threshold value, wherein the parameter comprises a measured energy of the set of propagated redundant symbols, and a switch operable in response to the fault signal to disconnect the transmission line from the high voltage DC power. ### Claim 2 (depends on 1) The fault detection system of claim 1, wherein the signal generator is configured to mix the set of message symbols with the set of redundant symbols in accordance with a permutation matrix. ### Claim 3 (depends on 2) The fault detection system of claim 2, wherein the signal receiver is configured to extract the set of propagated redundant symbols using an inverse permutation matrix that is the inverse of the permutation matrix. ### Claim 4 (depends on 1) The fault detection system of claim 1, wherein the set of propagated redundant symbols comprises the set of redundant symbols modified by the channel frequency response, and wherein the energy is determined based on a trace function applied to a matrix-based expression of the set of propagated redundant symbols. ### Claim 5 (depends on 1) The fault detection system of claim 1, wherein the fault detection circuit is configured to determine the change in the parameter by determining a magnitude of a difference between the measured energy of the set of propagated redundant symbols and a measured energy of a previously-propagated set of redundant symbols and comparing the magnitude of the difference to the threshold value. ### Claim 6 (depends on 5) The fault detection system of claim 5, wherein the fault detection circuit is further configured to adaptively adjust the threshold value based on a history of measured energy tracking changes in the channel frequency response over a time period. ### Claim 7 (depends on 6) The fault detection system of claim 6, wherein the fault detection circuit is configured to adaptively adjust the threshold value by determining a probability distribution of energy magnitude changes over the time period and setting the threshold value as a function of the probability distribution so as to exclude a substantial portion of the probability distribution attributable to environmental noise. ### Claim 8 (depends on 1) The fault detection system of claim 1, wherein the set of redundant symbols comprises a sequence of predetermined symbols. ### Claim 9 (depends on 1) The fault detection system of claim 1, further comprising a termination impedance at the power transmitter, wherein the termination impedance is selected to match a characteristic impedance of the transmission line. ### Claim 10 (depends on 1) The fault detection system of claim 1, further comprising a discharge circuit configured to receive the fault signal and to couple the transmission line to ground in response to the fault signal. ### Claim 11 A fault detection system for detecting a fault condition in a direct current (DC) system, the system comprising: a power transmitter to energize a transmission line with high voltage DC power; a power receiver to couple the transmission line to a load; at the power receiver, a signal generation means, including, means to generate and propagate a high frequency signal on the transmission line using multiple subbands and orthogonal frequency division multiplexing to encode a bitstream that includes a set of message symbols and a set of redundant symbols, and wherein the set of redundant symbols are transmitted on one or more of the multiple subbands; and at the power transmitter, means to receive the high frequency signal, to extract a set of propagated redundant symbols, and to measure, using the set of propagated redundant symbols, a parameter proportional to a channel frequency response of the transmission line, means to output a fault signal based on a change in the parameter that exceeds a threshold value, and means to, in response to the fault signal, disconnect the transmission line from the high voltage DC power. ### Claim 12 A method of detecting a fault condition on a transmission line, the method comprising: energizing a transmission line with high voltage DC power from a power transmitter, wherein the transmission line is coupled to a load at a power receiver; generating and propagating a high frequency signal on the transmission line using multiple subbands and orthogonal frequency division multiplexing to encode a bitstream that includes a set of message symbols and a set of redundant symbols, and wherein the set of redundant symbols are transmitted on one or more of the multiple subbands; receiving, at the power transmitter, the high frequency signal and extracting a set of propagated redundant symbols; measuring, using the set of propagated redundant symbols, a parameter proportional to a channel frequency response of the transmission line, wherein the parameter comprises a measured energy of the set of propagated redundant symbols; outputting a fault signal based on a change in the parameter that exceeds a threshold value; and disconnecting the transmission line from the high voltage DC power in response to the fault signal. ### Claim 13 (depends on 12) The method of claim 12, wherein the generating and propagating includes mixing the set of message symbols with the set of redundant symbols in accordance with a permutation matrix. ### Claim 14 (depends on 13) The method of claim 13, wherein extracting the set of propagated redundant symbols includes using an inverse permutation matrix that is the inverse of the permutation matrix. ### Claim 15 (depends on 12) The method of claim 12, wherein determining the measured energy includes using a trace function applied to a matrix-based expression of the set of propagated redundant symbols. ### Claim 16 (depends on 12) The method of claim 12, wherein outputting the fault signal includes determining the change in the parameter by determining a magnitude of a difference between the measured energy of the set of propagated redundant symbols and a measured energy of a previously-propagated set of redundant symbols and comparing the magnitude of the difference to the threshold value. ### Claim 17 (depends on 16) The method of claim 16, further including adaptively adjusting the threshold value based on a history of measured energy tracking changes in the channel frequency response over a time period. ### Claim 18 (depends on 17) The method of claim 17, wherein adaptively adjusting the threshold value includes determining a probability distribution of energy magnitude changes over the time period and setting the threshold value as a function of the probability distribution so as to exclude a substantial portion of the probability distribution attributable to environmental noise.