Method and device for fault location in a two-terminal transmission or distribution power line
View Patent ↗A method for locating a fault in a two-terminal power transmission or distribution line. Measurements of the three phase currents are received from both terminals. Measurements of the three phase voltages are received from one line terminal. Parameters of the line are received. The fault type is received. Based on this received information the distance to fault from the one terminal where the phase voltages were measured is determined and output. Since only the phase voltages of one line terminal are needed, the functionality of a device, in particular a current differential relay, can be expanded to determine the distance to fault in an off-line mode.
1. A method for locating a fault in a two-terminal power transmission or distribution line, the method comprising:
receiving measurements of three phase currents from each of the two terminals,
receiving measurements of three phase voltages from one of the two terminals,
receiving transmission parameters of the distribution line,
receiving the fault type,
determining the symmetrical current and voltage components corresponding to the phase currents and phase voltages,
determining a fault loop voltage seen from the one of the two terminals based on the corresponding symmetrical voltage components and on the fault type,
determining a fault loop current seen from the one of the two terminals based on the symmetrical current components of the one of the two terminals, on the transmission parameters and on the fault type,
determining a total fault current based on the symmetrical current components and on the fault type,
determining the distance to fault seen from the one of the two terminals based on the fault loop voltage on the fault loop current and on the total fault current, and
outputting the distance to fault to an output interface.
2. The method according to claim 1 , wherein the distance to fault is determined according to
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3. The method according to claim 1 , further comprising:
an iteration which starts from the distance to fault and outputs the distance to fault determined in the last iteration step after a predefined number of iteration steps are reached or after a predefined convergence of the distance to fault is achieved, where each iteration comprising:
determining a fault loop quantity qualifying the voltage drop between the one of the two terminals and the fault based on the symmetrical current and voltage components of the one of the two terminals, on the transmission parameters, on the fault type and on a former distance to fault determined in a former iteration,
determining an iterative total fault current based on the symmetrical current and voltage components, on the transmission parameters, on the fault type and on a former distance to fault determined in a former iteration, and
determining the distance to fault based on the fault loop voltage, on the fault loop quantity and on the iterative total fault current.
4. The method according to claim 3 , where the distance to fault of the current interations is determined according to
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5. The method according to claim 3 , where the iterative total fault current is determined by eliminating its zero sequence current component.
6. A device for locating a fault in a two-terminal power transmission or distribution line, the device comprising:
a processing unit,
an output interface connected to the processing unit,
a receiver configured to receive measurements of three phase currents from each of the two terminals connected to the processing unit,
a receiver configured to receive measurements of three phase voltages from one of the two terminals connected to the processing unit,
a receiver configured to receive transmission parameters of the line connected to the processing unit,
a receiver configured to receive the fault type connected to the processing unit,
wherein the processing unit is configured to
determine the symmetrical current and voltage components corresponding to the phase currents and phase voltages,
determine a fault loop voltage seen from the one of the two terminals based on the corresponding symmetrical voltage components and on the fault type,
determine a fault loop current seen from the one of the two terminals based on the symmetrical current components of the one of the two terminals, on the transmission parameters and on the fault type,
determine a total fault current based on the symmetrical current components and on the fault type,
determine the distance to fault seen from the one of the two terminals based on the fault loop voltage on the fault loop current and on the total fault current, and
output the distance to fault to an output interface.
7. The device according to claim 6 , wherein the device is a current differential relay to protect the transmission or distribution line.
8. A computer program product, comprising:
a non-transitory computer readable medium; and
computer program recorded on the computer readable medium and executable by a processor for carrying out the steps of the method comprising receiving measurements of three phase currents from each of two terminals,
receiving measurements of three phase voltages from one of the two terminals of a two-terminal power transmission or distribution line,
receiving transmission parameters of the distribution line,
receiving the fault type,
determining the symmetrical current and voltage components corresponding to the phase currents and phase voltages,
determining a fault loop voltage seen from the one of the two terminals based on the corresponding symmetrical voltage components and on the fault type,
determining a fault loop current seen from the one of the two terminals based on the symmetrical current components of the one of the two terminals, on the transmission parameters and on the fault type,
determining a total fault current based on the symmetrical current components and on the fault type,
determining the distance to fault seen from the one of the two terminals based on the fault loop voltage, on the fault loop current and on the total fault current, and
outputting the distance to fault to an output interface.