Transient based method for identifying faults in a high / medium voltage electric power transmission system
The invention relates to a transient based method for identifying faults in an electric power transmission and/or distribution system ( 100 ) having at least one current transmission line (L 12 , L 13 , L 23 ) comprising the following steps: —generation of a physical model of the at least one current transmission line (L 12 , L 13 , L 23 ), the physical model depending on the fault parameters and describing the behavior of voltage and/or current transients due to the fault in the at least one current transmission line, fault parameters comprising a fault location parameter on said current transmission line (L 12 , L 13 , L 23 ) and a fault impedance parameter, —measurement of voltage and/or currents evolution at least at one specific location in the said power system ( 100 ), —iterative simulation of the voltage and/or current evolution by the physical model at the measurement point with a set of fault parameters where at each step of iteration, simulated and measured voltage and/or current evolutions are compared and the set of fault parameters is adapted according to a convergence criterion, —identification of a fault with its fault parameters when convergence of the measured voltage and/or current evolutions and simulated voltage and/or current evolutions is reached in a limited number of iterations.
1. A transient based method for identifying faults in an electric power transmission and/or distribution system comprising a current transmission line, said method comprising
generating a physical model of the current transmission line, the physical model depending on fault parameters and describing the behavior of voltage and/or current transients due to a fault in the current transmission line, said fault parameters comprising a fault location parameter on said current transmission line and a fault impedance parameter,
measuring voltage and/or current evolution at a specific location in said power system,
iteratively simulating the voltage and/or current evolution by the physical model at a measurement point with a set of fault parameters, wherein each step of iteration comprises comparing simulated and measured voltage and/or current evolutions and adapting the set of fault parameters according to a convergence criterion, and
identifying a fault and fault parameters thereof upon having reached convergence of the measured voltage and/or current evolution and the simulated voltage and/or current evolution,
wherein the physical model is based on a telegraph equation for describing the fault parameters and the behavior of travelling waves due to the fault in said electrical power transmission and/or distribution system, and
wherein the only traveling waves are taken into account when iteratively simulating the voltage and/or current evolution are those that can reach the measurement point before a predetermined maximum time t max between one and ten milliseconds.
2. The method according to claim 1 , wherein the measurements of voltage and/or current evolution are carried out at several specific locations in the said power system, each corresponding to a measurement point and wherein the steps of iteratively simulating of the voltage and/or current evolution and identifying a fault with its fault parameters are carried out for each measurement point independently from the other measurement points.
3. The method according claim 1 , further comprising extending the physical model to take into account soil resistivity.
4. The method according to claim 3 , wherein extending the physical model for taking into account soil resistivity comprises implementing a filtering function.
5. The method according to claim 1 , wherein said electrical power transmission and/or distributor system is a high or medium voltage DC grid comprising overhead current transmission lines and/or underground and/or submarine current transmission lines.
6. The method according to claim 1 , wherein said electrical power transmission and/or distributor system is a high or medium voltage AC grid.
7. The method according to claim 1 , wherein said physical model takes into account modal voltage and current.
8. The method according to claim 1 , wherein the convergence criterion comprises the minimization of a cost function of the difference of simulated and measured voltage and/or current evolutions.
9. The method according to claim 1 , wherein identifying identification of a fault comprises verifying that the obtained fault parameters belong to a predefined validity domain.
10. The method according to claim 1 , wherein each iteration step comprises completing voltage and/or current evolutions at specific locations in said electrical power transmission and/or distribution system with ongoing measurements at said measurement point.
11. The method according to claim 1 , wherein the specific location is at one of an end of said current transmission line (L 12 , L 13 , L 23 ), a relay, a breaker module, and a station.
12. The method according to claim 1 , further comprising detecting unusual behavior with respect to a nominal functioning of the electrical power transmission and/or distribution system and thereafter iteratively simulating the voltage and/or current evolution by the physical model.
13. The method according to claim 12 , wherein detecting said unusual behavior comprises detecting at least one of a voltage drop, a current increase, and a crossing of a threshold.
14. The method according to claim 1 , further comprising, after having identified said fault, generating an output in order to activate protection circuits in said electrical power transmission and/or distribution system.
15. An apparatus comprising
a fault-identification module for identifying faults in an electrical power transmission and/or distribution system having a current transmission line (L 12 , L 13 , L 23 ) the fault-identification module being configured for:
memorization of a physical model of the electrical power transmission and/or distribution system with said current transmission line, the physical model describing fault parameters and behavior of travelling waves due to a fault in the electrical power transmission and/or distribution system and, in case of a fault, fault parameters comprising a fault-location parameter on said current transmission line (L 12 , L 13 , L 23 ) and a fault-impedance parameter,
measurement of voltage and/or current evolution at a specific location in said power system,
iterative simulation of the voltage and/or current evolution by the physical model at the measurement point with a set of fault parameters, wherein, at each iteration of said iterative simulation, simulated and measured voltage and/or current evolutions are compared and the set of fault parameters is adapted according to a convergence criterion,
identification of a fault and fault parameters thereof when convergence of the measured voltage and/or current evolutions and simulated voltage and/or current evolutions has been reached,
wherein the physical model is based on a telegraph equation for describing the fault parameters and the behavior of travelling waves due to the fault in said electrical power transmission and/or distribution system, and
wherein the only traveling waves are taken into account when iteratively simulating the voltage and/or current evolution are those that can reach the measurement point before a predetermined maximum time t max between one and ten milliseconds.
16. The apparatus according to claim 15 , wherein the physical model is based on a telegraph equation for describing the fault parameters and the behavior of travelling waves due to the fault in said electrical power transmission and/or distribution system.
17. The apparatus according to claim 15 , wherein the physical model is extended to take into account soil resistivity.
18. The apparatus of claim 15 , further comprising a system that comprises said fault identification module for controlling at least one protection circuit said system in case of a fault identification, wherein said system is high or medium voltage electric power transmission and/or distribution system.