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CN-122029711-A - Method, device and system for determining faults in a dual-loop line

CN122029711ACN 122029711 ACN122029711 ACN 122029711ACN-122029711-A

Abstract

The present disclosure relates to a method for determining a fault in a dual-loop line, the dual-loop line comprising a first line and a second line. The method includes calculating a first angle of power at a start of a monitored line length of a first line, calculating a second angle of power at an end of the monitored line length of the first line, performing an operation on the first angle and the second angle to calculate a first fault factor, and determining whether a fault is on the first line or the second line based on a polarity of the first fault factor. The present disclosure further relates to corresponding devices and systems.

Inventors

  • O.D. Naidoo
  • N. GEORGE

Assignees

  • 日立能源有限公司

Dates

Publication Date
20260512
Application Date
20240926
Priority Date
20231019

Claims (14)

  1. 1. A method for determining a fault in a dual-loop line (2) comprising a first line (L1) and a second line (L2), the method comprising: obtaining local voltage and current measurements of said first line (L1) and said second line (L2), Calculating (M1) a first angle of power at a start of a monitored line length of the first line (L1) based on the local voltage and current measurements, Calculating (M2) a second angle of power at the end of the monitored line length of the first line (L1) based on the local voltage and current measurements, Performing (M3) an operation on the first angle and the second angle to calculate a first fault factor, and -Determining (M4) whether the fault is on the first line (L1) or the second line (L2) based on the polarity of the first fault factor.
  2. 2. The method of claim 1, wherein the operation is a multiplication, and Wherein the fault is determined to be on the first line (L1) in case the first fault factor has a first polarity and the fault is determined to be on the second line (L2) in case the sign of the first fault factor has a second polarity.
  3. 3. A method according to claim 1 or 2, wherein the polarity comprises a sign of the first fault factor, and preferably Wherein the fault is determined to be on the first line (L1) if the sign of the first fault factor is negative and the fault is determined to be on the second line (L2) if the sign of the first fault factor is positive.
  4. 4. The method of any one of claim 1 to 3, further comprising calculating a fault angle within a complete monitored line length of the line having the fault, Wherein the location of the fault is determined based on the zero crossing of the fault angle.
  5. 5. The method of any one of claims 1 to 4, further comprising: Calculating a first bus voltage at an end of a monitored line length of the first line (L1) based on local voltage and current measurements of the first line (L1), Calculating a second bus voltage at the end of the monitored line length of the second line (L2) based on the local voltage and current measurements of the second line (L2), and Determining whether the fault is inside or outside the monitored line length based on the first bus voltage and the second bus voltage.
  6. 6. The method of claim 5, wherein the fault is determined to be outside the monitored line length if a difference between the norm of the first bus voltage and the norm of the second bus voltage is equal to or less than a predetermined threshold, and the fault is determined to be inside the monitored line length if the difference between the norm of the first bus voltage and the norm of the second bus voltage is greater than the predetermined threshold.
  7. 7. The method according to any one of claims 1 to 6, wherein the monitored line lengths of the first line (L1) and the second line (L2) are equal.
  8. 8. The method of any one of claims 1 to 7, further comprising: Calculating a third angle of power at the start of the monitored line length of the second line (L2), Calculating a fourth angle of power at the end of the monitored line length of the second line (L2), Multiplying the third angle and the fourth angle to calculate a second fault factor, and -Determining whether the fault is on the first line (L1) or the second line (L2) based on the sign of the second fault factor.
  9. 9. The method according to claim 8, wherein the fault is determined to be on the second line (L2) if the second fault factor is negative and the fault is determined to be on the first line (L1) if the second fault factor is positive.
  10. 10. The method according to claim 8 or 9, Wherein the calculation of the third angle and the fourth angle is performed using local voltage and current measurements of the first line (L1) and the second line (L2).
  11. 11. The method according to any of claims 1 to 10, wherein the power is calculated as the sum of positive sequence power, negative sequence power and zero sequence power of the first line (L1) and/or the second line (L2).
  12. 12. An apparatus (1) for determining a fault in a dual-loop line (2), the dual-loop line comprising a first line (L1) and a second line (L2), wherein the apparatus (1) is connected to the first line (L1) and the second line (L2) and comprises a processor (10) configured to: obtaining local voltage and current measurements of said first line (L1) and said second line (L2), Calculating a first angle of power at a start of a monitored line length of the first line (L1) based on the local voltage and current measurements, Calculating a second angle of power at an end of the monitored line length of the first line (L1) based on the local voltage and current measurements, Performing an operation on the first angle and the second angle to calculate a first fault factor, and -Determining whether the fault is on the first line (L1) or the second line (L2) based on the first fault factor.
  13. 13. The apparatus (1) of claim 12, wherein the processor (10) is further configured to perform the method of any one of claims 2 to 11.
  14. 14. A system for determining a fault in a dual-loop line (2), the system comprising: A first line (L1) and a second line (L2), The device (1) according to claim 12 or 13.

Description

Method, device and system for determining faults in a dual-loop line Technical Field The present disclosure relates to a method, apparatus and system for determining faults in a dual loop line. In particular, the present disclosure relates to safe distance protection and accurate fault location for dual loop lines connected to conventional and/or renewable energy sources. Background Dual-loop lines are widely used on power transmission systems due to their significant efficiency, reliability, economic and environmental advantages over single-loop lines. For example, currently, more than 50% of the transmission line loop length in india consists of 400 kV and 765 kV lines [1], most of which are dual loop lines. However, due to the mutual coupling effect between the two loops, the transient signal induced on the two loops (due to a fault on one loop) is quite different from the transient signal encountered on the single loop line. This makes the protection of these lines more complex. Currently, the most common protection technique for dual-loop transmission lines is the individual current differential protection for each line along with the distance protection technique as a backup [2]. The former is a unitary protection that depends on the communication between the two terminals. Non-unitary protection (e.g., distance protection) based only on local measurements is further critical and necessary. However, distance protection presents some challenges when applied to lines in systems integrated with inverter-based renewable energy resources (IBRs) [3]. Integration of utility-scale renewable energy power plants at the power transmission level grows exponentially and thus single-ended protection of dual-loop lines (using only local measurements) in power transmission systems with renewable energy resources is a problem and currently the most urgent need. Several protection methods based on local measurements have been proposed in recent literature for transmission lines connected to IBRs. Various approaches have been explored, including fixed zone-based settings, adaptive zone-based settings, communication assistance, modified control-based, and neural network-based solutions. Improved distance relay techniques have been proposed in [4], [5] to compensate for the effects of fault resistance by calculating the section impedance of a fault in the presence of a remote feed. However, these techniques either ignore the equivalent source impedance at each end of the protected line or consider them to be homogenous with the line impedance. However, this is not the case for IBR connected systems. An improved communication-assisted trip scheme is proposed for IBR-derived lines in [6], [7 ]. However, these schemes have delay problems associated with protection decisions and there is no solution in the event of a communication failure. In [8] a control-based solution is provided that adjusts the fault current angle according to IBR mimicking the characteristics of a synchronous generator. However, it is difficult to popularize different renewable energy power plants with various control schemes. [9] An apparent impedance correction method by estimating the non-uniformity angle introduced by IBR is presented in [10 ]. These methods were developed for the terminal to which IBR is connected, assuming that the remote end is connected only to a conventional generator. These methods are not universal, i.e. not applicable to lines connected to a traditional generator based grid or lines with IBRs connected at both ends. Additionally, these approaches do not address the problem of mutual coupling in dual loop lines. Recently, also in the literature, general distance protection methods have been proposed that can be applied to lines connected to IBRs at either or both ends. [13] The proposed method uses a time domain based method that requires measurements at high sampling frequencies. Retrofitting such solutions into existing installation foundations is a challenge. Furthermore, the source independent approach presented in this approach and [14] does not take into account the mutual coupling effect in dual loop lines. Fig. 1 and 2 illustrate an exemplary dual loop wiring system configuration and specific problems associated therewith. The downward stepped arrows each indicate the location of the fault, and V x and I x represent voltage and current, respectively. Fig. 1 and 2 show a dual loop line connecting an inverter based renewable energy source (IBR) to a power grid. Fig. 1A and 1B indicate two failure scenarios. For the first fault scenario in fig. 1A, current on line 2 flows out of IBR through the remote end into the fault. Thus, the current experienced by relay R1 Are essentially fully controlled. In this case, the conventional phasor-based distance element [11] will fail, whereas the distance protection methods proposed in recent documents [9], [10] for the IBR-connected line will work reliably. Now consider a second fail