System and method for determining distance to fault in power system network

Abstract

A method for determining a distance to a fault in a power system network is provided. The method may involve: determining a set of processed voltage samples based on a set of measured voltage samples; determining a set of processed reactive current samples, a set of processed resistive current samples, a set of processed negative sequence current samples, and a set of processed zero sequence current samples based on the set of measured current samples; selecting a selected processed voltage sample, a selected processed reactive current sample, a selected processed resistive current sample, and a selected processed negative or zero sequence current sample based on an indication from the faulty phase indicator; determining, based on the selected processed reactive current sample, that no distortion occurs due to current transformer (CT) saturation; and calculating a distance to the fault based on a determination that no distortion occurs.

Description

[0001] Cross-reference to related applications This application claims the benefit of U.S. Application No. 18 / 188219, filed March 22, 2023, the entire contents of which are hereby incorporated by reference. Technical Field

[0002] This application and the resulting patents generally relate to power system networks, and more specifically to systems and methods for determining the distance to a fault in a power system network. Background Technology

[0003] Generally speaking, fault location in cable and / or overhead line systems using phasor-based single-ended fault locator algorithms is inaccurate during current transformer (CT) saturation conditions. Therefore, there is a growing need for a method to accurately calculate the distance to a fault in certain types of systems based on single-ended measurement samples unaffected by CT saturation.

[0004] This not only reduces the requirements for existing CTs, but also reduces the error rate of fault location using single-ended measurements to less than 2% for both single-wire-to-ground (SLG) faults and phase-to-phase (ground) faults with a resistance of 20 ohms and a source impedance ratio (SIR) of 10. Furthermore, fault location remains accurate even during severe CT saturation, reaching ¼ cycle of saturation start time and ½ cycle of maximum saturation duration in each fundamental frequency cycle. Summary of the Invention

[0005] Therefore, this application and the resulting patents provide a method for determining the distance to a fault in a power system network. The method may include the following steps: determining a set of processed voltage samples based at least in part on a set of measured voltage samples; determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on a set of measured current samples; determining a set of processed negative-sequence current samples and a set of processed zero-sequence current samples based at least in part on the set of measured current samples; and selecting, at least in part on an indication from a faulty phase indicator, a selected processed voltage sample from the set of processed voltage samples, a selected processed reactive current sample from the set of processed reactive current samples, and a selected processed resistive current sample from the set of processed resistive current samples. The selected processed resistive current sample in the current sample and the selected processed negative-sequence or zero-sequence current sample in the set of processed negative-sequence current samples or the set of processed zero-sequence current samples; based at least in part on the selected processed reactive current sample, it is determined that no distortion occurs in the set of measured voltage samples and the set of measured current samples due to current transformer (CT) saturation; and based at least in part on the determination that no distortion occurs, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample and the selected processed negative-sequence or zero-sequence current sample, the distance to the fault is calculated.

[0006] This application and the resulting patent also provide a method for determining the distance to a fault in a power system network. The method may include the following steps: receiving a set of measured voltage samples and a set of measured current samples; determining a set of processed voltage samples based at least in part on the set of measured voltage samples; determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on the set of measured current samples; determining a set of processed negative-sequence current samples and a set of processed zero-sequence current samples based at least in part on the set of measured current samples; receiving an indication from a faulty phase indicator; and selecting, at least in part on the indication, a selected processed voltage sample from the set of processed voltage samples and a selected processed reactive current sample from the set of processed reactive current samples. The current sample, a selected processed resistive current sample from the set of processed resistive current samples, and a selected processed negative-sequence or zero-sequence current sample from the set of processed negative-sequence current samples or the set of processed zero-sequence current samples; determining, at least in part based on the selected processed reactive current sample, that no distortion occurs on the set of measured voltage samples and the set of measured current samples due to current transformer (CT) saturation; and calculating the distance to the fault, at least in part based on the determination that no distortion occurs, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative-sequence or zero-sequence current sample.

[0007] This application and the resulting patents also provide a power system network. The power system network may include: a power line, wherein a set of measured voltage samples and a set of measured current samples are associated with a segment of the power line; and a fault located on the power line, wherein a set of processed voltage samples is determined at least partially based on the set of measured voltage samples, wherein a set of processed reactive current samples, a set of processed resistive current samples, a set of processed negative-sequence current samples, and a set of processed zero-sequence current samples are determined at least partially based on the set of measured current samples, and wherein a selected processed voltage sample from the set of processed voltage samples and a selected processed negative-sequence current sample from the set of processed reactive current samples are selected at least partially based on an indication from a faulty phase indicator. The determination that no distortion occurs due to current transformer (CT) saturation on the set of measured voltage samples and the set of measured current samples is made based at least in part on the selected processed reactive current samples, the selected processed reactive current samples, the selected processed resistive current samples, and the selected processed negative-sequence or zero-sequence current samples, and the distance to the fault is calculated based at least in part on the determination that no distortion occurs, the selected processed voltage samples, the selected processed reactive current samples, the selected processed resistive current samples, and the selected processed negative-sequence or zero-sequence current samples.

[0008] These and other features and improvements of this application and the resulting patents will become apparent to those skilled in the art upon examination of the following detailed description, taken in conjunction with the accompanying drawings and claims. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of an algorithm for calculating the distance to a fault according to one or more example embodiments of the present disclosure.

[0010] Figure 2 This is a schematic diagram of a power system network according to one or more exemplary embodiments of the present disclosure.

[0011] Figure 3 It is based on Figure 1 A schematic diagram of the algorithm used to prepare voltage and current samples.

[0012] Figure 4 It is based on Figure 1 A schematic diagram of the algorithm used to select fault phase voltage and current samples.

[0013] Figure 5 It is based on Figure 1 A schematic diagram of the algorithm used to detect CT saturation.

[0014] Figure 6 It is based on Figure 1 The algorithm depicts a flowchart of the calculation of the distance to the fault. Detailed Implementation

[0015] Referring now to the accompanying drawings, which run through several views, similar numbers refer to similar elements. Figure 1 This is a schematic diagram 100 of an algorithm for calculating the distance to a fault. This schematic diagram 100 can be applied to fault distance calculation in power system networks. At box 102, voltage and current samples can be prepared and processed to remove any attenuating DC components in order to formulate an equation for calculating the distance to the fault. This process can be performed within... Figure 3 Further details are provided. At box 104, processed voltage and current samples of the relevant faulty phase can be selected to formulate an equation for calculating the distance to the fault. This can be used... FtPhsInd The input is used to select the relevant faulty phase's processed voltage and current samples from a variety of processed voltage and current samples. This process can be performed within... Figure 4 Further details are provided below. At box 104, the algorithm can then output... U P ( n ), I 0_Neg ( n ), I PR ( n )and I PX ( n The relevant parameters of ).

[0016] At box 106, I can be processed. PX (n) Output for determining whether a voltage or current sample is distorted due to current transformer (CT) saturation. If the sample is not distorted due to CT saturation, box 106 can output a CT saturation indication digital signal. CTSatInd = 1. If the sample is distorted due to CT saturation, then box 106 can output a CT saturation indicator digital signal. CTSatInd =0. This process can be performed at... Figure 5 Further details are provided below. At block 108, if a digital signal indicating no CT saturation has been received from block 106, the distance to the fault can be calculated by formulating an equation using the output of block 104, which is associated with processed voltage and current samples of the relevant faulty phase. This process can be performed within... Figure 6 Further details are provided.

[0017] Figure 2 This is a schematic diagram of a power system network, 200. (For example...) Figure 2As described, a power system network may have multiple power sources. Therefore, faults... F Points that may be located in the power system network M and N Between. Point M and N The distance between them can be expressed as L .exist Figure 2 In the middle, to the fault F Distance (e.g., using) x (This indicates that) is where fault locators are deployed. M With the malfunction that occurred F The distance between them. At point M At this point, the applicable voltage and current can be expressed as: U M and I M These are measured by the fault locator. Assuming a fault... F With fault resistor R g Then the fault F Voltage can be further used U F and current I F To characterize.

[0018] Therefore, regarding x The time-domain equality might be as follows: (For ascending order) (For negative order) (For zero order) In the case of a single-phase ground fault, the following time-domain equality can be applied: In the case of phase-to-phase faults, the following time-domain equality can be applied: In the above equation, p = A , B or C , pp = AB , BC or CA , ,as well as .

[0019] When regarding x When sampling using time-domain equality, the following equation can be applied: In other words, as well as These equations can then be applied when calculating the distance to the fault. For example, such as... Figure 6 As described in the generating matrix Y M The equation can be applied at that time.

[0020] Figure 3 It is based on Figure 1 The diagram 300 illustrates the algorithm for preparing voltage and current samples. The algorithm for preparing voltage and current samples can be applied to... Figure 1 In box 102, the algorithm prepares voltage and current samples by executing functions such as the averaging function 320, the resistive and reactive current determination function 322, the negative-sequence transducer function 324, and the differential function 326. Samples of each phase voltage and phase current can be measured at the local terminal. Samples may include: three-phase voltage samples, such as... u A ( n )302A、 u B ( n )302B and u C ( n )302C; and three-phase current samples, for example i A ( n 304A i B ( n )304B and i C ( n )304C. Three-phase voltage samples 302A-C and three-phase current samples 304A-C can be inputs to algorithms used to prepare voltage and current samples. Although Figure 3 Not depicted in the text, but another set of inputs for the algorithm used to prepare voltage and current samples may include the positive-sequence impedance per unit length. z 1 and zero-sequence impedance per unit length z 0 ,in z 1 = R 1 + jX 1 and z 0 = R 0 + jX 0 ,like Figure 1 As shown in the image.

[0021] The averaging function 320 calculates the average of two samples. For example, if the averaging function 320 receives input... x ( n Then the average function 320 can be calculated. x ( n )and x(n-1) The sum of these values ​​is multiplied by 0.5. Therefore, the output y(n) of the average function 320 can be calculated as follows: Therefore, the output of the average function 320 y ( n It can be at least partially based on the input. x ( n )application z-1 The function determines this.

[0022] Therefore, by analyzing the three-phase voltage samples... u A ( n 302A u B ( n ) 302B and u C ( n The 302C uses an averaging function 320 to determine the processed three-phase voltage samples. U A ( n 306A U B ( n ) 306B and U C ( n 306C. That is, the following equation can be applied: Resistance and reactive current determination function 322 based on phase current samples i x ( n )(For example, i A ( n 304A i B ( n )304B and i C ( n )304C) and the total current sample i0(n) 308 calculate resistive and reactive current, where the total current sample i 0 ( n )308 isi A ( n 304A i B ( n ) 304B and i C (n) The sum of 304C. That is, i 0 ( n ) = i A ( n ) + i B ( n ) + i C ( n The processed current sample can be determined by applying the averaging function 320 to the total current sample i0(n) 308. I 0 ( n 310. In other words, the following equation can be applied: If the resistivity and reactive current determine the function 322, the input is received. i x ( n )and i 0 ( n ) 308, then the resistive part of the current It can be measured, where K R It is a coefficient used to compensate resistive current with zero-sequence current, and where ,in R n This indicates the resistance of the circuit. In other words, Subsequently, an averaging function 320 can be applied to the resistive portion of the current to determine the processed resistive current. I xR ( n In other words, Therefore, the processed resistive current I AR ( n 312A I BR ( n ) 312B and I CR ( n )312C can be determined as follows: If the resistance and reactive current determine the function 322 receiving input i x ( n )and i 0 ( n )308, then the reactive part of the current It can be measured, where K X It is the coefficient for compensating reactive current using zero-sequence current, and where X n This indicates the reactive power of the line. In other words, Subsequently, the differential function 326 can be applied to the reactive component of the current to determine the processed resistive current. I xX ( n ).

[0023] Differential function 326 calculates the differential of two samples. For example, if differential function 326 receives input... x ( n Then the differential function 326 can be calculated. x ( n ) and x （n-1） The difference, and multiply that difference by Therefore, the output of the differential function 326 y ( n It can be calculated as follows: Where N spc This is the number of samples per period. Therefore, the output of the differential function 326... y ( n It can be based at least in part on the input. x ( n )application z-1 The function determines this.

[0024] Therefore, when the differential function 326 is applied to the reactive component of the current, the processed reactive current is obtained. I xX ( n In other words, Therefore, the processed reactive current I AX ( n 314A I BX ( n ) 314B andI CX ( n 314C can be identified as follows: N spc This indicates the number of samples per period. For example, if... N spc If there are 64 samples per cycle at 50 Hz, then the sampling frequency will be 64 samples divided by 0.02 to obtain a sampling frequency of 3.2 kHz.

[0025] Negative-sequence transducer function 324 is based on phase current samples (e.g., i A ( n 304A i B ( n 304B and i C ( n (304C) Calculate the negative current sample. Therefore, the output of the negative sequence transducer function 324. i X2 ( n It can be based at least in part on the application of the input (which is a sample of the phase current). z -Nspc / 3 The function determines this. Therefore, the negative-sequence transducer function 324 is configured to output a negative current sample using the following equation. i A2 ( n 316A i B2 ( n )316B and i C2 ( n 316C: Then, by analyzing the negative current sample... i A2 ( n The 316A uses the differential function 326 to determine the processed negative current sample. I A2 ( n 318A. That is to say, By analyzing negative current samples i B2 ( n )316B uses the differential function 326 to determine the processed negative current sample. I B2 (n 318B. That is to say, By analyzing negative current samples i C2 ( n The 316C uses the differential function 326 to determine the processed negative current sample. I C2 ( n 318C. That is to say, Figure 4 This is a schematic diagram 400 of an algorithm for selecting faulty phase voltage and current samples. To select faulty phase voltage and current samples, the fault type can be indicated. The faulty phase indicator 402 can indicate a number from 1 to 10 to indicate the type of fault present in the power system network. For example, the faulty phase indicator can indicate 1 for a phase-A to ground fault, 2 for a phase-B to ground fault, 3 for a phase-C to ground fault, 4 for a phase-B to phase-C fault, 5 for a phase-C to phase-A fault, 6 for a phase-A to phase-B fault, 7 for a phase-B to phase-C ground fault, 8 for a phase-C to phase-A ground fault, 9 for a phase-A to phase-B ground fault, and 10 for either a phase-A to phase-B to phase-C fault or a phase-A to phase-B to phase-C ground fault.

[0026] If the faulty phase indicator 402 indicates 1, then U P ( n ) = U A ( n ) ，I PR ( n ) = I AR ( n ) ，I PX ( n ) = I AX ( n ),and I 0_Neg ( n ) = I 0 ( n If the faulty phase indicator 402 indicates 2, then... U P ( n ) = U B ( n ) ，I PR ( n )= I BR ( n ) ，I PX ( n ) = I BX ( n ),and I 0_Neg ( n ) = I 0 ( n If the faulty phase indicator 402 indicates 3, then... U P ( n ) = U C ( n ) ，I PR ( n ) = I CR ( n ) ，I PX ( n ) = I CX ( n ),and I 0_Neg ( n ) = I 0 ( n If a faulty phase indicator 402 indicates 4 or 7, then... U P ( n ) = U B ( n ) -U C ( n ) ，I PR ( n ) = I BR ( n ) –I CR ( n ) ，I PX ( n ) = I BX ( n ) –I CX ( n ) ， and I 0_Neg( n ) = I A2 ( n If a faulty phase indicator 402 indicates 5 or 8, then... U P ( n ) = U C ( n ) -U A ( n ) ，I PR ( n ) = I CR ( n ) –I AR ( n ) ，I PX ( n ) = I CX ( n ) -I AX ( n ),and I 0_Neg ( n ) = I B2 ( n If a faulty phase indicator 402 indicates 6, 9, or 10, then... U P ( n ) = U A ( n ) –U B ( n ) ，I PR ( n ) = I AR ( n ) –I BR ( n ) ，I PX ( n ) = I AX ( n ) –I BX ( n ),and I 0_Neg ( n ) = IC2 ( n ).

[0027] Figure 5 A schematic diagram 500 depicts an algorithm for indicating whether a current sample is distorted due to current transformer (CT) saturation. The algorithm for detecting CT saturation can receive... I PX ( n ) as input, I PX ( n ) is the output of a faulty phase indicator, for example Figure 4 The output of the faulty phase indicator 402. I PX ( n This can represent the processed reactive current. Input I PX ( n The input can be fed into the short-window algorithm 502 used to calculate the full-cycle Fourier phasor. That is, the short-window algorithm 502 used to calculate the full-cycle Fourier phasor can be a 1 / 4-cycle Fourier phasor. Then, the short-window algorithm 502 used to calculate the full-cycle Fourier phasor can be processed by inputting... I PX ( n ) and a set of complex coefficients h ( k Convolution is used to output PhsI PX ( n Convolution can be performed by applying the following equation: in M This corresponds to a window length of 1 / 4 of the period length (e.g., if the number of samples per period is 64, then...). M This will equal 1 / 4 of 64, which is 16), where h ( k ) k = 1, 2,…, M It is done by using a matrix H The second line is obtained.

[0028] matrix H It can be done H = (A T A） -1 A H To calculate, where And among them , and As mentioned above, Nspc This represents the number of samples per period. T s Indicates the sampling period, and T a This represents the attenuation period of the DC component. If N spc If it's 50Hz with 64 samples per cycle, then the sampling period is... The attenuation period of the DC component. X1 and R1 were previously used to calculate the coefficient K. R and K X .

[0029] In calculation PhsI PX ( n After that, it can be determined PhsI PX ( n The amplitude of ). PhsI PX ( n The amplitude of ) can reflect PhsI PX ( n The absolute value of ). It can be used for PhsI PX ( n Applying the absolute value function 504, where, PhsI PX ( n absolute value I MP The calculation is as follows: In calculation I MP ( n After that, the average component 506 can be applied to calculate the period within one-eighth. I MP ( n (average) I MPav ( n This can be achieved by applying the following equation: After calculating the average value I MPav ( n After that, it can be maintained for ¼ of the cycle time following the fault (that is, half the cycle of the fault signature). Therefore, it is possible to determine before CT saturation (that is, the average value). I MPav ( n (Stay within a quarter of the cycle time) Average I MPav ( nconstant of I MPavConst ( n )。

[0030] Then, the difference component 508 can receive I MP ( n ) and I MPavConst ( n ) as inputs and determine I MP ( n ) and I MPavConst ( n ) between the difference. That is, Then, the difference can be input into the absolute difference component 510 to determine its absolute value. That is, Then, the absolute value | ΔI MP ( n )| can be input into the threshold function 512. The threshold function 512 can also receive a predetermined error threshold as an input. For example, the predetermined error threshold can be set to 1. If the absolute value | ΔI MP ( n )| is less than the predetermined error threshold, the sample is qualified and the algorithm can output CTSatInd = 1. This indicates that the sample is not currently saturated and distorted by the CT. If the absolute value | ΔI MP ( n )| is not less than the predetermined error threshold, the sample is unqualified and the algorithm can output CTSatInd = 0. This indicates that the sample is currently saturated and distorted by the CT.

[0031] In some instances, the algorithm may only output I PX ( n ) and determine that all three | ΔI MP ( n )| values are less than the predetermined error threshold or not less than the predetermined error threshold when it receives multiple inputs CTSatInd .

[0032] Figure 6 is the flowchart 600, which depicts the calculation of the distance to the fault. If the output through the algorithm is CTSatInd= 1 indicates that a sample is qualified, and the voltage and current parameters, along with other parameters corresponding to that sample, can be used to generate a matrix for calculating the distance to the fault. For example, if I PX ( n ) is what causes the algorithm output CTSatInd For a sample with a value of 1, the corresponding parameters may include: U P ( n ), I PR ( n )and I PX ( n To calculate the distance to the fault, a matrix can first be constructed. Y M and A M A matrix can be defined as follows: ,as well as .

[0033] It is worth noting that if a single-phase ground fault is detected, then at the fault location... But for all other faults . X 1 and R 1 Previously used to calculate coefficients K R and K X The matrix is ​​depicted in box 602. Y M and A M The generation of .

[0034] Then, the distance to the fault can be calculated by solving the following matrix equation: in By applying the least squares method to these two matrices, the following can be used to determine... X .

[0035] matrix X The generation of the matrix is ​​depicted in box 604. X The first element can be the distance to the fault.

[0036] Once the distance to the fault is determined, control actions can be performed based on that distance. For example, control actions might include generating an alarm for the operator.

[0037] It should be apparent that the foregoing only relates to certain embodiments of this application and its related patents. Many changes and modifications can be made herein by those skilled in the art without departing from the general spirit and scope of the invention as defined by the appended claims and their equivalents.

[0038] Further aspects of the invention are provided by the subject matter of the following provisions: 1. A method for determining the distance to a fault in a power system network, comprising: determining a set of processed voltage samples based at least in part on a set of measured voltage samples; determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on a set of measured current samples; determining a set of processed negative-sequence current samples and a set of processed zero-sequence current samples based at least in part on the set of measured current samples; and selecting, at least in part on an indication from a faulty phase indicator, a selected processed voltage sample from the set of processed voltage samples, a selected processed reactive current sample from the set of processed reactive current samples, and the... The selected processed resistive current sample from the set of processed resistive current samples and the selected processed negative-sequence or zero-sequence current sample from the set of processed negative-sequence current samples or the set of processed zero-sequence current samples; at least in part based on the selected processed reactive current sample, it is determined that no distortion occurs on the set of measured voltage samples and the set of measured current samples due to current transformer (CT) saturation; and at least in part based on the determination that no distortion occurs, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative-sequence or zero-sequence current sample, the distance to the fault is calculated.

[0039] 2. The method of Clause 1, wherein calculating the distance to the fault based at least in part on the determination that no distortion has occurred further comprises: formulating a set of equations for calculating the distance to the fault, wherein the set of equations is based at least in part on the set of measured voltage samples and the set of measured current samples; and calculating the distance to the fault based at least in part on the set of equations, the determination that no distortion has occurred, selected processed voltage samples, selected processed reactive current samples, selected processed resistive current samples, and selected processed negative-sequence or zero-sequence current samples.

[0040] 3. The method as described in any of the foregoing clauses, wherein calculating the distance to the fault based at least in part on the determination that no distortion has occurred further comprises: developing a first matrix based at least in part on the selected processed voltage samples; developing a second matrix based at least in part on the selected processed reactive current samples, the selected processed resistive current samples, and the selected processed negative-sequence or zero-sequence current samples; and calculating the distance to the fault based at least in part on the first matrix and the second matrix.

[0041] 4. The method as described in any of the foregoing clauses, wherein determining that no distortion occurs due to current transformer (CT) saturation is based at least in part on the selected processed reactive current sample, further comprising: calculating a full-cycle Fourier phasor current over a portion of the full cycle based at least in part on the selected processed reactive current sample; calculating the magnitude of the full-cycle Fourier phasor current; calculating the average magnitude of the full-cycle Fourier phasor current over one-eighth of the cycle; and determining the difference between the average magnitude of the full-cycle Fourier phasor current over one-eighth of the cycle and a constant, wherein the constant is determined at least in part based on the magnitude of the full-cycle Fourier phasor current over a portion of the full cycle after the fault occurs.

[0042] 5. The method as described in any of the foregoing clauses, wherein determining, at least in part, that no distortion due to CT saturation occurs based on the selected processed reactive current samples further comprises: determining that the difference is less than a predetermined error threshold; determining that no distortion due to CT saturation occurs in response to the determination that the difference is less than the predetermined error threshold; and outputting an output of “1” based on the determination that no distortion due to CT saturation occurs on a set of measured voltage samples and a set of measured current samples.

[0043] 6. The method as described in any of the foregoing clauses, wherein determining a set of processed voltage samples based at least in part on a set of measured voltage samples further comprises: receiving the set of measured voltage samples; applying an averaging function to the set of measured voltage samples; and determining the set of processed voltage samples, wherein the set of processed voltage samples includes the output of the averaging function.

[0044] 7. The method as described in any of the foregoing clauses, wherein determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on a set of measured current samples further comprises: receiving the set of measured current samples; determining a set of processed resistive currents based at least in part on the set of measured current samples; applying an averaging function to the set of processed resistive currents; and determining the set of processed resistive current samples, wherein the set of processed resistive current samples includes the output of the averaging function.

[0045] 8. The method as described in any of the foregoing clauses, wherein determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on a set of measured current samples further comprises: receiving the set of measured current samples; determining a set of processed reactive currents based at least in part on the set of measured current samples; applying a differential function to the set of processed reactive currents; and determining the set of processed reactive current samples, wherein the set of processed reactive current samples includes the output of the differential function.

[0046] 9. The method as described in any of the foregoing clauses, wherein the indication from the faulty phase indicator indicates the type of fault associated with the fault.

[0047] 10. A method for determining the distance to a fault in a power system network, comprising: receiving a set of measured voltage samples and a set of measured current samples; determining a set of processed voltage samples based at least in part on the set of measured voltage samples; determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on the set of measured current samples; determining a set of processed negative-sequence current samples and a set of processed zero-sequence current samples based at least in part on the set of measured current samples; receiving an indication from a faulty phase indicator; and selecting, at least in part on the indication, a selected processed voltage sample from the set of processed voltage samples and a selected processed reactive current sample from the set of processed reactive current samples. Selected processed reactive current samples, selected processed resistive current samples from the set of processed resistive current samples, and selected processed negative-sequence or zero-sequence current samples from the set of processed negative-sequence current samples or the set of processed zero-sequence current samples; determined, at least in part based on the selected processed reactive current samples, that no distortion occurs on the set of measured voltage samples and the set of measured current samples due to current transformer (CT) saturation; and calculated, at least in part based on the determination that no distortion occurs, the selected processed voltage samples, the selected processed reactive current samples, the selected processed resistive current samples, and the selected processed negative-sequence or zero-sequence current samples, the distance to the fault.

[0048] 11. The method as described in any of the foregoing clauses, wherein calculating the distance to the fault based at least in part on a set of equations and a determination that no distortion has occurred further comprises: developing a set of equations for calculating the distance to the fault, wherein the set of equations is based at least in part on the set of measured voltage samples and the set of measured current samples; and calculating the distance to the fault based at least in part on a determination that no distortion has occurred, selected processed voltage samples, selected processed reactive current samples, selected processed resistive current samples, and selected processed negative-sequence or zero-sequence current samples.

[0049] 12. The method as described in any of the foregoing clauses, wherein calculating the distance to the fault based at least in part on the determination that no distortion has occurred further comprises: developing a first matrix based at least in part on selected processed voltage samples; developing a second matrix based at least in part on selected processed reactive current samples, selected processed resistive current samples, and selected processed negative-sequence or zero-sequence current samples; and calculating the distance to the fault based at least in part on the first matrix and the second matrix.

[0050] 13. The method as described in any of the foregoing clauses, wherein determining that no distortion occurs due to current transformer (CT) saturation based at least in part on selected processed reactive current samples further comprises: calculating, at least in part on selected processed reactive current samples, a full-cycle Fourier phasor current over a portion of the full cycle; calculating the magnitude of the full-cycle Fourier phasor current; calculating the average magnitude of the full-cycle Fourier phasor current over one-eighth of the cycle; and determining the difference between the average magnitude of the full-cycle Fourier phasor current over one-eighth of the cycle and a constant, wherein the constant is determined at least in part on the magnitude of the full-cycle Fourier phasor current over a portion of the full cycle after the fault occurs.

[0051] 14. The method as described in any of the foregoing clauses, wherein determining that no distortion due to CT saturation occurs based at least in part on selected processed reactive current samples further comprises: determining that the difference is less than a predetermined error threshold; determining that no distortion due to CT saturation occurs in response to the determination that the difference is less than the predetermined error threshold; and outputting an output of “1” based on the determination that no distortion due to CT saturation occurs on a set of measured voltage samples and a set of measured current samples.

[0052] 15. The method as described in any of the foregoing clauses, wherein determining a set of processed voltage samples based at least in part on a set of measured voltage samples further comprises: receiving a set of measured voltage samples; applying an averaging function to the set of measured voltage samples; and determining a set of processed voltage samples, wherein the set of processed voltage samples includes the output of the averaging function.

[0053] 16. The method as described in any of the foregoing clauses, wherein determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on a set of measured current samples further comprises: receiving a set of measured current samples; determining a set of processed resistive currents based at least in part on the set of measured current samples; applying an averaging function to the set of processed resistive currents; and determining a set of processed resistive current samples, wherein the set of processed resistive current samples includes the output of the averaging function.

[0054] 17. The method as described in any of the foregoing clauses, wherein determining a set of processed reactive current samples and a set of processed resistive current samples based at least in part on a set of measured current samples further comprises: receiving a set of measured current samples; determining a set of processed reactive currents based at least in part on the set of measured current samples; applying a differential function to the set of processed reactive currents; and determining a set of processed reactive current samples, wherein the set of processed reactive current samples includes the output of the differential function.

[0055] 18. A power system network comprising: a power line, wherein a set of measured voltage samples and a set of measured current samples are associated with a segment of the power line; and a fault located on the power line, wherein a set of processed voltage samples is determined at least partially based on the set of measured voltage samples, wherein a set of processed reactive current samples, a set of processed resistive current samples, a set of processed negative-sequence current samples, and a set of processed zero-sequence current samples are determined at least partially based on the set of measured current samples, wherein a selected processed voltage sample from the set of processed voltage samples, a selected processed reactive current sample from the set of processed reactive current samples, and a selected processed reactive current sample from the set of processed resistive current samples are... The selected processed resistive current sample and the selected processed negative-sequence or zero-sequence current sample from the set of processed negative-sequence current samples or the set of processed zero-sequence current samples are selected at least in part based on indications from the faulty phase indicator, wherein at least in part based on the determination that no distortion occurs on the set of measured voltage samples and the set of measured current samples due to current transformer (CT) saturation, and wherein at least in part based on the determination that no distortion occurs, the distance to the fault is calculated from the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative-sequence or zero-sequence current sample.

[0056] 19. A power system network as described in any of the foregoing clauses, wherein the distance to a fault is calculated at least in part based on a set of equations, the selected processed voltage samples, the selected processed reactive current samples, the selected processed resistive current samples, the selected processed negative-sequence or zero-sequence current samples, and the distance to the fault, the set of equations being at least in part based on the set of measured voltage samples and the set of measured current samples.

[0057] 20. A power system network as described in any of the foregoing clauses, wherein determining, at least in part, that no distortion occurs due to current transformer (CT) saturation based on the selected processed reactive current samples further comprises: calculating, at least in part, a full-cycle Fourier phasor current over a portion of the full cycle based on the selected processed reactive current samples; calculating the magnitude of the full-cycle Fourier phasor current; calculating the average magnitude of the full-cycle Fourier phasor current over one-eighth of the cycle; determining the difference between the average magnitude of the full-cycle Fourier phasor current over one-eighth of the cycle and a constant, wherein the constant is determined at least in part based on the magnitude of the full-cycle Fourier phasor current over a portion of the full cycle after a fault occurs; determining that the difference is less than a predetermined error threshold; determining, in response to the determination that the difference is less than the predetermined error threshold, that no distortion occurs due to CT saturation; and outputting an output of "1" based on the determination that no distortion occurs due to CT saturation on the set of measured voltage samples and the set of measured current samples.

Claims

1. A method for determining a distance to a fault in a power system network, comprising: determining a set of processed voltage samples (306A-C) based at least in part on a set of measured voltage samples (302A-C); determining a set of processed reactive current samples (314A-C) and a set of processed resistive current samples (312A-C) based at least in part on a set of measured current samples (304A-C); determining a set of processed negative sequence current samples (318A-C) and a set of processed zero sequence current samples based at least in part on the set of measured current samples (304A-C); selecting a selected processed voltage sample of the set of processed voltage samples (306A-C), a selected processed reactive current sample of the set of processed reactive current samples (314A-C), a selected processed resistive current sample of the set of processed resistive current samples (312A-C), and a selected processed negative sequence or zero sequence current sample of the set of processed negative sequence current samples (318A-C) or the set of processed zero sequence current samples based at least in part on an indication from a faulted phase indicator (402); determining that no distortion occurred on the set of measured voltage samples (302A-C) and the set of measured current samples (304A-C) based at least in part on the selected processed reactive current sample; and calculating the distance to the fault based at least in part on the determination that no distortion occurred, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative sequence or zero sequence current sample.

2. The method of claim 1, wherein, calculating the distance to the fault based at least in part on the determination that no distortion occurred further comprises: developing a set of equations for calculating the distance to the fault, wherein the set of equations is based at least in part on the set of measured voltage samples (302A-C) and the set of measured current samples (304A-C); and calculating the distance to the fault based at least in part on the set of equations, the determination that no distortion occurred, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative sequence or zero sequence current sample.

3. The method of claim 2, wherein, calculating the distance to the fault based at least in part on the determination that no distortion occurred further comprises: developing a first matrix based at least in part on the selected processed voltage sample; developing a second matrix based at least in part on the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative sequence or zero sequence current sample; and calculating the distance to the fault based at least in part on the first matrix and the second matrix.

4. The method of claim 1, wherein, determining that no distortion occurred due to current transformer (CT) saturation based at least in part on the selected processed reactive current sample further comprises: calculating a full-cycle Fourier phasor (502) current over a portion of a full cycle based at least in part on the selected processed reactive current samples; calculating a magnitude of the full-cycle Fourier phasor (502) current; calculating an average of the magnitude of the full-cycle Fourier phasor (502) current over an eighth of a cycle; and determining a difference between the average of the magnitude of the full-cycle Fourier phasor (502) current over the eighth of a cycle and a constant, wherein the constant is determined based at least in part on the magnitude of the full-cycle Fourier phasor (502) current over the portion of the full cycle after the fault occurs.

5. The method of claim 4, wherein, determining that no distortion occurred due to CT saturation based at least in part on the selected processed reactive current samples further comprises: determining that the difference is less than a predetermined error threshold; in response to a determination that the difference is less than the predetermined error threshold, determining that no distortion occurred due to the CT saturation; and outputting an output of "1" based on the determination that no distortion occurred due to the CT saturation over the set of measured voltage samples and the set of measured current samples.

6. The method of claim 1, wherein, determining the set of processed voltage samples based at least in part on the set of measured voltage samples (302A-C) further comprises: receiving the set of measured voltage samples (302A-C); applying an averaging function (320) to the set of measured voltage samples (302A-C); and determining the set of processed voltage samples (306A-C), wherein the set of processed voltage samples (306A-C) comprises an output of the averaging function (320).

7. The method of claim 1, wherein, determining the set of processed reactive current samples (314A-C) and the set of processed resistive current samples (312A-C) based at least in part on the set of measured current samples (304A-C) further comprises: receiving the set of measured current samples (304A-C); determining a set of processed resistive current (312A-C) based at least in part on the set of measured current samples (304A-C); applying an averaging function (320) to the set of processed resistive current (312A-C); and determining the set of processed resistive current samples (312A-C), wherein the set of processed resistive current samples (312A-C) comprises an output of the averaging function (320).

8. The method of claim 7, wherein, determining the set of processed reactive current samples (314A-C) and the set of processed resistive current samples (312A-C) based at least in part on the set of measured current samples (304A-C) further comprises: receiving the set of measured current samples (304A-C); determining a set of processed reactive current (314A-C) based at least in part on the set of measured current samples (304A-C); applying a differentiation function (326) to the set of processed reactive current (314A-C); and determining the set of processed reactive current samples (314A-C), wherein the set of processed reactive current samples (314A-C) comprises an output of the differentiation function (326). determining the set of processed reactive current samples (314A-C), wherein the set of processed reactive current samples (314A-C) comprises an output of the derivative function (326).

9. The method of claim 1, wherein, the indication from the faulty phase indicator (402) indicates a fault type associated with the fault.

10. A power system network, comprising: a power line, wherein a set of measured voltage samples (302A-C) and a set of measured current samples (304A-C) are associated with a section of the power line; and a fault located on the power line, wherein a set of processed voltage samples (306A-C) is determined based at least in part on the set of measured voltage samples (302A-C), wherein a set of processed reactive current samples (314A-C), a set of processed resistive current samples (312A-C), a set of processed negative sequence current samples (318A-C), and a set of processed zero sequence current samples are determined based at least in part on the set of measured current samples (304A-C), wherein a selected processed voltage sample of the set of processed voltage samples (302A-C), a selected processed reactive current sample of the set of processed reactive current samples (314A-C), a selected processed resistive current sample of the set of processed resistive current samples (312A-C), and a selected processed negative or zero sequence current sample of the set of processed negative sequence current samples (318A-C) or the set of processed zero sequence current samples are selected based at least in part on an indication from a faulty phase indicator (402), wherein a determination that no distortion due to current transformer (CT) saturation occurred on the set of measured voltage samples (302A-C) and the set of measured current samples (304A-C) is made based at least in part on the selected processed reactive current sample, and wherein a distance to the fault is calculated based at least in part on the determination that no distortion occurred, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative or zero sequence current sample.

11. The power system network of claim 10, wherein, the distance to the fault is further calculated based at least in part on a set of equations, the selected processed voltage sample, the selected processed reactive current sample, the selected processed resistive current sample, and the selected processed negative or zero sequence current sample, the distance to the fault, the set of equations based at least in part on the set of measured voltage samples (302A-C) and the set of measured current samples (304A-C).

12. The power system network of claim 11, wherein, calculating the distance to the fault based at least in part on the determination that no distortion occurred further comprises: formulating a first matrix based at least in part on the selected processed voltage sample, formulating a second matrix based at least in part on the selected processed reactive current samples, the selected processed resistive current samples, and the selected processed negative or zero sequence current samples; and calculating the distance to the fault based at least in part on the first matrix and the second matrix.

13. The power system network of claim 10, wherein, determining that no distortion occurred due to current transformer (CT) saturation based at least in part on the selected processed reactive current samples further comprises: calculating a full-cycle Fourier sequence (502) current over a portion of a full cycle based at least in part on the selected processed reactive current samples; calculating a magnitude of the full-cycle Fourier sequence (502) current; calculating an average of the magnitude of the full-cycle Fourier sequence (502) current over an eighth of a cycle; determining a difference between the average of the magnitude of the full-cycle Fourier sequence (502) current over the eighth of a cycle and a constant, wherein the constant is determined based at least in part on the magnitude of the full-cycle Fourier sequence (502) current over the portion of the full cycle after a fault occurs.

14. The power system network of claim 13, wherein, determining that no distortion occurred due to current transformer (CT) saturation based at least in part on the selected processed reactive current samples further comprises: determining that the difference is less than a predetermined error threshold; in response to a determination that the difference is less than the predetermined error threshold, determining that no distortion occurred due to the CT saturation; and outputting an output of "1" based on the determination that no distortion occurred due to the CT saturation over the set of measured voltage samples (302A-C) and the set of measured current samples (304A-C).

15. The power system network of claim 10, wherein, the indication from the faulted phase indicator (402) indicates a fault type associated with the fault. the indication from the faulted phase indicator (402) indicates a fault type associated with the fault.

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