TWI383162B - Fault location method - Google Patents

Description

Fault location method

The invention relates to a detection technology of a power transmission line, in particular to a fault location method.

In the power layout, the two transformers are usually connected by a power transmission line, so the maintenance of the quality of the transmission line is a prerequisite for effective power supply. When the power supply is unstable, most of the systems require that the fault location of the power line be found within 3 to 5 cycles of the transmitted power signal to remove the obstacle as soon as possible.

A fault location method is known in which the power line is first measured to know the voltage and current of the transmitted power signal, and then the voltage and current are respectively filtered by a discrete Fourier transform (DFT) to extract the fundamental frequency phase. The amount of phasor is finally compared with the characteristic relationship of the current phasor of the voltage phasor and the characteristic impedance of the power line to analyze the fault location.

However, this positioning method is mainly based on the steady state phasor. However, after a fault occurs, the phasor calculated by the DFT, in addition to the steady-state component, usually carries a transient component (eg, attenuating the DC component), so that the accuracy of the fault location is greatly affected. To this end, CS Yu proposed an improved version in "A Discrete-Fourier-transform based adaptive mimic phasor estimator for distance relaying applications," IEEE Trans. Power Delivery, vol. 21, no. 4, pp. 1836-1846 . The DFT architecture attempts to remove the attenuating DC component, but the computational cost is significantly larger than expected.

Therefore, the object of the present invention is to provide a fault location method capable of providing a fault location on a power transmission line within a time required by the system, which not only has high positioning accuracy, but also can effectively control the calculation cost.

Therefore, the fault location method of the present invention is adapted to calculate a fault location for contacting a power transmission line between a first power transformer and a second power transformer, and includes the following steps: (A) separately measuring the first change a first reference voltage at the electrical device and a first reference current and a second reference voltage and a second reference current at the second power transformer; (B) setting an initial value of a fault parameter, the fault parameter is a ratio of a fault location to the second power transformer to a total length of the power line; (C) obtaining a first set of impedances based on a total length of the power line, a characteristic impedance and a propagation constant, and the fault parameter, The first set of impedances represents an equivalent circuit model of the power line between the fault location and the first power transformer; (D) using the first reference voltage and the first reference current and the first set of impedances a first fault voltage; (E) obtaining a second set of impedances based on the total length of the power line, the characteristic impedance and the propagation constant, and the fault parameter, the second set of impedances indicating the fault location and the second Between transformers An equivalent circuit model of the wire; (F) using the second reference voltage, the second reference current, and the second set of impedances to obtain a second fault voltage; (G) calculating a difference between the first and second fault voltages And using the difference to update the fault parameter, and repeating steps (C)~(G) based on the updated fault parameter until the updated fault parameter causes the first and second fault voltages to approach; and H) Find the fault location by using the fault parameter completed by the update.

The fault location method of the present invention is applicable to calculate a fault location for contacting a power transmission line between a first power transformer and a second power transformer, and includes the following steps: (A) separately measuring the first power transformer a first reference voltage and a first reference current and a second reference voltage and a second reference current at the second power transformer; (B) based on a total length of the power line, a characteristic impedance, and a propagation a constant, a set of factors representing a ratio of an equivalent impedance of the power line between the fault location and the first power transformer to a fault parameter, and the fault parameter is the fault location and the The ratio of the distance of the second power transformer to the total length of the power line; (C) calculating a fault parameter that satisfies a first fault voltage equal to a second fault voltage based on the reference voltage, the reference current, and the set of factors Wherein the first fault voltage refers to a voltage based on the first reference voltage at the fault location, the second fault voltage refers to a voltage based on the second reference voltage at the fault location; and (D) utilizes the fault parameter Find the fault location.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention.

Before the present invention is described in detail, it is noted that in the following description, similar elements are denoted by the same reference numerals.

Introduction and derivation of the principle of the first preferred embodiment

Referring to Figure 1, a two-terminal three-phase power system 100 is illustrated. The two end points refer to the first power transformer 1 and the second power transformer 2, which are divided into two places, and three power signals having different phases are respectively transmitted by the power line 3 of a total length W. In order to locate the fault location of the power line 3, in order to synchronously obtain the voltage and current of the power signals at the transformers 1, 2, it is preferably monitored in conjunction with a Global Positioning Satellite (GPS) system 200.

According to JJ Grainger and WD Stevenson in Power System Analysis, New York: McGraw-Hill, 1994 , it can be seen that for one of the power signals, it is assumed that the fault location F occurs at a distance dW from the transformer 2, then the input The electric wire 3 is equivalently formed between the transformer 1 and the fault position F to form a first group of impedances as shown in FIG. 2, wherein the fault parameter d represents "the distance between the fault location F and the transformer 2" to "the total length of the transmission line "proportion, .

The first set of impedances includes a first impedance Z1(d) and two second impedances Y1(d), and the values change with the fault parameter d. The first impedance Z1(d) is connected between the transformer 1 and the fault location F, and each of the second impedances Y1(d) is coupled to one of the bridges and the ground point. The detailed parameters are defined as follows:

Where Zc is the characteristic impedance of the power line 3, γ is the propagation constant of the power line 3, and .

Note that in addition to the phase difference, the three power signals transmitted by the power line 3 have the same absolute value of the voltage and the same absolute value of the current, so the equivalent circuit corresponding to each power signal will include the same impedance element. value. Therefore, it is sufficient to use the circuit model of one of the aforementioned related power signals to investigate the fault location F.

Further, the first impedance Z1(d) can also be equivalent to a resistor R1(d) connected in series with an inductor L1(d), and the second impedance Y1(d) can also be equivalent to a conductance G1(d) connected in parallel. Capacitor C1(d), ie:

While Re al [ x ] represents the real part of x, Im ag [ x ] represents the imaginary part of x.

It is worth noting that since the power signal of the general system generally falls at the frequency of 60 Hz, the angular frequency ω ₁ = 2π × 60 is preferable, the sampling time Δ t is 1/(60N), and N is a positive integer.

Since the capacitance C1 (d) and an inductor L1 (d) to the circuit is non-linear effects, the present embodiment is particularly S. Chapra and R. Canale introduced in ^{Numerical Methods for Engineers, 5 th Edition} , McGraw-Hill, New York, a dynamic way to describe the amount of 2005 phase mentioned, mainly in the case where the sampling time is Δ t, the sampling time index k, k-1 described power signal, and will be particularly emphasized inductor L1 (d And the transient characteristics of the capacitor C1(d), that is, the current flowing through L1(d), and the change in the voltage across C1(d).

Assuming that the power signal at the measuring transformer 1 obtains a first reference voltage V ₁ (k) and a first reference current I ₁ (k), then the first fault voltage V at the distance dW from the transformer 2 _F1 (k,d) is:

Here, the first fault current I _z1 (k,d) represents: I ₁ (k) minus the result of "current flowing to Y1 (d)", which can be further written as:

Note that the index values for each sampling time k, a first reference voltage V ₁ (k) and the first reference current I ₁ (k) will be somewhat different. The fault may occur at every place of the power line 3, so the first fault voltage V _F1 (k, d) and the first fault current I _z1 (k, d) may vary with d except for k.

On the other hand, the general knowledge in the field of the invention can be reasonably inferred: when the fault parameter is d, a second set of impedance between the transformer 2 and the fault position F will be as shown in FIG. 3, and the first included The impedance Z2(d) has a resistor R2(d) and an inductor L2(d) connected in series, and the two second impedances Y2(d) included respectively have a conductance G2(d) and a capacitor C2 connected in parallel. (d).

Assuming that the power signal at the measuring transformer 2 obtains a second reference voltage V ₂ (k) and a second reference current I ₂ (k), then the second fault voltage V at the distance dW from the transformer 2 _F2 (k,d) is:

The second fault current I _z2 (k,d) represents: I ₂ (k) deducting the result of "current flowing to Y2 (d)", which can be further written as:

Finally, because of the GPS system 200, the synchronous voltage and current of the power signal to the power transformers 1, 2 can be accurately measured. Therefore, regardless of which transient state (eg, sampling time index value k), the same value is obtained from the converter 1 or the voltage level of the fault location F from the transformer 2. In short, as long as the d is found to satisfy V _{F 1} ( k , d )- V _{F 2} ( k , d )=0, it can be concluded that the power line 3 has failed at a distance dW from the transformer 2. .

Implementation of the first preferred embodiment

Referring to FIG. 4, the first preferred embodiment of the fault locator 5 of the present invention is adapted to be coupled to a first measurement module 11 built in the transformer 1 and coupled to a built-in system. The second measurement module 21 of the transformer 2. The two modules 11, 21 respectively measure the power signal on the power line 3 for the fault locator 5 as a reference for calculating the fault location.

The fault locator 5 includes a setting unit 51, a first current computing module 52, a first voltage computing module 53, a second current computing module 55, a second voltage computing module 56, and an approaching module. 57. A positioning module 58, and an impedance calculating unit 59. The modules 52 and 53 are coupled, and the modules 55 and 56 are coupled, and the approaching module 57 is coupled to the modules 53, 56 and 58, respectively. Preferably, the current computing modules 52, 55 and the voltage computing modules 53, 56 are integrated into an computing device 50.

The first preferred embodiment of the fault location method of the present invention performed by the measurement modules 11, 21 and the fault locator 5 includes the following steps of FIG. 5:

Step 70: The first measurement module 11 receives a synchronization time kΔ t transmitted by the GPS system 200, and measures the first reference voltages V ₁ (k), V ₁ (k-1), and V ₁ ( K-2) and the first reference current I ₁ (k), I ₁ (k-1). On the other hand, the second measurement module 21 also receives the synchronization time, and accordingly measures the second reference voltages V ₂ (k), V ₂ (k-1), V ₂ (k-2) and the second Reference currents I ₂ (k), I ₂ (k-1).

Step 71: The setting unit 51 sets an initial value for the fault parameter d.

Step 72: The impedance calculation unit 59 obtains the first set of impedance sums based on the length W of the power transmission line 3, the characteristic impedance Zc, the propagation constant γ, and the fault parameter d based on the equations (1), (2), and (5). The second set of impedances.

That is, the first impedance Z1(d), the second impedance Y1(d), the inductance L1(d), the capacitance C1(d), and the first impedance Z2(d), the second impedance Y2(d), Inductor L2 (d), capacitor C2 (d).

Step 73: The operation modules 52 to 53 use the first reference voltages V ₁ (k), V ₁ (k-1), V ₁ (k-2), and the first reference current based on equations (2) to (4). I ₁ (k), I ₁ (k-1) and the first set of impedances, the first fault voltage V _F1 (k, d) is obtained; and the operation modules 55-56 are based on equations (5) to (7), Utilizing a second reference voltage V ₂ (k), V ₁ (k-1), V ₁ (k-2), and a second reference current I ₂ (k), I ₂ (k-1), and a second set of impedances, The second fault voltage V _F2 (k, d) is obtained.

And step 73 includes the following sub-steps of Figure 6:

Sub-step 731: The first current calculation module 52 subtracts the currents I ₁ (k) and I ₁ (k-1) from the steady flow to the second impedance Y1 (d) based on equations (2) and (4). The state and the transient current are used to find the currents I _z1 (k, d) and I _z1 (k-1, d) flowing to the first impedance Z1 (d).

In detail, the embodiment of the present embodiment is: first calculating the average result of V ₁ (k) and V ₁ (k-1) by a steady-state unit SU and amplifying Y1 (d) times, and then by a temporary The state unit TU calculates the result of dividing the two subtractions V ₁ (k) and V ₁ (k-1) by Δ t and amplifying C1 (d) times, and then using a picking unit PU to make the current I ₁ (k) The output of the steady state unit SU and the transient unit TU is subtracted to obtain a current I _z1 (k, d).

Please note that as time passes, the first current calculation module 52 can calculate the index values k=1, 2, 3... in order, so that not only V ₁ (k), V ₁ (k-1) ), I ₁ (k) to obtain a current I _z1 (k, d), _{also), V 1 (k-2} ), I 1 (k-1) obtained according to the current I _z1 V _{1 (k-1} ( K-1, d).

Sub-step 732: The first voltage calculation module 53 calculates the steady state and transient voltage drop of the first impedance Z1(d) by subtracting the voltage V ₁ (k) based on equations (2) and (3). The first fault voltage V _F1 (k, d).

In detail, in this embodiment, the average result of I _z1 (k,d) and I _z1 (k-1,d) is first calculated by a steady-state unit SU and amplified by Z1(d) times. Calculating the result of dividing the two subtraction of I _z1 (k,d) and I _z1 (k-1,d) by Δ t by a transient unit TU and amplifying L1(d) times, and then using a capture unit The PU subtracts the output of the steady state unit SU and the transient unit TU from the voltage V ₁ (k) to obtain the voltage V _F1 (k, d).

Sub-step 733: The second current calculation module 55 subtracts the currents I ₂ (k) and I ₂ (k-1) from the flow to the second impedance Y2 (d) based on equations (5) and (7), respectively. The state and the transient current are used to find the currents I _z2 (k, d) and I _z2 (k-1, d) flowing to the first impedance Z2 (d).

Sub-step 734: The second voltage calculation module 56 derives the voltage V ₂ (k) from the steady state and transient voltage drop of the first impedance Z2 (d) based on equations (5) and (6). The second fault voltage V _F2 (k, d).

In this example, the implementations of the voltage computing modules 52, 55 are similar, and the implementations of the current computing modules 53, 56 are similar. The execution order of the sub-steps 733-734 is not limited to after sub-steps 731-732. In order to obtain a shorter positioning time, sub-steps 733-734 are preferably performed in parallel with sub-steps 731-732.

Step 74: The setting unit 51 sets a comparison parameter to: "fault parameter" plus "one approach step δ", that is, d + δ.

Step 75: The computing modules 52-53, 55-56 obtain a first comparison voltage V _{F1 of} the power signal at the distance (d+δ) W from the transformer 2 based on equations (2) to (7). (k, d + δ) and a second comparison voltage V _F2 (k, d + δ).

Since this step is performed in a similar manner to step 73, it will not be described again.

Step 76: The approach module 57 calculates the difference f ( k , d ) of the first and second fault voltages, and uses the difference to update the fault parameter d, and repeats step 73 based on the updated fault parameter d. 76. Until the updated fault parameter d causes the first and second fault voltages to approach, a positioning parameter d _opt is equal to d.

That is to say, the approximation module 57 performs approximation according to a nonlinear function f ( k , d )= V _{F 1} ( k , d )− V _{F 2} ( k , d )=0. In order to find a solution that satisfies this nonlinear function f(k,d) as quickly as possible, this embodiment is implemented by the improved secant method mentioned in the aforementioned Numerical Methods for Engineers . According to this method, the approximation module 57 includes a calculation unit 572 and a determination unit 573, and step 76 includes the following sub-steps of FIG. 7:

Sub-step 761: The calculating unit 572 calculates the difference between the fault voltages V _F1 (k, d) and V _F2 (k, d) to obtain a pre-approximation signal f ( k , d ), and calculates the comparison voltage V _F1 (k, d + δ), the difference _{V F2 (k, d + δ} ) to obtain a comparison signal f (k, d + δ) , then the secant method proposed by the equation (8), one obtains The parameter d _{NEW is} approximated.

Sub-step 762: The judging unit 573 compares whether | d _NEW - d | < ε, ε is an error tolerance value, and | x | represents an absolute value of x. When the result of the determination is no, sub-step 763 is performed; if true, then sub-step 764 is skipped.

Sub-step 763: The judging unit 573 compares whether "the number of times the sub-step 761 has been executed" is equal to a count-tolerance value η. If so, sub-step 764 is performed, and if not, the next fault parameter d is set to this d _NEW and jumps back to step 73.

Sub-step 764: The setting unit 51 sets the positioning parameter d _opt to the post-approximation parameter d _NEW , and thus achieves the purpose of the approach module 57.

Step 77: The positioning module 58 further multiplies the positioning parameter d _opt by the total length W of the power transmission line, and regards the position of the power transmission line that is "distance from the power converter 2 by d _opt ‧ W " as the position where the fault occurs, and ends the fault. The process of the positioning method.

It is worth noting that the computational modules 52, 53, 55, 56 of this example are retained in a dynamic phasor description as compared to conventional techniques that always attempt to ignore or remove transient components such as attenuating DC components. The transient components caused by the capacitors C1(d), C2(d) and the inductors L1(d), L2(d), so the function f ( k , d ) according to the module 57 is approached compared to the prior art. ) = V _{F 1} ( k , d ) - V _{F 2} ( k , d ) = 0 can more closely express the actual circuit situation, so that the accuracy of fault location is greatly improved.

In addition, the dynamic phasor description mode of the computing modules 52, 53, 55, 56 is simple, and the approaching module 57 adopts a relatively simple modified secant method, so the circuit implementation cost is far superior to the conventional DFT technology. Moreover, in the sub-step 763, the judging unit 573 checks the "number of times of repeating the sub-step 761" to ensure that the fault locator 5 can find the fault of the power line 3 in the time required by the system as scheduled. position.

Introduction and derivation of the principle of the second preferred embodiment

In general, transmission lines of less than 80 km (km) are called short-distance transmission lines, 80 to 250 km are called medium-range, and more than 250 km are called long-range. Basically, the first preferred embodiment is applicable to any short, medium, and long-range power transmission line. In order to provide a more economical and rapid practice, the second preferred embodiment further discloses a fault locator and method dedicated to short-range and medium-range transmission lines.

In the aforementioned Power System Analysis book, it has been shown that when using a medium-range transmission line, sinh( x ) approximates x, and tanh( x ) also approximates x. Therefore, the first impedance Z2(d) and the second impedance Y2(d) may approach the equation (9), and the equation (9) further interprets Z2(d) as "a first impedance factor Z _E ". Times, and Y2(d) is interpreted as d times the "a second impedance factor Y _E ". Wherein, each factor exhibits a complex number type due to the nonlinear characteristic of the corresponding element, and has a real part and an imaginary part.

Therefore, the inductance L2(d) and the capacitance C2(d) can be organized into the equation (10), and the equation (10) further interprets L2(d) as d times the "one inductance factor L _E " and C2 ( d) is interpreted as d times the "one capacitance factor C _E ".

By analogy, the inductance L1(d) is equivalent to (1-d) times the "inductance factor L _E ", and the capacitance C1 (d) is equivalent to (1-d) times the "capacitance factor C _E ".

Further, these equivalent elements Z1(d), L1(d), Y1(d), C1(d), Z2(d), L2(d), Y2(d), C2(d) are substituted into f ( k , d )= V _{F 1} ( k , d )- V _{F 2} ( k , d )=0, a quadratic polynomial (12) with a variable d is prepared, and its solution is as in equation (13).

A × d ² + B × d + C =0 (12)

Among them, the coefficients A, B, and C of the polynomial are also introduced into the dynamic phasor description, as follows:

And I _{z 1_ E} ( k ) represents the result of substituting the factors Y _E and C _E into the equation (4) at the index value k. I _{z 2_ E} ( k ) represents the result of substituting the factors Y _{E and} C _E into the equation (7) at the index value k. In addition, since all factors are in a complex form, it is expected that the coefficient signals A, B, C and "the possible solution d of the equation (13)" will be plural.

Furthermore, with such a solution to the quadratic equation method, the obtained d can be directly used as the positioning parameter d _opt without the repeated iterative operation as in the first preferred embodiment, so the second embodiment can be further Effectively shorten the time to find the location of the fault.

In addition, the coefficient signals A, B, and C are related not only to the voltage changes of the voltages V ₁ (k), V ₂ (k) at two sampling times, but also to the currents I _{z 1_ E} ( k ), I _{z 2_ E} ( k ) The change in the two sampling times, so this example can also achieve the purpose of aptly depicting the transient characteristics of the circuit.

Implementation of the second preferred embodiment

Referring to FIG. 8 , the second preferred embodiment of the fault locator 6 of the present invention is adapted to be coupled to a first measurement module 11 built in the transformer 1 and coupled to a second built in the transformer 2 . Measurement module 21. The fault locator 6 includes a factor generating unit 61, a first current computing module 62, a second current computing module 63, a coefficient generating unit 64, a solving unit 65, and a positioning module 66.

The second preferred embodiment of the fault location method of the present invention performed by the fault locator 6 includes the following steps of FIG. 9:

Step 80: The first measurement module 11 receives a synchronization time kΔ t transmitted by the GPS system 200, and measures the first reference voltages V ₁ (k), V ₁ (k-1), and V ₁ ( K-2) and the first reference current I ₁ (k), I ₁ (k-1). On the other hand, the second measurement module 21 also receives the synchronization time, and accordingly measures the second reference voltages V ₂ (k), V ₂ (k-1), V ₂ (k-2) and the second Reference currents I ₂ (k), I ₂ (k-1).

Step 81: The factor generating unit 61 generates a set of factors including a first impedance factor Z _E , a second impedance factor Y _E , an inductance factor L _E , and a capacitance factor C _E . The production method is: multiplying the propagation constant γ of the transmission line by the total length W, and multiplying the characteristic impedance Zc to obtain the first impedance factor Z _E ; multiplying the propagation constant γ of the transmission line by the total length W, and dividing by two The characteristic impedance Zc is multiplied to obtain a second impedance factor Y _E ; the imaginary part of the first impedance factor Z _E is taken out, divided by the angular frequency ω ₁ to obtain the inductance factor L _E ; and the virtual value of the second impedance factor Y _E is taken out Then, divide by the angular frequency ω ₁ to obtain the capacitance factor C _E .

Step 82: The first current calculation module 62 adjusts the first reference currents I ₁ (k) and I ₁ (k-1) by the factors Y _E and C _E respectively on the basis of the equation (4) to generate one. The first factor current I _{z1_E} (k), I _{z1_E} (k-1).

In detail, in this embodiment, the average result of V ₁ (k) and V ₁ (k-1) is first calculated by a steady-state cell SU and amplified by Y _E times, and then by a transient unit. The TU calculates the result of dividing the two subtractions V ₁ (k) and V ₁ (k-1) by Δ t and amplifying the C _E times, and then deducting the steady state unit from the current I ₁ (k) by using a pumping unit PU. SU and the output of the transient unit TU, and the first factor current I _{z1_E} (k) is obtained. And I _{z1_E} (k-1) is calculated from V ₁ (k-1), V ₁ (k-2), and I ₁ (k-1) in a similar manner.

Step 83: The second current calculation module 63 adjusts the second reference currents I ₂ (k) and I ₂ (k-1) by the factors Y _E and C _E respectively on the basis of the equation (7) to generate one. The second factor current I _{z2 — E} (k), I _{z2 — E} (k-1).

The embodiment is similar to step 82 and is preferably performed in parallel with step 82.

Step 84: The coefficient generating unit 64 is based on the reference voltages V ₁ (k), V ₁ (k-1), V ₂ (k), V ₂ (k-1) and the factor currents I _{z1_E} (k), I _{z1_E} (k -1), I _{z2_E} (k), I _{z2_E} (k-1), and in combination with all the factors obtained in step 81, on the basis of equation (14), three coefficients representing coefficients A, B, and C, respectively, are generated. signal.

Step 85: The solving unit 65 substitutes the three coefficient signals into the equation (13) to calculate two possible solutions having a real part and an imaginary part, and further selects a possible solution in which the imaginary part approaches 0, so that In fact, the department is used as the positioning parameter d _opt .

Step 86: The position of the power transmission line 3 of the positioning module 66 "distance from the transformer 2 by d _opt ‧ W " is regarded as the position where the failure occurs.

The possible solution that the imaginary part approaches 0 is selected because the "distance d _opt ‧W " used to describe the fault location F must be a real number, so the imaginary part of the parameter d _opt is definitely preferably 0, The second preferred embodiment is based on the approximation, so that the imaginary part is selected to be close to zero.

In summary, in the foregoing embodiment, the computing modules 52-53, 55-56, and 62-63 introduce a dynamic phasor description mode, so that the approximating module 57 and the solving unit 65 can retain the transient components. The positioning parameter d _opt is calculated under the condition, so the accuracy of the fault location is better than that of the prior art, and the circuit used is also simpler than the DFT, so the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

100. . . Three-phase power system

200. . . Global positioning satellite system

1, 2. . . G

11. . . First measurement module

twenty one. . . Second measurement module

3. . . Power line

5, 6. . . Fault locator

50. . . Arithmetic device

51. . . Setting unit

52, 62. . . First current computing module

53. . . First voltage computing module

55, 63. . . Second current computing module

56. . . Second voltage computing module

57. . . Approach module

572. . . Calculation unit

573. . . Judging unit

58, 66. . . Positioning module

59. . . Impedance calculation unit

61. . . Factor generation unit

64. . . Coefficient generating unit

65. . . Solution unit

SU. . . Steady state unit

TU. . . Transient unit

PU. . . Capture unit

C1(d), C2(d). . . capacitance

G1(d), G2(d). . . Conductance

L1(d), L2(d). . . inductance

R1(d), R2(d). . . resistance

Y1(d), Y2(d). . . Second impedance

Z1(d), Z2(d). . . First impedance

70~77. . . Implementation steps of the first embodiment

731~734. . . Steps to find the fault voltage

761~764. . . Approaching module execution steps

80~86. . . Implementation steps of the second embodiment

Figure 1 is a schematic view showing that a power line has failed between two transformers;

Figure 2 is a block diagram showing the equivalent circuit between the first power transformer and the fault location;

Figure 3 is a circuit diagram illustrating the equivalent circuit between the fault location and the second transformer;

Figure 4 is a block diagram showing a first preferred embodiment of the fault locator of the present invention;

Figure 5 is a flow chart showing a first preferred embodiment of the fault location method of the present invention;

Figure 6 is a flow chart illustrating the flow of obtaining a fault voltage;

Figure 7 is a flow chart illustrating the execution steps of the approaching module;

Figure 8 is a block diagram showing a second preferred embodiment of the fault locator of the present invention;

Figure 9 is a flow chart showing a second preferred embodiment of the fault location method of the present invention.

11. . . First measurement module

twenty one. . . Second measurement module

5. . . Fault locator

50. . . Arithmetic device

51. . . Setting unit

52. . . First current computing module

53. . . First voltage computing module

55. . . Second current computing module

56. . . Second voltage computing module

57. . . Approach module

572. . . Calculation unit

573. . . Judging unit

58. . . Positioning module

59. . . Impedance calculation unit

SU. . . Steady state unit

TU. . . Transient unit

PU. . . Capture unit

Claims (14)

A fault locating method is adapted to calculate a fault location for contacting a power line between a first power transformer and a second power transformer, comprising the following steps: (A) separately measuring at the first power transformer a first reference voltage and a first reference current and a second reference voltage and a second reference current at the second power transformer; (B) setting an initial value of a fault parameter, the fault parameter being the fault location and a ratio of the distance of the second power transformer to the total length of the power line; (C) obtaining a first set of impedances based on a total length of the power line, a characteristic impedance and a propagation constant, and the fault parameter, the first group The impedance represents an equivalent circuit model of the power line between the fault location and the first power transformer; (D) using the first reference voltage and the first reference current and the first set of impedances to obtain a first a fault voltage; (E) obtaining a second set of impedances based on the total length of the power line, the characteristic impedance and the propagation constant, and the fault parameter, the second set of impedances indicating the fault location and the second power transformer Power line (F) using the second reference voltage, the second reference current, and the second set of impedances to obtain a second fault voltage; (G) calculating the difference between the first and second fault voltages, and utilizing The difference is used to update the fault parameter, and steps (C) to (G) are repeated based on the updated fault parameter until the updated fault parameter causes the first and second fault voltages to approach; and (H) utilize The fault parameter is updated to find the fault location. The fault locating method of claim 1, wherein the first set of impedances includes a first impedance across the fault location and the first power transformer and a crossover of the first variable a second impedance between the electrical device and the ground, and the second impedance has a capacitance; and step (D) is to subtract the current flowing to the second impedance by the first reference current to determine a current flowing through the first impedance The current, in turn, obtains the first fault voltage, wherein the current flowing to the second impedance includes a change in voltage across the capacitor. The fault locating method of claim 1, wherein the first set of impedances includes a first impedance across the fault location and the first power transformer and a crossover of the first variable a second impedance between the electrical device and the ground, and the first impedance has an inductance; and the step (D) is to subtract the voltage drop of the first impedance from the first reference voltage to obtain the first fault voltage, wherein the first The voltage drop across the impedance includes a change in current through the inductor. According to the fault location method of claim 1, wherein the step (D) further utilizes a first set of impedances associated with a comparison parameter to obtain a first comparison voltage, and step (F) further utilizes the correlation parameter. The second set of impedances obtains a second comparison voltage; the step (G) calculates a difference between the first and second fault voltages, and calculates a difference between the first and second comparison voltages to approximate an approximation After the parameter. The method for fault location according to claim 4, wherein when the difference between the parameter after the approximation and the fault parameter is not less than an error tolerance value, the step is repeated as the next fault parameter after the approximation parameter ( C)~(G); when the difference between the parameter and the fault parameter is less than the error tolerance value, the fault parameter is updated by the approximated parameter. According to the fault location method of claim 1, wherein the step (A) measures the first reference voltage and the second reference voltage at the current sampling time, the previous sampling time, and the first two sampling times; And steps (D) and (F) are respectively calculating the first fault voltage and the second fault voltage according to the reference voltages of the three sampling times. The fault location method according to claim 1, wherein the step (H) is to multiply the fault parameter by the total length of the power line to obtain the distance of the fault location from the second power transformer. A fault locating method is adapted to calculate a fault location for contacting a power line between a first power transformer and a second power transformer, comprising the following steps: (A) separately measuring at the first power transformer a first reference voltage and a first reference current and a second reference voltage and a second reference current at the second power transformer; (B) based on a total length of the power line, a characteristic impedance, and a propagation constant, Obtaining a set of factors representing a ratio of an equivalent impedance of the power line between the fault location and the first power transformer to a fault parameter, and the fault parameter is the fault location and the second The ratio of the distance of the transformer to the total length of the power line; (C) calculating, based on the reference voltage, the reference currents, and the set of factors, a fault parameter that satisfies a first fault voltage equal to a second fault voltage, wherein The first fault voltage refers to a voltage based on the first reference voltage at the fault location, the second fault voltage refers to a voltage based on the second reference voltage at the fault location; and (D) utilizes the fault parameter The fault location. According to the fault location method of claim 8, wherein the step (C) is a function representing that the first fault voltage is equal to the second fault voltage, and the plurality of calculations respectively have a real part and an imaginary part. The possible solution, and take out the possible solution that the imaginary part is close to zero, so that the actual part is regarded as the fault parameter. The fault locating method according to claim 9, wherein the function according to the step (C) is related to a voltage change of the first reference voltage at two sampling times, and is related to the second reference voltage. The voltage change of the two sampling times. The fault location method according to claim 9, wherein the set of factors includes a first impedance factor and a second impedance factor, and the second impedance factor has a capacitance factor, and step (C) includes the following Sub-step: (c-1) adjusting the first reference current by using the first reference voltage, the first reference current, and the first impedance factor and the capacitance factor to obtain a first factor current; (c- 2) using the second reference voltage, the second reference current, and the second impedance factor and the capacitance factor to adjust the second reference current to obtain a second factor current; and (c-3) to the function The fault parameter is calculated and the function is controlled by the factor currents. The fault location method according to claim 11, wherein the function according to step (C) is controlled by the change of the first factor current at two sampling times and is controlled by the second factor current. Changes in two sampling times. According to the fault location method of claim 8, wherein the step (A) measures the first reference voltage and the second reference voltage at the current sampling time, the previous sampling time, and the first two sampling times; And step (C) is to calculate the fault parameter according to the reference voltages of the three sampling times. The fault location method according to claim 8, wherein the step (D) is to multiply the fault parameter by the total length of the power line to obtain the distance of the fault location from the second power transformer.