JP2715090B2 - Fault location device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault point locating device for locating a distance to a fault point of a power transmission system, and more particularly, to a fault point even when a branch power source exists on a branch line. The present invention relates to a fault point locating device for accurately locating a distance to a fault.

[Conventional technology]

In a conventional fault locator (fault locator), as described in Japanese Patent Application Laid-Open No. 60-204220, a distance to a fault is measured by a voltage drop of a transmission line. In addition, in order to cope with the case where there is a branch in the transmission line, the distribution ratio of the branch load power is set in advance, and the distribution ratio and the current and voltage values at the fault locator set point are used to determine the distribution to the fault point. The voltage drop is obtained, and the distance is calculated from the voltage drop.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, the distance is evaluated by the voltage drop of the system. In this method, no consideration was given to the case where there is a branch power supply on the branch line, so that the error was increased by the influence of the branch power supply, and a great deal of labor was required for finding a fault point and repairing the system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a digital fault locating device that can accurately calculate a distance to a fault even when a branch power source is present on a branch line of a system.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a faulty phase detecting means for detecting a faulty phase in which a ground fault of a transmission line has occurred in a power transmission system including a branch power source, and a voltage and current value at an installation point of the detecting means. A first digital unit that calculates a reactive power based on a zero-phase current up to a failure point of the failed phase, and outputs a value obtained by adding a reactive power generated by an outflow current flowing from the branch power supply as a reactive power value; Calculating means for calculating a reactive power based on a zero-phase current per unit length of the transmission line from the current value at the installation point and a line constant of the transmission line, and generating a reactive power generated by an outflow current flowing out of the branch power source. A second digital operation means for outputting a value obtained by adding the divided values as a reactive power value per transmission line unit length, and a reactive power value from the first digital operation means to a transmission line from the second digital operation means. unit There is provided a third digital computing means and fault point locating system having a for calculating the distance from the split the installation point to the fault point in reactive power value per the.

It is preferable that the distance to the failure point is calculated a predetermined number of times at different times, and the average value is calculated and displayed only when the variation in the calculated value of the distance is within a certain range.

Further, the value of the outflow current from the branch power supply can be estimated from the current values of phases other than the failed phase at the installation point.

Further, a transmission means for transmitting the outflow current value from each power supply of the transmission line and the inflow current value to each load to the installation point is provided, and inputting the current values to the first and second calculation means,
A reactive power value corrected for the branch power source may be calculated.

[Action]

 Next, the principle of the present invention will be described.

For simplicity, FIG. 2 shows a system diagram in which a fault locating device according to the present invention is installed in a power system without a branch power supply. Although the transmission line 1 is shown simply here, it is one line of three-phase alternating current or a plurality of lines thereof. The current transformer 2 and the voltage transformer 3 take in the current and voltage signals of the transmission line 1 into the fault locator 100 of the present invention. Here, both the current transformer 2 and the voltage transformer 3 are treated as ideal characteristics with a conversion ratio of 1. Further, the fault locator 100 includes a filter, an A / D converter, a processor, and the like. Power from the power supply 6 is supplied to the transmission line 1 via the transformer 4. The neutral point of the transformer 4 is grounded by a neutral point grounding resistor 5. P ₀ indicates an installation point of the fault locator 100, F indicates a failure point, and P ₁ indicates a connection point of the load 7. Distance from fault locator installation point P ₀ to fault point F
l _F is the value to be found. I _F is a current flowing into a fault point F, a current flowing through the I _L is the load 7.

Now, the operating principle of the fault locator 100 when an a-phase ground fault occurs at the point F will be described. The input signal voltage from the voltage transformer _{3 V a, V b, V} c, the input signal current from the current transformer 2, _{I a, I b, I c} . Of course, these are functions of t that vary with the capture time t. The reactive power Q _F relative to the zero-phase current to the fault point F from the point P ₀ with these input signals, Is obtained. Here, T is the cycle of the system voltage and current, t is time, I ₀ is the zero-phase current at point P ₀ , and given by I ₀ = (1/3) (I _a + I _b + I _c ) (2) Can be Further, when a uniform distribution line constant of the transmission line 1 with respect to length, the reactive power Q _u were unit length (for example 1km) zero-phase current per the criteria, Given by Where V _au (t−T / 4) = R _aa I _a (t−T / 4) + R _ab I _b (t−T / 4)
+ R _ac I _c (t−T / 4) + X _aa I _a (t) + X _ab I _b (t) + X _ac I
_c (t) (4) Here, R _aa , R _ab , and R _ac are resistance values per km between the a phase, ab phase, and ac phase, and X _aa , X _ab , and X _ac are also reactance values. Therefore, the desired rating value l _F
(Km) is given by l _F = Q _F / Q _u (5).

In the case of a three-phase multi-line transmission line, the induced voltage between the phases with respect to the failed phase may be added by the number of the induced lines according to the equation (4). Also, when a failure occurs in the b-phase or the c-phase other than the a-phase, the input signals rotated in the homologous order by matching the phase order a, b, c shown in the equations (3) and (4) with the failure phase. I just need.

The procedure of the distance l _F orientation by fault locator of the present invention based on the above principle is shown in Figure 3. In the figure,
Input signal of the filter 101, the voltage elaborate taken at point P ₀ of FIG. 2 is a current. The filter 101 removes harmonic components generated at the time of sampling these input signals to prevent aliasing errors, and removes transient DC components to reduce quantization errors. Filter.

 This part is realized by hardware in this embodiment.

An analog-to-digital converter (A / D) 102 samples and quantizes an input signal at a predetermined interval by a clock having a predetermined frequency, and samples and takes in voltage and current values at the same time. Therefore, a hold circuit is also included, and these are all realized by hardware. The ground fault fault phase selection relay process (FD) 103 may be any one that can detect a single-wire ground fault phase, and may be, for example, a phase voltage shortage detection relay. This and the following processing 104 to 108
Is executed by the program processing of the processor.

The failure phase determination processing 104 determines the amount detected by the relay 103 (such as an undervoltage).
Then, the input signal at that time is stored in the data memory. When the determination process 104 is performed in this manner, in the case where there is no failure, the uncertainty of the distance orientation value l _F to the failure point due to the zero-phase current being zero is eliminated, and the orientation result is valid only when the failure phase is clear. It can be.

Fault locator processing 106 executes the operation based on equation (1) to (5), calculates the orientation value l _F. here,
For example, in the calculation of the expression (1), assuming that the sampling interval Δt is every 30 degrees of the commercial frequency, Made by Similarly, for the equation (3), the desired reactive power can be easily obtained by a method of adding the product operation of the sample values of the voltage and the current.

In the display process 107, the variation in the orientation value l _F which is the operation result for each of several sample values is checked, and the orientation value l _F
Is stable, the average value is obtained and output to the display means. If there is a variation exceeding a predetermined value, it may be in a transient response state or an inconvenient case such as a data error may be handled as the orientation output.

The end determiner 108 determines the end of the calculation, and checks the elapse of a predetermined time after the failure detection by the failure phase determination processing 104 by using a counter function. Here, the fixed time is preferably about 0.1 to 0.2 seconds in consideration of the occurrence of the next failure.

As described above, the reactive power up to the fault point of the fault phase is obtained as the reactive power between the voltage at the fault point and the zero-phase current (the sum of the phase currents), and the reactive power per unit length is Since it is easily obtained from the self and mutual impedances and the current, the distance can be determined by taking the ratio of these.

〔Example〕

One embodiment of the fault point locating apparatus according to the present invention when the power supply is branched to the fault point will be described with reference to FIG. Here the branch power supply 8 is branched from the P ₂ point of the transmission line 1,
It is assumed that the outflow current _IL2 flows out. Also, the route length between point P ₂ branch power supply is connected from the fault locator installation point P ₀ l _1, the route length from the branch point P ₂ to the fault point F and l _F2. In this case, reactive power between the power branch point P ₂ from the fault locator installation point P ₀ is for also occur due to components of the drain current I _L2, it is necessary to compensate for this amount. This means that, when the system has three phases, first, equation (1) is changed to the following equation (7).

However, the second term on the right side, the third term is a correction term by the branch power supply, and R ₁ is a positive phase resistance of the section L _1, a positive-phase reactance of X ₁ the interval L _1, I _L2 is branched supply positive phase current It is. Also,
Equation (4) is changed to equation (8).

However, a is an operator that gives the (T / 3 in the time) 120 ° delay 1 of a ² I _L2 is 240 degrees delayed value I _L2, aI _L2 is I _L2
Indicates a value of 20 degrees delay.

In both equations (7) and (8), the outflow current I _L2 is used. This may be set in the processor as operating value data in advance, or may be estimated by a current other than the fault locator target phase. . This latter estimate is for example a phase failure time of orientation from the b-phase current I _b and c-phase current I _c in the fault locator installation point _{P 0, I L2 = k 2} (-I b -I c) ... (9) Determined by Where k ₂ is the fault locator installation point P ₀
Of the branch power supply current _{IL2 with} respect to the current of FIG. Further, as shown in FIG. 4, the values of the load current I _L and the outflow current I _L2 may be directly transmitted from each installed electric station via the transmission lines 21 and 22, and may be taken in. (7)
Calculated value of the distance I _F using the formula and (8) is of course only valid when l _F> l _1.

When there are a large number of branch power supplies, the orientation can be performed by adding the component by the branch power supply to the reactive power of each branch section as in the embodiment of FIG.

In the present embodiment, the case of a ground fault has been described, but in the case of a short circuit, it can be located in exactly the same procedure.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, even if there exists outflow current from a branch power supply, the distance to a fault point can be pinpointed accurately based on reactive power, without being affected.

Further, the fault point can be located in any of the ground fault and the short circuit.

[Brief description of the drawings]

FIG. 1 is a view showing an installation state of an embodiment of a fault point locating device according to the present invention when there is a branch power source, and FIG. 2 is a diagram showing a transmission system having no branch power source in order to explain the principle of the device in FIG. FIG. 3 is a flow chart showing a procedure for locating a fault in the situation shown in FIG. 2, and FIG. 4 is a view showing a system configuration in a case where an outflow current and a load current are directly taken in. 1 ... transmission line, 2 ... current transformer, 3 ... voltage transformer, 4 ...
... Transformer, 5 ... Neutral ground resistor, 6 ... Power supply, 7 ...
... Load, 8 ... Branch power supply, 21,22 ... Transmission line, 100 ... Fault locator, P ₀ ... Fault locator installation point, F ...
... failure points.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Takiguchi 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant, Hitachi, Ltd. (72) Inventor Minoru Seya 1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture No. 1 Inside the Kokubu Plant of Hitachi, Ltd. (56) References JP-A-63-124970 (JP, A)

Claims (4)

(57) [Claims] A fault phase detecting means for detecting a fault phase in which a ground fault of a transmission line has occurred in a power transmission system including a branch power source, from a voltage and current value at an installation point of the detecting means to a fault point of the fault phase. Calculating a reactive power based on the zero-phase current, and adding a reactive power generated by an outflow current flowing from the branch power supply to output a value as a reactive power value.
Digital operation means, calculates reactive power based on the zero-phase current per unit length of the transmission line from the current value at the installation point and the line constant of the transmission line, and calculates the reactive power generated by the outflow current flowing out of the branch power supply. A second digital operation means for outputting a value obtained by adding the electric power as a reactive power value per unit length of the transmission line; and a reactive power value from the first digital operation means,
And a third digital calculating means for calculating a distance from the installation point to the fault point by dividing the reactive power value per unit length of transmission line from the digital calculating means. 2. The control device according to claim 1, wherein the first, second, and third calculation means perform the calculation of the distance to the fault point a predetermined number of times at different times. And a fourth digital calculating means for calculating an average value of the calculated distances when the dispersion of the distances calculated a predetermined number of times is within a predetermined range. 3. The fault point locating device according to claim 1, wherein the first and second calculating means estimate the value of the outflow current from a current value of a phase other than the fault phase at the installation point. A fault point locating device, which is a means. 4. The fault point locating device according to claim 1, further comprising: a transmission unit configured to transmit an outflow current value from each power supply and an inflow current value to each load to the installation point on the transmission line. First
And a second calculating means for calculating a reactive power value corrected for the branch power supply using the outflow and inflow current values of each power supply sent by the transmission means.