JPH0574788B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a power transmission line fault locator (hereinafter abbreviated as a fault locator) that measures the location of a fault occurring in a power transmission line. .

[Prior art]

In general, the impedance per unit length of a power transmission line can be easily determined by measuring the voltage and current at the time of a failure at an electrical station, as long as the tower structure, power source type, etc. are the same.

A conventional device using the above-mentioned principle is shown in FIG. In the figure, 1 is a generator;
2 is the power transmission line, and CT4 (current transformer) is installed at point P in the diagram.
and PT5 (voltage transformer) are installed to transmit the current and voltage signals of the power transmission line to the fault locator 6.

If an A-phase ground fault occurs at point F in the one-line system shown in FIG. 1, the A-phase voltage V _a at point P, where the fault locator is installed, is expressed by equation (1).

V _a = Z _f (I _a + KI _p ) + R _f I _f ...(1) However, Z _f : Positive sequence impedance between points P and F I _a : A phase current at point P I _p : Zero sequence current R _f : Fault point resistance I _f : Current flowing to the fault point K = | Z ₀ − _{Z 1} /Z ₁ | Z ₀ : Zero-sequence impedance of the transmission line Z ₁ : Positive-sequence impedance of the transmission line Generally, in a directly grounded system The current I _f flowing at the fault point, the A-phase current I _a at point P, and I _a +KI _p , which is obtained by multiplying the zero-sequence current I _p by a coefficient K, are almost in phase.

In addition, in the case of a 2-wire or 3-wire fault, the relationship between the line voltage and line current of the faulty phase is expressed by equation (2): V _bc = Z _f (I _b - I _c ) + R _f (I _bf −I _cf ) ...(2) However, V _bc : Line voltage at point P I _b , I _c : Current of B phase and C phase at point P I _bf , I _cf : B phase flowing to the fault point and c-phase current In this case as well, in a directly grounded system, (I _b −I _c )
and (I _bf −I _cf ) are almost in phase, and can be expressed as V=Z _f I+R _f I _f (3) by combining equations (1) and (2). Therefore, the impedance Z _x obtained from the fault voltage and current is Z _x =V/I=Z _f +I _f /IR _f (4). Here, since the current I _f flowing to the fault point and the fault current I are almost in phase, the second term in equation (4) can be considered to be only the pure resistance component, and the reactance component X _f of the impedance Z _x is the fault point resistance. not affected by

Therefore, the distance l to the fault point is l = X _f /X, where X: reactance of positive sequence impedance per unit length of transmission line. Figure 2 shows the configuration of a conventional fault locator that embodies this. Shown below. Reference numeral 7 denotes an input switching circuit, which introduces an appropriate input to the reactance measuring circuit 8 according to the type of failure, calculates the reactance X _f in the reactance measuring circuit 8, and calculates the distance l to the failure point in the arithmetic circuit 9 in the subsequent stage. The distance l is calculated and displayed on the display circuit 10.

Conventional fault locators for power transmission lines were constructed as described above, and although they could be used in directly grounded systems, they were considered inappropriate for use in high-resistance grounded systems. The reason for this is that in equation (3), the current I _f flowing to the fault point and the fault current I are not in phase, so (I _f /I)·R _f cannot be considered as a pure resistance component. Therefore, as a fault locator in a high-resistance grounding system, it is necessary to introduce a concept different from the above-mentioned principle.
In addition, it is necessary to switch the input signal to be calculated depending on the type of failure, which makes the circuit complicated, and
There were drawbacks such as the need for a separate external device to accurately determine the type of failure.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and by measuring the positive sequence voltages at both ends of a power transmission line and calculating those positive sequence voltages, it can be used in high resistance grounding systems. Another object of the present invention is to provide a power transmission line fault locator that can accurately display fault points and that can use the same input data as fault locator calculation input regardless of the type of fault.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, the same parts as in FIG. 1 are designated by the same reference numerals. In FIG.
2 is a fault locator at the parent end, and 13 is a fault locator at the slave end. The fault locator 12 at the parent end is configured to receive a transmission signal from the fault locator 13 at the slave end and display the fault point. ing. That is, the fault locator 1 at the child end
3 inputs the voltage signal at the other end of the power transmission line, synthesizes a positive sequence voltage from the voltage signal, and transmits it to the fault locator 12 at the parent end via the transmission line 11. At the parent end, the positive sequence voltage at its own end and the positive sequence voltage at the other end from the fault locator 13 at the child end are calculated and the failure point is displayed. FIG. 4 is a diagram illustrating the internal configuration of the fault locator, which illustrates a specific example of the circuit configuration described above. 15 is a positive phase synthesis circuit at the parent end, which synthesizes the voltages of each phase input from _PT5A to create a positive phase voltage. Further, 20 is a positive phase synthesis circuit at the terminal terminal, which synthesizes the voltages of each phase inputted from _PT5B to generate a positive phase voltage. Reference numeral 19 denotes a fault detection circuit, which outputs a positive phase voltage signal by a positive phase synthesis circuit 20 only when a failure occurs in the power transmission line, inputs it to a transmitting circuit 21, and transmits it to the fault locator 12 at the parent end. Similarly, in the fault locator 12 at the parent end, the output signal of the positive phase synthesis circuit 15 is input to the arithmetic circuit 17 only when the fault finding circuit 14 operates, that is, when a fault occurs. The transmission signal from the fault locator 13 at the child end is demodulated by the receiving circuit 16 in the fault locator 12 at the parent end, and is input to the arithmetic circuit 17 together with the output signal of the positive phase synthesis circuit 15. Based on the input positive sequence voltages of the parent terminal and child terminal, the arithmetic circuit 1
At step 7, calculations to be described later are performed, and the calculation results are input to the failure point display circuit 18 to display the distance from the parent end to the failure point.

Next, the operating principle of the present invention will be explained below.

First, consider the case where a one-wire ground fault with fault resistance R _f occurs on power transmission line 2. In the equivalent circuit, the fifth
It is shown as shown in the figure. Here, x _p1 ... Positive phase power impedance seen from the installation point of the fault locator 12 at the parent end x _q1 ... Positive phase power impedance seen from the installation point of the fault locator 13 at the child end x _l1 ... of the transmission line 2 Main end fault locator 1
Positive-sequence line impedance between the fault locator 12 and the terminal fault locator 13 k...Ratio indicating the fault point V _p1 ... Positive-sequence voltage at the fault locator 12 at the parent terminal V _q1 ... Positive-sequence voltage at the fault locator 13 at the terminal terminal E...Power supply voltage However, the subscript "2" in Figure 5 is for the reverse phase, "0"
indicates the zero phase component.

Figure 5 is simply summarized and rewritten as shown in Figure 6. Here, V _F is the positive sequence voltage at the fault point. Furthermore, if E, V _p1 , V _q1 , and V _F are considered as effective values, the relationship can be rewritten as shown in FIG. 7. That is, E, x _p1 and x _q1 are known and are stored in the arithmetic circuit 17, and
Since V _p1 and V _q1 are measured by the positive phase synthesis circuits 15 and 20 in the fault locators 12 and 13 at the parent terminal and child terminal, respectively, calculate the value of k indicating the failure point from Fig. 7. Then, it can be expressed by equation (7).

E-V _p1 /E-V _F =x _p1 /x _p1 +kx _l1 ...(5) E-V _q1 /E-V _F =x _q1 /x _q1 +(1-k)x _l1 ...(6) Solving equations (5) and (6), k=(1-n)・x _l1 ^-1 +x _q1 ^-1 /n・x _p1 ^-1 +x _q1 ^-1 …
...(7) However, n=E-V _p1 /E-V _q1 ...(8) That is, from equations (7) and (8), the fault point can be indicated by k x Can be displayed with _l1 .

In this example, we have explained the 1-phase ground fault, but the equivalent circuit can be expressed as shown in Figure 6 for all faults such as 2-phase short circuit fault, 2-phase ground fault, and 3-phase short circuit. The value of k can be calculated using equations (7) and (8). Further, in this example, for the sake of simplicity, the case of a single-circuit power transmission line has been described, but the present operating principle can be similarly applied to a two-circuit power transmission line.

In the above embodiment, the fault detection circuits 14 and 19 were installed in FIG. 4, but these circuits were not implemented and the operation of the fault locator was controlled by the operation signal of the power transmission line protection relay outside the fault locator. You may also do this.

〔Effect of the invention〕

As described above, according to the present invention, when a fault occurs in a power transmission line, the fault point is immediately calculated using the positive-sequence voltage at both ends of the transmission line, so the input signal conditions can be adjusted depending on the type of fault. This eliminates the need for complicated circuit operations such as switching input circuits to change input circuits, and has the advantage that it can be applied to high-resistance grounding systems.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of a conventional fault locator, Fig. 2 is a block diagram of a conventional fault locator, and Fig. 3 is a system diagram of a fault locator showing an embodiment of the present invention. , FIG. 4 is an internal configuration diagram of a fault locator showing an embodiment of the present invention. FIG. 5 is an equivalent circuit diagram of a one-phase ground fault, FIG. 6 is a simplified equivalent circuit diagram of FIG. 5, and FIG. 7 is a voltage distribution diagram showing the voltage relationship of FIG. 5. 1...power supply, 2...power transmission line, 3...fault resistance,
4... Current transformer, 5... Voltage transformer, 6... Conventional fault locator, 7... Input switching circuit,
8... Reactance measurement circuit, 9... Arithmetic circuit,
10... Display circuit, 11... Transmission line, 12...
Fault locator at the parent end of the example of the present invention, 13...
Fault locator at the child end of the example of the present invention, 14,1
9... Fault finding circuit, 15, 20... Positive phase synthesis circuit, 16... Receiving circuit, 17... Arithmetic circuit, 18
... Display circuit, 21 ... Transmission circuit.

Claims (1)

[Scope of Claims] 1 Fault locators at the main terminal and terminal which are installed at two places across a power transmission line, and when a ground fault occurs in the transmission line, the fault locators at the main terminal and terminal A positive phase synthesis circuit at the parent terminal and the child terminal that measures voltage and synthesizes the positive sequence voltage, and a transmitting/receiving circuit that transmits the output signal V _q1 of the positive phase synthesis circuit at the child terminal to the fault locator side at the parent terminal. and an arithmetic circuit that calculates a failure point by substituting the output signal V _q1 transmitted by the transmitting/receiving circuit and the output signal V _p1 of the positive phase synthesis circuit at the parent end into the arithmetic expression shown below, and the arithmetic circuit. A fault locator for a power transmission line, comprising: a display circuit that displays a fault point calculated by the power transmission line; K=(1-n)・x ₁₁ ^-1 +x _q1 ^-1 /n・x _p1 ^-1 +x _q1 ^-1However , n=E−v _p1 /E−v _q1 x _p1 : Parent end fault locator Positive phase power impedance seen from the installation point x _q1 : Positive phase power impedance seen from the installation point of the fault locator at the slave end x ₁₁ : Between the fault locator at the parent end and the fault locator at the slave end Positive phase line impedance E: Power supply voltage k: Ratio 2 indicating the fault point A fault detection circuit is implemented to monitor the operation of the positive phase composite circuit in the fault locators at the parent terminal and the child terminal, and is used to detect faults that occur on the power transmission line. 2. The fault locator for a power transmission line according to claim 1, wherein the fault detection circuit automatically detects a fault and links the fault locators at the parent end and the child end.