JPH0224093B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a distance relay for protecting a power system. Conventionally, there has been a device of this type as shown in FIG. In Fig. 1, 1A, 1B, and 1C are detection units installed for each phase of A, B, and C of the power transmission line and serve as detection elements for detecting failures, and 2 is the current I _A detected from each phase of the power transmission line. , I _B , I _C , voltage V _A , V _B , V _C
and signals 1A _a , 1B _a ,
1C _a is input and the signals V _F , V _H ,
A switching unit outputs Z _R I _F (Z _R is the impedance of the power transmission line), 3 is a subtraction circuit that subtracts between the signals V _F and Z _R I _F , and 4 is a shifter that shifts the phase of the signal V _H by the signal 5a. Phase box, 5 is the signal 1A _a of the detection unit 1A, 1B, 1C,
A control circuit outputs a signal 5a which is a control signal from 1B _a and 1C _a , and 6 is a phase discrimination circuit which receives the signal E _OP output from the subtraction circuit 3 and the signal E _POL output from the phase shifter 4 as inputs. Yes, and outputs signal 6a. Next, the operation will be explained. Now, if a single line ground fault occurs in the A phase, the detection unit 1A detects this and outputs a signal _1Aa . This results in
The switching unit 2 knows the type of failure and outputs the calculation vector signals V _F , Z _R I _F and the reference vector signal V _H in accordance with the type of failure. This is shown in Table 1 in correspondence with the type of failure. The subtraction circuit 3 takes the difference between the signals V _F and Z _R I _F and uses the result as a signal E _OP which is an operation vector.
Output as . The phase shifter 4 advances the phase of the reference vector signal V _H by 60 degrees or 90 degrees as explained below in accordance with the signal 5a of the control circuit 5, and outputs a signal E _POL which is a reference vector. Table 1 also shows the signals E _OP and E _POL .

[Table] If the phase difference between the signals E _OP and E _POL is less than ±90°, the phase discrimination circuit 6 determines that there is an internal failure and outputs a signal 6a. Here, operations in the case of A-phase single-line ground fault and three-phase short-circuit fault will be explained with reference to vector diagrams and characteristic diagrams shown in FIGS. 2 to 5. (b) In the case of an A-phase single-line ground fault, from Table 1, E _OP = V _A − Z _R I _A E _POL = V _CB ∠90°, and the relationship shown in the vector diagram shown in Figure 2 is established. As shown in FIG. 2, the signal E _POL is in opposite phase to the vector V _A forming the signal E _OP . As a result, the range of internal failure in the case of an A-phase one-line ground fault exists inside a circle whose diameter is the vector of _the signal _ZRIA , as shown in the characteristic diagram shown in FIG. (b) In the case of a three-phase short circuit fault, from Table 1, E _OP = V _CA −Z _R I _CA E _POL = V _BC ∠60°, resulting in a vector diagram as shown in Figure 4. In this case as well, the signal E _POL , which is the reference vector, is in opposite phase to the vector V _CA. As a result, the range of the internal failure exists inside a circle whose diameter is the vector of _the signal _ZRICA , as shown in the characteristic diagram shown in FIG. What the two types of failures described above have in common is that the reference vector signal _EPOL is in opposite phase to the calculation vectors V _A and V _CA. In order to create such a reference vector, conventionally, in the case of a one-line ground fault in the A phase, the vector V _CB is advanced by 90 degrees, while in the case of a three-phase short circuit, the vector V _BC is advanced by 60 degrees. That is, conventional distance relays are complex, expensive, and unreliable because they require controlling the phaser so that the phase shift angle is 60° or 90° depending on the type of fault. There was a drawback. This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is necessary to make the phase shift angle of the phase shifter for creating a reference vector constant for all types of failures. The objective is to provide an inexpensive and highly reliable distance relay. An embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is a block diagram of a distance relay according to the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals. Reference numeral 7 denotes a switching unit, which has the same inputs as switching unit 2 in Fig. 1, but which discriminates the type of failure as shown in Table 2 and outputs the corresponding calculation vector voltage signal V _F and calculation vector current. It outputs the signal Z _R I _F and the phase voltage reference vector signal V _H. 8 is a phase shifter which introduces the reference vector signal _VH , advances its phase by 60 degrees, and outputs it as a signal E _POL .

[Table] Next, the operation will be explained. (b) In the case of an A-phase single-line ground fault, from Table 2, E _OP = V _A − Z _R I _A E _POL = V _C ∠60°, and the relationship between the two is shown in a vector diagram in Figure 7. . In this case, the signal for the phase voltage reference vector
The output signal E _POL of the phase shifter 8, which is obtained by shifting the phase of V _H by a predetermined amount, is in opposite phase to the vector V _A as the voltage signal for calculation vector. Therefore, the range of the internal failure exists inside a circle whose diameter is _the vector _ZRIA , as shown in FIG. 3, as in the conventional device. (b) In the case of a three-phase short circuit fault, from Table 2, E _OP = V _CA −Z _R I _CA E _POL = V _BC ∠60°, and the relationship shown in the vector diagram shown in Figure 4 is established. Therefore, as described above, the vector of the signal E _POL and the vector V _CA have opposite phases. As a result, the range of internal faults is as shown in Figure 5.
It exists inside the circle whose diameter is the vector by Z _R I _CA. The calculation vector voltage signal V _F and the calculation vector current signal output from the switching unit 7 in this way
_{ZRIF is} input to the subtraction circuit 3, subtraction is performed between the two, and a signal _EOP is output. In addition, the reference vector signal V _H is phase-shifted by 60° by the phase shifter 8, and the signal
Becomes E _POL . If the phase difference between the signals E _OP and E _POL is, for example, ±90° or less, the phase determination circuit 6 determines that there is an internal failure and outputs a signal 6a. The signal 6a causes a circuit breaker (not shown) to shut off to protect the system. As described above, according to the present invention, the phase shift angle of the phase shifter for creating the reference vector is made constant for all types of failures, so the device can be constructed easily and inexpensively, and has a high cost. This has the effect of providing a reliable distance relay.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional distance relay, Figure 2 is a block diagram of a conventional distance relay.
The figures are the vector diagram of the distance relay shown in Fig. 1, and the vector diagram of the distance relay shown in Fig. 3.
The figure is a characteristic diagram of the distance relay shown in Figure 1, Figure 4 is a vector diagram of the distance relay shown in Figures 1 and 6, and Figure 5 is a characteristic diagram of the distance relay shown in Figures 1 and 6. , FIG. 6 is a block diagram of a distance relay according to an embodiment of the present invention, and FIG. 7 is a vector diagram of the distance relay shown in FIG. 1A, 1B, 1C...Detection section, 2, 7...Switching section, 3...Subtraction circuit, 4, 8...Phase shifter, 6...
Phase discrimination circuit. In addition, in the figures, the same reference numerals indicate the same parts.

Claims (1)

[Claims] 1. Introducing a detection element provided for each phase of the power transmission line to detect a fault, and vector signals of current and voltage detected from each phase of the power transmission line, and calculating the voltage and current corresponding to each fault. In addition to generating a vector signal, it determines whether it is a single line ground fault, other short circuit, or ground fault based on the output signal of the detection element, and if it is a single line ground fault, it detects the phase voltage, other short circuit, or ground fault. In the event of a failure, a switching unit generates the line voltage as a reference vector signal, an arithmetic circuit that takes the difference between the voltage and current arithmetic vector signals, and a predetermined phase shift by introducing the reference vector signal. and a phase shifter whose phase shift angle for creating a reference vector is constant for all types of failures, and a phase difference between the output signal of the arithmetic circuit and the output signal of the phase shifter is within a predetermined range. and a phase discrimination circuit that outputs a signal to protect the power transmission line, indicating that there is an internal failure in the power transmission line.