JPH0424933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a protective relay system that detects a step-out phenomenon in a power system and separates the system to avoid a power outage in the entire system.

[Prior art]

In order to maintain the stability of power systems, it is effective to use a system outage prediction separation method that detects the initial phenomenon of a system outage and performs system separation before the disturbance progresses.
For this reason, the inventor took advantage of the fact that when the locus of active and reactive power is captured, it exhibits circular motion at the time of a step-out, to predict and detect the step-out in the system in the initial state of the step-out, and to locate the electrical center point of the step-out. We proceeded with research and development on a completely new method for grasping information.

[Summary of the invention]

In this invention, the direction of the back power supply terminal to be detected is not determined when the current value is relatively small during system oscillation.
This was done to prevent the value of active power on the plane of active power and reactive power from fluctuating between positive and negative values, and the system begins to fluctuate, causing the trajectory of active power and reactive power on the plane to move in a circular arc. By fixing the direction of the rear power supply when the system is started, it is extremely easy to process active power and reactive power on a plane. Furthermore, we have developed a protective relay system that protects the system by highly accurate and reliable step-out detection. is intended to provide.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, 1 is the first of the reduced system of two aircraft.
power supply, 2 is another second power supply, 3 is the first
The voltage vector of the power supply 1, 4 the voltage vector of the second power supply 2, 5 the current vector of the system, and 6 the system protection device. Figure 2 is a locus diagram showing the locus of each vector shown in Figure 1 during oscillation, where 7 is the locus of V〓 _B with respect to V〓 _A of voltage vector 3, and 8 is the locus of I〓 of current vector 5. shows.

Figure 3 shows that when the system is shaken, the back power source is connected to the first power source 1,
Alternatively, the locus is shown when detecting the active power P on the horizontal axis and the reactive power Q on the vertical axis as the second power source 2,
Broken line 9 is the PQ locus of the first power supply end, broken line 10 is the second
Shows the PQ locus at the power supply end.

Figure 4 is a voltage vector diagram, Figure 5 is active power P.
FIG. 3 is a vector diagram showing the locus of reactive power Q.

In FIG. 6, 7a is a first logical operation section; 8a
9a is a direction determining section, 10a is a determination output, and 11a is a power direction calculating section.

First, the operation will be explained with reference to vector diagrams shown in FIGS. 2 to 5. Active power P and reactive power Q are detected from the back power supply end voltage vector calculated from the voltage and current vectors of the system measured by the system protection device 6. The detected active power P and reactive power Q are taken as a PQ locus for each sampling on the PQ plane. Next, we will measure how the PQ trajectory moves during agitation. If we assume that the direction of the rear power source used when making the measurements is, for example, the first power source 1, then the fourth
As shown in the figure, the direction of the rear power source determined with respect to the measured voltage vector is fixed as the voltage vector V〓 _A. Therefore, the PQ trajectory shown in FIG. 3 becomes a trajectory as shown in FIG. 5. In this way, step-out is detected using the PQ trajectory with the backing power source fixed, and then the center point of the step-out is located in the grid to select the point where the system is to be separated. It can be determined whether the direction of the rear power supply is reversed or not when the PQ locus moves by a set amount.

The operation of the present invention will be explained using the block diagram of FIG. 6 with reference to the operation explanation of the vector diagram described above.

FIG. 6 is a block diagram showing a protective relay system according to an embodiment of the present invention, in which the first logic operation section 7a uses the input electrical quantities as voltage 4a and current 5a to determine the effective power Pa.
and calculate the reactive power Qa. The second logical operation unit 8a, which receives the active power Pa and reactive power Qa, creates a string from the locus of the active power Pa and reactive power Qa at each time. A direction determination section 9a to which the output of the second calculation section 8a is supplied determines a change in the direction of the string, and sends out a direction determination output 10a. The power direction calculation unit 11a receives input from the first logical calculation unit during system fluctuation, and calculates PQ on the plane of active power P and reactive power Q.
Detects the direction of the rear power source from the trajectory. In this case, during the signal processing of the first logic operation section 7a, that is, when the back power supply terminal voltage is detected from the measured voltage vector, the power supply direction calculation section 11a sends a command signal to fix the rear power supply direction to the first logic operation section 11a. supply to.

In addition, in the above-mentioned embodiment, when detecting agitation, the direction is fixed at one time in the rear direction, but the present invention is not limited to this, and the determination may be made by performing multiple detections and comparing with the direction in the rear direction. In addition, the PQ is fixed from the beginning and is the back power source.
Step-out can be detected by determining the trajectory and determining whether it is reversed or not, and the same effect as in the above embodiment is achieved.

〔Effect of the invention〕

As described above, according to the present invention, when measuring the voltage of the back power source from the voltage vector measured during system fluctuation, the direction of the back power source is fixed, so the PQ
Since the locus is detected based on one circle on the plane of the active power P and the reactive power Q, step-out detection based on the PQ locus can be extremely easily performed, and a highly accurate protective relay system can be obtained.

[Brief explanation of drawings]

Figure 1 is a simulated power system diagram with the first and second power sources, Figures 2 and 4 are vector diagrams showing each vector in Figure 1, and Figures 3 and 5 are diagrams showing the effective power. FIG. 6, a locus diagram of reactive power, is a block diagram of a protective relay system according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...First power supply, 2...Second power supply, 6...System protection device, 7a...First logic operation section, 8a...Second logic operation section, 9a...Direction determination section, 10a...
Judgment output, 11a...Power direction calculation section.

Claims (1)

[Claims] 1. The transition of active power and reactive power measured from the voltage and current at the power supply end of the power system is calculated on a rectangular coordinate plane, and the circular motion locus of active power and reactive power is calculated when the power system loses synchronization. In the protective relay method that detects out-of-step by detecting the power supply end vector from the voltage vector measured in the above-mentioned power system, the direction of the power supply behind the measurement point determined for each sampling of each electrical quantity is detected as the start of system fluctuation. , the out-of-step was detected by fixing the active power and reactive power from the start of their transition until the stop of the fluctuation, and making the loci of the active power and reactive power on the plane change in the positive direction of the reactive power axis or in the negative direction of the reactive power axis. A protective relay system featuring: 2. The protective relay system according to claim 1, wherein the fixed period of the back power source uses the amount of movement of active power and reactive power on a plane over a predetermined time. 3. A patent claim characterized in that the amount of movement of active power and reactive power on a plane is measured after the determination of a fixed back power source is fixed, and the determination is made by comparing with the back power source from within a plurality of predetermined values. Protective relay method described in scope 1.