JPH0222605B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective relay device for protecting a power system.

Conventionally, there has been a device of this type as shown in FIG. 1 and 2 are power supplies, 3 and 4 are circuit breakers, 5 is a power transmission line to which power supplies 1 and 2 are connected via circuit breakers 3 and 4, 6a and 6b are busbars of power supplies 1 and 2, 7a and 7b
8 is a current transformer provided on the power transmission line 5 near the circuit breakers 3 and 4, 8 is a transformer connected to the bus bar 6a, and 9 is a protective relay device.

FIG. 2 is a block diagram showing the configuration of the protective relay device. 10 inputs the current signal I ₁ (t) of the transmission line 5 from the current transformer 7, inputs the voltage signal V ₁ (t) of the bus 6a from the transformer 8, and inputs the impedance Z
(t)(=V ₁ (t)/I ₁ (t)) and an arithmetic circuit that calculates and outputs it.
A determination circuit 12 inputs a signal representing Z(t) (hereinafter referred to as signal Z(t)), determines the zone passage time and the presence or absence of zone passage based on its locus, and outputs the results as signals 11a and 11b. A detector 13 performs an AND operation of the signal 12a of the detector 12 and the signal 11b of the determination circuit 11.
A cutoff signal 9a is supplied to the circuit breaker 3 at the gate.

Next, the operation will be explained. Figure 3 is a signal
V ₁ is fixed in the Y-axis direction, and the voltage signal of bus 7 is V ₂
shows the vector relationship when increasing the angle Θ relative to the signal V ₁ . When the voltage signal V ₂ of the bus 6b is in phase with the signal V ₁ , there is no voltage difference between them, and the signal I ₁ (0) is zero. However, when this angle Θ is 90°, a voltage difference occurs between the two,
The signal I ₁ (90) is no longer zero. Below, similarly showing the relationship for each angle Θ, the signal I ₁ (t) moves on the circular locus 14. When the system is normal, the signals V ₁ and V ₂ are almost in phase or have a slight difference. Therefore, the position of the signal Z(t) on the R, jX coordinates is at a point where the R component is large and the jX component is approximately 0. FIG. 4 shows such a relationship in relation to the angle Θ.

As an example of a process in which synchronization progresses due to a disturbance such as a system accident, when the angle between signals V ₁ and V ₂ increases, the impedance locus passes through the center of the R-jX coordinate and becomes the second Or it can be seen that it moves to the third quadrant. Therefore, the determination circuit 11 determines the time it takes for impedance Z(t) to pass through the detection zone as shown by Z in FIG. The occurrence of the synchronization phenomenon is detected, and the results are output as signals 11a and 11b. The level of the signal 11a is determined by the detector 12 and becomes a signal 12a. AND gate 13 outputs signal 9a by ANDing signals 11a and 12a to cause circuit breaker 8 to shut off.

Conventional protective relay devices are configured as described above, and have the disadvantage that it is difficult to respond to changes in the power grid because the response to power outages is based on grid network calculations and verification with oscillation tests. In addition, since the system is detected by converting the step-out determination into the coordinates of the impedance locus, it is not possible to detect it at a singular phenomenon point or an inflection point of the state quantity, and it is difficult to determine the detection setting value. There were flaws.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and detects the step-out phenomenon from changes in the signals P and Q indicating the amount of electricity calculated from the signals I and V and the angle Θ between them. In order to do so, the signal P
By determining that the value of is maximum and the value of signal Q continues to increase, it is possible to clearly determine step-out and execute protective action without being affected by the system configuration and with fewer setting items. The purpose is to provide a protective relay device.

An embodiment according to the present invention will be described below with reference to the drawings. The connection between the protective relay device 9 and the grid is similar to that shown in FIG. The structure of the protective relay device 9 according to the present invention is shown in FIG. In FIG. 6, 14 is the signal V(t), I
(t) a calculation unit that calculates signals P and Q; 15 a setting unit that sets P-Q coordinates from signals P and Q; 16
is a logic unit that makes a logical decision based on the output of the setting unit 15, which will be explained below.

Next, the operation will be explained. The calculation unit 14 inputs the signals V(t) and I(t), and calculates that P=VIcosΘ, Q=
It calculates VIsinΘ and outputs signals P and Q. The signals P and Q are shown as 7th with respect to the angle
The changes occur as shown in the figure, with signal P showing a maximum value at an angle Θ=90°, signal Q showing a maximum value at an angle Θ=180°, and both become equal at point A. The setting unit 15 detects this point A and outputs signals P ₂ and Q ₂ indicating it.

In general, in power systems, the magnitude of the synchronization force is also relevant, but if the angle Θ opens by 90 degrees or more, it can be determined that synchronization has occurred. However, the signal Q at this time continues to increase. Therefore, in the present invention, the logic unit 16 indicates the point at which the signal P, which indicates step-out, changes from increasing to decreasing, that is, the peak of vibration of the signal P due to system fluctuation, and the angle Θ at both ends is 90°. The condition for determining the occurrence of step-out is that the signal P reaches its maximum value due to the opening, and that the signal Q increases at that time. Note that at point A, where the signal P is at its maximum and the value of the signal Q is also at its maximum, the signals P and Q are oscillating within an angle Θ of 90°. That is, when the signal P reaches a maximum and the value of the signal Q is increasing beyond a certain value k, that is, when dQ/dt>k, the logic unit 16 determines that the signal Θ has increased beyond 90°. and is determined to be out of synch. This state is shown on the P-Q coordinates in FIG. In the case of vibration where both the signals P and Q are maximum, the trajectories P and Q reciprocate on a fixed ellipse like B. At this time, the signal P has a maximum value _P1 , the signal Q has a maximum value _Q1 , and the signals P and Q have no combination of values larger than these. When the angle Θ exceeds 90°, the trajectories P and Q reach the maximum value _P2 when passing through point A in the figure, as shown by C, and then begin to decrease, and the signal Q becomes _Q1. There is a tendency to increase from →Q ₂ →Q ₃ . Step-out is determined by passing through such a point A, and the determining section 16 outputs a signal 9a.

Although the above embodiment describes the case of step-out, an analog calculation circuit may be provided to perform peak detection (P) + time differential amount level detection (Q), or digital sampling value of electrical quantity may be used. A microcomputer that performs program control may also be used. Furthermore, it is assumed that the time derivative of Q at point A in Figure 8 is greater than a certain value, but Q ₂
The device may include a logic unit that determines that the time passing between both values of ±ΔQ is within a certain value. however,
ΔQ is a minute value of signal Q.

As described above, according to the present invention, since the protection operation is performed using the signal P being at its maximum and the signal Q being increasing as the condition for determining step-out, the angle
It is possible to respond correctly to situations such as opening to 90 degrees, and it is also easier to set the setting values that determine the judgment conditions, making it easier to respond to changes in the system.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of the protective relay device and the system, Fig. 2 is a block diagram of a conventional protective relay device, Fig. 3 is a vector diagram of the voltage and current of the system shown in Fig. 1, and Fig. 4 is Figure 1 is a vector diagram of the voltage and current of the system and its impedance graph. Figure 5 is a diagram for explaining the detection zone on the impedance plane when detecting a step-out phenomenon with a conventional protective relay device. , FIG. 6 is a block diagram of a protective relay device according to an embodiment of the present invention, and FIGS. 7 and 8 are graphs of signals of the protective relay device shown in FIG. 6. 1, 2... Power source, 3, 4... Circuit breaker, 5... Power transmission line, 7a, 7b... Current transformer, 8... Transformer, 9
...Protective relay device, 14... Calculation section, 15... Setting section, 16... Logic section. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. The first and second signals are obtained from the voltage signal V indicating the voltage of the bus connected to the power supply at the own end and the current signal I indicating the current at the own end in the transmission line connecting the power supply at the own end and the power supply at the opposite end. Electric energy P, Q (however, P
=I(t)・V(t) cosΘ, Q=I(t)V(t)
sinΘ, Θ is the angle formed by I and V); and a calculation unit that detects the maximum value of the first power amount P;
and a logic unit that outputs a signal indicating step-out when it is detected that the second power amount Q increases by a predetermined value or more, and the power transmission line is controlled in accordance with the signal indicating step-out. A protective relay device designed to protect the user.