JP2664791B2 - System separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention detects an out-of-system outage due to a transmission line accident or the like at an early stage, cuts off a target interconnecting line, and obtains out-of-step spread. The present invention relates to a system separation device for preventing the occurrence of a problem.

(Prior art) Conventional means for determining out-of-step between interconnected systems mainly uses a voltage phase comparison relay or an impedance relay to determine whether or not the center of out-of-step enters the target transmission line. Met.

FIG. 7 is an example of a system separation device using a voltage phase comparison relay as step-out determination means. As shown in the figure, the conventional system separation device includes the bus voltages V _A , V _{B at} both ends of the interconnection line l.
And detect a phase angle to determine the terminal portion 1a or opening the CB of both ends of the tie-line l, and 1b, V _A, based on the V _B voltage phase angle difference Δθ of the bus A and bus B Based on the difference between the voltage phase angle difference Δθ and the detected voltage phase angle difference Δθ, it is determined whether or not the value has crossed 180 degrees as an electrical angle, for example, as shown in FIG.
If the degree crosses, it is determined that the step-out occurs and the terminals 1a and 1b
And a step-out determination unit 3 for sending a B opening command.

(Problems to be Solved by the Invention) In the above-described conventional system separation device, if the center of the out-of-step is shifted from the target interconnection line for some reason such as a change in the system configuration, the out-of-step is detected as a result. Therefore, the function of the system separation device cannot be performed. Further, even if the center of the step-out enters the target interconnection line, the step-out determination is made after the step-out, and the separation of the interconnection line may be delayed, and the step-out phenomenon may spread. .

The present invention has been made in view of the above circumstances, and provides a highly reliable system separation device that is not affected by the position of a step-out center and that can predict inter-system step-out in advance. It is an object.

[Means for Solving the Problems] In order to achieve the above object, in a power system in which two systems are interconnected at one location, at least one or more of generators in both systems Means for detecting the phase angle of the generator, means for predicting and calculating an estimated value of the phase angle ahead of a short time based on the detected phase angle of the generator, and a plurality of generators respectively from the two systems Means for selecting a representative generator, using an estimated value of the relative phase angle between each of the representative generators, and determining whether or not the combination of all generators of both systems is out of step; Means for interrupting the interconnection when it is determined that the combination is out of step.

(Operation) First, the concept of step-out determination according to the present invention will be described.

The step-out phenomenon of the electric power system occurs when the angular speed deviation of the generator is unbalanced due to a system accident or the like, and the relative phase angle difference is enlarged. Therefore, in order to capture the step-out phenomenon more accurately, it is effective to monitor the relative phase angle difference between the generators and determine the step-out based on the transition. FIG. 3 shows the movement of the relative phase angle difference Δδ between the generators in parallel with both systems in the event of a system step-out.
As is clear from the figure, the movement of the relative phase angle difference when step-out occurs tends to diverge with time. Therefore, if the movement of the relative phase angle difference can be detected early by the predicting means, a quick and appropriate step-out determination can be made. Specifically, as shown in Figure 4, shows the short destination estimate .DELTA..delta ^* is divergent relative phase angle difference, and out-of-step if it becomes more than the threshold value [delta] _C set in advance Is determined. In practice, considering reliability, a plurality of generators are selected from both systems, and when all combinations between the representative generators of both systems satisfy the conditions shown in FIG. It is determined that the system is out of synchronization.

FIG. 5 shows the synchronization and step-out relationship between the representative generators when both systems are referred to as system A and system B. In FIG.
X indicates out-of-step and o indicates synchronization. FIG. 5 (a) shows an example of step-out between systems, in which system separation is required. This example is a phenomenon in which the system A is out of synchronization with the system B, and it is determined that all the representative generators in the system A are out of step based on each representative generator in the system B. On the other hand, FIG. 6B shows a single unit out-of-step mode of the representative generator GA1 of the system A. From the viewpoint of each representative generator of the system B, it is determined that only the representative generator GA1 in the system A is out of synchronization. No systematic separation is required. The final step-out determination captures such a relationship and outputs it.

Next, a method of detecting the phase angle and estimating the phase angle ahead of a short time will be described.

First, in a steady state before the occurrence of an accident, the number of revolutions of the representative generator is detected by an electromagnetic pickup, and the value is set to a steady number of revolutions ω (0). Next, when an accident occurs in the grid,
Based on the rotational speed ω (t) of the representative generator detected at the Δt interval, the angular velocity deviation Δω (t) is calculated from the equation (1),
The phase angle δ is obtained from the equation of motion shown in the equation (2).

Δω (t) = (ω (t) −ω (0)) / ω (0) (1) In the estimation of the next phase angle in a short time, as shown in FIG. 6, the coefficients of the quadratic estimation formula are calculated by the least squares method based on the calculation results of the past several phase angles δ, An estimated value δ ^* of the phase angle is obtained as a point on the extension. The estimated time is 200 to 300 milliseconds from the current time, depending on the accuracy.

The operation will be described based on the above concept. First, when an accident occurs in a power system in which two systems are interconnected at one point, the phase angle of at least one or more representative generators interconnected to each system is detected by the phase angle detecting means,
The signal is input to the phase angle prediction calculation means via the transmission system. In the phase angle prediction calculation means, when the system fault is removed, an estimated value of the phase angle in a short time ahead is obtained based on the phase angles detected up to the present time of each representative generator. Next, the out-of-step determining means performs out-of-step determination based on the estimated value of the phase angle of the representative generator shortly ahead obtained by the phase angle prediction calculating means. The step-out determination is performed using the magnitude of the phase angle difference between the representative generators of both systems, and when all the combinations exceed a preset threshold value, it is determined that the system is out of step. If the step-out determination means determines that there is step-out between the systems, the CBs at both ends of the interconnection line are opened, and both systems are separated to prevent the spread of step-out and stabilize the system.

(Example) Hereinafter, an example is described with reference to drawings.

FIG. 1 shows a configuration example of a power system to which a system separation device of the present invention is applied. In FIG. 1, GA1 and GA2 are representative generators of the A system, GB1 and GB2 are representative generators of the B system, C
B1 and CB2 are circuit breakers for interconnecting lines connecting the A system and the B system.

On the other hand, reference numerals 41a to 41d denote rotation speed detectors for detecting the rotation speeds of the respective representative generators via an electromagnetic pickup or the like.
Reference numerals a to 42d denote phase angle calculation units for calculating the phase angles of the respective representative generators based on the detected rotation speeds of the generators, thereby constituting the phase angle detection means 4a to 4d. Also, 5a
Reference numerals 5d denote phase angle transmitting means for transmitting the phase angles of the representative generators from the phase angle detecting means 4a-4d, respectively. 6 more
Is a phase angle prediction calculation means for inputting the phase angle of each representative generator transmitted via the phase angle transmission means 5a to 5d, and calculating an estimated value of the phase angle ahead of a short time based on these. 7 is based on the estimated value of the phase angle of each representative generator shortly ahead calculated by the phase angle prediction calculation means 6 for all combinations between the representative generators of the A system and the B system. A step-out determining means for determining that there is an inter-system step-out on condition that the absolute value of the difference between the estimated phase angles has increased and exceeded a preset threshold value; When the determination means 7 determines that there is a step-out between the systems, a disconnection command transmission means for transmitting a disconnection command for the interconnection line, respectively, 9a and 9b are interconnections transmitted via the disconnection command transmission means 8a and 8b. Interconnection line disconnecting means that opens the interconnection line breakers CB1 and CB2 in accordance with the line interruption command.

Next, the operation of the system separation device configured as described above will be described with reference to the flowchart of FIG.

First, in the steady state, the representative generators GA1, GA2, B
The rotation speed of the system's representative generators GB1 and GB2 is determined by the phase angle detection
The rotation speed detection units 41a to 41d of a to 4d detect the rotation speed, and the results are sent to the phase angle calculation units 42a to 42d, and the steady rotation speeds ω _Ai (0) and ω _Bi (0) (i = 1, 2) (step S1).

Next, when an accident occurs in the system in such a state, the representative generators GA1, GA2, B
Revolutions ω _Ai (t), ω of representative generators GB1 and GB2 in the system
_Bi (t) (i = 1, 2) is detected at intervals of Δt by the rotation speed detectors 41a to 41d of the phase angle detectors 4a to 4d, and the result is sent to the phase angle calculators 42a to 42d. Phase angle calculator
In the case of 42a to 42d, the A system and the B system are obtained from the above equations (1) and (2).
Phase angles δ _Ai (t), δ _Bi (t) (i
= 1, 2) is calculated (step S2). This result is input to the phase angle prediction calculation means 6 by the phase angle transmission means 5a to 5d. Prediction calculation means 6 for phase angle at which accident is eliminated
Then, by the operation of step S3, the phase angles δ ^* _Ai ▼, δδ ^* _Bi ▼ of the representative generators of the A system and the B system in a short time ahead (i = 1,
2) is estimated, and the result is input to the step-out determination means 7. The step-out determination means 7 synchronizes the representative generator of the A system with the representative generator of the B system in accordance with the operation of step S4.
Investigate the step-out relationship. If the relationship is as shown in FIG. 5 (a), it is determined that the system is out of step, and a command to open the circuit breakers CB1 and CB2 at both ends of the interconnection line is issued. Output to the interconnection line breaking means 9a, 9b via the breaking command transmission means 8a, 8b. As a result, the interconnection line breaking means 9a and 9b respectively open the circuit breakers CB1 and CB2 of the interconnection line to separate the A system and the B system, thereby preventing out-of-step (step S5).

If the step-out determination means 7 determines that there is no step-out between systems, the process returns to step S2, and the above-described processing is continuously performed for a certain period of time.

As described above, in the system separation device according to the present embodiment,
It is possible to reliably detect out-of-step due to transmission line accidents before the out-of-step occurs before the out-of-step occurs.Therefore, if the system is separated using this system separation device, the spread of out-of-step can be minimized. Can be stopped.

In this embodiment, the number of the representative generators of the A system and the B system is two each. However, it is needless to say that the same can be implemented with three or more generators.

[Effect of the Invention] As described above, according to the present invention, when examining the estimated value of the relative phase angle between the representative generators of both systems, all combinations of the plurality of representative generators are out of step. After examining whether or not all of the combinations are out of sync,
Since the interconnection is cut off, the step-out between systems can be detected early and reliably, and a highly reliable system separation device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a power system to which a system separation device of the present invention is applied, FIG. 2 is a flowchart for explaining the operation of the present invention, and FIG. FIG. 4 is a diagram for explaining a step-out determination method between representative generators, and FIG. 5 is a diagram illustrating representative generators of system A and system B. FIG. 6 is a diagram showing a method of estimating a phase angle a short time ahead based on the phase angle up to the present time, and FIG. 7 is a diagram showing a conventional system separation device. FIG. 8 is a diagram for explaining an example of a step-out determination condition of a conventional system separation device. 4a to 4d: phase angle detecting means 5a to 5d: phase angle transmitting means 6: phase angle prediction calculating means 7: out-of-step determining means 8a, 8b ... shut-off command transmitting means 9a, 9b ... interconnection Wire breaking means 41a to 41d: Rotation speed detectors 42a to 42d: Phase angle calculator GA1, GA2, GB1, GB2 ... Representative generators CB1, CB2 ... Breakers at both ends of the interconnecting line

Continued on the front page (72) Inventor Kazuo Sonohara 11th Wakao-ji Temple, Amagasaki-shi, Hyogo Kansai Electric Power Company R & D Co., Ltd. (72) Inventor Kazuya Omata 1 Toshiba-cho, Fuchu-shi, Tokyo 72) Inventor Masahiro Sato 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu factory (56) References JP-A-62-89421 (JP, A) JP-A-57-183218 (JP, A)

Claims (1)

(57) [Claims] In a power system in which two systems are interconnected at one point, at least one of generators in both systems is connected.
Means for detecting the phase angle of one or more generators, means for predicting and calculating an estimated value of the phase angle ahead of a short time based on the detected phase angle of the generator, Means for selecting a generator as a representative generator, and using an estimated value of the relative phase angle between each of these representative generators to determine whether or not the combination of all generators of both systems is out of step; Means for interrupting the interconnection when all of the combinations are determined to be out of synchronization.