JPH03212124A - Network separation device - Google Patents

Abstract

PURPOSE:To predict out-of-phase independent of a position of the center of out-of-phase in advance by a method wherein the title device comprises a phase angle detection means, a means for predicting and computing the phase angle, a means for deciding out-of-phase between networks and a means for breaking connected-lines. CONSTITUTION:When an accident happens in a network, the number of revolutions of generators GA1, GA2, GB1 and GB2 is detected at an interval of t. Phase angle computing sections 42a-42d compute a phase angle of the generators GA1, GA2, GB1 and GB2. A means 6 for predicting and computing the phase angle predicts the phase angle of the generators GA1, GA2, GB1 and GB2 expected a short time ahead. A means 7 for deciding out-of-phase checks synchronous and out-of-phase conditions of the generators GA1, GA2, GB1 and GB2. When the condition is decided as of out-of-phase between networks, an order is given to means 9a and 9b for breaking the connected lines to open circuit breakers CB1 and CB2.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention detects inter-grid out-of-sync due to transmission line accidents at an early stage, cuts off the target interconnection line, and prevents the out-of-step from spreading. This invention relates to a system separation device that prevents.

(Prior art) Conventional means for determining out-of-step between interconnected systems uses a voltage phase comparison relay or an impedance relay to determine whether the center of the out-of-step falls on the target power transmission line. It was the subject.

FIG. 7 is an example of a system separation device that uses a voltage phase comparison relay as a step-out determining means. As shown in the figure, the conventional system separation device has bus voltages V, V,
terminal parts 1a and 1b for detecting and opening the CB at both ends of the interconnection line O^;
Based on VA, V, the voltage phase angle difference Δθ between bus A and bus B
Based on the detected voltage phase angle difference Δθ, the phase angle difference detection unit 2 determines whether the value crosses, for example, 180 degrees in electrical angle, as shown in FIG. If it crosses the
It is composed of a disjunction determining section 3 which sends a CB opening command to the terminal b.

(Problem to be solved by the invention) In the conventional system separation device described above, changes in system configuration, etc.
If the center of the out-of-step shifts from the target interconnection line for some reason, the out-of-step cannot be detected as a result, and the system separation device cannot function. Furthermore, even if the center of the out-of-step enters the target interconnection line, the A-key determination will be made after the out-of-step, which may delay the separation of the interconnection line and cause the out-of-sync phenomenon to spread. .

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a highly reliable system separation device that is not affected by the position of the center of synchronization and is capable of predicting inter-system synchronization in advance. It is an object.

[Structure J of the Invention (Means for Solving the Problem) In order to achieve the above object, the present invention provides that in an electric power system in which two systems are interconnected at one point, at least one of the generators connected to each system means for detecting the phase angle of one or more units one by one; means for predicting and calculating the estimated value of the phase angle for a short period of time based on the detected value; It consists of means for determining step-out, and means for cutting off the interconnection line according to the determination result.

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

A power system out-of-step phenomenon occurs when the angular velocity deviation of the generator becomes unbalanced due to a system fault or the like, and the relative phase angle difference increases. Therefore, in order to more accurately capture the step-out phenomenon, it is effective to monitor the relative phase angle difference between the generators and determine the step-out based on its transition. Third
The figure shows the movement of the relative phase angle difference Δδ between the generators parallel to both systems when a step-out occurs between the systems. As is clear from the figure, the movement of the relative phase angle difference when synchronization occurs tends to diverge with time. Therefore, if the movement of such a relative phase angle difference can be detected early by the prediction means, a quick and appropriate out-of-step determination can be made. Specifically, as shown in FIG. 4, the estimated value ΔδX of the relative phase angle difference for a short period of time shows a tendency to diverge, and
If the value exceeds a preset threshold value δ, it is determined that synchronization has occurred. In reality, considering reliability, multiple generators are selected from each system, and when all combinations of representative generators from both systems satisfy the conditions shown in Figure 4, It is determined that there is a step-out between systems.

FIG. 5 shows the synchronization and step-out relationships between representative generators when both systems are referred to as system A and string system. In Figure 5,
× indicates step-out, and ○ indicates synchronization. Figure 5 (
A) is an example of inter-system step-out, and system separation is required. This example is a phenomenon in which system A is out of step with respect to system B, and if each representative generator of system B is used as a reference, it is determined that all representative generators of system A are out of step. On the other hand, the same figure (b
) is the single machine out-of-step mode of the representative power generator 11GA1 of the system A, and from the perspective of each representative generator of the system B, it is determined that only the representative generator GA1 in the system A is out of step, and system separation is not necessary. The final out-of-step determination will capture and output such a relationship.

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

First, in a steady state before an accident occurs, the rotation speed of the representative generator is detected by an electromagnetic pickup, and the detected value is set as the steady rotation speed ω(0). Next time an accident occurs in the grid, Δ
tr Rotation speed ω of the representative generator detected by WIVa (1)
Based on this, the angular velocity deviation Δω(1) is calculated from equation (1), and the phase angle δ is determined from the equation of motion shown in equation (2).

Δω(1) = (ω(1)−ωto))/ω(o)・
...(1) δ(t) = δ(-Δt) +1(Δωft)+Δω(7~Δ1))Δt
(2) Next, as shown in Figure 6, the short-term estimation of the phase angle is carried out using the least squares method based on the calculation results of the phase angle δ at several points in the past. The coefficients of the estimation formula are calculated, and the estimated value δX of the phase angle is obtained as a point on the extension. Depending on accuracy, an appropriate estimation time is 200 to 300 milliseconds from the current time.

The action will be explained based on the above idea. First, when an accident occurs in a power system where two systems are interconnected at one point, the phase angle of at least one representative generator connected to each system is detected by the phase angle detection means, and the transmission The signal is input to the phase angle prediction calculation means via the system. With this phase angle prediction calculation means, once the system fault is removed,
Based on the phase angle detected up to the present moment of each representative generator,
Find an estimate of the phase angle for a short period of time. Next, the step-out determination means performs a step-out determination based on the estimated phase angle of each representative generator obtained by the phase angle prediction calculation means for a short period of time. Out-of-step determination is performed using the magnitude of the phase angle difference between the representative generators of both systems, and when all combinations exceed a preset threshold, it is determined that inter-system out-of-step has occurred. When the out-of-step determination means determines that the out-of-step is between systems, the CBs at both ends of the interconnection line are opened to separate the two systems, thereby preventing the out-of-step from spreading and stabilizing the system.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of a power system to which the system separation device of the present invention is applied. In Figure 1, G^1,
GA2 is the representative generator of A system, GBL, CB2 is B
The representative generators of the system, CB1 and CB2, are circuit breakers for the interconnection line connecting the A system and the B system.

On the other hand, 41a to 41d are rotation speed detection units that respectively detect the rotation speed of each representative generator via an electromagnetic pickup, etc., and 42a to 42d are rotation speed detection units for each representative generator based on the detected rotation speed of the generator. This is a phase angle calculation unit that calculates a phase angle, and these components constitute phase angle detection means 4a to 4d. Further, 5a to 5d are phase angle detection means 4a to 4d.
This is a phase angle transmitting means for transmitting the phase angle of each representative generator. Furthermore, 6 indicates phase angle transmission means 5a to 5d.
7 is a phase angle prediction calculation means for inputting the phase angle of each representative generator transmitted through the , and calculating an estimated value of the phase angle for a short period of time based on these; 7 is a phase angle prediction calculation means; Based on the estimated value of the short-term future phase angle of each representative generator calculated in step 6, the absolute difference in estimated phase angle is calculated for all combinations between the representative generators of system A and system B. The value expands,
and out-of-step determining means 8a, 8b for determining that inter-system out-of-step occurs on the condition that a preset threshold value is exceeded.
9a and 9b are cutoff command transmission means 8a and 8 which respectively transmit a cutoff command for the interconnection line when the stepout determination means 7 determines that there is a step out between systems;
According to the interconnection line cutoff command transmitted via interconnection line breaker Ca1. This is an interconnection line disconnection means that opens CB2.

Next, the operation of the system separation device configured as described above will be explained based on the flowchart of FIG. 2.6 First, during steady state, the representative generator GA1 of the A system.

The rotational speed of the representative generators GB1 and CB2 of the GA2 and B systems is determined by the rotational speed detection section 41 of the phase angle detection means 4a to 4d.
a to 41d, and the result is sent to the phase angle calculation unit 42a.
~42d, and the steady rotational speed ωA of each representative generator, (
0).

ωBH(0) (+=1.2) (
Step Sl).

Next, if an accident occurs in the system under such conditions, the representative generators GAI, G of system A
A2, B system representative generator G81, rotation speed ω of 0B2, (1), ω8. (t) (i=1.2> is detected by the rotational speed detection units 41a to 41d of the peak means 48 to 4d at intervals of Δ, and the result is transmitted to the phase angle calculation unit 42.
The 0 phase angle calculation units 42a to 42d sent to the 0 phase angles a to 42d calculate the phase angles of the representative generators of the A system and B system from the above equations (1) and (2), (1), δBH(t)
(+=1°2) is calculated (step 82). This result is input to the phase angle prediction calculation means 6 by the phase angle transmission means 5a to 5d. In the phase angle prediction calculation means 6 for which the accident is removed, the A system,
The phase angles δ, δ (i
=1.2) is estimated, and the result is input to the Ai Bi step-out determining means 7. The step-out determination means 7 examines the synchronization/step-out relationship between the representative generator of the A system and the representative generator of the B system according to the action of step S4. If the relationship is as shown in Figure 5 (a),
It is determined that there is an inter-grid step out, and the circuit breaker C at both ends of the interconnection line is
interconnection line cutoff means 9a, which transmits the command to open the CB2 via the cutoff command transmission means 8a, 8b;
Output to 9b. As a result, the interconnection line + disconnection means 9a,
9b are interconnection line circuit breakers CB1. CB2
is opened to separate the A system and the B system to prevent out-of-step spread (step S5).

If the step-out determination means 7 determines that there is no inter-system step-out, the process returns to step S2 and the above-described process is continued for a certain period of time.

As mentioned above, the system separation device according to this embodiment can reliably detect inter-system out-of-sync due to power transmission line accidents, etc., before the system becomes out-of-step. By implementing system separation, the spread of synchronization can be minimized.

In this embodiment, the number of representative generators in the A system and the B system was two each, but it goes without saying that the same implementation can be carried out even if there are three or more.

[Effects of the Invention] As explained above, according to the present invention, an estimated value of the phase angle of at least one generator among the generators connected to each system is obtained for a short period of time, and this estimation is performed. Since out-of-step is judged based on the time change of the value, inter-system out-of-step can be detected at an early stage.
Moreover, it is possible to provide an extremely reliable system separation device that can perform reliable detection.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the configuration of a power system to which the system separation device of the present invention is applied, Fig. 2 is a flowchart explaining the invention in detail, and Fig. 3 is a diagram showing both systems when a step-out occurs between the systems. Figure 4 is a diagram to explain the step-out determination method between representative generators, and Figure 5 is a diagram showing representative generators of system A and system B. Figure 6 is a diagram showing the synchronization and out-of-sync relationships between
The figure is an example of a conventional system separation device, and FIG. 8 is a diagram for explaining step-out determination conditions of the conventional system separation device. 48-4d...Phase angle detection means 5a-5d...Phase angle transmission means 6...Phase angle prediction calculation means 7...Step-out determination means 8a, 8b...Shutoff command transmission means 9a, 9b・
...Interconnection line cutoff means 1a 2a AI GBI ~41d ~42d, OA2 B2...Rotation speed detection unit...Phase angle calculation unit, GBI, GB2...Representative generator...Both ends of the interconnection line breaker

Claims (1)

[Claims] In a power system where two systems are interconnected at one point,
means for detecting the phase angle of at least one of the generators connected to each system; means for predictively calculating an estimated value of the phase angle for a short period of time based on the detected value; 1. A system separation device comprising: means for determining step-out between both systems based on the estimated value; and means for cutting an interconnection line according to the determination result.