JPS6030189B2 - System stabilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing a power system comprising two systems operated separately from each other on the low voltage side by means of a plurality of transformers synchronized on the high voltage side.

The system stabilization devices that have been considered in the past or have been implemented in some areas can be used in cases where the main interconnection lines in the relevant power system are disrupted, main trunk lines within the system are separated, or large-capacity power plants within the system are dropped. In order to prevent the spread of power outage to the entire system due to the low frequency protection of large turbines, the power flow is balanced by automatically cutting off the load commensurate with the insufficient amount of power generated, which has been calculated in advance. This device is designed to ensure stable and continuous operation of each separation system.

Monitoring and control methods for this purpose include an all-system integrated monitoring and control method and an individual monitoring and control method that deals with each expected separated system. In any case, the secondary system focuses on power flow balance only within the system, so if there is excess generation capacity within the separate system, the output is reduced by governor operation or the power is shut off. On the other hand, if the power generation capacity is insufficient for the load power amount, it is necessary to resort to load switching. From the perspective of public utilities, these conventional methods are not necessarily the best solution. The purpose of the present invention is to stabilize the power system, which has almost no negative impact on power consumers and can also be expected to improve the reliability of power supply, by taking active measures for the power system configured as described at the beginning. The objective is to provide a method for

The purpose of this is that in a power system that has two systems separated from each other on the low-voltage side by multiple transformers synchronized on the high-voltage side, when one of the two systems fails, both The means for monitoring the opening/closing status of transformers and disconnectors in the system is based on the parallel access permission condition that is issued after the faulty transformer and disconnector is opened, and the means for monitoring the power flow in both systems is the same as the condition for parallel entry that is issued after the faulty transformer and disconnector are opened. In response to the parallel entry permission condition that occurs when the combined value of the transformer preliminary power flow of the system does not exceed the transformer capacity of the healthy system, the voltage vector difference between both systems is within the specified value and the faulty system's When it is directly or indirectly confirmed that the differential coefficient of frequency is negative, "by giving a closing command to the normally open system circuits and disconnectors installed in the two systems, both systems are reclosed on the low pressure side. This is achieved by

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of a system configuration to which the system stabilization method according to the present invention can be advantageously applied.

According to this, the high voltage side (X
A normally closed system connection or disconnection NC is provided between the two bus lines X, , X2 of the KV system), and two transformers T, ? T2 is striped, and a transformer T3 is connected to the busbar X2. Therefore, three transformers T. ~T3 is synchronized on the high voltage side. Low voltage side of transformer T, ~T3 (Yk
v system) has two bus lines Y,,Y2, one bus line Y
, are connected to system A, and the other bus Y2 is connected to system B, respectively. The low voltage sides of the two transformers T, T2 are connected to bus Y, which belongs to system A, and one is operated as a backup.

The low voltage side of the remaining transformer circle is connected to bus Y, which belongs to system B.
Connected to 2. The system connection and disconnector NO installed between the two buses Y and Y2 on the low voltage side are always open due to disconnection capacity or ground current.
Therefore, both systems A and B are separated from each other on the secondary side of the transformer. In addition, 1 to 14 are the breakers. In the system configuration shown in Figure 1, if a similar failure occurs on the high-voltage side (Xkv system) in the case of a failure in transformer T3, for example, the circuit breaker will be tripped, and system B becomes a single system.

If system B becomes an independent system, an imbalance within the system will occur. That is, the difference between the total generator output value 2PG and the total load value ZPL, △P=value 2PG-value 2PL, △P>
In the case of ○, the power supply capacity of the entire system will be insufficient, and △
If P<○, the power supply capacity of system B, which has become an independent system, will be insufficient. In such cases, conventionally the load is disconnected or the governor is operated, but in order to avoid this as much as possible in the present invention, the system is connected at all times and the disconnect switch is turned on.
Prevent system B from becoming an independent system. As shown in Figure 2, when calculating the phase difference angle fluctuation of system B under the condition of a short-circuit accident on the transformer T3 side, the Yubin generator first accelerates, and after the fault is removed, it decelerates and the phase difference angle returns to the original value. Show trends. Therefore, if the system is connected or the disconnector WO is turned on when a predetermined time T has elapsed after the occurrence of a transformer failure, both systems A and B at that time
The voltage vector difference between them is minute, and synchronous reparalleling can be smoothly executed. The parallel connection of both systems A and B on the low-voltage side by connecting the system or turning on the disconnection NO after an accident occurs is not only done after a predetermined time in which the voltage phases of both systems are expected to match, but also Needless to say, it is also possible and preferable to confirm the parallel entry conditions beforehand. Fig. 3 shows an example of the configuration of a control device for checking the re-parallel entry conditions in principle.

According to this, first. A monitoring element 21 is provided to check the sequence conditions for rejoining both systems A and B on the low-pressure side by switching on the system connection or disconnector NO.
In the case of this embodiment, the monitoring element 21' is a grid system under the conditions that, for example, the shield disconnectors 3 to 6 are closed and the shield disconnectors 7 and 8 are opened due to the occurrence of an accident. It emits a signal that allows communication and disconnection NO. In order to perform smoother re-paralleling, there is a voltage vector difference between both systems A and B! △
A monitoring element 22 for confirming that VI is below the specified value K, and a monitoring element 22 for confirming that the differential coefficient df/dt of the frequency f of the system B that does not have the approved transformer is negative. A monitoring element 23 is provided, and these monitoring elements 22,
The output signal of 23 is input to an AND gate 24, and the output signal of this AND gate 24 and the output signal of the aforementioned monitoring element 21 are input to an AND gate 25.

When predetermined conditions in the monitoring elements 21 to 23 are simultaneously satisfied, the system connection or disconnection N from the AND gate 25 is activated.
A signal instructing the injection of O is issued. In addition, it is preferable to provide a preliminary power flow monitoring element 26 and a hold circuit 27 so that the output signal of the hold circuit 27 is input to the AND gate 25.

This monitoring element 26 controls the power flow P, , P of each transformer T, ~T3.
2, P3 is detected taking into account the direction (see Fig. 1), and the capacitance P.2 of the transformers T, , T2 is detected. o, P2. (KVA) is subjected to the calculation process ΔP=P, o+P2o−(P, 10P20P3), and it is checked whether ΔPZO is satisfied.

The hold circuit 27 constantly follows the output signal of the monitoring element 26, and shifts to a hold operation as soon as a failure occurrence signal is received. Trend P. , P2, and P3 do not satisfy the condition that △PZO, and when the transformer L on the system B side fails, if both systems are parallelized on the low voltage side, the power flow of the healthy side transformers T, , T2 will exceed, If the above conditions are not satisfied, the system communication or disconnection NO closing command is blocked. As a modification of monitoring elements for power flow conditions, for example, when transformer T3 on the system B side fails, if both systems are connected in parallel on the low voltage side, the healthy transformer T. , T2, it is possible to cut off the load equivalent to the excess power flow before or after turning on the system connection or disconnector NO.

In this case, for example, ΔP:P.

The calculation 10P2o-(P, 10P20P3> is always performed, and if △P<○, the load corresponding to △P must be cut off in advance before contacting the grid or turning on the disconnection NO. After satisfying the conditions of △P and ○, you can connect the system or turn on the disconnector NO. Alternatively, you can connect the system or turn on the disconnector after giving a closing command to it, then load and disconnect. As described above, according to the present invention, when a similar failure occurs in the transformer of one of the two systems, the always-open system connection or disconnector on the low voltage side By introducing the system, both systems are connected in parallel, thereby preventing the system on the faulty side from becoming an isolated system, making it possible to avoid load interruptions as much as possible, and with almost no negative impact on electricity consumers. , the reliability of power supply can be increased.

Brief Explanation of the Drawings Figure 1 shows an example of a system configuration to which the method of the present invention can be applied, Figure 2 is an auxiliary diagram for explaining the method of the present invention, and Figure 3 shows the method of the present invention. An example of the basic configuration of a control device for implementing the following is shown.

X,, X2...High voltage side bus bar, Y,, Y2......Low voltage side bus bar, T, ~ T3......Transformer, A, B...
・0 line, NC: Always-closed system connection or disconnection, NO: Always-open system connection or disconnection, 1 to 1
4...Shield breaker, 21...Re-entry sequence condition monitoring element, 22...Voltage vector difference monitoring element, 23...Frequency fluctuation differential coefficient monitoring element, 2
4, 25...AND gate, 26...Preliminary power flow monitoring element, 27...Hold circuit. Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] 1 In a power system that has two systems separated from each other on the low voltage side by multiple transformers synchronized on the high voltage side, when one of the two systems fails, the transformer of both systems The means to monitor the opening/closing status of the transformer and disconnector is the parallel access permission condition that is issued after the transformer on the faulty side is opened, and the means to monitor the power flow in both systems is the transformer in both systems immediately before the failure occurs. In response to the parallel entry permission condition that is issued when the composite value of the power flow before the transformer does not exceed the transformer capacity of the healthy side system,
When it is confirmed directly or indirectly that the voltage vector difference between the two systems is within the specified value and the differential coefficient of the frequency of the faulty system is negative, the normally open system installed in the two systems is A system stabilization method characterized in that both systems are reclosed on the low pressure side by giving a closing command to the disconnector.