JPH05122835A - Reverse power flow preventer for power system - Google Patents

Abstract

PURPOSE:To reduce facility cost of lower substation by preventing reverse power flow due to the unbalance of load of double bus upon opening of bus circuit breaker without providing a reverse power re lay. CONSTITUTION:A power system wherein power is received at a lower substation 20 through double transmission lines 7, 8 from an upper substation 1 with a bus circuit breaker 25 being connected between buses B1, B2 is provided with a reverse power flow notifying contact 4a which closes when the current flowing through the bus circuit breaker 2S exceeds a set value determined by the capacity of transmission line, circuit breakers 2R, 5R, 6R located at the power receiving terminals of respective transmission lines and close at the time of double line power receiving, and means for disabling opening of the bus circuit breaker 2S on conditions that the reverse power flow notifying contact 4a and the circuit breakers 2R, 5R, 6R are closed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the operation of a mother circuit breaker in an upper substation in order to prevent reverse power flow returning from a lower substation on the load side to an upper substation having a double bus configuration in an electric power system. The present invention relates to a reverse power flow prevention device that limits the flow of a reverse power flow and quickly detects and shuts it off.

[0002]

2. Description of the Related Art A two-line power receiving system is widely used as a power system blackout preventive measure. However, if a main circuit breaker is opened in a host substation having a double bus during simultaneous power reception of two lines, the transmission line And reverse power flow may flow toward the upper substation through the lower substation on the power receiving side. This power flow is determined by the power rating of the upper substation, so depending on the rating, a current that exceeds several times the rating of the lower substation will flow, causing equipment overload, and the operation of the overcurrent relay installed in each transmission line. Due to this, there was a risk that both of the power transmission lines would trip, resulting in a total blackout of the facility. Therefore, as an example of conventional reverse power flow prevention measures, some substations have a reverse power relay installed in the power receiving line, and when reverse power flow is detected, one of the receiving end circuit breakers is tripped by the reverse power relay and the power receiving line is set to 1 The method of blocking the reverse flow by using a line is adopted.

[0003]

SUMMARY OF THE INVENTION In the above conventional method,
The reverse power relay itself is relatively expensive, and it is meaningless unless the reverse power relay is installed in two lines of the power receiving line, resulting in a problem of increased equipment cost. Further, since it is necessary to measure the voltage in order to know the direction of the tidal current, it is necessary to provide an instrument transformer or the like, which also contributes to the high cost. Even in this case, a two-line trip cannot be avoided depending on the settling, so the installation of a reverse power relay was the only absolute countermeasure.

The present invention has been made to solve the above problems, and its purpose is to prevent the occurrence of reverse power flow or to detect it immediately without using an expensive reverse power relay or the like. It is to provide a reverse flow prevention device that can be shut off.

[0005]

In order to achieve the above object, a first aspect of the present invention is to provide a first and a second transmission from an upper substation in which a bus breaker is connected between each bus having a double bus configuration. In a power system that receives two lines at a lower substation via an electric wire,
A reverse power flow advance notice contact point that closes when the current flowing through the main circuit breaker exceeds a set value determined by the capacity of the transmission line, a circuit breaker at each receiving end of each transmission line that closes when receiving two lines, and It is provided with means for prohibiting the opening of the mother circuit breaker under the interlock condition that the power flow advance notice contact and the circuit breaker at the receiving end of each transmission line are closed.

A second aspect of the present invention is to install a power line in each of the power lines in the above power system, and detect a reverse flow flowing toward the upper substation through the respective transmission lines and the lower substation when the main circuit breaker is opened. The reverse power flow detection means and the circuit breaker installed on each power transmission line and one of which is opened by the reverse power flow detection means are provided.

[0007]

According to the first aspect of the present invention, the first condition that the lower substation is receiving two lines and the current flowing through the main circuit breaker of the upper substation exceeds the set value determined by the capacity of the transmission line. By prohibiting the opening of the master circuit breaker by using the second condition as the interlock condition, the occurrence of reverse power flow due to the opening of the mother circuit breaker is prevented.

According to the second aspect of the invention, when the mother circuit breaker is opened and a reverse power flow flowing through the transmission line is detected, for example, by opening the transmission end circuit breaker of one line in the upper substation, Block reverse power flow. At this time, since the other line is sound, there is no power failure on the load side.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the first invention together with a system configuration. In the figure, 1 is an upper substation on the side of the system power supply, and this upper substation 1 has a double bus line configuration consisting of bus lines B1 and B2. A mother circuit breaker 2S is connected between these bus lines B1 and B2.
The current flowing through S is taken into the ammeter with contacts (meter relay) 4 via the current transformer 3, and the current flowing through the mother breaker 2S exceeds the set value determined by the capacity of the transmission line to be protected. At this time, the reverse power flow advance notice contact 4a is configured to be closed.

A first power transmission line 7 having circuit breakers 5S and 5R installed at both ends is connected to the bus B1, and a second power transmission line 7 having circuit breakers 6S and 6R installed at both ends to the bus B2. 8
Are connected. The receiving ends of these power transmission lines 7 and 8 are
In the lower substation 20, they are respectively connected to the lower bus B3 having the circuit breaker 2R. Here, when the lower substation 20 is unmanned, the circuit breakers 5R, 6R,
The state of 2R is sent to the upper substation 1 by the remote monitoring control device (T / C). In FIG. 1, 9 is a circuit breaker and 10 is a distribution transformer.

Next, the reverse power flow preventing operation in this embodiment will be described. Now, if the loads on the buses B1 and B2 are biased while the two lines are being received by the power transmission lines 7 and 8, a tidal current flows between the buses B1 and B2 via the mother circuit breaker 2S at the upper substation 1. If the mother circuit breaker 2S is opened at this time, the tidal current flows to the lower substation 20 via the power transmission line 7 and returns to the upper substation via the lower bus B3 and the power transmission line 8 (reverse power flow (see FIG. 1). (Refer to the broken line) may occur.

In this embodiment, the reverse power flow is prevented by the following operation without opening the breaker 6R by the current transformer 31 and the reverse power relay 32 shown by the broken line in FIG. 1 as in the conventional case. And That is, the transmission lines 7 and 8 to be protected by the current flowing through the mother circuit breaker 2S of the upper substation 1
When it exceeds the set value determined by the capacity of, the ammeter 4 with a contact detects this via the current transformer 3. Then, by closing the reverse power flow advance contact 4a, the driver is notified as an alarm that there is a danger of reverse power flow.

On the other hand, the mother circuit breaker 2S is designed so that its operation is suppressed under the interlock condition as shown in FIG. That is, as the first condition, the transmission lines 7 and 8
Therefore, the lower substation 20 is receiving two lines (the circuit breakers 2R, 5R, and 6R are closed), and the second condition is that the contact 4a is closed. The operation of the relay that drives the circuit breaker 2S is suppressed, and opening of the mother circuit breaker 2S is prohibited. Here, the states of the circuit breakers 2R, 5R, and 6R are grasped at the upper substation 1 by the remote monitoring control device (T / C) as described above.

If the mother circuit breaker 2S is operated via the supervisory control computer, a similar interlock circuit can be realized as a software sequence. Further, when the load of each feeder is measured by the supervisory control computer in the upper substation 1, it is possible to calculate the load bias.

As described above, according to this embodiment, the reverse power flow is prevented from occurring by prohibiting the opening of the mother circuit breaker 2S when the reverse power flow is likely to occur. There is an advantage that it is not necessary to provide an expensive reverse power relay at the place 20, and the space for installing this relay, a transformer for instruments, a current transformer, etc. can be reduced.

Next, FIG. 3 shows an embodiment of the second invention. The same components as those of the embodiment of FIG. 1 are denoted by the same reference numerals and detailed description thereof is omitted. Hereinafter, different parts will be mainly described. In this embodiment, the current transformer in the upper substation 1 in FIG. 3, ammeter 4 with contacts and reverse power flow advance notice contact 4a have been removed. On the other hand, a current transformer 11,
13 are installed, and overcurrent direction relays 12 and 14 are connected to these current transformers 11 and 13, respectively. The current transformers 11 and 13 and the overcurrent direction relay 1
Reference numerals 2 and 14 constitute reverse power flow detecting means.

Next, the reverse power flow preventing operation in this embodiment will be described. Here, conventionally, when a reverse power flow occurs, the circuit breaker in the lower substation 20, for example, 6R, is opened by the reverse power relay. However, the reverse power flow is blocked by the circuit breaker in the lower substation 20. The circuit breaker in the upper substation 1 is not limited to this. Therefore, in the present embodiment, the load of the busbars B1 and B2 is biased during the two-line power reception, the tidal current flows, and the busbar breaker 2S is opened and installed at the power transmission ends of the power transmission lines 7 and 8. The current transformers 11 and 13 and the overcurrent direction relays 12 and 14 detect an overcurrent due to reverse power flow in the direction of flowing into the busbar B1 or B2, and any one of the circuit breakers 5S and 6S at the power transmission end, For example, by opening 6S, excessive reverse power flow is cut off for the transmission lines 7 and 8 and the lower substation 20. In addition, it is either one of the circuit breakers 5S and 6S that is opened,
Since the other transmission line is sound, there will be no power outage on the load side.

In this embodiment, in addition to the existing overcurrent relays (not shown) used to protect the transmission lines 7 and 8 in the upper substation 1, overcurrent direction relays 12 and 14 are required. An existing one can be used for the current detection element such as. If a digital relay is already installed in the upper substation 1, the bus B1 or B2
It is possible to realize a reverse current prevention relay having the same function by simply adding on software the directional element that detects the tidal current flowing into the power transmission line and the overcurrent element that considers the capacity of the transmission lines 7 and 8. There is no need to modify the hardware such as the board.

[0019]

As described above, in the first aspect of the invention, the first condition that the lower substation receives two lines and the current flowing through the mother breaker of the upper substation are determined by the capacity of the transmission line. The second condition of exceeding the set value is used as an interlock condition to prohibit the opening of the master circuit breaker to prevent the occurrence of reverse power flow due to the opening of the mother circuit breaker. For this reason, it is possible to prevent the occurrence of reverse power flow without using an expensive reverse power relay, and it is possible to improve the economical efficiency and safety accompanying the reduction of the equipment of the lower substation. Further, in the upper substation, the present invention can be realized only by setting an existing ammeter with an ammeter with a contact or the like and setting a predetermined interlock condition, so that no major modification of equipment is required.

In the second invention, when the reverse power flow flowing through the power transmission line is detected by opening the main circuit breaker, the reverse power flow is detected, for example, by opening the power transmission end circuit breaker of one line at the upper substation. Can be shut off. Therefore, the expensive reverse power relay is not required as in the first invention. In addition,
The upper substation needs to be equipped with an overcurrent direction relay as reverse power flow detection means, but as mentioned above, existing ones can be used for the current detection elements, etc. However, the amount of equipment to be added is practically small, and there is an effect that the burden on the transformer is not so large.

In any of the inventions, since at least one line can be always received, there is no possibility of causing a total power failure on the load side.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the first invention together with a system configuration.

FIG. 2 is an explanatory diagram of an interlock condition for prohibiting opening of a master circuit breaker in the embodiment of FIG.

FIG. 3 is a diagram showing an embodiment of the second invention together with a system configuration.

[Explanation of symbols]

 1 High-order substation 2S Mother circuit breaker 3, 11, 13 Current transformer 4 Ammeter with contact (meter relay) 4a Reverse power flow advance notice contact 2R, 5S, 5R, 6S, 6R, 9 Circuit breaker 7, 8 Transmission line 10 Distribution transformer 12,14 Overcurrent direction relay 20 Lower substation B1, B2 Bus B3 Lower bus

Claims (2)

[Claims] 1. A power system in which two lines are received at a lower substation from a higher substation through first and second transmission lines from a higher substation in which a bus breaker is connected between each bus having a double bus configuration. A reverse power flow advance notice contact that closes when the current flowing through the continuous circuit breaker exceeds a set value determined by the capacity of the power transmission line; a circuit breaker at each power receiving end of each power transmission line that closes when receiving two lines; Reverse power flow in a power system characterized by including means for prohibiting the opening of the master circuit breaker on the condition that the contact for notice and the circuit breaker at the receiving end of each transmission line are closed, as an interlock condition. Prevention device. 2. A power system in which two lines are received at a lower substation from a higher substation, in which a bus breaker is connected between each bus having a double bus configuration, via a first and a second transmission line, Reverse power flow detection means installed in each transmission line to detect reverse power flow toward the upper substation through each transmission line and lower substation when the main circuit breaker is opened, and reverse power flow detection means installed in each transmission line. A reverse power flow prevention apparatus in a power system, comprising: a circuit breaker, one of which is opened by a power flow detection means.