Circuit applicable to switching overvoltage suppression of shunt reactor reactive power compensation device

Abstract

The invention belongs to the technical field of electrical engineering, and particularly relates to a circuit suitable for switching overvoltage suppression of a shunt reactor reactive power compensation device, and a shunt reactor group interval comprises a main isolation switch QS1, a switching branch circuit breaker QF, a current transformer CT and a lightning arrester MOA; the head end of the main isolating switch QS1 is connected to a main transformer low-voltage bus M, and the tail end of the main isolating switch QS1 is sequentially connected in series with the current transformer CT and the reactor group and then is grounded; the lightning arrester MOA is connected in parallel between the head end of the reactor group and the ground; the suppression branch circuit is formed by connecting a suppression branch circuit breaker QF1, a resistor R and a capacitor C in series; and the suppression branch circuit is connected in parallel with the switching branch circuit where the switching branch circuit breaker QF is located. Operating overvoltage can be effectively damped and absorbed, and the threat of the operating overvoltage to insulation of the reactor set is remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of electrical engineering technology, specifically relating to a circuit for overvoltage suppression when switching a reactive power compensation device for a parallel reactor. Background Technology

[0002] With the rapid increase in the proportion of cable lines in power systems, the focus of reactive power balance is gradually shifting from traditional capacitor compensation to reactor compensation. However, there are currently no unified technical specifications for the capacity configuration, layout principles, and operation management of parallel reactor groups. As a result, many reactor groups put into operation in the early stages remain idle for a long time after the substations are built, lacking the necessary experience in switching operations.

[0003] As the service life increases, the insulation performance of reactor banks and their supporting equipment gradually ages. In particular, the reignition characteristics of circuit breakers and the insulation withstand capability of the reactors themselves become key factors affecting system safety. According to statistics, in recent years, overvoltage accidents caused by switching on and off parallel reactor banks account for 70% to 80% of all overvoltage accidents in the power system, seriously threatening the stable operation of power equipment.

[0004] Currently, common measures to suppress overvoltage during switching of shunt reactors include: selecting circuit breakers with extremely low re-ignition rates, limiting the current-cutting level of circuit breakers, installing metal oxide surge arresters (MOAs), and installing RC absorption devices. Among these, RC absorption devices, which connect a series resistor and a capacitor in parallel between the reactor bank and ground, have been proven to be an effective overvoltage suppression method.

[0005] However, during long-term parallel operation, the resistive elements of existing RC absorption devices continuously generate heat, especially in the early-designed reactor rooms where the space is small and ventilation and heat dissipation conditions are poor, resulting in excessive temperature rise of the device, posing a fire hazard, and also increasing operation and maintenance costs.

[0006] Therefore, how to effectively suppress switching overvoltage while avoiding continuous heating of the device under non-switching conditions has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a circuit suitable for overvoltage suppression during switching of a shunt reactor reactive power compensation device, so as to solve the problems existing in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a circuit suitable for overvoltage suppression during switching of a shunt reactor reactive power compensation device, wherein the shunt reactor group includes a main disconnect switch QS1, a switching branch circuit breaker QF, a current transformer CT, and a surge arrester MOA; the first end of the main disconnect switch QS1 is connected to the low-voltage bus M of the main transformer, and its end is connected in series with the current transformer CT and the reactor group before being grounded; the surge arrester MOA is connected in parallel between the first end of the reactor group and the ground; It also includes a suppression branch, which is composed of a suppression branch circuit breaker QF1, a resistor R and a capacitor C connected in series; the suppression branch is connected in parallel with the switching branch where the switching branch circuit breaker QF is located. The suppression branch circuit breaker QF1 and the switching branch circuit breaker QF are linked for control: When the reactor group branch needs to be closed, the suppression branch circuit breaker QF1 closes first, and then the switching branch circuit breaker QF closes again, so that the resistor R and capacitor C are put into operation during the closing process of QF to suppress overvoltage; after QF is closed, QF1 is opened. When the reactor group branch needs to be tripped, the suppression branch circuit breaker QF1 is closed first, and then the switching branch circuit breaker QF is tripped, so that the resistor R and capacitor C are put into operation during the tripping process of QF to suppress overvoltage; after QF is tripped, QF1 is tripped.

[0009] Preferably, the suppression branch is only put into operation during the transient process when the circuit breaker QF of the switching branch performs a closing or opening operation; when QF is in a stable closing or stable opening state, the suppression branch is in an open state.

[0010] Preferably, the circuit further includes a controller for acquiring the status signals of the switching branch circuit breaker QF and the suppression branch circuit breaker QF1, and outputting linkage control commands according to the predetermined closing / opening logic to control the opening and closing sequence of QF1 and QF.

[0011] Preferably, the suppression branch is modified from an existing parallel resistor-capacitor absorption device. The modification method is to connect the suppression branch circuit breaker QF1 in series between the first end of the original series branch of resistor R and capacitor C and the low-voltage bus M of the main transformer.

[0012] Preferably, the resistor R is a resistor cage and the capacitor C is an oil-immersed capacitor.

[0013] The beneficial effects of this invention are as follows: By setting up a resistor-capacitor suppression branch connected in parallel with the main switching branch and controlled by the circuit breaker, and employing a "first-in, then-out" linkage control logic, the suppression circuit is precisely engaged during the transient process of the circuit breaker's opening and closing. This effectively dampens and absorbs operational overvoltages, significantly reducing their threat to the insulation of the reactor group. Simultaneously, this suppression branch is disconnected after the reactor group enters a stable operating or disconnected state, fundamentally avoiding the continuous heating problem caused by the long-term energization of the resistive element. This solves the safety hazard of temperature rise caused by poor heat dissipation in existing RC absorption devices within confined spaces, significantly improving the safety and reliability of the system operation.

[0014] The beneficial effects of this invention are also reflected in its high engineering practicality and economy. This circuit can be easily modified from widely used existing RC snubber devices, requiring only the addition of a circuit breaker in series with a simple controller. The modification work is minimal, cost-effective, and easy to implement, greatly reducing the technical barriers to modification and operation and maintenance costs. This design not only effectively balances overvoltage suppression and low-power operation, but also provides an efficient and reliable technical path for upgrading reactive power compensation devices in existing substations, possessing extremely high promotional value. Attached Figure Description

[0015] Figure 1 This is a structural diagram of the device of the present invention; Figure 2 This is the control logic diagram of the present invention. Detailed Implementation

[0016] In the description of this disclosure, it should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0017] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0018] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0019] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments. Example

[0020] refer to Figure 1 This embodiment provides a complete overvoltage suppression circuit for a shunt reactor reactive power compensation device. The circuit is connected to the low-voltage bus M of the main transformer and mainly includes two parallel branches: a switching branch and a suppression branch.

[0021] The switching branch is the main circuit of the reactor group, and its electrical connection is as follows: the first end of the disconnecting switch QS1 is connected to the low-voltage bus M of the main transformer, and its end is connected in series with the current transformer CT, the switching branch circuit breaker QF, and the reactor group L. The other end of the reactor group L is grounded. The surge arrester MOA is connected in parallel between the first end of the reactor group L (i.e., the connection point of QF and L) and the ground to limit extreme overvoltages.

[0022] The suppression branch is the core improvement of this invention, and it consists of a suppression branch circuit breaker QF1, a resistor R, and a capacitor C connected in series. One end of this suppression branch is connected to the end of the main disconnecting switch QS1 (i.e., the busbar M side), and the other end is connected to the connection point between the switching branch circuit breaker QF and the reactor group L. Therefore, the suppression branch and the reactor group L are connected in parallel.

[0023] The key to this invention lies in the linkage control logic between the suppression branch circuit breaker QF1 and the switching branch circuit breaker QF. This logic is executed by a controller (not shown in the figure, but can be a PLC or a dedicated relay protection device). The controller collects the opening and closing states of QF and QF1 in real time through a switch state sampling device and issues commands to control their action sequence. The specific process is as follows: Figure 2 As shown: Closing operation procedure (connecting the reactor bank): When the system needs to activate reactor group L, the controller first issues a closing command to close the suppression branch circuit breaker QF1. At this time, the RC snubber device composed of resistor R and capacitor C is pre-activated in the circuit.

[0024] After QF1 is confirmed to be closed, the controller issues a command to close the switching branch circuit breaker QF. During the closing process of QF, since QF1 is already closed, the inrush current and operational overvoltage will be effectively damped and absorbed by the RC branch.

[0025] After QF closes stably and the reactor bank L enters normal operation, the controller delays for a short time (e.g., 0.5-2 seconds) to ensure the transient process ends, and then issues a trip command to disconnect the suppression branch circuit breaker QF1. At this point, the suppression branch is taken out of operation, avoiding the problem of continuous overheating of resistor R during long-term operation of the reactor bank.

[0026] Tripping operation procedure (disconnection of reactor bank): When the system needs to disconnect reactor group L, in order to prevent overvoltage from being generated due to current cutting or reignition when QF is tripped, the controller first issues a closing command, then closes the suppression branch circuit breaker QF1 again, and puts the RC branch into operation.

[0027] After QF1 is confirmed to be closed, the controller issues a command to disconnect the switching branch circuit breaker QF. During the opening process of QF, the RC branch provides a release path for the electromagnetic energy stored in the system, effectively suppressing overvoltage.

[0028] Once QF is stably tripped and reactor group L is completely disconnected, the controller immediately issues a tripping command to disconnect the suppression branch circuit breaker QF1, thus restoring the suppression branch to its open state.

[0029] Through the above-mentioned linkage control, the resistor R and capacitor C only work during the transient process of switching operation (usually within a few seconds), perfectly balancing the two major requirements of "effectively suppressing overvoltage" and "avoiding heat generation during long-term operation". Example

[0030] This embodiment, as a preferred implementation of the present invention, focuses on illustrating how to carry out low-cost retrofitting of existing substations.

[0031] In many early-built substations, a fixed RC snubber device (i.e., a series branch of resistor R and capacitor C) was installed in parallel between the reactor bank and ground to suppress overvoltage. The circuit of this invention can be easily modified based on this existing configuration.

[0032] The specific modification method is as follows: In the existing RC absorption branch, the connection point between its first end and the end of the main disconnecting switch QS1 is disconnected, and then an additional circuit breaker, namely the suppression branch circuit breaker QF1 in this invention, is connected in series at this point. At the same time, a new controller is added, and the auxiliary contact signal of the original switching branch circuit breaker QF and the control circuit of the newly added QF1 are connected to the controller, and the linkage control logic program as described in Example 1 is written or set.

[0033] This renovation scheme does not require changes to the original main wiring structure or replacement of large resistor and capacitor equipment. It only adds a circuit breaker and a control unit. The renovation workload is small, the construction period is short, the on-site implementation is strong, and the economic benefits are significant. It is particularly suitable for the technical upgrade of the reactive power compensation device of the existing shunt reactor in the substation.

[0034] It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A circuit for overvoltage suppression during switching in a shunt reactor reactive power compensation device, characterized in that, The parallel reactor group includes a main disconnect switch (QS1), a switching branch circuit breaker (QF), a current transformer (CT), and a surge arrester (MOA); the first end of the main disconnect switch (QS1) is connected to the low-voltage busbar (M) of the main transformer, and its end is connected in series with the current transformer (CT) and the reactor group before being grounded; the surge arrester (MOA) is connected in parallel between the first end of the reactor group and the ground; It also includes a suppression branch, which is composed of a suppression branch circuit breaker (QF1), a resistor (R), and a capacitor (C) connected in series; the suppression branch is connected in parallel with the switching branch where the switching branch circuit breaker (QF) is located; The suppression branch circuit breaker (QF1) and the switching branch circuit breaker (QF) are linked for control: When the reactor group branch needs to be closed, the suppression branch circuit breaker (QF1) closes first, and then the switching branch circuit breaker (QF) closes again, so that the resistor (R) and capacitor (C) are put into operation during the closing process of QF to suppress overvoltage; after QF is closed, QF1 is opened. When the reactor group branch needs to be tripped, the suppression branch circuit breaker (QF1) is closed first, and then the switching branch circuit breaker (QF) is tripped, so that the resistor (R) and capacitor (C) are put into operation during the tripping process of QF to suppress overvoltage; after QF is tripped, QF1 is tripped.

2. The circuit according to claim 1, characterized in that, The suppression branch is only put into operation during the transient process when the switching branch circuit breaker (QF) performs closing or opening operations; when QF is in a stable closing or stable opening state, the suppression branch is in an open state.

3. The circuit according to claim 1 or 2, characterized in that, The circuit also includes a controller for acquiring the status signals of the switching branch circuit breaker (QF) and the suppression branch circuit breaker (QF1), and outputting linkage control commands according to the predetermined closing / opening logic to control the opening and closing sequence of QF1 and QF.

4. The circuit according to claim 1, characterized in that, The suppression branch is modified from the existing parallel resistor-capacitor absorption device. The modification method is to connect the suppression branch circuit breaker (QF1) in series between the first end of the original series branch of resistor (R) and capacitor (C) and the low-voltage bus (M) of the main transformer.

5. The circuit according to claim 1, characterized in that, The resistor (R) is a resistor cage, and the capacitor (C) is an oil-immersed capacitor.

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