Automatic switching circuit of low-voltage single bus reactive power compensation device

Abstract

The utility model belongs to the electrical design technical field, specifically discloses automatic switching circuit of low -voltage single bus reactive power compensation device, the current transformer 1BC2 and 2BC2 are installed on the mother circuit of circuit, and the closed loop is formed in series with power factor controller 1PFC after the parallel connection of current transformer 1BC1 and 1BC2 output, and power factor controller 1PFC is electrically connected with the reactive power compensation device on the section I bus, the closed loop is formed in series with power factor controller 2PFC after the parallel connection of current transformer 2BC1 and 2BC2 output, and power factor controller 2PFC is electrically connected with the reactive power compensation device on the section II bus, the utility model has the characteristics of simple circuit, less investment, safe and reliable.

Description

Technical Field

[0001] This utility model relates to the field of electrical design technology, specifically to an automatic switching circuit for a low-voltage single busbar reactive power compensation device that is simple in circuitry, requires little investment, and is safe and reliable. Background Technology

[0002] A typical single-busbar segmented low-voltage power distribution system, such as Figure 1 As shown, two transformers supply power to primary and secondary loads, each capable of handling the full load. Under normal operation, the two transformers operate separately, with the low-voltage bus tie circuit breaker 3QA disconnected, and the automatic power factor compensation devices connected to their respective busbars activated. When one transformer (e.g., ...) is in operation... Figure 1 When the 2TA is out of operation, the incoming circuit breaker (such as...) Figure 1 When the 2QA transformer is disconnected, the 3QA transformer is closed, and then the entire load is transferred to another transformer (such as...). Figure 1 Power is supplied via 1TA (with the incoming circuit breaker 1QA closed simultaneously). Since there is no current in the second incoming line and the power factor controller on section II busbar is not operational, the capacitor bank on this section busbar will be disconnected. If the capacitor bank connected to section I busbar is insufficient to compensate for all reactive loads on both busbars, the power factor requirement of greater than 0.92 will not be met. While configuring the compensation capacitors for each busbar to compensate for all reactive loads could solve the above problem, it would also result in some reactive power compensation devices being idle for extended periods, leading to increased investment, which is neither economical nor reasonable.

[0003] In the prior art, to solve the above problems, there is a patent CN112865126B entitled "Shared Sampling Current Circuit of Reactive Power Compensation Device for Low-Voltage Single Busbar Sectional System". This patent adds two intermediate relays to the low-voltage cabinet, connects the wiring of the two incoming circuit breakers and the bus tie circuit breaker, and connects the auxiliary contacts of these two intermediate relays to the sampling current transformer of the reactive power compensation device. This allows the reactive power compensation devices in the low-voltage single busbar sectional system to share the sampling current, thus enabling the provision of sufficient reactive power compensation capacity under various operating conditions. While this patent can provide sufficient reactive power compensation capacity, the control circuit is complex due to the need to ensure the current transformer remains uncircuited and the sampling current is shared, reducing its reliability. Furthermore, since the sampling current is the total current and simultaneously supplies two reactive power compensation control devices, it cannot guarantee that the capacity provided by each compensation device matches the required compensation capacity of the busbar section, making precise control of the capacity provided by each compensation device impossible.

[0004] In the existing technology, there is also a patent CN215835134U entitled "A Configuration Device for Saving Reactive Power Compensation Capacity in a Single Busbar Segmented Low-Voltage Power Distribution System." This patent adds a relay to the control circuit, with the relay's auxiliary contacts connected to the compensation device's operation circuit, enabling the provision of sufficient reactive power compensation capacity under various operating modes. While this patent can provide sufficient reactive power compensation capacity and ensure that the capacity provided by each compensation device matches the required compensation capacity for the current busbar segment, its control circuit remains relatively complex, and the control process is also quite cumbersome.

[0005] Therefore, researching an automatic switching circuit for a low-voltage single busbar reactive power compensation device is crucial. This circuit can achieve reactive power compensation for various operating modes of low-voltage single busbar segments with a relatively simple circuit, while also saving reactive power compensation capacity and improving safety and reliability. It is one of the key technologies that urgently needs to be solved in current low-voltage power distribution systems with single busbar segments. Utility Model Content

[0006] To address the problems existing in the prior art, this utility model provides an automatic switching circuit for a low-voltage single busbar reactive power compensation device that is simple in design, requires less investment, and is safe and reliable.

[0007] The automatic switching circuit of the low-voltage single busbar reactive power compensation device of this utility model is implemented as follows: The low-voltage single busbar reactive power compensation device includes a busbar section I and a busbar section II. A bus tie circuit is provided between the busbar section I and the busbar section II through a bus tie circuit breaker 3QA. Corresponding reactive power compensation devices are respectively configured on the busbar section I and the busbar section II. The primary winding of a current transformer 1BC1 is installed on one incoming line of the busbar section I, and the primary winding of a current transformer 2BC1 is installed on the two incoming lines of the busbar section II. The bus tie circuit is equipped with the primary windings of current transformer 1BC2 and current transformer 2BC2. The automatic switching measurement circuit includes measurement circuit I and measurement circuit II. Measurement circuit I consists of a closed loop formed by connecting the secondary windings of current transformer 1BC1 and current transformer 1BC2 in parallel and then connecting them in series with power factor controller 1PFC. The connection terminal of the secondary winding of current transformer 1BC1 is grounded to the connection terminal of power factor controller 1PFC. Power factor controller 1PFC is electrically connected to the reactive power compensation device configured on bus section I. Measurement circuit II consists of a closed loop formed by connecting the secondary windings of current transformer 2BC1 and current transformer 2BC2 in parallel and then connecting them in series with power factor controller 2PFC. The connection terminal of the secondary winding of current transformer 2BC1 is grounded to the connection terminal of power factor controller 2PFC. Power factor controller 2PFC is electrically connected to the reactive power compensation device configured on bus section II.

[0008] Furthermore, the primary windings of current transformer 1BC1 and current transformer 2BC1 are simultaneously installed on any one of the three phases A, B, and C, and the primary windings of current transformer 1BC2 and current transformer 2BC2 have opposite polarities.

[0009] Furthermore, the primary windings of the current transformer 1BC1 and the current transformer 1BC2 are both installed in the same phase and have opposite polarities.

[0010] Furthermore, the primary windings of the current transformer 2BC1 and the current transformer 2BC2 are both installed in the same phase but with opposite polarities.

[0011] Furthermore, the primary windings of current transformer 1BC1 and current transformer 1BC2 have the same transformation ratio, and the primary windings of current transformer 2BC1 and current transformer 2BC2 have the same transformation ratio.

[0012] Furthermore, the reactive power compensation capacity of the reactive power compensation devices configured in each of the I-section busbar and the II-section busbar is determined by the power factor detected by the power factor controller 1PFC and the power factor controller 2PFC corresponding to each busbar segment during operation.

[0013] Furthermore, the primary windings of the current transformer 1BC2 and the current transformer 2BC2 are installed at the same end of the bus tie circuit breaker 3QA or connected in series at the front and rear ends of the bus tie circuit breaker 3QA.

[0014] The beneficial effects of this utility model are as follows: 1. In terms of simplifying the circuit structure, compared with the existing technology that requires the addition of multiple intermediate relays (such as CN112865126B) or complex relay circuits (such as CN215835134U) to achieve reactive power compensation control, this utility model achieves current vector synthesis by installing specific current transformers (1BC2, 2BC2) in the bus tie circuit and designing a measurement circuit composed of the incoming current transformer and the bus tie current transformer connected in parallel. No additional relay components or complex control circuits are required. This not only greatly simplifies the structure of the control circuit, but also completely eliminates the risk of relay contact sticking, coil burnout and other faults, and improves the long-term stability of the automatic switching circuit.

[0015] 2. Regarding the improvement of compensation accuracy, this utility model, when both incoming lines are operating simultaneously and the single busbar is running in sections, allows the power factor controllers of the two busbar sections to independently control the compensation devices based on the current signals from their respective incoming line current transformers, ensuring that the compensation capacity of each busbar section matches its own load requirements. When only one incoming line is operating and the single busbar is not running in sections, the measuring circuit provides an accurate signal to the corresponding power factor controller through the vector sum current output from the current transformers (1BC2, 2BC2) installed in the bus tie circuit. Similarly, precise control can also be achieved when both incoming lines are operating and the single busbar is not running in sections. This not only enables the operation of the two reactive power compensation devices when both transformers are running in sections, but also ensures that when any transformer supplies power to both busbar sections simultaneously, the compensation capacity on both busbar sections always matches the real-time load of each busbar section. This saves reactive power compensation capacity and effectively avoids the problems of low power factor or idle devices caused by mismatch between compensation capacity and demand in existing technologies, ensuring that the power factor remains stable above 0.92 under various operating modes.

[0016] 3. In terms of economic optimization, this utility model does not require configuring compensation capacitors for each bus section according to the total reactive load as in the prior art. The compensation devices of each bus section can be flexibly put into operation according to the actual operating mode, which reduces the redundant configuration of compensation capacity, avoids the situation of some devices being idle for a long time, significantly reduces the initial investment cost, and improves the equipment utilization rate.

[0017] 4. Regarding enhanced safety and reliability, this utility model simplifies the circuit structure, reduces potential fault points, and lowers the probability of failure due to circuit complexity. Furthermore, by rationally designing the polarity and transformation ratio of the current transformer, it ensures the accuracy and stability of current signal acquisition, avoids risks such as open circuits of the current transformer, and further enhances the safety and reliability of the entire reactive power compensation system. It can stably adapt to various operating conditions of a single-bus segmented low-voltage power distribution system. Moreover, the power factor controller (PFC) can directly and automatically control compensation based on the vector-synthesized current, thus eliminating the need for external switching signals or logic judgments, reducing maintenance complexity, and avoiding the adverse effects of manual intervention on compensation accuracy and operational safety.

[0018] In summary, this utility model utilizes an innovative measurement circuit formed by connecting the output terminals of current transformers for reactive power compensation on two incoming power lines in parallel with current transformers on the segmented busbars. This enables the power factor controller (PFC) to adaptively synthesize and match the power factor of the load on the corresponding busbar based on the current vector, thereby achieving precise matching between the compensation capacity and the segmented / single busbar operation. This not only effectively simplifies the control circuit, thereby improving the reliability of the automatic switching circuit and significantly reducing costs, but also effectively avoids the problems of low power factor or idle devices, fundamentally solving the problems of insufficient economy, reliability, and accuracy of reactive power compensation in single busbar segmented systems. Attached Figure Description

[0019] Figure 1 This is the main wiring diagram for a low-voltage power distribution system in the prior art; Figure 2 This is the control circuit diagram of the automatic switching circuit of this utility model; Figure 3 The diagram shows the current flow of the measurement circuit I of the automatic switching circuit in the embodiment, operating in mode 2. Figure 4 The diagram shows the current flow of the measurement circuit II of the automatic switching circuit in the embodiment, operating in mode 2. Figure 5 The current flow diagram of the measurement circuit I of the automatic switching circuit in the embodiment is shown in mode 3. Figure 6 The current flow diagram of the measurement circuit II of the automatic switching circuit in the embodiment is shown in mode 3. In the diagram: Ⅰ1 - Current flowing through Power Factor Controller 1PFC, Ⅰ11 - Current flowing through the output terminal of Current Transformer 1BC1, Ⅰ12 - Current flowing through the output terminal of Current Transformer 1BC2, Ⅱ2 - Current flowing through Power Factor Controller 2PFC, Ⅱ21 - Current flowing through the output terminal of Current Transformer 2BC1, Ⅱ22 - Current flowing through the output terminal of Current Transformer 2BC2, * indicates the positive terminal of the current transformer. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this utility model.

[0021] like Figures 2 to 6 As shown, the automatic switching circuit of the low-voltage single bus reactive power compensation device of this utility model includes a bus section I and a bus section II. The bus section I and the bus section II are connected by a bus tie circuit connected by a bus tie circuit breaker 3QA. Corresponding reactive power compensation devices are respectively configured on the bus section I and the bus section II. The primary winding of a current transformer 1BC1 is installed on one incoming line of the bus section I, and the primary winding of a current transformer 2BC1 is installed on the second incoming line of the bus section II. The bus tie circuit is equipped with the primary windings of current transformer 1BC2 and current transformer 2BC2. The automatic switching measurement circuit includes measurement circuit I and measurement circuit II. Measurement circuit I consists of a closed loop formed by connecting the secondary windings of current transformer 1BC1 and current transformer 1BC2 in parallel and then connecting them in series with power factor controller 1PFC. The connection terminal of the secondary winding of current transformer 1BC1 is grounded to the connection terminal of power factor controller 1PFC. Power factor controller 1PFC is electrically connected to the reactive power compensation device configured on bus section I. Measurement circuit II consists of a closed loop formed by connecting the secondary windings of current transformer 2BC1 and current transformer 2BC2 in parallel and then connecting them in series with power factor controller 2PFC. The connection terminal of the secondary winding of current transformer 2BC1 is grounded to the connection terminal of power factor controller 2PFC. Power factor controller 2PFC is electrically connected to the reactive power compensation device configured on bus section II.

[0022] The primary windings of current transformer 1BC1 and current transformer 2BC1 are simultaneously installed on any one of the three phases A, B, and C. The primary windings of current transformer 1BC2 and current transformer 2BC2 have opposite polarities.

[0023] The primary windings of current transformer 1BC1 and current transformer 1BC2 are both installed in the same phase but with opposite polarities.

[0024] The primary windings of current transformers 2BC1 and 2BC2 are both installed in the same phase but with opposite polarities.

[0025] The primary windings of current transformer 1BC1 and current transformer 1BC2 have the same transformation ratio, and the primary windings of current transformer 2BC1 and current transformer 2BC2 have the same transformation ratio.

[0026] The reactive power compensation capacity of the reactive power compensation devices configured in each of the I-section busbar and the II-section busbar is determined by the power factor detected by the power factor controller 1PFC and the power factor controller 2PFC corresponding to each busbar section during segmented operation.

[0027] The primary windings of current transformer 1BC2 and current transformer 2BC2 are installed at the same end of bus tie circuit breaker 3QA or connected in series at the front and rear ends of bus tie circuit breaker 3QA.

[0028] Example 1

[0029] like Figures 2 to 6 As shown, the automatic switching circuit of the low-voltage single-bus reactive power compensation device operates in the following segmented mode: Method 1: Simultaneous operation of two incoming lines and segmented operation of single busbar (most common operating mode): When circuit breaker 1QA of busbar section I is closed and circuit breaker 2QA of busbar section II is closed, and bus tie circuit breaker 3QA is open, the primary winding currents of current transformers 1BC2 and 2BC2 in the bus tie circuit are both zero. The corresponding power factor controllers 1PFC and 2PFC on measurement circuit I and measurement circuit II respectively detect the load power factor of their respective busbar sections according to the current provided by the secondary windings of current transformers 1BC1 and 2BC1, and then control the reactive power compensation device to work accordingly.

[0030] Method 2: Single incoming line operation, single busbar without segmentation: such as Figure 2 , 3 As shown in Figure 4, the circuit breaker 1QA of bus section I is closed, and the circuit breaker 2QA of bus section II is open, while the bus tie circuit breaker 3QA is closed. At this time, the current direction in the bus tie circuit is from bus section I to bus section II. Since the primary winding current of current transformer 1BC2 is opposite to that of current transformer 1BC1, the secondary winding current I12 of current transformer 1BC2 in measuring circuit I is negative. This makes the vector resultant current I1 in the power factor controller 1PFC in measuring circuit I I I11-I12. The vector resultant current I1 corresponds to the load current on bus section I. Therefore, the power factor detected by the power factor controller 1PFC is the power factor of the load on bus section I. The power factor controller 1PFC controls the automatic switching of the capacitor bank of the reactive power compensation device on bus section I according to the vector resultant current I1, that is, according to the power factor of the load on bus section I. Meanwhile, the polarity of the primary winding of current transformer 2BC2 is the same as the current direction, and the current I22 is positive, making the vector resultant current I2 in the power factor controller 2PFC in measurement circuit II I21+I22. However, since the 2QA circuit breaker is open, I21=0, and the current in the power factor controller 2PFC is I22, which corresponds to the load current on bus II. The power factor detected by the power factor controller 2PFC is the power factor of the load on bus II. The power factor controller 2PFC on measurement circuit II controls the capacitor bank of the reactive power compensation device on bus II to automatically switch on and off according to the current provided by current transformer 2BC2.

[0031] Method 3: Two incoming lines operating, single busbar without segmentation: such as Figure 2 , 5As shown in Figure 6, the circuit breaker 2QA of bus section II is closed, and the circuit breaker 1QA of bus section I is open, while the bus tie circuit breaker 3QA is closed. At this time, the current direction in the bus tie circuit is from bus section II to bus section I. Since the primary winding current of current transformer 2BC2 and current transformer 2BC1 are opposite, the secondary winding current I22 of current transformer 2BC2 in measuring circuit II is negative. This makes the vector resultant current I2 in the input power factor controller 2PFC of measuring circuit II I2 I21-I22, and I1 I12. Similarly, it can ensure that power factor controller 1PFC automatically switches the capacitor bank on bus section I according to the power factor of the load on bus section I, and power factor controller 2PFC automatically switches the capacitor bank on bus section II according to the power factor of the load on bus section II.

[0032] The above description is merely a preferred embodiment of this utility model, but the scope of protection of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this utility model should be included within the scope of protection of this utility model. Therefore, the scope of protection of this utility model should be determined by the scope of the claims.

Claims

1. An automatic switching circuit for a low-voltage single busbar reactive power compensation device, wherein the low-voltage single busbar reactive power compensation device includes a busbar section I and a busbar section II, wherein a bus tie circuit is provided between the busbar section I and the busbar section II and connected by a bus tie circuit breaker 3QA, wherein a corresponding reactive power compensation device is configured on the busbar section I and the busbar section II respectively, wherein a primary winding of a current transformer 1BC1 is installed on one incoming line of the busbar section I, and a primary winding of a current transformer 2BC1 is installed on the two incoming lines of the busbar section II; characterized in that The bus tie circuit is equipped with the primary windings of current transformer 1BC2 and current transformer 2BC2. The automatic switching circuit includes measurement circuit I and measurement circuit II. Measurement circuit I consists of a closed loop formed by connecting the secondary windings of current transformer 1BC1 and current transformer 1BC2 in parallel and then connecting them in series with power factor controller 1PFC. The connection terminal of the secondary winding of current transformer 1BC1 is grounded to the connection terminal of power factor controller 1PFC. Power factor controller 1PFC is electrically connected to the reactive power compensation device configured on bus section I. Measurement circuit II consists of a closed loop formed by connecting the secondary windings of current transformer 2BC1 and current transformer 2BC2 in parallel and then connecting them in series with power factor controller 2PFC. The connection terminal of the secondary winding of current transformer 2BC1 is grounded to the connection terminal of power factor controller 2PFC. Power factor controller 2PFC is electrically connected to the reactive power compensation device configured on bus section II.

2. The automatic switching circuit of the low-voltage single bus reactive power compensation device according to claim 1, characterized in that: The primary windings of current transformer 1BC1 and current transformer 2BC1 are simultaneously installed on any one of the three phases A, B, and C. The primary windings of current transformer 1BC2 and current transformer 2BC2 have opposite polarities.

3. The automatic switching circuit of the low-voltage single bus reactive power compensation device according to claim 2, characterized in that: The primary windings of current transformer 1BC1 and current transformer 1BC2 are both installed in the same phase but with opposite polarities.

4. The automatic switching circuit of the low-voltage single bus reactive power compensation device according to claim 3, characterized in that: The primary windings of current transformers 2BC1 and 2BC2 are both installed in the same phase but with opposite polarities.

5. The automatic switching circuit of low-voltage single bus reactive power compensation device according to claim 4, characterized in that: The primary windings of current transformer 1BC1 and current transformer 1BC2 have the same transformation ratio, and the primary windings of current transformer 2BC1 and current transformer 2BC2 have the same transformation ratio.

6. The automatic switching circuit of the low-voltage single bus reactive power compensation device according to any one of claims 1 to 5, characterized in that: The reactive power compensation capacity of the reactive power compensation devices configured in each of the I-section busbar and the II-section busbar is determined by the power factor detected by the power factor controller 1PFC and the power factor controller 2PFC corresponding to each busbar section during segmented operation.

7. The automatic switching circuit of the low-voltage single bus reactive power compensation device according to any one of claims 1 to 5, characterized in that: The primary windings of current transformer 1BC2 and current transformer 2BC2 are installed at the same end of bus tie circuit breaker 3QA or connected in series at the front and rear ends of bus tie circuit breaker 3QA.

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