0.4 kV low-load capacitor assembling equipment

Abstract

The utility model discloses 0.4 kV low-load capacitor assembling equipment, particularly relates to a low-voltage light-load reactive compensation combination device, and belongs to the field of power supply systems. The reactive compensation device is mainly used for providing accurate reactive compensation for a 0.4 kV low-voltage low-load electrical system during operation, automatic compensation is realized by utilizing a small-capacity capacitor bank and a small-step control mode, meanwhile, the capacity of the combined device can be expanded and reduced according to the actual load condition within a certain load range, the operation reactive requirement can be effectively met, the practicability is high, and the application range is wide. The power factor of a power grid can be improved, loss of a power supply transformer and a transmission line is reduced, power supply efficiency is improved, and a power supply environment is improved.

Description

Technical Field

[0001] The utility model discloses 0.4kV low-load capacitor assembly equipment, in particular to a low-voltage light-load reactive power compensation combination device, belonging to the field of electric power supply systems. Background Art

[0002] Currently, low-voltage reactive power compensation devices used in power systems are typically supplied by Germany's Saitong Electric Co., Ltd. These reactive power compensation devices feature individual capacitor banks of 50kvar and 25kvar, controlled by thyristor switching in 50kvar or 25kvar increments. The complete system only comes in two series: the 50kvar and 25kvar series. This system cannot effectively compensate for the required reactive power in a 0.4kV lightly loaded system. Especially when the primary load is below 50A, the control system cannot detect the load current, preventing it from switching on the capacitor bank. This results in substandard power factor, impacting system power quality, increasing reactive power compensation from the external grid, and increasing metered electricity costs. When manual switching is used, demand is less than 25kvar or between 25kvar and 50kvar, so only 25kvar or 50kvar can be switched on, resulting in overcompensation. Furthermore, the unavailable capacitors are no longer operational, wasting equipment resources. Manually switching on and off capacitors increases operator risk and poses a threat to human safety.

[0003] The document with the utility model patent authorization announcement number CN219892969U introduces a new type of technology related to the power system technology field, specifically, a high and low voltage reactive power compensation device, including a switching unit and a compensation unit. The utility model controls the switching unit to switch between the capacitive power module and the inductive power module according to the voltage and power factor of the power supply bus through the switching controller, and energy is exchanged between the two loads. The reactive power required by the inductive power module can be compensated by the reactive power output by the capacitive power module. The high and low voltage reactive power compensation device is characterized in that it includes a switching unit and a compensation unit, the switching unit includes a switching controller and a switching module, the compensation unit includes a capacitive power module and an inductive power module, the switching controller is connected to the switching unit, and the switching unit is connected to the capacitive power module and the inductive power module; the switching controller controls the switching module to switch between the capacitive power module and the inductive power module.

[0004] The high and low voltage reactive power compensation device disclosed in this patent also cannot solve the problem that there is no dedicated reactive power compensation device for light load of 0.4kV system in the prior art. Utility Model Content

[0005] The purpose of this utility model is to design a 0.4kV low-load capacitor assembly device, specifically a low-voltage, light-load reactive power compensation assembly device, to address the current lack of dedicated reactive power compensation devices for 0.4kV systems with light loads. The technology provided by this utility model can avoid human intervention in capacitor operation, reduce operations, and ensure human safety. It also provides precise reactive power compensation for 0.4kV low-voltage, low-load electrical systems during operation, meeting the reactive power requirements of 0.4kV systems with light loads, thereby conserving resources, improving the power supply quality of the power factor-grade system, reducing the reactive power requirements of the external power grid, and saving on metered electricity bills.

[0006] The technical solution proposed in the utility model is implemented as follows: a 0.4kV low-load capacitor assembly device includes an intelligent controller, a thyristor, a capacitor, a reactor, a fuse, a power knife fuse, and a fixed bracket. The intelligent controller in the secondary control is connected to the capacitor bank through the thyristor. There are multiple capacitor banks, and the minimum capacity of the capacitor bank is 7.5kvar. There are multiple capacitor banks in the secondary control, and the capacity of each capacitor bank is 50kvar, 25kvar, 12.5kvar, and 7.5kvar respectively. Each capacitor bank is connected to the primary system through the thyristor. The thyristor in the secondary control that controls the on and off of each capacitor bank with the primary system is connected to the control signal output end of the intelligent controller. The control signal output end of the intelligent controller is connected to capacitor banks of different capacities through thyristors respectively, and the minimum capacity that can be controlled to be put in and out is 7.5kvar. By controlling the control signal output end of the intelligent controller connected to the thyristor, a single capacitor bank or multiple groups of capacitor banks can be put in and out of the power supply system at the same time. The port used by the intelligent controller to collect primary system load current is connected to the current output of the current transformer (CT). The control and measurement voltage input used by the intelligent controller for reactive power compensation calculation is connected to the low-voltage busbar system of the distribution system. The number of capacitor banks added to or removed from the primary system is determined by the optimal compensation capacity calculated from the load current collected by the intelligent controller. Reactive power compensation capacitor banks are added in small steps of at least 7.5 kvar via thyristors. The optimal compensation capacity also depends on the power factor, which should be ≥ 0.95.

[0007] This controller collects load current and calculates the optimal compensation capacity. It also uses thyristors to gradually activate reactive power compensation capacitors, starting with a minimum of 7.5 kvar. The controller also sets the power factor parameter value in advance based on operational requirements, enabling automatic activation and deactivation.

[0008] The low-voltage and light-load reactive power compensation combination device provided by the utility model has a simple structure, a reliable structure, a wide range of applications and strong adaptability; it does not require human intervention in reactive power injection and withdrawal, and there is no operation required, which ensures life safety and high power supply safety; within a certain load range, the capacity of the combination device can be expanded or reduced according to the actual load conditions, and it can be arbitrarily combined in the capacity of 50kvar, 25kvar, 12.5kvar and 7.5kvar, which can easily meet the reactive power requirements of the 0.4kV low-voltage and low-load system distribution room and is extremely practical; it is also extremely simple to modify the system in use, and can effectively make up for and improve the reactive power compensation of the entire power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the primary system of the utility model.

[0010] Figure 2 This is the original circuit diagram of the secondary control circuit of the utility model.

[0011] Figure 3 It is the circuit and phasor diagram of parallel capacitor compensation for reactive power;

[0012] Figure 4 It is a workflow diagram.

[0013] Figure 1 In the middle: L1-L3 is the 0.4kV three-phase distribution room power supply, QS is the equipment power supply fuse, TA1-TA6 is the reactive power compensation device current transformer, KS1-KS4 is the switching thyristor, C1-C6 is the free combination capacitor bank, SPD is the overvoltage protection device;

[0014] Figure 2 1) The capacitor intelligent controller collects the primary system load current through the CT, takes the voltage of the low-voltage bus system as the working voltage, and takes another voltage as the control measurement voltage for the calculation of reactive compensation;

[0015] 2) The controller issues a switch-on / off command through the 14 to 24 output nodes, and the command is passed through the thyristor to switch the capacitor bank on and off.

[0016] 3) The reactive power stored in capacitors is directly incorporated into the primary system to compensate for the system.

[0017] Figure 3 (a) Circuits; Figure 3 (b) phasor diagram (undercompensation); Figure 3 (c) Phase diagram (overcompensation). DETAILED DESCRIPTION

[0018] The above technology is used to construct the original reactive power compensation equipment framework of the 0.4kV system, which can be installed and combined according to actual conditions. The control system is composed of an intelligent controller combined with a thyristor. The core components such as the primary capacitor and the reactor are assembled on a movable and detachable fixed bracket according to actual needs. The capacity and the reactor can be composed of a combination of 50kvar, 25kvar, 12.5kvar, and 7.5kvar. The combined use capacity is calculated according to the design load, and can also be installed in combination according to the load changes after the actual system is put into operation.

[0019] Used in 0.4kV system chemical production low-voltage load power supply system: 1) The compensation module part adopts 7% tuned filter capacitor reactor group, with a capacity of 7.5kvar, 12.5kvar, and 25kvar small-capacity capacitor group, with a quantity combination of 2*7.5+12.5+2*25kvar;

[0020] 2) The cabinet body uses the cabinet body of Germany Saitong Electric Co., Ltd., and adds accessories such as contactors, fuses, cables, secondary wiring in the cabinet and supporting beams. The main switch and current transformer use the original cabinet products;

[0021] 3) Adjust the controller acquisition signal and modify its calculation method. The original controller only operates on 50kvar or 25kvar. Modify the internal logic and add 12.5kvar and 7.5kvar capacity level operations.

[0022] 4) After the change is completed, according to calculations, the operating requirements can be met and the power factor can be used above 0.95.

[0023] This utility model uses the control signal output terminal of an intelligent controller connected to thyristors to enable the simultaneous switching on and off of individual capacitor banks or multiple groups of capacitor banks in the power supply system. The port used by the intelligent controller to collect primary system load current is connected to the current output terminal of the current transformer (CT). The control and measurement voltage input terminal of the intelligent controller, used for reactive power compensation calculation, is connected to the low-voltage busbar system of the power distribution system. The number of capacitor banks added to or removed from the primary system is determined by the optimal compensation capacity calculated from the load current collected by the intelligent controller. The reactive power compensation capacitor banks are switched on and off in small steps of at least 7.5 kvar via thyristors.

[0024] The optimal compensation capacity of the utility model also depends on the power factor, and the power factor is ≥0.95.

[0025] The reactive power Q provided by the capacitor bank of the utility model C , terminal voltage U and capacitor capacitive reactance X C The relationship between the three is determined by the following formula: X CThe minimum value is 7.5. The equivalent circuit of the power system whose load includes asynchronous motors is a circuit with resistance R and inductance L in series. The reactive compensation capacitor group C after being put into operation is connected in parallel with the circuit with resistance R and inductance L in series. The current equation of this circuit is: The power factor is:

[0026] This controller collects load current and calculates the optimal compensation capacity. It also uses thyristors to gradually activate reactive power compensation capacitors, starting with a minimum of 7.5 kvar. The controller also sets the power factor parameter value in advance based on operational requirements, enabling automatic activation and deactivation.

[0027] The low-voltage and light-load reactive power compensation combination device provided by the utility model has a small calculation step, can detect the reactive power demand under low-load conditions, can compensate according to the reactive power demand, and can also compensate through power factor control.

[0028] 1) The capacity of the capacitor bank can be large or small, and can be used in a centralized or decentralized manner, making it more flexible to use.

[0029] Reactive power Q supplied by the capacitor C It is proportional to the square of its terminal voltage U.

[0030] Right now Where (X C ——capacitive reactance of capacitor).

[0031] In this design, X C It can be as low as 7.5. Therefore, the controller has greater calculation accuracy, and the adjustable reactive power compensation capacity range is wider and more flexible, which can be adjusted according to the reactive power demand of the system.

[0032] 2) According to the reactive power compensation principle: In actual power systems, most loads are asynchronous motors. The equivalent circuit of most electrical equipment, including asynchronous motors, can be regarded as a circuit of resistance R and inductance L in series, and its power factor is

[0033]

[0034] Where X L =ωL

[0035] After connecting the R and L circuits in parallel and then connecting them to the capacitor C, the circuit becomes as follows Figure 3 (a). The current equation of this circuit is:

[0036]

[0037] Depend on Figure 3From the phasor diagram, we can see that the phase difference between voltage U and current I becomes smaller after the parallel capacitor is connected, that is, the power factor of the power supply circuit is improved. At this time, the phase of the supply current I lags behind the voltage U, which is called undercompensation.

[0038] If the capacitance of capacitor C is too large, the phase of supply current I will be ahead of voltage U. This situation is called overcompensation. Its phasor diagram is as follows: Figure 3 (c) Over-compensation and under-compensation can be controlled by setting the power factor limiting controller to switch capacitor banks in and out.

Claims

1. A 0.4kV low-load capacitor assembly device, including an intelligent controller, a thyristor, a capacitor, a reactor, a fuse, a power knife fuse, and a fixing bracket, characterized by: The intelligent controller in the secondary control is connected to the capacitor bank through thyristors. There are multiple capacitor banks with a minimum capacity of 7.5kvar.

2. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: There are multiple capacitor banks in the secondary control, with the capacity of each capacitor bank being 50kvar, 25kvar, 12.5kvar, and 7.5kvar respectively. Each capacitor bank is connected to the primary system through a thyristor.

3. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: In the secondary control, the thyristor for controlling the switching between each group of capacitors and the primary system is connected to the control signal output terminal of the intelligent controller.

4. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: The control signal output end of the intelligent controller is connected to capacitor banks of different capacities through thyristors, and the minimum capacity that can be controlled to be put in and out is 7.5kvar.

5. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: By controlling the signal output terminal of the intelligent controller connected to the thyristor, a single capacitor bank or multiple capacitor banks in the power supply system can be switched on and off simultaneously.

6. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: The port for collecting the primary system load current of the intelligent controller is connected to the current output terminal of the current transformer CT, and the control measurement voltage input terminal of the intelligent controller for reactive compensation calculation is connected to the low-voltage bus system of the distribution system.

7. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: The number of capacitor banks added to the primary system is determined by the optimal compensation capacity calculated from the load current collected by the intelligent controller. The reactive compensation capacitor banks are added in small steps of at least 7.5kvar through thyristors.

8. The 0.4kV low-load capacitor assembly equipment according to claim 1, characterized in that: The optimal compensation capacity also depends on the power factor, which should be ≥0.95.

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