CN203562784U - Reactive Power Compensation Device for 10kV Line - Google Patents

Abstract

A reactive compensation device of a 10kV line mainly comprises a control unit, vacuum contactors, capacitors, a voltage transformer, current transformers, lightning arresters and outdoor drop-out fuses. The control unit comprises a controller connected with the voltage transformer capable of collecting high-voltage electric grid cable voltage signals, an outdoor current transformer capable of collecting line current signals and a group of indoor current transformers collecting capacitor current signals. Through a control loop, the controller is connected with a group of the vacuum contactors and further connected with the capacitors capable of completing a switching operation. The reactive compensation device has the advantages of low investment, high earning and feasibility, takes effect rapidly, is capable of reducing line loss greatly and improves power quality.

Description

Reactive Power Compensation Device for 10kV Line

technical field

The utility model relates to a reactive power compensation device for a 10kV line, which belongs to the technical field of power grid configuration equipment.

Background technique

With the rapid development of the national economy, the power consumption of urban and rural power grids is increasing day by day, and the power supply quality of the power grid has been paid more and more attention by the power supply department. With the completion of the first-phase and second-phase power grid transformation, the power supply quality of the power grid has been greatly improved and improved, but there are still problems such as low power factor, unreasonable reactive power compensation, and large line loss. For this reason, the State Grid Corporation requires power supply companies at all levels to pay attention to the management of line loss, reasonably compensate reactive power, improve power factor, and improve grid efficiency.

Utility model content

The purpose of the utility model is to overcome the deficiencies in the prior art, and provide a method that can compensate the reactive power consumed by the power transformer distributed in the line, thereby reducing the reactive power transmission of the upper substation to the 10kV line and improving The power factor of the distribution line is a reactive power compensation device for a 10kV line that can reduce losses and save energy on the line.

The purpose of this utility model is accomplished through the following technical scheme, which is mainly composed of a control unit, a vacuum contactor, a capacitor, a voltage transformer and a current transformer, a lightning arrester, and an outdoor drop-out fuse; it is characterized in that the control The unit includes a controller which is respectively connected to a voltage transformer capable of collecting the voltage signal of the high-voltage grid line, an outdoor current transformer capable of collecting the line current signal, and a group of indoor current transformers capable of collecting the capacitor current signal. The loops are respectively connected with a group of vacuum contactors and then connected with capacitors which can complete the switching action.

In the utility model, an outdoor drop-type fuse and a lightning arrester which can provide short-circuit protection for the device are connected in series in the switching circuit of the capacitor; The control circuit provides power; the outdoor current transformer is an outdoor feed-through current transformer, which is placed on the A-phase line of the high-voltage power grid to obtain line current signals.

The controller described in the utility model is a single-chip microcomputer with memory capable of signal acquisition, processing and control output. The single-chip microcomputer is connected to the vacuum contactor through a control circuit composed of two relay outputs, and is also connected to a digital display respectively. , Operation keyboard, watchdog and serial communication interface.

The utility model can compensate the reactive power consumed by the power transformer distributed in the line, thereby reducing the reactive power transmission of the upper substation to the 10kV line, improving the power factor of the power distribution line, and achieving the effect of reducing loss and energy saving on the line; It has the characteristics of small investment, quick effect, high income, practicability, can greatly reduce line loss, and improve power quality.

Description of drawings

Fig. 1 is a composition schematic diagram of the overall structure of the utility model.

Fig. 2 is a block diagram of the overall structure of the utility model.

Fig. 3 is a structural block diagram of the controller described in the present invention.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings: shown in Figures 1 and 2, the utility model is mainly composed of a control unit 1, a vacuum contactor 2, a capacitor 3, a voltage transformer 4 and a current transformer 5, a lightning arrester 6, The outdoor drop-out fuse 7 is composed of; the control unit 1 includes a voltage transformer 4 capable of collecting high-voltage grid line voltage signals, an outdoor current transformer 5 capable of collecting line current signals, and a group of capacitors 3 for collecting current signals. The indoor current transformer 8 is connected to the controller 11, the controller 11 is respectively connected to a group of vacuum contactors 2 through the control circuit 12, and then connected to the capacitor 3 that can complete the switching action.

In the utility model, an outdoor drop-out fuse 7 and a lightning arrester 6 which can provide short-circuit protection for the device are connected in series in the switching circuit of the capacitor; the voltage transformer 4 is connected between phases B and C of the high-voltage power grid, and is The controller 11 and the control circuit 12 provide power; the outdoor current transformer 5 is an outdoor feed-through current transformer, which is placed on the A-phase line of the high-voltage power grid to obtain line current signals.

As shown in Fig. 3, the controller 11 described in the utility model is a single-chip microcomputer 13 with a memory 14 capable of signal acquisition processing and control output, and the single-chip microcomputer 13 is connected by a control loop 12 formed by two relay outputs. The vacuum contactor 2 is also respectively connected with a digital display 15 , an operation keyboard 16 , a watchdog 17 and a serial communication interface 18 .

The utility model can realize step-by-step switching, so that the reactive power compensation of the high-voltage line is finer. As we all know, a single set of reactive power compensation device cannot achieve fine compensation, while multiple sets of equal-capacity devices can achieve relatively fine compensation, but the number of sets of capacitors is large, and each set of capacitors must be equipped with corresponding switches and protection. Equipment, which greatly increases the cost of equipment, makes the initial investment cost of energy saving and loss reduction larger, and also reduces the benefits of energy saving and loss reduction. If you use unequal volume switching, you can greatly reduce equipment costs and maximize the benefits of users. For example, to compensate a capacitance of 300kVar, the level difference is 100kVar. If equal-capacity switching is used, 3 capacitors and 3 switches are needed. If unequal-capacity switching is used, the method of compensating one 100kVar and one 200kVar will be Only two capacitors and two switches are needed, which saves the cost of one switch and one protective device, and reduces the point of failure.

The utility model uses a vacuum contactor to switch capacitors. The contacts of vacuum contactors are made of special materials which are especially suitable for breaking capacitive currents.

The utility model can also realize short-distance control and remote measurement and remote adjustment through communication methods such as wireless communication modules, GPRS or CDMA.

The utility model can integrate the high and low voltage components into the respective boxes, which is convenient for users to operate.

After the utility model is implemented, there are very large economic and social benefits, mainly manifested in:

1. Reduce the power loss and electric energy loss in the grid, the power factor of the line is increased from 0.84 to 0.98, and the calculation is based on 0.5 yuan per kilowatt-hour. If it is operated for one year, it is calculated that installation point 1 can save 46,000 yuan. Using Using the same calculation method, it can be calculated that the cost saved at installation point 2 is 47,000 yuan a year. Therefore, after installing reactive power compensation on the 10kV Zhushan 012 line, the total cost saved a year is about 93,000 yuan.

2. Improve the power supply capacity of the equipment

3. Improve power quality and increase the voltage qualification rate of 10kV lines on the user side

4. Optimize the reactive power flow of power grids above 10kV at all levels, and improve the safety and stability of electricity

5. Due to the improvement of power supply quality, it can encourage the enthusiasm of users to use electricity.

Example:

The reactive power compensation device on the 10kV pole is based on the actual situation of the power grid, using the compensation function of the reactive power source to realize the comprehensive control of voltage and reactive power, which has a great effect on improving the voltage qualification rate and reducing network loss. It adopts the method of connecting capacitors in parallel, which can not only automatically compensate the reactive power loss of the 10kV transmission line, but also stabilize the line voltage. At the same time, after using the computer network and communication technology, the remote monitoring and remote control of the automatic control device can be realized, which improves the automation of the power transmission and distribution system in a real sense and increases the economic benefits of the power system.

Therefore, the best location for single-point centralized compensation on the 10kV line is at the concentrated point of the load. The lower line can adopt multi-point compensation, and the location of compensation can be determined by selecting multiple points where the load is concentrated. According to the distribution of the load, in order to compensate the line reasonably and effectively, the 10kV Zhushan 012 line should use multiple points for decentralized compensation.

Installation point 1 is temporarily selected at the front end of a switch in front of the Zhupu switch on the main line; installation point 2 is suspended at two-thirds of the distribution transformer capacity between the Zhupu switch on the main line and the previous switch (see the installation position schematic diagram for details) , The compensation reactive capacity selection leaves a margin on the basis of the usual load, and the compensation method is selected according to the compensation reactive capacity.

The reactive power compensation on the 10kV line is mainly to compensate the reactive power consumed by the power transformer distributed in the line, so as to reduce the reactive power transmission of the upper substation to the 10kV line, improve the power factor of the distribution line, and achieve the power factor of the line. loss reduction and energy saving effect.

Therefore, the best location for single-point centralized compensation on the 10kV line is at the concentrated point of the load. The lower line can adopt multi-point compensation, and the location of compensation can be determined by selecting multiple points where the load is concentrated. According to the distribution of the load, in order to compensate the line reasonably and effectively, the 10kV Zhushan 012 line should use multiple points for decentralized compensation.

Installation point 1 is temporarily selected at the front end of a switch in front of the Zhupu switch on the main line; installation point 2 is suspended at two-thirds of the distribution transformer capacity between the Zhupu switch on the main line and the previous switch (see the installation position schematic diagram for details) , The compensation reactive capacity selection leaves a margin on the basis of the usual load, and the compensation method is selected according to the compensation reactive capacity.

1). According to statistics, the total capacity of distribution transformers after installation point 1 to installation point 2 is 3550kVA.

The load rate of the line is calculated according to the maximum current provided by the user:

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; UI</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 43</span>}<span\; class="notranslate">\; \%</span>$

In the formula, S': the actual apparent power of the line, kVA;

S: total line capacity, kVA;

U: substation outlet voltage, kV;

I: the maximum current of the line, A;

Active power: P=η×S×cosφ ₁

In the formula, S: the total capacity between installation point 1 and installation point 2, kVA;

cosφ ₁ : power factor before compensation

The power factor before compensation is calculated as 0.84, and the power factor after compensation reaches 0.98. The reactive capacity to be compensated is:

Q _c ＝P×(tg(cos ^-1 φ ₁ )-tg(cos ^-1 φ ₂ ))

Where cosφ ₂ is the power factor after compensation

The calculation data used in the above calculations are calculated values under the rated voltage of 10kV. For the safe operation of the capacitor, a capacitor with a rated voltage of 11kV is selected. According to the relationship between the installed capacity of the capacitor and the effective compensation capacity (Qc=ωCU2 ), it can be calculated that the actual reactive capacity to be compensated at the installation point is 687kVar, and the actual compensation can be 650kVar, and the compensation method is: static compensation 50kVar + dynamic compensation 200kVar + dynamic compensation 400kVar.

2). According to statistics, the total capacity of the distribution transformer from installation point 2 to the end of the line is 3465kVA.

The load rate of the line is calculated according to the maximum current provided by the user:

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; UI</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 43</span>}<span\; class="notranslate">\; \%</span>$

In the formula, S': the actual apparent power of the line, kVA;

S: total line capacity, kVA;

U: substation outlet voltage, kV;

I: the maximum current of the line, A;

Active power: P=η×S×cosφ ₁

In the formula, S: the total capacity from installation point 2 to the end of the line, kVA;

cosφ ₁ : power factor before compensation

The power factor before compensation is calculated as 0.84, and the power factor after compensation reaches 0.98. The reactive capacity to be compensated is:

Q _c ＝P×(tg(cos ^-1 φ ₁ )-tg(cos ^-1 φ ₂ ))

Where cosφ ₂ is the power factor after compensation

The calculation data used in the above calculations are calculated values under the rated voltage of 10kV. For the safe operation of the capacitor, a capacitor with a rated voltage of 11kV is selected. According to the relationship between the installed capacity of the capacitor and the effective compensation capacity (Qc=ωCU2 ), it can be calculated that the actual reactive capacity to be compensated at the installation point is 670kVar, the actual compensation can be 550kVar, and the compensation method is: static compensation 50kVar + dynamic compensation 200kVar + dynamic compensation 300kVar.

As shown in Figure 1, two high-voltage capacitors and high-voltage vacuum contactors are installed in the control cabinet, and the opening and closing of the high-voltage vacuum contactors are controlled by a single-chip microcomputer to complete the switching action. Capacitors are protected by high voltage fuses. The PT samples the line voltage between phase B and phase C of the high-voltage power grid. In addition to providing voltage signals, it also provides power for the controller and control loop. The CT samples the line current and provides a current sampling signal for the controller. CT1-CT4 samples the capacitor current, and provides hardware support for capacitor overcurrent protection and phase loss protection. The controller analyzes and calculates the collected signals of line voltage, line current, and capacitor current, and after judgment, outputs control signals to control the closing and opening of the vacuum contactor.

As shown in Figure 2, the utility model is mainly composed of seven parts such as a control unit, a vacuum contactor, a capacitor, a voltage transformer and a current transformer, a lightning arrester, and an outdoor drop-out fuse; Real-time data is processed and judged to control the switching of capacitors. The vacuum contactor receives and executes the instructions from the control unit to complete the switching action of the capacitor. The outdoor drop-out fuse provides short-circuit protection for the device. Once the device has a short-circuit fault, the drop-out fuse immediately jumps off to prevent damage to the device and the circuit.

As shown in Figure 3, the utility model adopts a single-chip microcomputer as the core of signal acquisition processing and control output, collects voltage and current through a new type of smart meter chip, and controls the output of two relays to realize the switching of capacitors after operation and processing by the single-chip microcomputer cut. Realized 10-minute protection, over-current protection, phase loss protection, delay protection and other protection functions, making the system work more stable and effective.

Structural and modular design methods are adopted in the software design of single-chip microcomputer. In the initialization program, in addition to assigning values to the registers, it is also necessary to read the data in the E2PROM to determine whether the capacitor failed before the last power-off. If there is a failure, it will not be controlled. The sampling data of the single-chip microcomputer is to read the calculated voltage, current, active power and other effective data from the measurement chip. In order to ensure that the capacitor is fully discharged after cutting, a 10-minute protection function is designed, and no control is performed during this period. When designing the program, it focuses on the protection of capacitors. The protection functions realized include: undervoltage protection, overvoltage protection, overcurrent protection and phase loss protection, which ensures the safe operation of the device from the software.

Type selection of the utility model:

(1) Reasonably select the installation point according to the specific line;

(2) Select the appropriate reactance rate according to the nature of the load;

(For example, when there are rectifier transformers, intermediate frequency furnaces, frequency converters, gates and other nonlinear loads in the line, the device must match the appropriate reactance rate) The principles are as follows:

The choice of reactance rate should make the nth harmonic content at the device connection and the nth harmonic value on the capacitor not exceed the limit value specified in the relevant standards.

When it is only necessary to limit the closing inrush current, a damping reactor with a reactance rate of 0.1% to 1% should be selected.

In order to suppress the 5th and above harmonic amplification, a reactor with a reactance rate of 4.5% to 6% should be selected; to suppress the 3rd and above harmonic amplification, a reactor with a reactance rate of 12% to 13% should be selected.

(3) Reasonably determine the compensation capacity and series;

The selection of the number of stages depends on the capacity of the capacitor and the change of the local load. When the reactive power deficit is large and the change is large, if the single-stage switching method is selected, the compensation will not be precise enough, the number of switching times is small, the utilization rate is low, and the energy-saving effect is not good. At this time, choosing a multi-stage switching method can achieve a better compensation effect; and when the reactive power gap is small and the change is relatively small, the unipolar switching method can meet the needs of reactive power compensation.

Claims (3)

1. A reactive power compensation device for a 10kV line, which is mainly composed of a control unit, a vacuum contactor, a capacitor, a voltage transformer and a current transformer, a lightning arrester, and an outdoor drop-out fuse; it is characterized in that: the control unit It includes a controller connected to a voltage transformer capable of collecting high-voltage power grid line voltage signals, an outdoor current transformer capable of collecting line current signals, and a group of indoor current transformers capable of collecting capacitor current signals. The controller passes through the control loop They are respectively connected to a group of vacuum contactors and then connected to capacitors that can complete the switching action. the 2. The reactive power compensation device for a 10kV line according to claim 1, characterized in that: an outdoor drop-out fuse and a lightning arrester that can protect the device from a short circuit are connected in series in the capacitor switching circuit; the voltage mutual inductance The transformer is connected between phases B and C of the high-voltage power grid, and provides power for the controller and the control loop; the outdoor current transformer is an outdoor feed-through current transformer, which is placed on the A-phase line of the high-voltage power grid Get the line current signal. the 3. The reactive power compensation device of 10kV line according to claim 1 or 2, characterized in that: the controller is a single-chip microcomputer with a memory capable of signal acquisition processing and control output, and the single-chip microcomputer The control loop composed of two relay outputs is connected to the vacuum contactor, and a digital display, an operation keyboard, a watchdog and a serial communication interface are respectively connected. the

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