First, in order to minimize the transmission loss of reactive power and improve the efficiency of power transmission and distribution equipment, the configuration of reactive power compensation equipment should be rationally laid out in accordance with the principle of “classified compensation and local balanceâ€.
(1) The overall balance is combined with the local balance, with the local focus.
(2) Combining power sector compensation with user compensation.
In the distribution network, the reactive power consumed by the user accounts for about 50% to 60%, and the rest of the reactive power is consumed in the distribution network. Therefore, in order to reduce the transmission of reactive power in the network, it is necessary to achieve local compensation and local balance as much as possible, so it must be jointly compensated by the power department and the user.
(3) The combination of decentralized compensation and centralized compensation mainly focuses on dispersion.
For centralized compensation, a large-capacity compensation capacitor is installed centrally in the substation. Decentralized compensation refers to reactive power compensation in distributed load areas such as distribution lines, distribution transformers, and users' electrical equipment. The centralized compensation mainly compensates the reactive power loss of the main transformer itself, and reduces the reactive power of the transmission line so as to reduce the reactive power loss of the power supply network. However, the reactive power loss of the distribution network cannot be reduced. Because the reactive power required by the user is transmitted to the load side through the distribution line below the substation. Therefore, in order to effectively reduce the line loss, it must be done where the reactive power occurs and where it should be compensated. Therefore, the medium and low-voltage distribution networks should be based on decentralized compensation.
(4) Combine reduction and pressure adjustment to reduce damage.
Second, the main factor affecting the power factor The power factor is mainly generated because the AC power equipment in its working process, in addition to the consumption of active power, but also need reactive power. When the active power P is constant, such as reducing the reactive power Q, the power factor can be increased. In extreme cases, when Q=0, its force rate=1. Therefore, the essence of improving the power factor problem is to reduce the reactive power requirements of the power equipment.
2.1. Asynchronous motors and power transformers are main equipments that consume reactive power. The air gap between the stator and the rotor of an induction motor is the main factor that determines the asynchronous motors need more reactive power. The reactive power consumed by the asynchronous motor is composed of two parts, reactive power at no load and reactive power at a certain load. Therefore, to improve the power factor of an asynchronous motor, it is necessary to prevent the motor from running idling and increase the load rate as much as possible. The main component of reactive power consumed by the transformer is its no-load reactive power, which is independent of the size of the load rate. Therefore, in order to improve the power factor of the power system and the enterprise, the transformer should not run idling or be in a low-load operation state.
2.2. The power supply voltage exceeding the specified range will also have a great influence on the power factor. When the power supply voltage is higher than 10% of the rated value, the reactive power will increase rapidly due to the influence of magnetic circuit saturation. According to statistics of the relevant data, When the supply voltage is 110% of the rated value, the normal factory's reactive power will increase by about 35%. When the supply voltage is lower than the rated value, the reactive power is also reduced accordingly so that their power factor is increased. However, lowering the supply voltage will affect the normal operation of electrical equipment. Therefore, measures should be taken to make the power system supply voltage as stable as possible.
2.3. The fluctuation of the grid frequency will also have a certain influence on the magnetizing reactive power of induction motors and transformers. 2.4. Some of the major factors that affect the power factor of the power system are discussed. Therefore, it is necessary to find some effective ones that can make the low voltage. Some practical methods for improving the power factor of the power network enable the low-voltage network to achieve reactive local balance and reduce energy consumption.
Third, the low voltage distribution network reactive power compensation method:
a. The stochastic compensation random compensation is to connect the low-voltage capacitor bank and the motor in parallel, and control and protect the device and the motor at the same time. The random compensation is suitable for compensating the reactive power consumption of the motor, and mainly compensating the excitation and reactive power. This method can better limit the reactive power load of the power unit. Advantages of random compensation: When the power equipment is in operation, the reactive power compensation is input, and when the power equipment is out of service, the compensation equipment also exits, and the compensation capacity does not need to be adjusted frequently. With less investment, small footprint, easy installation, convenient and flexible configuration, simple maintenance, low accident rate.
b. Accompanying device compensation The device compensating means that the low-voltage capacitor is connected to the secondary side of the distribution transformer through low-voltage protection to compensate for the no-load reactive power compensation method of the distribution transformer. The reactive load of the transformer during light load or no-load is mainly the no-load excitation and reactive power of the transformer, and the no-load reactive power distribution is the main part of the reactive power load per unit of electricity. For the light load distribution, this Part of the loss accounted for a large proportion of the power supply, resulting in an increase in the unit price of electricity. Advantages of the follower compensation: simple wiring, convenient maintenance and management, can effectively compensate for no-load reactive power distribution, limit the rural network base load, and make the part reactive and on-site balance, thereby improving the utilization ratio of distribution transformer, reducing the The loss of work network and high economic efficiency is one of the most effective means of compensating for reactive power.
c. Tracking Compensation Tracking compensation refers to the method of compensating the low voltage capacitor bank on the 0.4kv busbar of the large user with the reactive power compensation switching device as the control protection device. Applicable to special distribution transformers above 100kVA, it can replace random and follow-up two compensation methods, the compensation effect is good. The advantage of follow-up compensation is that the operation mode is flexible and the operation and maintenance workload is small. Compared with the first two compensation methods, the service life is relatively longer and the operation is more reliable. Priority should be given to tracking compensation.
IV. Reactive power compensation of high voltage distribution network:
1. State Power Corporation issued a document on the first-class power industry, requiring a 10kV power factor of not less than 0.9, a line loss of no more than 5%, and operation and management of voltage quality and reactive power compensation, etc. One of the key problems to be solved It is to put a certain capacitor in the 10kV line and use a fixed or automatic input method to realize reactive power compensation. If a fixed capacitor bank is put into a power supply line, it is generally calculated according to the low load of the line, and the automatic compensation amount is the value calculated when the line is at full load. One line has fixed and automatic compensation, and the two modes cooperate with each other. The desired effect can be achieved.
2. The principle of reactive power compensation is based on local balance. According to the actual situation of distribution network of rural power grids, it is more complicated and impossible to be a unified model. Therefore, it is necessary to use a combination of decentralized and centralized, fixed, and automatic methods, which is divided into three steps: First, Within the substation, a fixed compensation capacitor bank is installed at about 15% of the capacity of the main transformer. The second is to install a fixed compensation capacitor bank at the load center or somewhere along the reactive power demand at low load. The third is to install an automatic compensation capacitor bank on the upper side of the line load center.
3. For the 10kV distribution network system mainly used by rural power grids, the complete reactive power compensation should include substation centralized compensation, 10 kV line compensation and customer-side low-voltage compensation, plus random compensation, ie "3 compensation + random compensation" ("3+1" "mode). Empirical estimation: When COSφ is about 0.6 to 0.7, it can be compensated by about 15% of the actual load of the feeder or by 2/3 of the reactive power gap.
4. Taking into account the effect of reducing line losses and improving the power rate and voltage, the principle of line compensation is to implement single- or multi-point capacitor compensation by installing capacitors on the line poles. The single-point compensation point is selected at the 2/3 point from the head of the line. The compensation capacity should be 2/3 of the reactive load; the two points of compensation should be installed at 2/5 and 4/5 of the head end; if the line is longer, the load is larger, and the combination of fixed compensation and automatic compensation is implemented. Three points on the line are distributed: the first assembly is fixed at 2/7 of the line, and the second group is automatic compensation. It is installed at 4/7 of the line, which is also the location where the load is more concentrated; The group is a fixed compensation and installed at 6/7 of the line. The multi-point compensation uses the branch line segment compensation method to compensate for lines with large branches or low natural power factor with long line loads. According to the actual conditions in rural areas, compensation points for rural network lines should not be excessive; control methods should be simplified; protection methods can be used as fuses and lightning arresters as simple over-current and over-voltage protection.
5. To determine the compensation capacity of a certain distribution line, calculate the average reactive load and minimum reactive load of the line. When the minimum reactive load of the line is less than 2/3 of the average reactive load, consider that the reactive power should not be To reverse, a fixed compensation device can be installed, but the compensation capacity should be determined by the minimum reactive load. When there is a large reactive load point in the line, in addition to considering the distance from the beginning of the line, large reactive load points should also be considered. The actual installed compensation device is preferably 100-200 kvar per group.
(1) The overall balance is combined with the local balance, with the local focus.
(2) Combining power sector compensation with user compensation.
In the distribution network, the reactive power consumed by the user accounts for about 50% to 60%, and the rest of the reactive power is consumed in the distribution network. Therefore, in order to reduce the transmission of reactive power in the network, it is necessary to achieve local compensation and local balance as much as possible, so it must be jointly compensated by the power department and the user.
(3) The combination of decentralized compensation and centralized compensation mainly focuses on dispersion.
For centralized compensation, a large-capacity compensation capacitor is installed centrally in the substation. Decentralized compensation refers to reactive power compensation in distributed load areas such as distribution lines, distribution transformers, and users' electrical equipment. The centralized compensation mainly compensates the reactive power loss of the main transformer itself, and reduces the reactive power of the transmission line so as to reduce the reactive power loss of the power supply network. However, the reactive power loss of the distribution network cannot be reduced. Because the reactive power required by the user is transmitted to the load side through the distribution line below the substation. Therefore, in order to effectively reduce the line loss, it must be done where the reactive power occurs and where it should be compensated. Therefore, the medium and low-voltage distribution networks should be based on decentralized compensation.
(4) Combine reduction and pressure adjustment to reduce damage.
Second, the main factor affecting the power factor The power factor is mainly generated because the AC power equipment in its working process, in addition to the consumption of active power, but also need reactive power. When the active power P is constant, such as reducing the reactive power Q, the power factor can be increased. In extreme cases, when Q=0, its force rate=1. Therefore, the essence of improving the power factor problem is to reduce the reactive power requirements of the power equipment.
2.1. Asynchronous motors and power transformers are main equipments that consume reactive power. The air gap between the stator and the rotor of an induction motor is the main factor that determines the asynchronous motors need more reactive power. The reactive power consumed by the asynchronous motor is composed of two parts, reactive power at no load and reactive power at a certain load. Therefore, to improve the power factor of an asynchronous motor, it is necessary to prevent the motor from running idling and increase the load rate as much as possible. The main component of reactive power consumed by the transformer is its no-load reactive power, which is independent of the size of the load rate. Therefore, in order to improve the power factor of the power system and the enterprise, the transformer should not run idling or be in a low-load operation state.
2.2. The power supply voltage exceeding the specified range will also have a great influence on the power factor. When the power supply voltage is higher than 10% of the rated value, the reactive power will increase rapidly due to the influence of magnetic circuit saturation. According to statistics of the relevant data, When the supply voltage is 110% of the rated value, the normal factory's reactive power will increase by about 35%. When the supply voltage is lower than the rated value, the reactive power is also reduced accordingly so that their power factor is increased. However, lowering the supply voltage will affect the normal operation of electrical equipment. Therefore, measures should be taken to make the power system supply voltage as stable as possible.
2.3. The fluctuation of the grid frequency will also have a certain influence on the magnetizing reactive power of induction motors and transformers. 2.4. Some of the major factors that affect the power factor of the power system are discussed. Therefore, it is necessary to find some effective ones that can make the low voltage. Some practical methods for improving the power factor of the power network enable the low-voltage network to achieve reactive local balance and reduce energy consumption.
Third, the low voltage distribution network reactive power compensation method:
a. The stochastic compensation random compensation is to connect the low-voltage capacitor bank and the motor in parallel, and control and protect the device and the motor at the same time. The random compensation is suitable for compensating the reactive power consumption of the motor, and mainly compensating the excitation and reactive power. This method can better limit the reactive power load of the power unit. Advantages of random compensation: When the power equipment is in operation, the reactive power compensation is input, and when the power equipment is out of service, the compensation equipment also exits, and the compensation capacity does not need to be adjusted frequently. With less investment, small footprint, easy installation, convenient and flexible configuration, simple maintenance, low accident rate.
b. Accompanying device compensation The device compensating means that the low-voltage capacitor is connected to the secondary side of the distribution transformer through low-voltage protection to compensate for the no-load reactive power compensation method of the distribution transformer. The reactive load of the transformer during light load or no-load is mainly the no-load excitation and reactive power of the transformer, and the no-load reactive power distribution is the main part of the reactive power load per unit of electricity. For the light load distribution, this Part of the loss accounted for a large proportion of the power supply, resulting in an increase in the unit price of electricity. Advantages of the follower compensation: simple wiring, convenient maintenance and management, can effectively compensate for no-load reactive power distribution, limit the rural network base load, and make the part reactive and on-site balance, thereby improving the utilization ratio of distribution transformer, reducing the The loss of work network and high economic efficiency is one of the most effective means of compensating for reactive power.
c. Tracking Compensation Tracking compensation refers to the method of compensating the low voltage capacitor bank on the 0.4kv busbar of the large user with the reactive power compensation switching device as the control protection device. Applicable to special distribution transformers above 100kVA, it can replace random and follow-up two compensation methods, the compensation effect is good. The advantage of follow-up compensation is that the operation mode is flexible and the operation and maintenance workload is small. Compared with the first two compensation methods, the service life is relatively longer and the operation is more reliable. Priority should be given to tracking compensation.
IV. Reactive power compensation of high voltage distribution network:
1. State Power Corporation issued a document on the first-class power industry, requiring a 10kV power factor of not less than 0.9, a line loss of no more than 5%, and operation and management of voltage quality and reactive power compensation, etc. One of the key problems to be solved It is to put a certain capacitor in the 10kV line and use a fixed or automatic input method to realize reactive power compensation. If a fixed capacitor bank is put into a power supply line, it is generally calculated according to the low load of the line, and the automatic compensation amount is the value calculated when the line is at full load. One line has fixed and automatic compensation, and the two modes cooperate with each other. The desired effect can be achieved.
2. The principle of reactive power compensation is based on local balance. According to the actual situation of distribution network of rural power grids, it is more complicated and impossible to be a unified model. Therefore, it is necessary to use a combination of decentralized and centralized, fixed, and automatic methods, which is divided into three steps: First, Within the substation, a fixed compensation capacitor bank is installed at about 15% of the capacity of the main transformer. The second is to install a fixed compensation capacitor bank at the load center or somewhere along the reactive power demand at low load. The third is to install an automatic compensation capacitor bank on the upper side of the line load center.
3. For the 10kV distribution network system mainly used by rural power grids, the complete reactive power compensation should include substation centralized compensation, 10 kV line compensation and customer-side low-voltage compensation, plus random compensation, ie "3 compensation + random compensation" ("3+1" "mode). Empirical estimation: When COSφ is about 0.6 to 0.7, it can be compensated by about 15% of the actual load of the feeder or by 2/3 of the reactive power gap.
4. Taking into account the effect of reducing line losses and improving the power rate and voltage, the principle of line compensation is to implement single- or multi-point capacitor compensation by installing capacitors on the line poles. The single-point compensation point is selected at the 2/3 point from the head of the line. The compensation capacity should be 2/3 of the reactive load; the two points of compensation should be installed at 2/5 and 4/5 of the head end; if the line is longer, the load is larger, and the combination of fixed compensation and automatic compensation is implemented. Three points on the line are distributed: the first assembly is fixed at 2/7 of the line, and the second group is automatic compensation. It is installed at 4/7 of the line, which is also the location where the load is more concentrated; The group is a fixed compensation and installed at 6/7 of the line. The multi-point compensation uses the branch line segment compensation method to compensate for lines with large branches or low natural power factor with long line loads. According to the actual conditions in rural areas, compensation points for rural network lines should not be excessive; control methods should be simplified; protection methods can be used as fuses and lightning arresters as simple over-current and over-voltage protection.
5. To determine the compensation capacity of a certain distribution line, calculate the average reactive load and minimum reactive load of the line. When the minimum reactive load of the line is less than 2/3 of the average reactive load, consider that the reactive power should not be To reverse, a fixed compensation device can be installed, but the compensation capacity should be determined by the minimum reactive load. When there is a large reactive load point in the line, in addition to considering the distance from the beginning of the line, large reactive load points should also be considered. The actual installed compensation device is preferably 100-200 kvar per group.
Medical Industry Mass Flow Meter
Sealand is a professional manufacturer of Medical Mass Flow Meter, Medical Mass Flowmeter, Medical Coriolis Meter, Medical Flow Meter, Medical Flowmeter, ATEX, IECEx & CE approved.
There are 2 optical switches for operation. The SET and SELECT optical switches are used to navigate the transmitter display. To activate an optical switch, move your finger 1~2mm over the optical switch close to the glass.
Mark:
1. The display will timeout without any operation in 5 min.
2. During numbers input, the decimal point will come up automatically if the first digit is 0; if not 0, please activate SELECT until decimal point shows up.
The general operation is listed as follows.
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On Main Interfaces |
Activate SET to alternate mass and volume values. |
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Activate SELECT to alternate main interfaces. |
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Long activate SELECT to go to Setup Interface. |
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Long activate SET for total reset.
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Back to Main Interface |
Long activate SET & SELECT at the same time.
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Select Submenu, Parameters & Numbers |
Activate SELECT to select the submenu, parameters or numbers. |
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Activate SET to go to submenu or save parameters/numbers. |
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Save setup |
Long activate SET to save the modified setup. |
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Back or Exit |
Long activate SELECT. |
Medical Mass Flow Meter, Medical Mass Flowmeter, Medical Coriolis Meter, Medical Flow Meter, Medical Flowmeter
Zhejiang Sealand Technology Co., Ltd. , https://www.sealandflowmeter.com