CN105591396B - The three-phase imbalance guard method of the distribution transformer of low-voltage distributing line and device - Google Patents
The three-phase imbalance guard method of the distribution transformer of low-voltage distributing line and device Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
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Abstract
Three-phase imbalance guard method and device the invention discloses a kind of distribution transformer of low-voltage distributing line, the method comprising the steps of：It monitors low-voltage distributing line, acquires low-voltage distributing line three-phase current in real time, and obtain actual power load；According to the actual power load and three-phase current of low-voltage distributing line, distribution transformer load rate β and neutral point current I is calculated respectively0；As distribution transformer load rate β and neutral point current I0When meeting the first decision condition, the tri-phase unbalance factor of the distribution transformer of low-voltage distributing line is calculated；According to the size of tri-phase unbalance factor, to the three-phase load of low-voltage distributing line, corresponding Risk-warning rank is selected to be handled.The device includes monitoring acquisition module, the first computing module, the second computing module and execution module.The present invention can significantly reduce the degree of unbalancedness of three-phase current.
Description
Technical field
The present invention relates to field of relay protection in power more particularly to a kind of distribution transformers of low-voltage distributing line
Three-phase imbalance guard method and device.
Background technology
The quickening of Urbanization Construction so that the load electricity of low-voltage network (low pressure refers to less than 1 kilovolt voltage) is continuously increased,
Especially summer peak meeting and seasonal low pressure power load surges during the Spring Festival etc., causes part distribution transformer to be chronically at super negative
Lotus operating status.By the investigation to somewhere whole year distribution transformer damaged condition and analysis it is found that three-phase imbalance is to match
One of the main reason for piezoelectric transformer damages.
Three-phase imbalance：Associate power standard provides that the three-phase load of distribution transformer should balance as possible, must not use one
Mutually or two-phase is powered.Low pressure is not to be exceeded in the distribution transformer for being Yyn0 and Dyn11 for connection group, neutral current respectively
The 25% of side rated current and 40%.But due to low pressure power load at any time, space wave it is big, three-phase imbalance phenomenon exists
Rural power grids power distribution station is more common, and when three-phase imbalance occurs in distribution transforming, heavy load phase current is excessive (maximum can increase to 3 times),
Distribution transforming insulation ag(e)ing quickening, oil quality deterioration are easily led to, so as to which the insulation performance for making distribution transformer reduces rapidly, the lost of life,
Severe patient even burns distribution transformer.Meanwhile three-phase imbalance can also increase the loss of distribution transformer and circuit, influence to supply
Electric Business Economic Benefit.
At present, for the situation of three-phase imbalance, alleviate frequently with following measures：
1) circuit is transformed.Which boundary of works area is big, and since some areas power grid is distributed in mountain area, and circuit is integrally changed
Position workload is too big, therefore should not use at present.
2) scatteredload.Out-of-balance load dispersion is connected on different power supply points, load can be reduced in this way
Degree of unbalancedness caused by concentrating.
3) compensation device is added.If three-phase load unbalance, and power factor is relatively low, then can use the capacitance of different capabilities
Device group can add reactive power compensator as balancing device for the area of reactive capability scarcity.
More than regulative mode either manually or automatically adjusts feeder switch and carrys out distribution load, still passes through switching capacitance
Device group carries out load compensation, all a kind of only regulative mode of classification, can not dynamic, efficiently carry out three-phase imbalance tune
Section.
Invention content
Present invention aims at the three-phase imbalance guard method for providing a kind of distribution transformer of low-voltage distributing line and
Device, with distribution transformer aging and damage caused by solving three-phase imbalance, and existing regulative mode can not dynamic, efficiently
Ground carries out the technical issues of three-phase imbalance adjusting.
To achieve the above object, the present invention provides a kind of three-phase imbalance of distribution transformer of low-voltage distributing line guarantors
Maintaining method includes the following steps：
S1：It monitors low-voltage distributing line, acquires low-voltage distributing line three-phase current in real time, and obtain actual power load；
S2：According to the actual power load and three-phase current of low-voltage distributing line, distribution transformer load rate β and neutrality are calculated respectively
Point electric current I0；
S4：As distribution transformer load rate β and neutral point current I0When meeting the first decision condition, matching for low-voltage distributing line is calculated
The tri-phase unbalance factor of piezoelectric transformer；
S5：According to the size of tri-phase unbalance factor, to the three-phase load of low-voltage distributing line, corresponding Risk-warning is selected
Rank is handled.
Further improvements in methods as the present invention：
Preferably, step S2 includes the following steps：
S2.1：According to the actual power load of low-voltage distributing line, distribution transformer load rate β is calculated, formula is as follows：
Distribution transformer load rate β=[actual power load/substation's rated load] × 100% (1)
Wherein, rated load of substation's rated load for the main transformer of substation；
S2.2：According to the low voltage three-phase electric current I of distribution transformerA、IBAnd IC, calculate neutral point current I0, formula is as follows：
Neutral point current
Preferably, after the completion of step S2, method further includes step：
S3：As distribution transformer load rate β and neutral point current I0When meeting the second decision condition, return to step S1.
Preferably, the first decision condition is I0>15%IN or β>25%；Second decision condition is I0≤ 15%INAnd β≤
25%, wherein, INThe rated current of low-pressure side for distribution transformer.
Preferably, the calculation formula of tri-phase unbalance factor is as follows：
Tri-phase unbalance factor
Wherein, ImaxAnd IminMaximum value and minimum value respectively in distribution low-voltage three-phase current.
Preferably, step S5 includes the following steps：
S5.1：According to the size of tri-phase unbalance factor, make the following judgment：
S5.2：Work as ε<When 15%, into prime risk early warning, strengthen monitoring, and return to step S1；
S5.3：As 15%≤ε<When 50%, into two level Risk-warning, and cumulative time on same day t1Reach 2 hours, in time
Carry out balancing the load；
S5.4：As ε >=50%, into tertiary risk early warning, low-voltage reactive compensator, cumulative time on same day t are put into2
Reach 2 hours, carry out balancing the load in limited time.
Preferably, balancing the load is realized using cycle excision method, is included the following steps：
S5.3.1：Three corresponding degrees of unbalancedness are calculated, judge phase where maximum degree of unbalancedness, cut-out load；
S5.3.2：Cycle carries out above step, until degree of unbalancedness reaches distribution requirement.
The technical concept total as one, the present invention also provides a kind of three-phases of the distribution transformer of low-voltage distributing line
Unbalance protection device, including monitoring acquisition module, the first computing module, the second computing module and execution module.Wherein：
Monitor acquisition module, for monitoring low-voltage distributing line, and in real time the three-phase voltage of acquisition low-voltage distributing line and
Three-phase current, and actual power load is obtained, send result to the first computing module；
First computing module for the actual power load and three-phase current according to low-voltage distributing line, calculates match respectively
Variable load rate β and neutral point current I0, calculated value is sent to the second computing module；
Second computing module, in distribution transformer load rate β and neutral point current I0When meeting the first decision condition, calculate low
It is press-fitted the tri-phase unbalance factor of the distribution transformer of electric line；
Execution module, for the size according to tri-phase unbalance factor, to the three-phase load of low-voltage distributing line, selection is corresponding
Risk-warning rank handled.
As being further improved for the device of the invention：
Second computing module is additionally operable in distribution transformer load rate β and neutral point current I0When meeting the second decision condition, to prison
It is sent depending on acquisition module and performs signal.
Execution module includes the first execution module, the second execution module and third execution module, wherein, the first execution module
For meeting ε in tri-phase unbalance factor ε<When 15%, into prime risk early warning, strengthen monitoring, and monitor that acquisition module is sent
Perform signal；Second execution module is used to meet 15%≤ε in tri-phase unbalance factor ε<When 50%, into two level Risk-warning,
And cumulative time on same day t1Reach 2 hours, carry out balancing the load in time；Third execution module is used to expire in tri-phase unbalance factor ε
During sufficient ε >=50%, into tertiary risk early warning, low-voltage reactive compensator, cumulative time on same day t are put into2Reach 2 hours, limit
Shi Jinhang balancing the loads.
The invention has the advantages that：
1st, the three-phase imbalance guard method of the distribution transformer of low-voltage distributing line of the invention, is obtained by calculating in real time
Distribution transforming tri-phase unbalance factor is obtained, corresponding Risk-warning rank is selected to handle low-voltage three-phase load, three can be significantly reduced
The degree of unbalancedness of phase current can slow down the aging conditions of distribution transformer, extend the service life of distribution transformer, ensure low
Press the power supply reliability and power quality of user.
2nd, in a preferred approach, method of the invention carries out low-voltage three-phase load dynamic management and auto-reactive compensation,
The degree of unbalancedness of three-phase current is reduced, improves the safety and stability of low-voltage network；Increase for low-voltage distribution network transformation, system
Hold, distribution transforming layout selection etc. plannings scientific basis, by adjusting load, rational increase-volume is layouted, so as to reach radical cure
The unbalanced purpose of low voltage three-phase.
3rd, the three-phase imbalance protective device of the distribution transformer of low-voltage distributing line of the invention, can dynamically, efficiently
Ground carries out three-phase imbalance adjusting, improves low-voltage distribution network production management efficiency, ensures the safe and stable operation of low-voltage network.
Other than objects, features and advantages described above, the present invention also has other objects, features and advantages.
Below with reference to accompanying drawings, the present invention is described in further detail.
Description of the drawings
The attached drawing for forming the part of the application is used to provide further understanding of the present invention, schematic reality of the invention
Example and its explanation are applied for explaining the present invention, is not constituted improper limitations of the present invention.In the accompanying drawings：
Fig. 1 is the three-phase imbalance guard method of the distribution transformer of the low-voltage distributing line of the preferred embodiment of the present invention
Flow chart；
Fig. 2 is the three-phase imbalance protection side of the distribution transformer of the low-voltage distributing line of another preferred embodiment of the present invention
The flow chart of method；
Fig. 3 is the composition of the three-phase imbalance protection of the distribution transformer of the low-voltage distributing line of the preferred embodiment of the present invention
Functional block diagram；
Fig. 4 is 10 days 2 months three-phase current curve graphs before preferred embodiment of the present invention application；
Fig. 5 is the three-phase current curve graph on November 15 after preferred embodiment of the present invention application.
Specific embodiment
The embodiment of the present invention is described in detail below in conjunction with attached drawing, but the present invention can be defined by the claims
Implement with the multitude of different ways of covering.
Referring to Fig. 1, the three-phase imbalance guard method of the distribution transformer of the embodiment of the present invention includes the following steps：
S1：It monitors low-voltage distributing line, acquires low-voltage distributing line three-phase current in real time, and obtain actual power load；
S2：According to the actual power load and three-phase current of low-voltage distributing line, distribution transformer load rate β and neutrality are calculated respectively
Point electric current I0；
S4：As distribution transformer load rate β and neutral point current I0When meeting the first decision condition, matching for low-voltage distributing line is calculated
The tri-phase unbalance factor of piezoelectric transformer；
S5：According to the size of tri-phase unbalance factor, to the three-phase load of low-voltage distributing line, corresponding Risk-warning is selected
Rank is handled.
In above step, distribution transforming tri-phase unbalance factor is obtained by calculating in real time, low-voltage three-phase load is selected corresponding
Risk-warning rank is handled, and can significantly reduce the degree of unbalancedness of three-phase current, can slow down the aging conditions of distribution transformer,
Extend the service life of distribution transformer, ensure the power supply reliability and power quality of low-voltage customer.
Referring to Fig. 2, optimized as follows in practical application, the embodiment of the present invention can also increase step：
S1：It monitors low-voltage distributing line, acquires low-voltage distributing line three-phase current in real time, and it is straight to pass through electric detection system
It obtains and takes actual power load.
S2：According to the actual power load and three-phase current of low-voltage distributing line, distribution transformer load rate β and neutrality are calculated respectively
Point electric current I0.Include the following steps：
S2.1：According to the actual power load of low-voltage distributing line, distribution transformer load rate β is calculated, formula is as follows：
Distribution transformer load rate β=[actual power load/substation's rated load] × 100% (1)
Wherein, rated load of substation's rated load for the main transformer of substation；
S2.2：According to the low voltage three-phase electric current I of distribution transformerA、IBAnd IC, calculate neutral point current I0, formula is as follows：
Neutral point current
When distribution transformer load rate β and neutral point current I is calculated0Afterwards, condition judgment is first carried out, it is therefore an objective to judge distribution transforming three
Whether phase degree of unbalancedness needs to be included in calculating and statistics.
S3：As distribution transformer load rate β and neutral point current I0Meet I0(I when≤15%IN and β≤25%NFor distribution transformer
The rated current of the low-pressure side of device), distribution transforming tri-phase unbalance factor is not included in calculating and statistics, return to step S1.15%, 25% is
It is obtained according to practical engineering experience, in I0≤ 15%INAnd during β≤25%, three-phase imbalance level is very low, is not influencing resident just
Common electricity, at this time without the necessity of compensating three-phase unbalance, it is therefore not necessary to take any measure, when condition is not satisfied then
It needs distribution transforming tri-phase unbalance factor being included in calculating and statistics.
S4：As distribution transformer load rate β and neutral point current I0Meet I0>15%INOr β>When 25%, low-voltage distributing line is calculated
Distribution transformer tri-phase unbalance factor, if do not adopted an effective measure, tri-phase unbalance factor of leaving continues to increase, it will shadow
It rings resident's normal electricity consumption or even occurs using electric fault.The calculation formula of tri-phase unbalance factor is as follows：
Tri-phase unbalance factor
Wherein, ImaxAnd IminMaximum value and minimum value respectively in distribution low-voltage three-phase current.
S5：According to the size of tri-phase unbalance factor, to the three-phase load of low-voltage distributing line (and accumulation it is uneven when
Between), corresponding Risk-warning rank is selected to be handled, that is, sets taiwan area low-voltage load three-phase equilibrium alarm function, specifically such as
Under：
S5.1：According to the size of tri-phase unbalance factor, make the following judgment：
S5.2：Work as ε<When 15%, into prime risk early warning, strengthen monitoring, and return to step S1.Work as ε<When 15%, this
When three-phase imbalance problem can not be ignored, but degree does not influence resident's normal electricity consumption also, tri-phase unbalance factor does not reach
To 15% i.e. ε<15%, it need not temporarily take the concrete measures at this time, but due to the critical condition for being in three-phase imbalance, need
Strengthen monitoring dynamics, prevent the situation of degree of unbalancedness out-of-limit 15%.Such as 0.4t is once changed to by original t time monitorings
Monitoring is primary in time (surveillance style is constant, and monitoring time interval shortens), is accordingly arranged once being taken into three-phase imbalance
It applies.
S5.3：As 15%≤ε<When 50%, into two level Risk-warning, and cumulative time on same day t1Reach 2 hours, explanation
The degree of three-phase imbalance can not be ignored, and need to take certain measure to realize the balance of three-phase, carries out load in time and puts down
Weighing apparatus,.Balancing the load is realized using cycle excision method, is included the following steps：
S5.3.1：Three corresponding degrees of unbalancedness are calculated, judge phase where maximum degree of unbalancedness, cut-out load subtracts
Small tri-phase unbalance factor；
S5.3.2：Cycle carries out above step, until degree of unbalancedness reaches distribution requirement.
S5.4：As ε >=50%, into tertiary risk early warning, illustrate that the degree of three-phase imbalance is very serious, need to throw
Enter low-voltage reactive compensator, cumulative time on same day t2Reach 2 hours, carry out balancing the load, the realization side of balancing the load in limited time
Method is identical to step S5.3.2 with step S5.3.1.Low-voltage reactive compensator is a kind of power electronic equipment, and voltage-type is changed
It flows device (VSC) and power grid is accessed by reactor or connection transformers connected in parallel, according to the summing target of wanting of control targe, suitably adjust
It saves the amplitudes of VSC exchange side output voltages, phase or can just reactive power compensator be connected by directly controlling its ac-side current
Continuous adjustable output 100% is advanced or 100% lag is idle, so as to which system voltage stabilization, power factor be promoted to improve.Low-voltage reactive power
The input for compensating equipment obtains the reactive capability compensated needed for system by electric detection system；According to single group reactive capability, really
Fixed final input group number.
2 hours cumulative times were the engineering experience value of grid company engineers and technicians for a long time, and reason is rural power grids
Peak of power consumption generally at night 8:00-10:00.Other delay time length can also, it is but small less than 2 from probability
When, the electricity consumption of Residents can be influenced；If above 2 hours, and it can influence to adjust the real-time of three-phase imbalance.
Referring to Fig. 3, the three-phase imbalance protective device of the distribution transformer of the low-voltage distributing line of the embodiment of the present invention, packet
Include monitoring acquisition module, the first computing module, the second computing module and execution module.Wherein, monitoring acquisition module is used to supervise
Depending on low-voltage distributing line, and the three-phase voltage and three-phase current of low-voltage distributing line are acquired in real time, and obtain actual power load,
Send result to the first computing module；First computing module is used for actual power load and three-phase according to low-voltage distributing line
Electric current calculates distribution transformer load rate β and neutral point current I respectively0, calculated value is sent to the second computing module；Second calculates mould
Block is used in distribution transformer load rate β and neutral point current I0When meeting the first decision condition, the distribution for calculating low-voltage distributing line becomes
The tri-phase unbalance factor of depressor.Execution module is used for the size according to tri-phase unbalance factor, and the three-phase of low-voltage distributing line is born
Lotus selects corresponding Risk-warning rank to be handled.Device can dynamic, efficiently carry out three-phase imbalance adjusting, improve
Low-voltage distribution network production management efficiency ensures the safe and stable operation of low-voltage network.
In practical application, the second computing module of the embodiment of the present invention, can also set for distribution transformer load rate β and in
Property point electric current I0When meeting the second decision condition, sent to monitoring acquisition module and perform signal.The system external passes through optical fiber
It connects, there is stronger insulation and antijamming capability.
In the embodiment of the present invention, execution module includes the first execution module, the second execution module and third execution module,
In, the first execution module is used to meet ε in tri-phase unbalance factor ε<When 15%, into prime risk early warning, strengthen monitoring, and supervise
It is sent depending on acquisition module and performs signal；Second execution module is used to meet 15%≤ε in tri-phase unbalance factor ε<When 50%, enter
Two level Risk-warning, and cumulative time on same day t1Reach 2 hours, carry out balancing the load in time；Third execution module is used for three
When phase degree of unbalancedness ε meets ε >=50%, into tertiary risk early warning, low-voltage reactive compensator, cumulative time on same day t are put into2
Reach 2 hours, carry out balancing the load in limited time.
Since current financial cost limits, uneven scheme focuses primarily upon two kinds of load adjustment and reactive-load compensation, practical
Engineering experience shows if in tri-phase unbalance factor ε>It is still taken no action to after 15%, the power quality of resident will be by shadow
It rings, part electric appliance will be unable to normal use；And in ε>After 50%, can not also it be expired using the scheme of load adjustment three-phase equilibrium degree
Sufficient distribution requirement；Therefore, work as ε<When 15%, practical step is not taken；In 15%≤ε<When 50%, using switching load adjustment three
Degree of balancing each other；In ε >=50%, input reactive power compensator adjustment tri-phase unbalance factor.The selection of above-mentioned threshold value disclosure satisfy that
The requirement of distribution, and various schemes can be applied to it is ultimate attainment, belong to utilizing works experience acquisition optimal value.
In order to further verify the present invention method and device to low voltage three-phase unbalanced effect of integrated pest management, in state's net
Hunan Electric Power Company carries out field application test to it, and Fei Lian villages Bridge of Security taiwan area (capacity is had under its command with Xiang Tan Zao Cun power supply stations
80kV Α) it administers front and rear data and is compared.
Taiwan area method and device not using the present invention, taiwan area three-phase current basic condition is shown in Table 1 within 10 days 2 months, specifically
Three-phase current curve is as shown in Figure 4.As can be seen that three-phase current unbalance rate reaches 78.93%, the power supply of electric system is reliable
Property is too low, while has seriously affected the power quality of power consumer.
10 days 12 months taiwan area three-phase current basic condition tables of table
Taiwan area is in protection device for installing on April 21, through comprehensive treatment after a period of time, November 15 taiwan area three-phase current
Basic condition is shown in Table 2, and the three-phase current curve of different moments is as shown in Figure 5.At this point, the unbalance factor of three-phase current is reduced to
15.32%, for the system for not installing Intelligent power distribution terminal, the unbalance factor of three-phase current reduces 80.59%, and whole day is born
The imbalance problem of charged current has obtained effective alleviation.
The intelligent distribution transformer terminals pilot taiwan area basic condition table of table 2
In summary, the present invention obtains distribution transforming tri-phase unbalance factor by calculating in real time, low-voltage three-phase load is carried out dynamic
State management and auto-reactive compensation reduce the degree of unbalancedness of three-phase current, can slow down the aging conditions of distribution transformer, and extension is matched
The service life of piezoelectric transformer has ensured the power supply reliability and power quality of low-voltage customer, increases for low-voltage distribution network transformation, system
Hold, distribution transforming layout selection etc. plannings scientific basis, by adjusting load, rational increase-volume is layouted, so as to reach radical cure
The unbalanced purpose of low voltage three-phase.
The foregoing is only a preferred embodiment of the present invention, is not intended to restrict the invention, for the skill of this field
For art personnel, the invention may be variously modified and varied.All within the spirits and principles of the present invention, that is made any repaiies
Change, equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.
Claims (6)
1. a kind of three-phase imbalance guard method of the distribution transformer of low-voltage distributing line, which is characterized in that including following step
Suddenly：
S1：It monitors the low-voltage distributing line, acquires the low-voltage distributing line three-phase current in real time, and obtain actual power and bear
Lotus；
S2：According to the actual power load and three-phase current of the low-voltage distributing line, distribution transformer load rate β and neutrality are calculated respectively
Point electric current I0；
S4：As the distribution transformer load rate β and neutral point current I0When meeting the first decision condition, the low-voltage distributing line is calculated
Distribution transformer tri-phase unbalance factor, the calculation formula of the tri-phase unbalance factor is as follows：
Wherein, ImaxAnd IminMaximum value and minimum value respectively in distribution low-voltage three-phase current, first decision condition are I0
>15%INOr β>25%；Wherein, INThe rated current of low-pressure side for distribution transformer；
S5：According to the size of the tri-phase unbalance factor, to the three-phase load of low-voltage distributing line, corresponding Risk-warning is selected
Rank is handled, and is included the following steps：
S5.1：According to the size of the tri-phase unbalance factor ε, make the following judgment：
S5.2：Work as ε<When 15%, into prime risk early warning, strengthen monitoring, and return to step S1；
S5.3：As 15%≤ε<When 50%, into two level Risk-warning, and cumulative time on same day t1Reach 2 hours, carry out in time
Balancing the load；
S5.4：As ε >=50%, into tertiary risk early warning, low-voltage reactive compensator, cumulative time on same day t are put into2Reach 2
Hour, balancing the load is carried out in limited time.
2. three-phase imbalance guard method according to claim 1, which is characterized in that the step S2, including following step
Suddenly：
S2.1：According to the actual power load of the low-voltage distributing line, distribution transformer load rate β is calculated, formula is as follows：
Distribution transformer load rate β=[actual power load/substation's rated load] × 100% (1)
Wherein, rated load of substation's rated load for the main transformer of substation；
S2.2：According to the low voltage three-phase electric current I of distribution transformerA、IBAnd IC, calculate neutral point current I0, formula is as follows：
3. three-phase imbalance guard method according to claim 1, which is characterized in that described after the completion of the step S2
Method further includes step：
S3：As the distribution transformer load rate β and neutral point current I0When meeting the second decision condition, return to step S1, described second sentences
Fixed condition is I0≤ 15%INAnd β≤25%.
4. three-phase imbalance guard method according to claim 3, which is characterized in that the balancing the load is cut using cycle
Division is realized, is included the following steps：
S5.3.1：Three corresponding degrees of unbalancedness are calculated, judge phase where maximum degree of unbalancedness, cut-out load；
S5.3.2：Cycle carries out above step, until degree of unbalancedness reaches distribution requirement.
A kind of 5. three-phase imbalance protective device of the distribution transformer of low-voltage distributing line, which is characterized in that described device packet
It includes：
It monitors acquisition module, for monitoring the low-voltage distributing line, and acquires the three-phase electricity of the low-voltage distributing line in real time
Pressure and three-phase current, and actual power load is obtained, send result to the first computing module；
First computing module for the actual power load and three-phase current according to the low-voltage distributing line, is counted respectively
Calculate distribution transformer load rate β and neutral point current I0, calculated value is sent to the second computing module；
Second computing module, in the distribution transformer load rate β and neutral point current I0When meeting the first decision condition, meter
The tri-phase unbalance factor of the distribution transformer of the low-voltage distributing line is calculated, first decision condition is I0>15%INOr β>
25%；Wherein, INThe rated current of low-pressure side for distribution transformer；
Execution module, for the size according to the tri-phase unbalance factor, to the three-phase load of low-voltage distributing line, selection is corresponding
Risk-warning rank handled；The execution module includes：
First execution module, for meeting ε in tri-phase unbalance factor ε<When 15%, into prime risk early warning, strengthen monitoring, and
The monitoring acquisition module, which is sent, performs signal；
Second execution module, for meeting 15%≤ε in tri-phase unbalance factor ε<When 50%, into two level Risk-warning, and work as
Day cumulative time t1Reach 2 hours, carry out balancing the load in time；
Third execution module, for when tri-phase unbalance factor ε meets ε >=50%, into tertiary risk early warning, input low pressure without
Reactive power compensation installations, cumulative time on same day t2Reach 2 hours, carry out balancing the load in limited time.
6. three-phase imbalance protective device according to claim 5, which is characterized in that second computing module is also used
In in the distribution transformer load rate β and neutral point current I0When meeting the second decision condition, held to the monitoring acquisition module transmission
Row signal, second decision condition are I0≤ 15%INAnd β≤25%.
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| CN106786678A (en) * | 2016-12-13 | 2017-05-31 | 国网北京市电力公司 | Three-phase imbalance regulates and controls method and device |
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| CN111030126B (en) * | 2019-12-24 | 2022-06-21 | 广西电网有限责任公司电力科学研究院 | Load-voltage sensitivity-based low-voltage early warning method for power distribution network |
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