CN116667721A - Capacity and voltage regulating method of power transformer and power transformer - Google Patents
Capacity and voltage regulating method of power transformer and power transformer Download PDFInfo
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- CN116667721A CN116667721A CN202310945263.9A CN202310945263A CN116667721A CN 116667721 A CN116667721 A CN 116667721A CN 202310945263 A CN202310945263 A CN 202310945263A CN 116667721 A CN116667721 A CN 116667721A
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- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000004804 winding Methods 0.000 claims abstract description 79
- 238000005070 sampling Methods 0.000 claims abstract description 35
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 239000002826 coolant Substances 0.000 claims description 8
- 238000000819 phase cycle Methods 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 3
- 230000002035 prolonged effect Effects 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 9
- 230000008569 process Effects 0.000 description 5
- 230000009471 action Effects 0.000 description 3
- 238000010891 electric arc Methods 0.000 description 3
- 230000007363 regulatory process Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
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- 238000006243 chemical reaction Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P13/00—Arrangements for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output
- H02P13/06—Arrangements for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output by tap-changing; by rearranging interconnections of windings
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/2823—Wires
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/40—Structural association with built-in electric component, e.g. fuse
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/40—Structural association with built-in electric component, e.g. fuse
- H01F27/402—Association of measuring or protective means
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F29/00—Variable transformers or inductances not covered by group H01F21/00
- H01F29/02—Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
- H01F29/025—Constructional details of transformers or reactors with tapping on coil or windings
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/40—Structural association with built-in electric component, e.g. fuse
- H01F27/402—Association of measuring or protective means
- H01F2027/406—Temperature sensor or protection
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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
- Y02E40/30—Reactive power compensation
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- Control Of Electrical Variables (AREA)
Abstract
The application discloses a capacity and voltage regulating method of a power transformer and the power transformer, and belongs to the three-phase voltage control technology. According to the capacitance and voltage regulating method, apparent power is calculated through twice sampling, and then the winding is kept in a high-capacity access state or a low-capacity access state through a capacitance regulating switch. Meanwhile, a voltage regulating time sequence table is set according to the difference value between the primary effective voltage and the target voltage, a voltage regulating switch is controlled, the discharge loss ratio is predicted, and the reference capacity is regulated according to the discharge loss ratio. And setting a capacity-regulating threshold according to the medium temperature, and avoiding the temperature rise of the transformer caused by switching delay. The voltage regulating switch comprises a first contact and a second contact, and the first contact and the second contact are alternately switched according to a voltage regulating time sequence table. According to the application, the time period of the arc state is accurately determined from the instantaneous current through the voltage regulation time sequence table, so that the capacity threshold is regulated, and the service life of the voltage regulation switch is prolonged.
Description
Technical Field
The present application relates to a three-phase voltage control technology, and more particularly, to a capacity and voltage regulating method of a power transformer and a power transformer.
Background
The power transformer can adjust the capacity according to the load, and the no-load loss is reduced. The voltage regulation operation of the transformer can adjust the transformation ratio and ensure the stable output. The voltage and capacity regulation can be generally performed simultaneously, and the structure of the voltage and capacity regulation switch is like a vacuum on-load capacity regulation pressure regulation oil immersed transformer of CN 202110808241.9. Capacity and voltage regulation under load conditions is referred to as on-load capacity and voltage regulation. The capacity-regulating voltage-regulating winding and the capacity-regulating voltage-regulating method disclosed in CN201910153520.9 realize voltage regulation by separating the voltage-regulating winding from the capacity-regulating winding and connecting the voltage-regulating winding with the capacity-regulating winding. The voltage and capacity regulating switch is the only action part in the power transformer, and the service life of the switch directly influences the service life of the power transformer. In the occasions such as water conservancy and wind power stations, the capacity fluctuation of the power transformer is large, and the frequent capacity adjustment operation can accelerate the switch damage. In addition, due to the existence of a secondary winding load, during the working process of the voltage regulating switch, the contact may generate an electric arc, the size of the electric arc is related to the phase current of the coil where the contact is positioned, and the damage of an action part of the voltage regulating switch is accelerated by discharge loss generated by the electric arc. Therefore, it is necessary to adjust the parameters of voltage regulation and capacity regulation, and to extend the life of the power transformer.
Disclosure of Invention
In order to solve the defects in the prior art, the application provides a capacity and voltage regulating method of a power transformer and the power transformer, which are used for executing secondary sampling with higher precision after the primary sampling is completed, so as to avoid frequent switching of a capacity regulating switch caused by sampling errors. Further, in the voltage regulating process, the capacity threshold is regulated according to the discharge loss, so that the service life of the voltage regulating switch is prolonged.
The technical scheme of the application is realized as follows:
a capacity and voltage regulating method of a power transformer comprises the following steps:
step 1: the primary switch group and the secondary switch group of the capacity-regulating switch are respectively arranged on the primary winding and the secondary winding, the voltage-regulating switch is arranged on the primary winding, the capacity-regulating switch has a low capacity access state and a high capacity access state, and the voltage-regulating switch has a plurality of connection grades;
step 2: monitoring the medium temperature of a transformer, generating a capacity-regulating threshold lambda according to the medium temperature, collecting the instantaneous voltage and the instantaneous current of each phase of a secondary winding at intervals of a first sampling period to obtain a secondary effective voltage and a secondary effective current, and calculating apparent power S;
step 3: if the apparent power S is less than or equal to the lower capacity limit (1-lambda) S 0 Step 4, if the apparent power S is greater than or equal to the upper capacity limit (1+lambda) S 0 Step 5 is entered, if the apparent power S is greater than the lower capacity limit (1-lambda) S 0 And is smaller than the upper capacity limit (1+lambda) S 0 Go to step 6, S 0 Is the reference capacity;
step 4: in time period T 1 Collecting the instantaneous voltage and the instantaneous current of the secondary winding at each second sampling period, generating a secondary effective voltage and a secondary effective current, calculating apparent power S, and if the apparent power S is still smaller than or equal to the lower limit of capacity, keeping the capacity-regulating switch in a low-capacity access state, and entering a step 6;
step 5: in time period T 2 Collecting the instantaneous voltage and the instantaneous current of the secondary winding at each second sampling period, generating a secondary effective voltage and a secondary effective current, calculating apparent power S, and if the apparent power S is still more than or equal to the upper limit of capacity, keeping the capacity-regulating switch in a high-capacity access state, and entering a step 6;
step 6: measuring the instantaneous voltage of the primary winding to obtain primary effective voltage, calculating the difference value between the primary effective voltage and target voltage, and generating a voltage regulating time sequence table if the difference value is greater than or equal to the stage voltage;
step 7: controlling a voltage regulating switch according to the voltage regulating time sequence table, measuring the instantaneous current of the voltage regulating switch in the time for executing the voltage regulating time sequence table, and predicting the discharge loss ratio;
step 8: and (2) adjusting the reference capacity according to the discharge loss ratio, and returning to the step (2).
In the present application, in step 2, the second effective voltageSecond effective current +.>N is the sampling times, u 2x (n) is the instantaneous voltage of phase sequence x in the secondary winding acquired by the nth sampling, i 2x (n) is the instantaneous current of phase sequence x in the secondary winding acquired by nth sampling, x is a positive integer less than or equal to 3, and apparent power S= (P) 21 +P 22 +P 23 )/3，P 2x =U 2x •I 2x 。
In the present application, in step 2, the capacity adjustment threshold valueAlpha is the power factor of the power transformer, and R is the medium temperature.
In the present application, in step 5, the second sampling period is smaller than the first sampling period, the period T 2 Less than a period of time T 1 。
In the present application, in step 6, the voltage regulation schedule is composed of the time periods for which the voltage regulation switch is in the first connection state, the first arc state, the no-load state, the second arc state, and the second connection state.
In the present application, in step 7, the instantaneous current of the voltage regulating switch in the first arc state, the no-load state and the second arc state is extracted, the discharge loss of the voltage regulating switch in the first arc state, the no-load state and the second arc state is calculated, and the discharge loss ratio is predicted.
In the present application, in step 8, the reference capacity S 0 =2βS 1 •W 2 /(W 1 +W 3 )，W 1 Discharge loss of the first arc state, W 2 Discharge loss in no-load state, W 3 Discharge loss of the second arc state, 2W 2 /(W 1 +W 3 ) Beta is the economic load factor, S is the discharge loss ratio 1 Rated capacity for high capacity access state.
A power transformer, comprising: the device comprises a box body, an iron core, a primary winding, a secondary winding, a cooling medium, a sensor and a controller, wherein the iron core is fixed in the box body, the primary winding and the secondary winding are wound on the iron core, the cooling medium is filled in the box body, the sensor comprises a thermometer, a first voltmeter and a first ammeter, a second voltmeter and a second ammeter, the thermometer and the first ammeter are arranged in the box body, the second voltmeter and the second ammeter are arranged in the primary winding, the second ammeter is arranged in the controller, the controller comprises a data processing unit, a capacity regulating switch and a voltage regulating switch group,
the data processing unit is configured to calculate apparent power and primary effective voltage, and generate a voltage regulation time sequence table according to the primary effective voltage;
the capacitance-regulating switch is configured to maintain a high-capacity access state or a low-capacity access state according to apparent power;
the voltage regulating switch group is configured to maintain a connection level according to a voltage regulating timing schedule, wherein,
the controller predicts the discharge loss ratio and adjusts the reference capacity of the capacitance-adjusting switch according to the discharge loss ratio.
In the application, the capacity-regulating switch comprises a primary switch group and a secondary switch group, wherein in a high-capacity access state, the primary switch group regulates the primary winding to be in triangular connection, the secondary switch group regulates the secondary winding to be in series connection, and in a low-capacity access state, the primary switch group regulates the primary winding to be in star connection, and the secondary switch group regulates the secondary winding to be in parallel connection.
In the application, the voltage regulating switch comprises a first contact and a second contact, the first contact is connected with the second contact through a circuit breaker, the second ammeter is connected in series on the circuit breaker, the primary winding comprises a plurality of contact rings, the first contact and the second contact,
in the first connection state or the second connection state, the first contact and the second contact are both connected with the contact ring to form a closed loop;
in the second arc state or the second arc state, the first contact is connected with the second contact in parallel through the breaker;
in the idle state, the first contact or the second contact is disconnected from the contact ring.
The capacity and voltage regulating method for the power transformer and the power transformer have the following beneficial effects: and after the primary sampling is finished, secondary sampling with higher precision is performed, so that the capacity-adjusting switching frequency switching caused by sampling errors is avoided. According to the application, the capacity regulating threshold is set outside the reference capacity, and the capacity regulating threshold is set according to the medium temperature, so that the temperature rise of the transformer caused by capacity switching delay is avoided. And the capacity threshold value is adjusted according to the discharge loss, so that the service life of the voltage regulating switch is prolonged. Further, by setting the voltage regulating time sequence table of the voltage regulating switch, the discharge current can be more accurately determined from the instantaneous current.
Drawings
FIG. 1 is a flow chart of a capacity and voltage regulating method of a power transformer according to the present application;
FIG. 2 is a circuit diagram of a primary winding and a secondary winding of the present application;
FIG. 3 is a circuit diagram of a high capacity access state of the present application;
FIG. 4 is a circuit diagram of the low capacity access state of the present application;
FIG. 5 is a circuit diagram of a single phase primary winding and voltage regulating switch set of the present application;
FIG. 6 is a circuit diagram of another state of the primary winding and voltage regulating switch set of the present application;
FIG. 7 is a partial waveform diagram of a single phase instantaneous current of the voltage regulating switch of the present application;
FIG. 8 is a schematic diagram of a voltage regulation schedule according to the present application;
FIG. 9 is a system block diagram of a power transformer of the present application;
fig. 10 is a schematic structural diagram of a power transformer according to the present application.
Detailed Description
The present application will be described and illustrated with reference to the accompanying drawings and examples for a clearer understanding of the objects, technical solutions and advantages of the present application.
The power transformer can be used for the up-down voltage of power stations such as wind power stations, water conservancy stations and the like. The transformer inevitably generates loss during operation. After the transformer is changed from a large capacity state to a small capacity state, the iron loss is reduced to 1/3 of the original iron loss, thereby achieving the purpose of energy saving and loss reduction. The input voltage and power of the power station are unstable, and a capacity and voltage regulating switch is required to be used. When the input side power is reduced, the current capacity of the transformer can be reduced to improve the electric energy conversion rate. When the voltage on the input side fluctuates, the voltage on the output side can be maintained by the voltage regulating switch. The capacity and voltage regulating method of the power transformer improves the accuracy and timeliness of capacity and voltage regulating operation, reduces misoperation of a switch and prolongs the service life.
Example 1
The capacity and voltage regulating method of the power transformer according to the present embodiment as shown in fig. 1 to 7 includes the following steps:
step 1: the primary switch group and the secondary switch group of the capacity-regulating switch are respectively arranged on the primary winding and the secondary winding, the voltage-regulating switch is arranged on the primary winding, the capacity-regulating switch has a low capacity access state and a high capacity access state, and the voltage-regulating switch has a plurality of connection grades.
As shown in fig. 3, the primary windings of the power transformer are connected in a delta shape, and the secondary windings are connected in parallel, so that the power transformer is in a high-capacity access state. As shown in fig. 4, the primary windings of the power transformer are star-connected, and the secondary windings are series-connected, at which time the power transformer is in a low-capacity access state. Typically the secondary winding is divided into three sections of 30% turns, 35% turns and 35% turns. The secondary winding is connected in parallel, namely 35% of turns are connected in parallel with 35% of turns, and then connected in series with 30% of turns. The rated voltage and rated current of the high-capacity access state are both times that of the low-capacity access state, and the rated capacity is 3 times that of the low-capacity access state.
Step 2: monitoring the medium temperature of the transformer, generating a capacity-regulating threshold lambda according to the medium temperature, collecting the instantaneous voltage and the instantaneous current of each phase of the secondary winding at intervals of a first sampling period, obtaining a secondary effective voltage and a secondary effective current, and calculating apparent power S. The first sampling period is for example 1ms. The tuning threshold may be preset to 0.09. In this embodiment, the apparent power is used as a comparison basis of rated capacity, and the apparent power is the sum of active power and reactive power, and is equal in value to the product of the effective current and the effective voltage of the output end.
Due to the directionality of the alternating current, for the purpose ofThe power is calculated conveniently, and the instantaneous voltage and current are converted into effective voltage and current. Second effective voltageSecondary effective current. N is the sampling frequency, and N in the power frequency circuit can be 21.u (u) 2x (n) is the instantaneous voltage of phase sequence x in the secondary winding acquired by the nth sampling, i 2x (n) is the instantaneous current of phase sequence x in the secondary winding acquired by nth sampling, x is a positive integer less than or equal to 3, and apparent power S= (P) 21 +P 22 +P 23 )/3，P 2x =U 2x •I 2x . In this embodiment, the capacity adjustment threshold changes with the medium temperature, and the higher the medium temperature is, the more accurate the capacity adjustment is required, and the smaller the capacity adjustment threshold is. Capacity-regulating threshold valueAlpha is the power factor of the power transformer, R is the medium temperature, R 0 The temperature of the medium may take a value of 25 ℃ to 30 ℃ for the period of non-operation of the transformer. Therefore, the capacity-adjusting threshold value can be simplified to +.>。
Step 3: if the apparent power S is less than or equal to the lower capacity limit (1-lambda) S 0 Step 4, if the apparent power S is greater than or equal to the upper capacity limit (1+lambda) S 0 Step 5 is entered, if the apparent power S is greater than the lower capacity limit (1-lambda) S 0 And is smaller than the upper capacity limit (1+lambda) S 0 Go to step 6, S 0 Is the reference capacity. When apparent power fluctuates around a reference capacity, the application sets a section [ (1-lambda) S to avoid frequent operation of the capacity-regulating switch 0 ，(1+λ)S 0 When the apparent power is within the interval, the capacity-adjusting switch does not work. The reference capacity is usually preset to 0.48 times the rated capacity of the high-capacity access state.
Step 4: in time period T 1 Collecting instantaneous voltage and instantaneous current of the secondary winding at each second sampling period to generateAnd (3) the secondary effective voltage and the secondary effective current are calculated, and if the apparent power S is still smaller than or equal to the capacity lower limit, the capacity-regulating switch is kept in a low-capacity access state, and the step (6) is entered. Otherwise, directly enter step 6. The second sampling period is smaller than the first sampling period. In order to obtain a more accurate apparent power, the second sampling period is for example 0.05ms, i.e. the sampling frequency is 2000Hz, so that unlike step 2 the number of samples of one ac current period is 41. Time period T 1 May be 5s. Time period T 1 And the transformer can reliably reduce the capacity, and the misoperation of the voltage regulating switch is effectively reduced.
Step 5: in time period T 2 And acquiring the instantaneous voltage and the instantaneous current of the secondary winding at each second sampling period, generating a secondary effective voltage and a secondary effective current, calculating apparent power S, and if the apparent power S is still more than or equal to the upper limit of capacity, keeping the capacity-regulating switch in a high-capacity access state, and entering the step 6. Otherwise, directly enter step 6. Time period T 2 May be 2s. Time period T 2 Less than a period of time T 1 . When the load suddenly and greatly increases, the transformer can be quickly adjusted from a small capacity state to a large capacity state, and the transformer is prevented from being burnt during capacity adjustment delay judgment. The present embodiment does not limit T 1 And T is 2 The actual value of the power transformer can be remotely set through a background upper computer according to the actual running condition of the power transformer.
Step 6: measuring the instantaneous voltage of the primary winding to obtain primary effective voltage, calculating the difference value between the primary effective voltage and the target voltage, and generating a voltage regulating time sequence table if the difference value is greater than or equal to the stage voltage. The algorithm for calculating the effective voltage once according to this embodiment may refer to step 2. The target voltage is a preset output phase voltage. The difference between the primary effective voltage and the target voltage is smaller than the stage voltage, namely the difference is smaller than an adjustment level, and the voltage regulating switch group is not required to be started. For example, the level adjustment of the voltage-regulating switch group=round [ (U) Target voltage -U Primary effective voltage )/U Stage voltage ]. round [ ] is a rounding function. For example (U) Target voltage -U Primary effective voltage )/U Stage voltage When=1.3, 1 link is adjustedAnd (5) grading. In a specific embodiment, the stage voltage = 0.025 x phase voltage. The adjustment range of the 4 connection level adjustment is 0.025×4=10%, satisfying the output voltage change from 95% to 105%.
Referring to fig. 5 and 6, the voltage regulating switch may reduce the effective number of turns of the primary winding so that the output voltage may be adjusted between 95% and 105%. In the voltage regulating process, the contact of the voltage regulating switch group is connected into the other contact ring from one contact ring, and after the contact is connected to the other contact ring, the effective turns are reduced by 0.025, and the whole process lasts for 0.5 to 2 seconds. In this process, this occurs in sequence: the contact is connected with the previous contact ring and the switch is closed, the contact is connected with the previous contact ring and the switch is opened, the contact is separated from the previous contact ring, the contact is connected with the next contact ring and the switch is opened, and the contact is connected with the next contact ring and the switch is closed. Wherein, in the two stages of the contact connection of the former contact ring and the switch opening, the contact connection of the latter contact ring and the switch opening, the circuit breaker is closed to discharge, the moving contact generates arc, and the instantaneous current is shown in figure 7. And the voltage regulating time sequence table is composed of the duration that the voltage regulating switch is in a first connection state, a first arc state, an idle state, a second arc state and a second connection state corresponding to the working process of the voltage regulating switch group. In this embodiment, the voltage regulating switch has a first contact and a second contact in parallel. The instantaneous current of the voltage regulating switch refers to the sum of the instantaneous currents of the first contact and the second contact. The current of the second contact is sine wave in the first connection state, the current of the second contact fluctuates in the first arc state, and the current gradually drops to 0 in the no-load state. Unlike the first contact, the current of the first contact in the no-load state is equal to the primary effective current.
Step 7: and controlling the voltage regulating switch according to the voltage regulating time schedule, measuring the instantaneous current of the voltage regulating switch in the time for executing the voltage regulating time schedule, and predicting the discharge loss ratio. The application extracts the instantaneous current of the voltage regulating switch in the first arc state, the idle state and the second arc state, calculates the discharge loss of the voltage regulating switch in the first arc state, the idle state and the second arc state, and predicts the discharge loss ratio. Because the application determines the voltage regulating time sequence table, the corresponding wave band of the instantaneous current can be accurately intercepted according to the time period of the voltage regulating time sequence table,the accuracy of calculating the discharge loss is improved. W (W) 1 Discharge loss of the first arc state, W 2 Discharge loss in no-load state, W 3 Is the discharge loss of the second arc state. 2W (2W) 2 /(W 1 +W 3 ) Is the discharge loss ratio. Wherein the discharge loss is equal to the product of the current and the phase voltage of the first contact and the second contact.
Step 8: and (2) adjusting the reference capacity according to the discharge loss ratio, and returning to the step (2). Reference capacity S 0 =βS 1 •W 2 /(W 1 +W 3 ) Beta is an economic load factor, preset to 0.46 to 0.49, S 1 Rated capacity for high capacity access state. If the discharge loss ratio is increased in the voltage regulating process, the arc of the voltage regulating switch is larger, and the contact is easy to heat or damage the action parts. At the moment, the application properly increases the capacity threshold value and increases the power range of the transformer in the low-capacity access state. Because the phase voltage in the low-capacity access state is lower than the line voltage, the discharging loss of the voltage regulating switch connected with the three phase voltages of the primary winding can be controlled, so that the service life of the voltage regulating switch is prolonged.
Example two
The present embodiment further discloses a method of measuring the instantaneous current of a voltage regulating switch. The instantaneous current of each phase of the voltage regulating switch is sinusoidal in a normal period, and fluctuates in a period in which the voltage regulating timing chart is executed. As shown in fig. 8, the voltage regulation timing chart is (t 0 , t 1 , t 2 , t 3 , t 4 , t 5 ) The duration of the corresponding first arc state is t 2 -t 1 The duration of the idle state is t 3 -t 2 The duration of the second arc state is t 4 -t 3 . The instantaneous current of the first arc state, the no-load state and the second arc state voltage regulating switch is extracted. The time period of the arc state can be determined from the voltage regulation timing schedule, thereby determining the discharge loss. In a specific embodiment, the length of time that the second contact leaves the contact ring and the length of time that the second contact is connected with the next contact ring can be determined according to the rotation speed of the driving piece for driving the second contact.
In this embodiment, each of the voltage regulating switchesContacts are mounted on each phase of the primary coil. W (W) 11 '、W 12 ''、W 13 ' is the discharge loss of the three phases, respectively, the discharge loss W in the first arc state 1 =W 11 '+W 12 ''+W 13 '''=. Likewise, discharge loss in no-load stateDischarge loss in the second arc state +.>。u 11 (t)、u 12 (t)、u 13 (t) instantaneous voltages of the voltage regulating switches of three phases at the time t, i 11 (t)、i 12 (t)、i 13 (t) is the instantaneous current of the voltage regulating switches of the three phases at the time t respectively.
Example III
As shown in fig. 9 to 10, such a power transformer of the present embodiment is preferably an oil-immersed power transformer, and mainly includes a case 101, an iron core 102, a primary winding 104, a secondary winding 103, a cooling medium, a sensor, and a controller. The iron core 102 is fixed in the box 101, the secondary winding 103 and the primary winding 104 are wound on the iron core 102, a cooling medium is filled in the box 101, the sensor comprises a thermometer arranged in the box 101, a first voltmeter and a first ammeter arranged in the secondary winding 103, a second voltmeter arranged in the primary winding 104 and a second ammeter arranged in a controller, and the controller comprises a data processing unit, a capacity regulating switch and a voltage regulating switch group. The cooling medium is, for example, transformer oil, and the thermometer measures the medium temperature of the cooling medium. The data processing unit is configured to calculate apparent power, an effective voltage at a time, and generate a voltage regulation timing schedule based on the effective voltage at a time. The capacitance-regulating switch is configured to maintain a high-capacity access state or a low-capacity access state according to apparent power; the voltage regulating switch group is configured to maintain a connection level according to a voltage regulating timing schedule. The controller predicts the discharge loss ratio and adjusts the reference capacity of the capacitance-adjusting switch according to the discharge loss ratio.
The capacity-regulating switch comprises a primary switch group and a secondary switch group, and each switch group consists of a plurality of linkage switches. In the high capacity access state, the primary winding is adjusted to be in delta connection by the primary switch group, and the secondary winding is adjusted to be in series connection by the secondary switch group. At this time, as shown in fig. 2, the switches k11 and k12 in the primary switch group are closed, and the switch k13 is opened. The switch k21 in the secondary switch group is closed, and the switches k22 and k23 are opened. In the low capacity access state, the primary winding is adjusted to be star-connected by the primary switch group, and the secondary winding is adjusted to be parallel-connected by the secondary switch group. At this time, the switches k11 and k12 in the primary switch group are opened, and the switch k13 is closed. The switch k21 in the secondary switch group is opened, and the switches k22 and k23 are closed.
The voltage regulating switch is led out from the coil of the primary winding and is connected to another position of the coil, so that the effective number of turns of the coil is adjusted. Fig. 5 and 6 are two final states of the voltage regulating switch, respectively. The primary winding includes a plurality of contact rings 201, the number of turns of adjacent contact rings corresponding to 2 stage voltages. The voltage regulating switch comprises a first contact 202 and a second contact 203, wherein the first contact 202 and the second contact 203 are respectively connected with a fixed line of the voltage regulating switch through a switch k31 and a switch k 32. To reduce arcing, the first contact 202 and the second contact 203 are connected through a circuit breaker 204. In such a dual contact voltage regulating switch, the first contact 202 remains on during the upward movement of the second contact 203, avoiding current surge during single contact voltage regulation. Two sets of second current meters 205 are connected in series on the first contact 202 and the second contact 203, respectively, with a circuit breaker between the first contact 202 and the second current meters 205. The sum of the instantaneous currents measured by the second ammeter 205 in the arc state may be used to determine the discharge loss. In the moving process of the second contact, the first contact is always in a connection state, the current of the first contact is twice that of the first contact in a normal state, and the damage risk is increased. The capacity-adjusting threshold value is corrected in order to avoid contact damage.
In the first connection state, the first contact 202 and the second contact 203 are both connected to the contact ring 201, forming a closed loop. After the switch k32 is opened, the current of the second contact 203 does not drop to 0 immediately, and the current enters the switch k31 through the breaker, so that the breaker 204 plays a role in extinguishing arc, and the state is a first arc state. The second contact 203 is far from the contact ring 201, and the current of the second contact 203 gradually disappears, and the state is no-load. The second contact 203 continues to move to the next contact ring 201, and the second contact 203 generates a current that enters the switch k31 through the circuit breaker 204, which is in the second arc state. After the switch k32 is closed, the second contact 203 is restored to the second connection state. The first arc state, the no-load state, and the second arc state generate discharge losses. The application reduces the line voltage of the primary winding and improves the service life of the voltage regulating switch by adjusting the capacity threshold.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application.
Claims (10)
1. The capacity and voltage regulating method of the power transformer is characterized by comprising the following steps of:
step 1: the primary switch group and the secondary switch group of the capacity-regulating switch are respectively arranged on the primary winding and the secondary winding, the voltage-regulating switch is arranged on the primary winding, the capacity-regulating switch has a low capacity access state and a high capacity access state, and the voltage-regulating switch has a plurality of connection grades;
step 2: monitoring the medium temperature of a transformer, generating a capacity-regulating threshold lambda according to the medium temperature, collecting the instantaneous voltage and the instantaneous current of each phase of a secondary winding at intervals of a first sampling period to obtain a secondary effective voltage and a secondary effective current, and calculating apparent power S;
step 3: if the apparent power S is less than or equal to the lower capacity limit (1-lambda) S 0 Step 4, if the apparent power S is greater than or equal to the upper capacity limit (1+lambda) S 0 Step 5 is entered, if the apparent power S is greater than the lower capacity limit (1-lambda) S 0 And is smaller than the upper capacity limit (1+lambda) S 0 Go to step 6, S 0 Is the reference capacity;
step 4: in time period T 1 Collecting instantaneous voltage and instantaneous current of the secondary winding at each second sampling period to generate secondaryThe effective voltage and the secondary effective current are calculated, and if the apparent power S is still smaller than or equal to the capacity lower limit, the capacity-regulating switch is kept in a low-capacity access state, and the step 6 is entered;
step 5: in time period T 2 Collecting the instantaneous voltage and the instantaneous current of the secondary winding at each second sampling period, generating a secondary effective voltage and a secondary effective current, calculating apparent power S, and if the apparent power S is still more than or equal to the upper limit of capacity, keeping the capacity-regulating switch in a high-capacity access state, and entering a step 6;
step 6: measuring the instantaneous voltage of the primary winding to obtain primary effective voltage, calculating the difference value between the primary effective voltage and target voltage, and generating a voltage regulating time sequence table if the difference value is greater than or equal to the stage voltage;
step 7: controlling a voltage regulating switch according to the voltage regulating time sequence table, measuring the instantaneous current of the voltage regulating switch in the time for executing the voltage regulating time sequence table, and predicting the discharge loss ratio;
step 8: and (2) adjusting the reference capacity according to the discharge loss ratio, and returning to the step (2).
2. The method for regulating capacity and voltage of a power transformer according to claim 1, wherein in step 2, the secondary effective voltage isSecond effective current +.>N is the sampling times, u 2x (n) is the instantaneous voltage of phase sequence x in the secondary winding acquired by the nth sampling, i 2x (n) is the instantaneous current of phase sequence x in the secondary winding acquired by nth sampling, x is a positive integer less than or equal to 3, and apparent power S= (P) 21 +P 22 +P 23 )/3，P 2x =U 2x •I 2x 。
3. The method for regulating capacity and voltage of a power transformer according to claim 1, wherein in step 2, a capacity regulating threshold is setAlpha is the power factor of the power transformer, and R is the medium temperature.
4. The method of claim 1, wherein in step 5, the second sampling period is smaller than the first sampling period, and the period T is set to be equal to or longer than the first sampling period 2 Less than a period of time T 1 。
5. The method according to claim 1, wherein in step 6, the voltage regulation schedule is composed of a duration of time that the voltage regulation switch is in the first connection state, the first arc state, the no-load state, the second arc state, and the second connection state.
6. The method according to claim 5, wherein in step 7, the instantaneous currents of the voltage regulating switches in the first arc state, the no-load state, and the second arc state are extracted, the discharge losses of the voltage regulating switches in the first arc state, the no-load state, and the second arc state are calculated, and the discharge loss ratio is predicted.
7. The method for regulating capacity and voltage of a power transformer according to claim 6, wherein in step 8, the reference capacity S 0 =βS 1 •2W 2 /(W 1 +W 3 )，W 1 Discharge loss of the first arc state, W 2 Discharge loss in no-load state, W 3 Discharge loss of the second arc state, 2W 2 /(W 1 +W 3 ) Beta is the economic load factor, S is the discharge loss ratio 1 Rated capacity for high capacity access state.
8. A power transformer according to the capacity and voltage regulating method of the power transformer as claimed in claim 1, comprising: the device comprises a box body, an iron core, a primary winding, a secondary winding, a cooling medium, a sensor and a controller, wherein the iron core is fixed in the box body, the primary winding and the secondary winding are wound on the iron core, the cooling medium is filled in the box body, the sensor comprises a thermometer, a first voltmeter and a first ammeter, a second voltmeter and a second ammeter, the thermometer and the first ammeter are arranged in the box body, the second voltmeter and the second ammeter are arranged in the primary winding, the second ammeter is arranged in the controller, the controller comprises a data processing unit, a capacity regulating switch and a voltage regulating switch group,
the data processing unit is configured to calculate apparent power and primary effective voltage, and generate a voltage regulation time sequence table according to the primary effective voltage;
the capacitance-regulating switch is configured to maintain a high-capacity access state or a low-capacity access state according to apparent power;
the voltage regulating switch group is configured to maintain a connection level according to a voltage regulating timing schedule, wherein,
the controller predicts the discharge loss ratio and adjusts the reference capacity of the capacitance-adjusting switch according to the discharge loss ratio.
9. The power transformer of claim 8, wherein the capacity modulation switch comprises a primary switch group that adjusts the primary winding to a delta connection and a secondary switch group that adjusts the secondary winding to a series connection in the high capacity access state, and wherein the primary switch group adjusts the primary winding to a star connection and the secondary switch group adjusts the secondary winding to a parallel connection in the low capacity access state.
10. The power transformer of claim 8, wherein the voltage regulating switch comprises a first contact and a second contact, the first contact and the second contact are connected by a circuit breaker, the second ammeter is connected in series with the first contact and the second contact, the primary winding comprises a plurality of contact rings, the first contact and the second contact,
in the first connection state or the second connection state, the first contact and the second contact are both connected with the contact ring to form a closed loop;
in the second arc state or the second arc state, the first contact is connected with the second contact in parallel through the breaker;
in the idle state, the first contact or the second contact is disconnected from the contact ring.
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