CN113608011A - Direct-current high-voltage measuring device with self-calibration function and operation method thereof - Google Patents
Direct-current high-voltage measuring device with self-calibration function and operation method thereof Download PDFInfo
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Abstract
The invention discloses a direct current high voltage measuring device with a self-calibration function and an operation method thereof, wherein the device comprises: the direct current resistance divider comprises: high voltage arm resistor RHLow voltage arm resistor RN‑1And a low-voltage arm resistor RN(ii) a The measuring circuit is used for measuring and acquiring the resistance R of the low-voltage armNVoltage value of (d); the microprocessor includes: the direct-current high-voltage value acquisition module acquires a direct-current high-voltage value of a voltage bus to be detected; the direct current power quality state identification module is used for acquiring the direct current power quality state; the self-calibration module is used for obtaining the classification of the power quality state; the high-voltage arm resistance R is obtained by calculation through controlling the on and off of the electronic switch KHAnd calibrating the voltage division ratio of the direct current resistor divider through the calibration value to finish the calibration of the direct current high voltage measuring device. The invention can meet the self-calibration requirement in various voltage states and fit the practical engineering.
Description
Technical Field
The invention belongs to the field of electrical engineering, instrument science and technology, and particularly relates to a direct-current high-voltage measuring device with a self-calibration function and an operation method thereof.
Background
The measurement methods of the direct-current high voltage are mainly divided into three types: direct action physical effect methods, optical methods and partial pressure methods. The voltage division method is characterized in that direct current high voltage is measured by using a direct current resistance voltage divider and a low-voltage device, and after the low-voltage device measures the voltage of a low-voltage arm of the direct current resistance voltage divider, the value of the high voltage to be measured is calculated according to the voltage division ratio of the voltage divider.
The partial pressure method is the measurement scheme which is most widely applied, the most mature technology and relatively low in cost at present. Since the accuracy of the dc resistor divider can be made very high, the method can achieve very high accuracy: the uncertainty of the current 100kV/10V voltage ratio can reach 1 multiplied by 10-5The uncertainty of 300kV/30V voltage ratio can reach 3 multiplied by 10-5The accuracy of the device can reach 0.05 percent at most under the condition of 500 kV. However, since the high-voltage arm and the low-voltage arm of the dc resistor voltage divider are formed by serially connecting resistors, voltage dispersion and aging tendency of the resistor components are inconsistent, corona discharge of the high-voltage arm and insulation leakage of the voltage divider under high voltage conditions, environmental parameters such as temperature, humidity and objects near the measuring device can cause the resistance value of the high-voltage arm of the dc resistor voltage divider to change, thereby causing the voltage dividing ratio to change and causing measurement errors, and therefore, the dc resistor voltage divider needs to be calibrated frequently. Because the resistance value change of the high-voltage arm of the voltage divider is influenced by various factors, the resistance value change of the high-voltage arm of the direct-current resistance voltage divider under the actual use condition is different compared with that under the test state, and the change is difficult to predict and has great influence on the accuracy of measurement.
In order to solve the above problems, the chinese patent application with application number 201911235837.3 proposes a wide-range dc voltage measuring device based on resistance voltage division time-sharing sampling self-calibration, and provides a dc high voltage measuring method with a function of self-calibration of the high-voltage arm resistance of the dc resistance voltage divider, which is suitable for wide-range requirements; however, because the dc network is disturbed by the ac side transmission at the grid-connected point on one hand and by the internal network topology, the control strategy and the source-storage-load characteristic of the dc network on the other hand, the voltage value is difficult to maintain stable, and phenomena such as dc voltage deviation, dc voltage fluctuation, dc voltage ripple and dc voltage sag often exist, so that the self-calibration requirement is difficult to meet in the real situation, and the practical application is difficult; the self-calibration requirement is that the voltage fluctuation amplitude in the switching and data acquisition period of the electronic switch K is 3 times smaller than 1/5 which is the product of the measured voltage value and the accuracy grade.
In summary, a new dc high voltage measurement device with self-calibration function and its operation method are needed.
Disclosure of Invention
The present invention is directed to a dc high voltage measurement device with self-calibration function and a method for operating the same, which solves one or more of the above-mentioned problems. The invention provides the direct-current high-voltage measuring device based on the direct-current resistance voltage divider time-sharing sampling, which is suitable for engineering practice, has the direct-current resistance voltage divider high-voltage arm resistance self-calibration function, is good in stability and high in reliability, can meet the self-calibration requirement in various voltage states, and is suitable for engineering practice.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a direct current high voltage measuring device with a self-calibration function, which comprises:
a dc resistance divider comprising: high voltage arm resistor RHLow voltage arm resistor RN-1And a low-voltage arm resistor RN(ii) a The high-voltage arm resistor RHIs used for being electrically connected with a voltage bus, and the other end of the low-voltage arm resistor RN-1Is electrically connected with one end of the low-voltage arm resistor RN-1Another end of (3) and a low-voltage arm resistor RNIs connected to a low-voltage arm resistor RNThe other end of the first and second electrodes is used for grounding; the low-voltage arm resistor RN-1An electronic switch K is connected in parallel;
a measurement circuit for measuring and acquiring the low-voltage arm resistance RNVoltage value of (d);
a microprocessor, comprising: the device comprises a direct current high voltage value acquisition module, a direct current power quality state identification module and a self-calibration module;
the direct-current high-voltage value acquisition module is used for adopting a low-voltage arm resistor RNThe voltage value is multiplied by the voltage division ratio of the direct current resistance voltage divider to calculate and obtain a direct current high voltage value of the voltage bus to be measured;
the direct current power quality state identification module is used for acquiring the amplitude change of a direct current high voltage value of a voltage bus to be detected in a preset time period, and dividing the power quality state of the direct current high voltage to be detected at the current stage into 5 types based on the amplitude change, wherein the types are respectively as follows: a direct-current voltage rated state, a direct-current voltage deviation state, a direct-current voltage fluctuation state, a direct-current voltage sag state and a direct-current voltage ripple state;
the self-calibration module is used for obtaining the classification of the power quality state; when the electric energy quality state is in a direct current voltage rated state, a direct current voltage deviation state or a direct current voltage ripple state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHAnd calibrating the voltage division ratio of the direct current resistor divider through the calibration value to finish the calibration of the direct current high voltage measuring device.
The device of the invention is further improved in that the device also comprises:
and the protection circuit is arranged between the direct current resistance voltage divider and the measuring circuit and is used for isolating the front-stage circuit and the rear-stage circuit.
The device of the invention is further improved in that the device also comprises:
and the communication circuit is used for realizing the communication between the direct-current high-voltage measuring device and an upper computer or a display instrument and finishing the communication transmission of the measured voltage value.
The device of the invention is further improved in that the high-voltage arm resistor RHLow voltage arm resistor RN-1And a low-voltage arm resistor RNThe resistance value of the series circuit is determined by the voltage grade of a voltage bus to be tested, the current of the series circuit is in the hundred microamperes, and the output voltage range of the low-voltage arm is 0-10V; the precision of the resistance value is determined by the measurement accuracy grade, the resistance values are all low-temperature drift resistances, and the temperature drift is less than 1 ppm/DEG C.
The device of the invention is further improved in that the electronic switch K is a solid-state relay;
on-resistance RonWhen the following relation is satisfied, the influence of the relation on the accuracy level alpha of the direct current resistor divider is ignored:
the device of the present invention is further improved in that, in the dc power quality status identification module, the amplitude variation of the dc high voltage value of the voltage bus to be measured in a preset time period is obtained, and the power quality status of the current stage of the dc high voltage to be measured is classified into 5 types based on the amplitude variation, which are respectively: the steps of the DC voltage rated state, the DC voltage deviation state, the DC voltage fluctuation state, the DC voltage sag state and the DC voltage ripple state specifically include:
acquiring the amplitude change of a direct-current high voltage value of a voltage bus to be detected in a preset time period;
according to the support vector machine multi-classification model with the amplitude variation optimized based on the particle swarm parameters, optimizing a kernel parameter sigma and a penalty factor C in the support vector machine model by adopting a particle swarm optimization algorithm, and realizing classification and identification of the DC energy quality state, wherein the classification and identification is obtained by the following categories: the direct current voltage rated state, the direct current voltage deviation state, the direct current voltage fluctuation state, the direct current voltage ripple state and the direct current voltage sag state are 5 electric energy quality states.
A further development of the device according to the invention is that,
the DC voltage rated state is that the actual voltage of the voltage bus and the rated voltage value are maintained to be the same;
the direct-current voltage deviation state is that the actual voltage of a voltage bus is higher than or lower than the rated voltage, and the voltage deviation is lower than 10% of the rated voltage;
the direct-current voltage fluctuation state is that the actual voltage fluctuation of a voltage bus is irregular and does not contain voltage continuous fluctuation of fixed frequency components, and the change amplitude is lower than 10% of the rated voltage;
the direct-current voltage sag state is that the instantaneous voltage sag of the actual voltage of the voltage bus or the voltage preset amplitude reduction within the preset time occurs, and the reduction amount is greater than 10% of the rated voltage;
the direct-current voltage ripple state is that the actual voltage of a voltage bus is the alternating-current component superposed in direct current, and the direct-current bus voltage is divided into 1-time, 2-time, … -time and n-time ripples according to power frequency and 2, 3, … and n times of the power frequency.
The device is further improved in that the self-calibration module acquires the classification of the power quality state; when the power quality state is in a direct current voltage rated state or a direct current voltage deviation state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHThe step of calibrating the dc resistor divider by the calibration value to complete the calibration of the dc high voltage measuring device specifically includes:
when the voltage of the voltage bus to be measured is in the range of 80% -120% of the rated voltage and the voltage is in the DC voltage rated state, the DC voltage deviation state or the DC voltage ripple state,
controlling the electronic switch K to be switched on and off, and calculating to obtain the high-voltage arm resistance RHBy which the voltage dividing ratio of the direct current resistor divider is calibrated;
wherein, when being in DC voltage rated state and DC voltage deviation state:
when the electronic switch K is turned off, the low-voltage arm outputs a voltage VNIs shown as
High DC voltage value VHIs shown as
When the electronic switch K is conducted, the low-voltage arm outputs a voltage VN' is represented as
High DC voltage value VHIs shown as
Simultaneous DC high voltage value calculation equation to eliminate bus voltage VHCalculating to obtain RHThe calibration value of (a) is determined,expressed as:
the device is further improved in that the self-calibration module acquires the classification of the power quality state; when the electric energy quality state is in a direct-current voltage ripple state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHThe step of calibrating the dc resistor divider by the calibration value to complete the calibration of the dc high voltage measuring device specifically includes:
acquiring a preset number of voltage data points in a direct-current voltage ripple state, selecting the time of occurrence of ripple wave crests, wave troughs or other characteristic points in the selected time as t1, t2 and t3, and fitting the amplitude and the phase of each ripple by a least square algorithm;
predicting the occurrence time point t of the wave crest, the wave trough or other characteristic points of the ripple wave based on the amplitude and the phase of each ripple waven、tn+1、tn+2；
At tn、tn+1、tn+2The electronic switch K is turned off or turned on all the time, and the voltage of the voltage bus is kept the same when the electronic switch K is turned off or turned on;
when the electronic switch K is turned off, the low-voltage arm outputs a voltage VNIs shown as
High DC voltage value VHIs shown as
When the electronic switch K is conducted, the low-voltage arm outputs a voltage VN' is represented as
High DC voltage value VHIs shown as
Simultaneous DC high voltage value calculation equation to eliminate bus voltage VHCalculating to obtain RHIs given by the following calibration values:
the invention relates to an operation method of a direct current high voltage measuring device with a self-calibration function, which comprises the following steps:
the high-voltage arm resistor RHOne end for being electrically connected with the voltage bus is connected with the voltage bus to be tested, and the low-voltage arm resistor RNOne end used for grounding is grounded;
the electronic switch K is in a turn-off state;
the measuring circuit measures and obtains the resistance R of the low-voltage armNVoltage value of (d);
the direct current high voltage value acquisition module adopts a low-voltage arm resistor RNThe voltage value is multiplied by the voltage division ratio of the direct current resistance voltage divider to calculate and obtain a direct current high voltage value of the voltage bus to be measured; the direct current power quality state identification module acquires the amplitude change of the direct current high voltage value of the voltage bus to be detected in a preset time period, and the power quality state of the direct current high voltage to be detected at the current stage is divided into 5 types based on the amplitude change, wherein the types are respectively as follows: a direct-current voltage rated state, a direct-current voltage deviation state, a direct-current voltage fluctuation state, a direct-current voltage sag state and a direct-current voltage ripple state; the self-calibration module acquires the classification of the power quality state; when the electric energy quality state is in a direct current voltage rated state, a direct current voltage deviation state or a direct current voltage ripple state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHAnd calibrating the voltage division ratio of the direct current resistor divider through the calibration value to finish the calibration of the direct current high voltage measuring device.
Compared with the prior art, the invention has the following beneficial effects:
the direct-current high-voltage measuring device capable of self-calibrating in the multi-electric-energy-quality state can greatly increase the engineering practicability of the self-calibrating method by adding the electric-energy-quality identifying module, and is suitable for engineering practice, has the direct-current resistance voltage divider high-voltage arm resistance self-calibrating function, and is good in stability and high in reliability.
In the direct-current high-voltage measuring device, the direct-current power quality identification module is added before the direct-current resistance voltage divider performs self calibration, and after the voltage to be measured is measured, the microprocessor can classify the bus power quality according to the collected voltage data, wherein the bus power quality comprises 5 states including a direct-current voltage rated state, a direct-current voltage deviation state, a direct-current voltage fluctuation state, a direct-current voltage ripple state, a direct-current voltage sag state and the like. After the judgment of the microprocessor, the self-calibration operation can be carried out only in 3 states of a direct-current voltage rated state, a direct-current voltage deviation state and a direct-current voltage ripple state; because the measured voltage values in the three states have certain regularity, the bus voltage can be ensured not to change basically at the moment of opening and closing the switch, and the precision of the self-calibration method and the measurement precision of the device are improved.
In the invention, when the switch is in a DC voltage rated state and a DC voltage deviation state, and the switch is switched off and switched on, the bus voltage VHKeeping the voltage constant, and eliminating the bus voltage V through a simultaneous direct-current high-voltage value calculation equationHNamely to calculate RHThe actual value (calibration value) can realize the calibration of the voltage division ratio of the direct current resistor divider by calibrating the resistance value of the high-voltage arm, thereby improving the detection precision of the measuring device.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a schematic diagram of a DC resistance divider; fig. 1(a) is a schematic diagram of a conventional dc resistor voltage divider, fig. 1(b) is a simplified diagram of a conventional dc resistor voltage divider, and fig. 1(c) is a simplified diagram of a dc resistor voltage divider according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the overall design of a DC high voltage measurement device with self-calibration function according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a DC high voltage measurement apparatus with a self-calibration function according to an embodiment of the present invention; wherein, fig. 3(a) is an appearance schematic diagram, and fig. 3(b) is an internal structure schematic diagram;
FIG. 4 is a schematic diagram of the SHV12-1A85-78L4K solid state relay;
FIG. 5 is a schematic diagram of a power quality state in an embodiment of the present invention; fig. 5(a) is a schematic diagram of a rated state of a dc voltage, fig. 5(b) is a schematic diagram of a deviation state of the dc voltage, fig. 5(c) is a schematic diagram of a fluctuation state of the dc voltage, fig. 5(d) is a schematic diagram of a sag state of the dc voltage, and fig. 5(e) is a schematic diagram of a ripple state of the dc voltage;
FIG. 6 is a schematic flow chart of a particle swarm optimization algorithm in an embodiment of the present invention;
FIG. 7 is a schematic diagram of a self-calibration process in an embodiment of the present invention.
Detailed Description
In order to make the purpose, technical effect and technical solution of the embodiments of the present invention clearer, the following clearly and completely describes the technical solution of the embodiments of the present invention with reference to the drawings in the embodiments of the present invention; it is to be understood that the described embodiments are only some of the embodiments of the present invention. Other embodiments, which can be derived by one of ordinary skill in the art from the disclosed embodiments without inventive faculty, are intended to be within the scope of the invention.
Referring to fig. 1 and fig. 2, a dc high voltage measurement device capable of self-calibration in multiple energy quality states according to an embodiment of the present invention includes a hardware portion and a software portion; the hardware part comprises a direct current resistance voltage divider, a protection circuit, a signal conditioning circuit, a signal acquisition circuit and a communication circuit, and the software part comprises a direct current power quality state identification and self-calibration algorithm.
Referring to fig. 1, the main portion of the dc resistor divider according to the embodiment of the invention is a high arm resistor RHLow voltage arm precision resistor RN-1And a precision resistor RNThree resistors, voltage bus passing through high voltage lead end of voltage divider and high voltage arm resistor RHConnected, low voltage arm precision resistor RN-1One end and high-voltage arm resistor RHConnected with another end through a precision resistor RNThe low-voltage equalizing ring is connected to the voltage divider; low-voltage precision resistor RN-1Two ends of the low-voltage arm are connected in parallel with an electronic switch K, and the electronic switch K is controlled to be switched on and off by microprocessing so as to realize the sampling of the output voltage of the low-voltage arm.
Referring to fig. 2, the protection circuit according to the embodiment of the present invention is used for isolating a front-stage circuit from a rear-stage circuit and preventing a front-stage voltage from damaging a device of a rear-stage circuit board when an accident occurs, and mainly includes an isolation chip, a photoelectric coupler, a TVS diode, a fuse, and the like, where the isolation chip is used for isolating the front-stage and rear-stage signal circuits, the photoelectric coupler is used for isolating a main control chip from an electronic switch, and the TVS diode and the fuse are used for overvoltage protection and overcurrent protection, respectively.
The signal conditioning circuit comprises a filter circuit and an amplifying circuit, wherein the filter circuit filters high-frequency noise in the signal, and the amplifying circuit amplifies the filtered signal to a conditioning signal matched with the range of the analog-to-digital converter.
The signal acquisition circuit takes an analog-to-digital converter as a main component, samples the modulated signal and transmits the sampled signal to a microprocessor for operation, so that a direct-current high-voltage V is obtainedHA numerical value;
the communication circuit realizes the communication between the direct-current high-voltage measuring device and an upper computer or a display instrument and completes the communication transmission of the measured voltage value.
The direct current power quality state identification is used for classifying the state of the direct current voltage to be detected based on a support vector machine model and is used as a judgment condition for judging whether a subsequent self-calibration algorithm is operated or not and an operation strategy; the self-calibration algorithm is to allow the measured voltage to be subjected to the electric energy quality state identification and to be subjected to the operation after being identified as certain specific statesSelf-calibration algorithm operation, namely, the electronic switch K is switched on and off under the control of a microprocessor to realize the resistance R of the high-voltage armHThereby improving the measurement accuracy.
Referring to fig. 3, in the embodiment of the invention, the dc resistor divider of the hardware portion includes a high voltage lead terminal, a high voltage grading ring, and a high voltage arm resistor RHLow voltage arm resistor RN-1And a resistance RNThe low-voltage grading ring, the insulating sleeve, the insulating oil and the epoxy resin; high-voltage arm resistor R of direct-current resistor dividerHPlacing in insulating oil, sealing the bottom with polymerized organosilicon material, and making low-voltage arm resistor RN-1And RNPlacing the base flange piece in a base flange piece, and encapsulating by adopting epoxy resin; the high-voltage arm resistor and the low-voltage arm resistor are both wrapped by a shielding device, the upper end of the shielding device is a high-voltage lead end, the lower end of the shielding device is provided with a grounding lead post, the high-voltage terminal is connected with the high-voltage grading ring, and the grounding lead end is connected with the low-voltage grading ring; the appearance structure of the voltage divider is designed to be cylindrical, the voltage divider is connected with the base through an aluminum alloy flange, and the flange is internally connected with a high-voltage resistor in insulating oil in a screw hole opening mode.
In the embodiment of the invention, the high-voltage arm resistor R in the direct-current resistor divider of the hardware partHLow voltage arm precision resistor RN-1And a precision resistor RNThe resistance value of the low-voltage arm is determined by the grade of the voltage to be measured, the current of the series circuit is guaranteed to be hundreds of microamperes, and the output voltage range of the low-voltage arm is 0-10V; the precision of the resistance value is determined by the measurement accuracy grade, the resistance values are all low-temperature drift resistances, and the temperature drift is less than 1 ppm/DEG C.
In the embodiment of the invention, a protection circuit, a signal conditioning circuit, a signal acquisition circuit and a communication circuit in the hardware part are integrated on a PCB circuit board and are electrically connected with a resistor in a voltage divider through a lead; the PCB circuit board is fixed in the voltage divider base; the electronic switch is arranged at the bottom of the DC resistance voltage divider and connected with the low-voltage arm resistor RN-1Connected in parallel and lead to the PCB for control, or directly integrated on the PCB and lead to the low-voltage arm resistor RN-1Two ends; the protectionThe tail end of the circuit is provided with a voltage follower with quick response, and the front-stage circuit and the rear-stage circuit are isolated.
In the embodiment of the invention, the electronic switch K in the hardware part has the voltage resistance of more than 200V, small or no leakage current and high response speed, and is selected as a solid relay; on-resistance RonWhen the following relation is satisfied, the influence of the relation on the accuracy level alpha of the direct current resistor divider is ignored:
in the embodiment of the invention, the identification of the quality state of the direct current electric energy in the software part is a support vector machine multi-classification model based on particle swarm parameter optimization, a kernel parameter sigma and a penalty factor C in the support vector machine are optimized by adopting a particle swarm optimization algorithm, the generalization capability of a support vector machine SVM is improved, and the classification identification of the quality state of the direct current electric energy is realized, wherein the classification comprises the following steps: the direct current power quality state comprises 5 direct current power quality states including a direct current voltage rated state, a direct current voltage deviation state, a direct current voltage fluctuation state, a direct current voltage ripple state and a direct current voltage sag state. The 5 types of direct current power quality state classification are defined as follows:
in the rated state of the direct-current voltage, the actual voltage and the rated voltage value are basically maintained to be the same and are kept stable;
the direct-current voltage deviation state is that the actual voltage is higher than or lower than the rated voltage, and the voltage deviation is less than 10% of the rated voltage;
the direct-current voltage fluctuation state is that the actual voltage fluctuation is irregular and does not contain the rapid voltage continuous variation of fixed frequency components, and the variation amplitude does not exceed 10 percent of the rated voltage;
in a direct-current voltage sag state, instantaneous voltage sag occurs in actual voltage, or voltage is greatly reduced in a short time, and the reduction amount is required to exceed 10% of rated voltage;
in the dc voltage ripple state, the actual voltage is ac component superimposed on the dc power, and the dc bus voltage is generally divided into 1-order, 2-order, … -order, and n-order ripples according to the power frequency and 2, 3, …, and n-times of the power frequency.
In the embodiment of the invention, the self-calibration algorithm in the software part requires that when the measured voltage is near the rated voltage, namely in the range of 80-120% of the rated voltage, and after the direct-current power quality state identification, the measured voltage is in one of the three states of the direct-current voltage rated state, the direct-current voltage deviation state and the direct-current voltage ripple state, the self-calibration operation can be carried out, so that the high-voltage arm resistance calibration value R is obtainedHAnd a DC high voltage measurement value VHThe specific method comprises the following steps:
when the voltage to be measured is in a direct-current voltage rated state, the numerical value of the bus voltage is basically kept unchanged and is equal to the rated voltage; when the electronic switch K is turned off, the low-voltage arm outputs a voltage V according to the principle of resistance voltage divisionNIs shown as
Wherein VHIndicating a DC high voltage value, further obtaining
When the electronic switch K is switched on, the low-voltage arm outputs a voltage V according to the principle of resistance voltage divisionN' is represented as
Further obtain the
From the formulae (3) and (5)
When the measured voltage is in a direct-current voltage deviation state, the measured voltage value and the rated voltage value deviate in the state, namely the measured value is in a range of 90% -110% of the rated voltage, and the deviation value is basically kept stable, so that the self-calibration process is the same as that in the rated voltage state.
When the electronic switch K is turned off, the low-voltage arm outputs a voltage V according to the principle of resistance voltage divisionNIs shown as
When the electronic switch K is switched on, the low-voltage arm outputs a voltage V according to the principle of resistance voltage divisionN' is represented as
From the formulae (8) and (9)
When the measured voltage is in a direct-current voltage ripple state, the measured voltage value fluctuates according to a preset rule, and self-calibration operation is difficult to realize due to the fact that time is consumed in the working process of an electronic switch, the sampling process of an ADC (analog-to-digital converter) and the signal processing process; setting the voltage in a direct current voltage ripple state, acquiring sufficient voltage data points after program acquisition, wherein the time of ripple wave crests in a certain period of time is t1, t2 and t3, and the maximum passing time isFitting the amplitude and phase of each ripple by a small two-times algorithm, and predicting the occurrence time point t of the ripple wave crest on the basisn、tn+1、tn+2The microprocessor performs the opening or closing operation of the electronic switch at the corresponding moment to ensure that the bus voltage is basically kept the same when the electronic switch is opened and closed;
when the electronic switch K is turned off, the low-voltage arm outputs a voltage V according to the principle of resistance voltage divisionNIs shown as
When the electronic switch K is switched on, the low-voltage arm outputs a voltage V according to the principle of resistance voltage divisionN' is represented as
From the formulae (3) and (5)
To further increase the feasibility of the self-calibration operation in the dc voltage ripple state, the self-calibration operation may also be performed at the valley or other characteristic points during the ripple period.
In the embodiment of the invention, a direct current power quality identification module is added before the direct current resistance voltage divider performs self calibration, and after the voltage to be measured is measured, a microprocessor can classify the bus power quality according to the collected voltage data, wherein the bus power quality comprises 5 states, such as a direct current voltage rated state, a direct current voltage deviation state, a direct current voltage fluctuation state, a direct current voltage ripple state, a direct current voltage sag state and the like. After the judgment of the microprocessor, the self-calibration operation can be carried out only in 3 states of a direct-current voltage rated state, a direct-current voltage deviation state and a direct-current voltage ripple state. Because the measured voltage values in the three states have certain regularity, the bus voltage can be ensured not to change basically at the moment of opening and closing the switch, and the precision of the self-calibration method and the measurement precision of the device are improved. The direct-current high-voltage measuring device capable of self-calibrating in the multi-electric-energy-quality state can greatly increase the engineering practicability of the self-calibrating method by adding the electric-energy-quality identifying module, and is suitable for engineering practice, has the direct-current resistance voltage divider high-voltage arm resistance self-calibrating function, and is good in stability and high in reliability.
The invention provides an operation method of a direct current high voltage measuring device capable of self calibration in a multi-energy quality state. The voltage signal of the low-voltage arm of the direct-current resistance voltage divider passes through the protection circuit and enters the signal conditioning circuit, the signal conditioning circuit filters high-frequency clutter in the signal and amplifies the signal, the signal acquisition circuit samples the conditioned signal, the microprocessor calculates the direct-current high-voltage value according to the voltage division ratio, and monitors and records the voltage value in real time. Because the voltage dispersion and the aging trend of the resistor components are inconsistent, the resistance value of the direct current resistor divider can be changed under the high-voltage condition by high-voltage arm corona discharge, temperature and humidity change, electromagnetic radiation and the like, particularly the resistance of the high-voltage arm. After the direct current power quality identification, the voltage divider self-calibration work is carried out under the specific power quality state, the microprocessor outputs an instruction to control the on-off of the electronic switch K, and the direct current resistor voltage divider high-voltage arm resistor R is realizedHThe resistance value is corrected, so that stable, accurate and reliable direct current high voltage measurement is realized.
The low-voltage arm resistor of a direct-current resistor divider (shown in figures 1(a) and (b)) is divided into two precise resistors R connected in seriesN-1And RNAnd the high pressure arm RHDirectly connected precision resistor RN-1Upper parallel electronic switch K (e.g. switch K)As shown in fig. 1(c), the switching in and short-circuiting of the resistance is achieved by turning off and on the electronic switch K. Resistance RH、RN-1And RNThe resistance value of the series circuit is determined by the grade of the voltage to be measured, the current of the series circuit is guaranteed to be hundreds of microamperes, and the output voltage range is 0-10V; the precision of the resistance value is determined by the measurement accuracy grade, the resistances are all low-temperature drift resistances, and the temperature drift is less than 1 ppm/DEG C. The electronic switch K needs to withstand a voltage of 200V or more, has a small or no leakage current, has a high response speed, and has a small or no on-resistance, and it is preferable to select a relay or other devices that function as a switch in consideration of the influence of the leakage current of the fet.
The overall design scheme of the multi-level direct-current high-voltage measuring device based on time-sharing sampling of the direct-current resistor voltage divider is shown in figure 2, and the device comprises: the device comprises a direct current resistor voltage divider, a protection circuit, a signal conditioning circuit, a signal acquisition circuit and a communication circuit. The measuring device adopts an integrated design, the whole structure of the measuring device is shown in figure 3, a protection circuit, a signal conditioning circuit, a signal acquisition circuit and a communication circuit are all integrated on a PCB circuit board, the circuit board is fixed in a base of a direct current resistance voltage divider, an electronic switch can be selectively integrated on the PCB circuit board or directly connected in parallel with a resistor and fixed on a low-voltage equalizing ring, and the electronic switch is selectively connected in parallel and fixed on the low-voltage equalizing ring. The DC resistance voltage divider consists of high-voltage lead end, high-voltage equalizing ring and high-voltage arm resistor RHLow voltage arm precision resistor RN-1And RNThe low-voltage grading ring, the insulating wall, the insulating oil, the epoxy resin and the like: the high-voltage arm resistor is placed in the insulating oil, one end of the high-voltage arm resistor is connected with the high-voltage lead end, and the other end of the high-voltage arm resistor is connected with the low-voltage arm resistor in series in a screw punching mode; the low-voltage arm resistor is fixed inside the low-voltage grading ring, wherein the solid-state relay and the resistor RN-1The low-voltage arm is connected in parallel, the connection wire is led out to the PCB and then sealed through epoxy resin, the epoxy resin has excellent heat conductivity coefficient, and the influence of the environment temperature on the resistance of the low-voltage arm can be further weakened.
The protection circuit has two main functions: firstly, isolating a direct current resistance voltage divider, a rear-end signal conditioning circuit, a signal sampling circuit and the like; secondly, the microprocessor and the electronic switch are isolated, the level conversion between the control signal output by the microprocessor and the electronic switch is realized, the purpose of controlling the electronic switch is achieved, and a common protection circuit design mode can be adopted to prevent overvoltage and overcurrent from damaging a rear-stage circuit. The signal conditioning circuit filters high-frequency clutter in the signal passing through the protection circuit, then the signal enters the voltage follower to realize impedance matching of front and back and the circuit, and then the signal is amplified through the amplifying circuit to realize range matching with the analog-to-digital conversion chip.
The signal acquisition circuit takes a high-speed ADC chip as a main body, and the resolution ratio is not lower than 12 bits; and the microprocessor receives the voltage data sampled by the acquisition unit and then multiplies the voltage division ratio coefficient of the voltage divider to obtain the numerical value of the measured voltage at the sampling moment. The electric energy quality recognition module can record voltage values within a period of time, and the support vector machine model optimized by the particle swarm optimization is used for classifying the voltages, so that the electric energy quality state at the current moment is recognized and classified. When the measured voltage is in a direct-current voltage rated state, a direct-current voltage bias state and a direct-current voltage ripple state, different calibration strategies are respectively selected to realize high-voltage arm resistance correction of the direct-current resistance voltage divider. Therefore, the microprocessor has certain processing and response speed, meets the requirement of the response time of the measuring device and is matched with the speed of the signal acquisition element; the microprocessor can be a single chip microcomputer, a DSP, an FPGA, an embedded system or a common industrial personal computer and the like.
The embodiment of the present invention will briefly describe the implementation process by combining the overall design scheme of the measuring apparatus in fig. 2 and the overall structure diagram of the measuring apparatus in fig. 3.
Assuming that the range of the measured direct current voltage is 0-20 kV, in order to ensure that the current of the direct current resistance voltage divider is in the order of hundred microamperes, a high-voltage arm resistor R is selectedHThe resistance value of (1) is 200 MOmega, and the low-voltage arm precision resistor RN-1Is 2M omega, and a resistor RNThe resistance value of the voltage divider is 60k omega, the accuracy grade of the direct current resistor voltage divider is required to be 0.1 grade, and the measurement accuracy grade of the required measuring device is 0.2 grade. Thus, at full range, the low arm resistance RNIs about 6V.
Considering that the MOSFET tube has leakage current, which affects the measurement result, the electronic switch selects a solid-state relay, which is referred to as SHV12-1a85-78L4K, and its schematic diagram is shown in fig. 4. Control of the switch between pin 1 and pin 4 can be achieved by communication between pin 2 and pin 3. The resistance of the pin 1 and the pin 4 is 0.15 omega when the relay is switched on, the resistance is theoretically infinite when the relay is switched off, at least 1kV voltage can be endured, the switch closing time is 1.1ms, and the switch releasing time is 0.1 ms.
Selecting an FPGA as a microprocessor, wherein the model of the FPGA is EP4CE22E22C8N, and a control signal output by a GPIO of the FPGA controls a solid-state relay after passing through a photoelectric coupler and level conversion; the TVS diode and the isolation operational amplifier perform overvoltage protection, and the fuse performs overcurrent protection.
In the embodiment of the invention, the signal output by the protection circuit is firstly filtered by a second-order filter circuit to remove high-frequency clutter, and the filter circuit can be a 4-element SK type low-pass filter circuit or an MFB type low-pass filter composed of an operational amplifier. The filtered voltage signal is isolated from the front stage and the rear stage through the follower, so that the output voltage of the follower is about 6V and can be matched with the input range of a common analog-to-digital conversion chip, the amplification factor of the amplifying circuit can be set to be 1, theoretically, the amplifying process can be carried out for increasing the measurement precision of the measuring device, but the operation is not carried out in the embodiment.
Fig. 5 is a schematic diagram of 5 power quality states according to an embodiment of the present invention, where fig. 5(a) is a dc voltage rated state, (b) is a dc voltage deviation state, (c) is a dc voltage fluctuation state, (d) is a dc voltage sag state, and (e) is a dc voltage ripple state. Wherein the respective states are defined as follows: in the rated state of the direct-current voltage, the actual voltage and the rated voltage value are basically maintained to be the same and are kept stable; in a direct-current voltage deviation state, the actual voltage is higher than or lower than the rated voltage, and the general voltage deviation is less than 10% of the rated voltage; the direct-current voltage fluctuation state, the actual voltage fluctuation is irregular and rapid voltage continuous variation without frequency fixed components, and the variation amplitude is usually not more than 10% of the rated voltage; in a direct-current voltage sag state, instantaneous voltage sag occurs in actual voltage, or voltage is greatly reduced in a short time, and the reduction is generally required to exceed 10% of rated voltage; in the dc voltage ripple state, the actual voltage is ac component superimposed on the dc power, and the dc bus voltage is generally divided into 1-order, 2-order, … -order, and n-order ripples according to the power frequency and 2, 3, …, and n-times of the power frequency.
The direct current quality state identification is a support vector machine multi-classification model based on particle swarm parameter optimization, and the support vector machine is a common nonlinear classification method with good industrial applicability. The kernel parameter sigma and the penalty factor C of the support vector machine are optimized by adopting a particle swarm optimization algorithm to improve the generalization capability of the SVM (support vector machine), so that the classification and identification of the quality state of the direct current power are realized, and a flow chart of the particle swarm optimization algorithm is shown in fig. 6.
In the device design process, the overall error of the measuring device can be minimized by reasonably selecting components such as resistors, capacitors and chips of the measuring device, and reasonably designing a circuit and arranging a circuit board.
When the dc voltage measuring device continuously measures the voltage for a period of time, the resistance of the high-voltage arm may change under the action of various factors, that is, when the self-calibration operation needs to be performed, the operation flow chart is as shown in fig. 7. And after the detected voltage is identified by the electric energy quality identification module, the electric energy quality state at the moment is obtained. If the electric energy quality state is the ripple state, the amplitude and the phase of each stage of ripple can be fitted through a least square algorithm, the time point of the occurrence of the steady-state wave peak is predicted, the FPGA controls the solid-state relay to carry out the opening and closing operation at the corresponding moment, and therefore the low-voltage arm resistor R is achievedN-1The high voltage arm resistor is self-calibrated according to the acquired voltage value; if the power quality state is a rated state or a deviation state, the measured voltage is stable, and the FPGA can directly operate the solid-state relay to realize self calibration; if the power quality is in a temporary drop or fluctuation state, the self-calibration operation can be abandoned, and the next power quality identification is waited.
The invention provides a direct-current high-voltage measuring device capable of self-calibrating in a multi-energy quality state, which comprises the following components: the internal resistance of the direct-current resistance voltage divider is simplified into three resistors, namely a high-voltage arm resistor and two low-voltage arm resistors, wherein the high-voltage arm resistor is arranged in insulating oil in an insulating wall, one end of the high-voltage arm resistor is connected with a high-voltage lead end of the voltage divider, and the other end of the high-voltage arm resistor is connected to the bottom of the voltage divider through a screw hole. And the two low-voltage arm resistors are connected in series and fixed at the bottom of the voltage divider, one end of each low-voltage arm resistor is connected with the high-voltage arm resistor, and the other end of each low-voltage arm resistor is connected to the ground through a low-voltage equalizing ring. The electronic switch is connected in parallel with one of the low-voltage arm resistors close to the high-voltage arm resistor, the electronic switch and the two low-voltage arm resistors are sealed through epoxy resin, and the corresponding electric connecting wire is led to the PCB circuit board fixed to the bottom through the opening. The circuit board comprises a protection circuit, a signal conditioning circuit, a signal acquisition circuit, a communication circuit and the like, and realizes corresponding processing of signals. When the resistance of the high-voltage arm resistor of the voltage divider needs to be calibrated, the mode of the voltage to be measured is identified through the electric energy quality identification module, and the self-calibration operation can be realized through the FPGA control relay only when the state is in a certain state of the rated value, ripple waves or deviation, so that the long-term stable measurement of the direct-current high voltage is ensured, and the influence of external environmental factor interference and the like on the measurement result is reduced.
The method for identifying the power quality state and predicting the least square algorithm is adopted, so that the high-level voltage can be stably and accurately measured for a long time, the self-calibration operation can be performed under a plurality of power quality states by combining the characteristics of a current direct current power grid, and the influence of the reduction of the measurement accuracy caused by the resistance change of the high-voltage arm of the voltage divider can be effectively reduced.
The invention provides a direct-current high-voltage measuring device capable of self-calibrating in a multi-energy quality state, which comprises the following components: the hardware of the device is divided into a direct current resistance voltage divider and a low voltage measuring circuit; the internal resistance structure of the former is simplified into three series resistors, an electronic switch and a resistor positioned in the middle position form a parallel connection relation, and the low-voltage measuring circuit realizes corresponding processing of filtering, amplification, collection, operation, transmission and the like on signals. The device software is divided into direct current power quality state identification and self-calibration algorithms which are respectively used for direct current bus voltage state judgment and self-calibration operation execution. When the voltage divider runs for a long time and the resistance value of the high-voltage arm changes and needs to be calibrated, the microprocessor performs mode identification on the bus voltage, and when the power quality state is in a certain state of rating, ripple or deviation, the electronic switch can be controlled through the FPGA to realize the self-calibration operation, so that the self-calibration precision and the long-term stable measurement of the direct current high voltage are ensured, and the influence of factors such as voltage fluctuation on the measurement result is reduced.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.
Claims (10)
1. A direct current high voltage measuring device with a self calibration function, comprising:
a dc resistance divider comprising: high voltage arm resistor RHLow voltage arm resistor RN-1And a low-voltage arm resistor RN(ii) a The high-voltage arm resistor RHIs used for being electrically connected with a voltage bus, and the other end of the low-voltage arm resistor RN-1Is electrically connected with one end of the low-voltage arm resistor RN-1Another end of (3) and a low-voltage arm resistor RNIs connected to a low-voltage arm resistor RNThe other end of the first and second electrodes is used for grounding; the low-voltage arm resistor RN-1An electronic switch K is connected in parallel;
a measurement circuit for measuring and acquiring the low-voltage arm resistance RNVoltage value of (d);
a microprocessor, comprising: the device comprises a direct current high voltage value acquisition module, a direct current power quality state identification module and a self-calibration module;
the direct-current high-voltage value acquisition module is used for adopting a low-voltage arm resistor RNThe voltage value is multiplied by the voltage division ratio of the direct current resistance voltage divider to calculate and obtain a direct current high voltage value of the voltage bus to be measured;
the direct current power quality state identification module is used for acquiring the amplitude change of a direct current high voltage value of a voltage bus to be detected in a preset time period, and dividing the power quality state of the direct current high voltage to be detected at the current stage into 5 types based on the amplitude change, wherein the types are respectively as follows: a direct-current voltage rated state, a direct-current voltage deviation state, a direct-current voltage fluctuation state, a direct-current voltage sag state and a direct-current voltage ripple state;
the self-calibration module is used for obtaining the classification of the power quality state; when the electric energy quality state is in a direct current voltage rated state, a direct current voltage deviation state or a direct current voltage ripple state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHAnd calibrating the voltage division ratio of the direct current resistor divider through the calibration value to finish the calibration of the direct current high voltage measuring device.
2. The direct-current high-voltage measurement device with self-calibration function according to claim 1, further comprising:
and the protection circuit is arranged between the direct current resistance voltage divider and the measuring circuit and is used for isolating the front-stage circuit and the rear-stage circuit.
3. The direct-current high-voltage measurement device with self-calibration function according to claim 1, further comprising:
and the communication circuit is used for realizing the communication between the direct-current high-voltage measuring device and an upper computer or a display instrument and finishing the communication transmission of the measured voltage value.
4. The DC high voltage measurement device with self calibration function as claimed in claim 1, wherein the high voltage arm resistor RHLow voltage arm resistor RN-1And a low-voltage arm resistor RNThe resistance value of the series circuit is determined by the voltage grade of a voltage bus to be tested, the current of the series circuit is in the hundred microamperes, and the output voltage range of the low-voltage arm is 0-10V; the precision of the resistance value is determined by the measurement accuracy grade, the resistance values are all low-temperature drift resistances, and the temperature drift is less than 1 ppm/DEG C.
5. The direct-current high-voltage measurement device with self-calibration function according to claim 1, wherein the electronic switch K is a solid-state relay;
on-resistance RonWhen the following relation is satisfied, the influence of the relation on the accuracy level alpha of the direct current resistor divider is ignored:
6. the direct-current high-voltage measurement device with the self-calibration function according to claim 1, wherein in the direct-current power quality state identification module, an amplitude change of a direct-current high-voltage value of a voltage bus to be measured in a preset time period is obtained, and based on the amplitude change, the power quality states of the direct-current high-voltage bus to be measured at the present stage are classified into 5 types, which are respectively: the specific steps of the DC voltage rated state, the DC voltage deviation state, the DC voltage fluctuation state, the DC voltage sag state and the DC voltage ripple state comprise:
acquiring the amplitude change of a direct-current high voltage value of a voltage bus to be detected in a preset time period;
according to the support vector machine multi-classification model with the amplitude variation optimized based on the particle swarm parameters, optimizing a kernel parameter sigma and a penalty factor C in the support vector machine model by adopting a particle swarm optimization algorithm, and realizing classification and identification of the DC energy quality state, wherein the classification and identification is obtained by the following categories: the direct current voltage rated state, the direct current voltage deviation state, the direct current voltage fluctuation state, the direct current voltage ripple state and the direct current voltage sag state are 5 electric energy quality states.
7. The direct-current high-voltage measurement device with self-calibration function according to claim 1,
the DC voltage rated state is that the actual voltage of the voltage bus and the rated voltage value are maintained to be the same;
the direct-current voltage deviation state is that the actual voltage of a voltage bus is higher than or lower than the rated voltage, and the voltage deviation is lower than 10% of the rated voltage;
the direct-current voltage fluctuation state is that the actual voltage fluctuation of a voltage bus is irregular and does not contain voltage continuous fluctuation of fixed frequency components, and the change amplitude is lower than 10% of the rated voltage;
the direct-current voltage sag state is that the instantaneous voltage sag of the actual voltage of the voltage bus or the voltage preset amplitude reduction within the preset time occurs, and the reduction amount is greater than 10% of the rated voltage;
the direct-current voltage ripple state is that the actual voltage of a voltage bus is the alternating-current component superposed in direct current, and the direct-current bus voltage is divided into 1-time, 2-time, … -time and n-time ripples according to power frequency and 2, 3, … and n times of the power frequency.
8. The direct-current high-voltage measuring device with the self-calibration function according to claim 1, wherein in the self-calibration module, classification of power quality states is obtained; when the power quality state is in a direct current voltage rated state or a direct current voltage deviation state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHThe step of calibrating the dc resistor divider by the calibration value to complete the calibration of the dc high voltage measuring device specifically includes:
when the voltage of the voltage bus to be measured is in the range of 80% -120% of the rated voltage and the voltage is in the DC voltage rated state, the DC voltage deviation state or the DC voltage ripple state,
controlling the electronic switch K to be switched on and off, and calculating to obtain the high-voltage arm resistance RHBy which the voltage dividing ratio of the direct current resistor divider is calibrated;
wherein, when being in DC voltage rated state and DC voltage deviation state:
when the electronic switch K is turned off, the low-voltage arm outputs a voltage VNIs shown as
High DC voltage value VHIs shown as
When the electronic switch K is conducted, the low-voltage arm outputs a voltage VN' is represented as
High DC voltage value VHIs shown as
Simultaneous DC high voltage value calculation equation to eliminate bus voltage VHCalculating to obtain RHIs given by the following calibration values:
9. the direct-current high-voltage measuring device with the self-calibration function according to claim 1, wherein in the self-calibration module, classification of power quality states is obtained; when the electric energy quality state is in a direct-current voltage ripple state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHThe step of calibrating the dc resistor divider by the calibration value to complete the calibration of the dc high voltage measuring device specifically includes:
acquiring a preset number of voltage data points in a direct-current voltage ripple state, selecting the time of occurrence of ripple wave crests, wave troughs or other characteristic points in the selected time as t1, t2 and t3, and fitting the amplitude and the phase of each ripple by a least square algorithm;
predicting the occurrence time point t of the wave crest, the wave trough or other characteristic points of the ripple wave based on the amplitude and the phase of each ripple waven、tn+1、tn+2；
At tn、tn+1、tn+2The electronic switch K is turned off or turned on all the time, and the voltage of the voltage bus is kept the same when the electronic switch K is turned off or turned on;
when the electronic switch K is turned off, the low-voltage arm outputs a voltage VNIs shown as
High DC voltage value VHIs shown as
When the electronic switch K is conducted, the low-voltage arm outputs a voltage VN' is represented as
High DC voltage value VHIs shown as
Simultaneous DC high voltage value calculation equation to eliminate bus voltage VHCalculating to obtain RHIs given by the following calibration values:
10. a method of operating a dc high voltage measuring device with self calibration according to claim 1, comprising the steps of:
the high-voltage arm resistor RHOne end for being electrically connected with the voltage bus is connected with the voltage bus to be tested, and the low-voltage arm resistor RNOne end used for grounding is grounded;
the electronic switch K is in a turn-off state;
the measuring circuit measures and obtains the resistance R of the low-voltage armNVoltage value of (d);
direct current high voltage value acquisition moduleBy low-voltage arm resistor RNThe voltage value is multiplied by the voltage division ratio of the direct current resistance voltage divider to calculate and obtain a direct current high voltage value of the voltage bus to be measured; the direct current power quality state identification module acquires the amplitude change of the direct current high voltage value of the voltage bus to be detected in a preset time period, and the power quality state of the direct current high voltage to be detected at the current stage is divided into 5 types based on the amplitude change, wherein the types are respectively as follows: a direct-current voltage rated state, a direct-current voltage deviation state, a direct-current voltage fluctuation state, a direct-current voltage sag state and a direct-current voltage ripple state; the self-calibration module acquires the classification of the power quality state; when the electric energy quality state is in a direct current voltage rated state, a direct current voltage deviation state or a direct current voltage ripple state, the high-voltage arm resistor R is obtained through calculation by controlling the on and off of the electronic switch KHAnd calibrating the voltage division ratio of the direct current resistor divider through the calibration value to finish the calibration of the direct current high voltage measuring device.
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| CN116990738A (en) * | 2023-09-28 | 2023-11-03 | 国网江苏省电力有限公司营销服务中心 | Low-voltage-driven 1kV voltage proportion standard quantity value tracing method, device and system |
| CN116990738B (en) * | 2023-09-28 | 2023-12-01 | 国网江苏省电力有限公司营销服务中心 | Low-voltage-driven 1kV voltage proportion standard quantity value tracing method, device and system |
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