CN111900697A - Double sampling circuit for electric power secondary equipment - Google Patents
Double sampling circuit for electric power secondary equipment Download PDFInfo
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- CN111900697A CN111900697A CN202010643451.2A CN202010643451A CN111900697A CN 111900697 A CN111900697 A CN 111900697A CN 202010643451 A CN202010643451 A CN 202010643451A CN 111900697 A CN111900697 A CN 111900697A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/042—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers for current transformers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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Abstract
The invention discloses a double sampling circuit of electric power secondary equipment, which comprises a sampling resistance network connected with the secondary side output of a current transformer CT and two sets of sampling circuits, wherein each sampling circuit comprises a filter circuit, an ADC (analog-to-digital converter) circuit and a control chip; the sampling resistor network comprises two resistor networks which are connected in series, two sets of sampling circuits are used for collecting voltage signals of the two resistor networks, the two chips finish the exchange of sampling digital quantities through the data interaction module, and the sampling value judgment module is used for carrying out logic judgment on the two sets of sampling digital quantities to judge whether the resistance values of the two resistor networks are abnormal or not. The invention can determine the working state of the sampling resistor, discriminate the abnormal condition of the sampling resistor at the secondary side of the CT in real time and prevent the control abnormality of the electric secondary equipment or the false operation and the refusal operation of a protection outlet.
Description
Technical Field
The invention relates to a current sampling circuit based on a current transformer, in particular to a double sampling circuit of power secondary equipment.
Background
The analog sampling system is an information source for the work of the electric power secondary equipment, and when various faults occur in the power grid, the electric power secondary equipment uses the analog quantity sampling value to judge the faults so as to complete the functions of removing and isolating the faults. The power secondary equipment generally transmits a primary Current using a Current Transformer (CT). Based on the technology that current patent published, electric power secondary equipment such as current relay protection device, steady control device generally uses dualized sampling. A current analog quantity of one path in the device uses a CT, a sampling resistor is connected to the secondary side of the CT, and sampling voltage on the sampling resistor is simultaneously sent to two processor cores for calculation and judgment in a dual sampling mode, so that the sampling reliability is improved. However, when the sampling resistor is abnormal, for example, the sampling resistor generates resistance fluctuation, the validity and accuracy of the sampling value are directly affected, and in severe cases, errors can be caused in the control or protection logic of the power secondary equipment. If the device continues to use the sampled values for application calculations at this point, it may cause failure of the protection, control, etc. logic.
A double-AD sampling inconsistency judging method in an intelligent substation (CN2016105510754A) provides a double-AD sampling inconsistency judging scheme for the intelligent substation. According to the scheme, the same analog quantity is repeatedly sampled, the effectiveness of each path of AD sampling data is judged firstly, and whether the double AD sampling values are abnormal or not is judged by comparing whether the absolute value of the double AD sampling difference value of the measured electric quantity is larger than a set threshold value or not, so that the protection of malfunction tripping is facilitated. However, the scheme only uses the difference value of two paths of AD sampling to judge the abnormity, and the conditions of sampling resistor working abnormity such as short circuit, open circuit, resistance value change and the like can not be distinguished, judged and alarmed, which is very key to the reliable action of the power secondary equipment.
An intelligent substation relay protection method based on double-AD sampling (CN2015104410042A) discloses a double-AD sampling inconsistency judgment method, namely, the double-AD sampling inconsistency is judged by comparing the absolute value of the amplitude difference value of double-AD sampling data, and if the absolute value is larger than a set value. According to the technical scheme, only the same sampling resistor is repeatedly sampled, so that the method cannot identify the sampling resistor when the sampling resistor is abnormal, and the sampling reliability and the response accuracy of the secondary power equipment including the relay protection device are influenced. Namely, when the resistance value of the resistor changes, the system cannot monitor and respond in time, which is not favorable for the reliable action of the power secondary equipment.
In summary, the conventional dual sampling circuit cannot monitor the abnormal state of the CT secondary sampling resistor itself.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems, the invention provides a double sampling circuit of electric power secondary equipment, which can determine the working state of a sampling resistor, discriminate the abnormal condition of the sampling resistor on the secondary side of a CT (computed tomography) in real time and prevent the control abnormality of the electric power secondary equipment or the misoperation and the refusal action of a protection outlet.
The technical scheme is as follows: the technical scheme adopted by the invention is a double sampling circuit of electric power secondary equipment, which comprises a sampling resistance network connected with the secondary side output of a current transformer CT and two sets of sampling circuits, wherein each sampling circuit comprises a filter circuit, an ADC (analog-to-digital converter) circuit and a control chip; the sampling resistor network comprises two resistor networks which are connected in series, two sets of sampling circuits are used for collecting voltage signals of the two resistor networks, the two paths of voltage signals are filtered by the filter circuit respectively, the voltage is converted into sampling digital quantity by the ADC conversion circuit and is sent to the control chip, and the control chip controls the ADC conversion circuit to start conversion and receives the sampling digital quantity output by the ADC; the two chips finish the exchange of the sampling digital quantity through the data interaction module, and carry out logic judgment on the two sets of sampling digital quantities by using the sampling value judgment module, wherein the logic judgment is to compare the magnitude relation between the ratio of the two sets of sampling digital quantities and the voltage division ratio of the equivalent resistors of the two series resistor networks, and judge whether the resistance values of the two resistor networks are abnormal or not through the result of the logic judgment.
Preferably, the filter circuit is an RC filter circuit, and the control chip is an SoC integrated circuit chip.
In the above scheme, the logical judgment result is used to judge whether the resistance values of the two resistor networks are abnormal, and the criterion is as follows:
setting equivalent resistance values of the two series resistor networks as R1 and R2 respectively, grounding one end of the resistor network with the equivalent resistance value of R2, and setting the corresponding acquired sampling digital quantity as S1 and S2 respectively;
(1) if S1/S2 is (R1+ R2)/R2, judging that the sampling resistor works normally;
(2) if S1/S2 ≠ (R1+ R2)/R2, judging that the sampling resistance is abnormal, and further analyzing the type of the sampling resistance abnormality:
(a) if both S1 and S2 are zero, determining that at least one resistor network is open;
(b) if S1 is equal to S2, the resistor network with the equivalent resistance value of R1 is judged to be short-circuited;
(c) if S1 is not zero and S2 is zero, the resistor network with the equivalent resistance value of R2 is judged to be short-circuited;
(d) if the resistance of S1/S2 > (R1+ R2)/R2 or S1/S2 < (R1+ R2)/R2 is not in any of the cases (a) to (c), the resistance of at least one resistor network is determined to be changed.
A typical dual sampling circuit scheme is that the resistor network uses high-precision sampling resistors, and the sampling resistor network includes two high-precision sampling resistors connected in series.
Furthermore, the two high-precision sampling resistors have the same resistance value. Under the design, the result of logical judgment is used for judging whether the resistance values of the two resistance networks are abnormal or not, and the criterion is as follows:
(1) if S1 is 2S 2, judging that the sampling resistor works normally;
(2) if S1 ≠ 2 × S2, judging that the sampling resistance is abnormal, and further analyzing the type of the abnormal sampling resistance:
(a) if both S1 and S2 are zero, determining that at least one sampling resistor is open;
(b) if S1 is equal to S2, judging that the sampling resistor with two ends not grounded is short-circuited;
(c) if S1 is not zero and S2 is zero, judging that the sampling resistor with one end grounded is short-circuited;
(d) if S1 > 2 × S2 or S1 < 2 × S2, it is determined that the resistance value of at least one sampling resistor has changed.
Has the advantages that: compared with the prior art, the invention has the following advantages: the invention adopts a resistor network connected in series, preferably adopts two high-precision sampling resistors connected in series, access points of a duplex sampling channel are respectively placed on the two sampling resistors, the ratio of two sampling voltages is calculated and analyzed through a program, the working state of the sampling resistors is determined, the abnormal condition of the sampling resistors is discriminated in real time, and the control abnormality of the electric secondary equipment or the misoperation and the refusal operation of a protection outlet are prevented. Compared with the conventional sampling circuit, the double-sampling circuit can solve the problem that the sampling resistor in the double-sampling circuit of the current power secondary equipment cannot be judged in abnormal states such as short circuit, open circuit and resistance value fluctuation.
Drawings
Fig. 1 is a block diagram of a double sampling circuit system of a power secondary device according to the present invention;
fig. 2 is a typical circuit diagram of a power secondary device duplexed sampling circuit according to the present invention.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Fig. 1 is a block diagram of a dual sampling circuit system of a power secondary device according to the present invention. The secondary side output current of the current transformer 1(CT) is connected to the sampling resistor network 2. The sampling resistor network 2 comprises two resistor networks connected in series, and two voltage signals V1 and V2 are respectively output from output ends of the two resistor networks.
The first voltage signal V1 is connected to the A set of filter circuit 3 to be filtered and then is sent to the A set of ADC sample 4 to be subjected to analog-to-digital conversion, the A set of ADC sample 4 is converted under an ADC control module of the SOC5, and the digital quantity obtained by conversion is used as an A set of sample value S1 and is sent to the chip SOC 5.
And a second voltage signal V2 is connected to the B sets of filter circuits 6 to be filtered and then is sent to the B sets of ADC samples 7 to be subjected to analog-to-digital conversion, the B sets of ADC samples 7 are converted under an ADC control module of the SOC8, and digital values obtained by conversion are used as B sets of sample values S2 and sent to the chip SOC 8.
The chip SOC5 and the chip SOC8 complete data exchange through a data interaction module, a sampling value judgment module is used for carrying out sampling value logic judgment on the dualized sampling values, and whether the resistance values of the two resistance networks are abnormal or not is judged through the voltage division ratio of the two sets of sampling values and the equivalent resistance of the two series resistance networks, wherein the abnormal states comprise short circuit, open circuit, resistance value fluctuation and the like. The criterion for the working state of the sampling resistor is as follows, the equivalent resistors of the two series resistor networks are respectively R1 and R2, and one end of the resistor network with the resistance R2 is grounded:
(1) and if the S1/S2 is (R1+ R2)/R2, judging that the sampling resistor works normally. The threshold, i.e. the allowable error range, needs to be set in the equation judgment. Within this error range, equality is determined.
(2) And if S1/S2 is not equal to (R1+ R2)/R2, judging that the sampling resistance is abnormal, and setting the quality of the analog quantity sampling value to be abnormal. Meanwhile, the application software calculates to further analyze the sampling resistance abnormal type:
(a) if both S1 and S2 are zero, determining that at least one resistor network is open;
(b) if S1 is equal to S2, the resistor network with the resistance value of R1 is judged to be short-circuited;
(c) if S1 is not zero and S2 is zero, the resistor network with the resistance value of R2 is judged to be short-circuited;
(d) if the resistance of S1/S2 > (R1+ R2)/R2 or S1/S2 < (R1+ R2)/R2 is not in any of the cases (a) to (c), the resistance of at least one resistor network is determined to be changed.
In the system block diagram of fig. 1, the modules numbered 1, 2, 3, 4, 6 and 7 in the block diagram form an analog part of a duplexed sampling circuit, and the modules numbered 4, 5, 7 and 8 in the block diagram form a digital part of the duplexed sampling circuit, wherein the module 4 and the module 7 are analog-digital mixed parts.
Fig. 2 is a typical implementation circuit of the analog part of the duplexed sampling circuits according to the present invention. The CT secondary side sampling circuit adopts two high-precision sampling resistors connected in series to carry out double sampling on analog quantity to be processed by the electric power secondary equipment. After the voltage values sampled by the two sampling resistors are respectively sent to the two sets of ADC sampling circuits for sampling, the sampling values are sent to the SOC for analysis and logic judgment.
The secondary side of the CT adopts 2 high-precision sampling resistors R1 and R2 which are connected in series for sampling, the current of the secondary side of the CT is converted into voltage, and R1 and R2 are in a proportional relation.
After the current on the secondary side of the CT flows through the sampling resistors R1 and R2, the obtained sampling voltage V1 is used as the A set of sampling voltage in the double sampling, and is filtered by a low-pass filter consisting of a resistor R3 and a capacitor C1 and then is sent to an ADC chip U1. U1 performs analog-to-digital conversion, and the digital quantity obtained by the conversion is used as the A set of sampling values S1.
After the current on the secondary side of the CT flows through a sampling resistor R2, the obtained sampling voltage V2 is used as B set of sampling voltage in double sampling, and is filtered by a low-pass filter consisting of a resistor R4 and a capacitor C2 and then is sent to an ADC chip U2. U2 performs analog-to-digital conversion, and the digital quantity obtained by the conversion is used as the B set of sampling values S2.
The digital part of the double sampling circuit judges the working state of the sampling resistor by using the A set of sampling values S1 and the B set of sampling values S2 obtained by double sampling, and the judgment result is used as the quality parameter of the analog quantity sampling value to participate in logic judgment of protection, control and the like of the power secondary equipment, so that abnormal control or misoperation and refusal of a protection outlet of the power secondary equipment are prevented. The criterion for the working state of the sampling resistor is as follows, and R1 and R2 have the same resistance value for analysis:
(1) if S1 is 2S 2, judging that the sampling resistor works normally;
(2) and if S1 is not equal to 2 × S2, judging that the sampling resistance is abnormal, and setting the quality of the analog quantity sampling value to be abnormal. Meanwhile, the application software further analyzes the sampling resistance abnormity type:
(a) if S1 and S2 are both zero, determining that R1 or R2 is open;
(b) if S1 is equal to S2, R1 is short-circuited;
(c) if S1 is not zero and S2 is zero, determining that R2 is short-circuited;
(d) not in any of (a) to (c), and when S1 > 2 × S2 or S1 < 2 × S2, it is determined that the resistance value of R1 or R2 changes.
Claims (6)
1. The utility model provides a power secondary equipment dualization sampling circuit which characterized in that: the circuit comprises a sampling resistor network and two sets of sampling circuits, wherein the sampling resistor network is connected with the secondary side output of the current transformer CT, and each sampling circuit comprises a filter circuit, an ADC (analog-to-digital converter) circuit and a control chip; the sampling resistor network comprises two resistor networks which are connected in series, two sets of sampling circuits are used for collecting voltage signals of the two resistor networks, the two paths of voltage signals are filtered by the filter circuit respectively, the voltage is converted into sampling digital quantity by the ADC conversion circuit and is sent to the control chip, and the control chip controls the ADC conversion circuit to start conversion and receives the sampling digital quantity output by the ADC; the two chips finish the exchange of the sampling digital quantity through the data interaction module, and carry out logic judgment on the two sets of sampling digital quantities by using the sampling value judgment module, wherein the logic judgment is to compare the magnitude relation between the ratio of the two sets of sampling digital quantities and the voltage division ratio of the equivalent resistors of the two series resistor networks, and judge whether the resistance values of the two resistor networks are abnormal or not through the result of the logic judgment.
2. The power secondary device duplexed sampling circuit according to claim 1, characterized in that: the filter circuit adopts an RC filter circuit, and the control chip adopts an SoC integrated circuit chip.
3. The power secondary device duplexed sampling circuit according to claim 1, characterized in that: the logical judgment result is used for judging whether the resistance values of the two resistor networks are abnormal or not, and the criterion is as follows:
setting equivalent resistance values of the two series resistor networks as R1 and R2 respectively, grounding one end of the resistor network with the equivalent resistance value of R2, and setting the corresponding acquired sampling digital quantity as S1 and S2 respectively;
(1) if S1/S2 is (R1+ R2)/R2, judging that the sampling resistor works normally;
(2) if S1/S2 ≠ (R1+ R2)/R2, judging that the sampling resistance is abnormal, and further analyzing the type of the sampling resistance abnormality:
(a) if both S1 and S2 are zero, determining that at least one resistor network is open;
(b) if S1 is equal to S2, the resistor network with the equivalent resistance value of R1 is judged to be short-circuited;
(c) if S1 is not zero and S2 is zero, the resistor network with the equivalent resistance value of R2 is judged to be short-circuited;
(d) if the resistance of S1/S2 > (R1+ R2)/R2 or S1/S2 < (R1+ R2)/R2 is not in any of the cases (a) to (c), the resistance of at least one resistor network is determined to be changed.
4. The power secondary device duplexed sampling circuit according to claim 1, characterized in that: the resistance network adopts high accuracy sampling resistance, sampling resistance network includes two high accuracy sampling resistance of establishing ties.
5. The power secondary device duplexed sampling circuit according to claim 4, characterized in that: the two high-precision sampling resistors have the same resistance value.
6. The power secondary device duplexed sampling circuit according to claim 5, characterized in that: the logical judgment result is used for judging whether the resistance values of the two resistor networks are abnormal or not, and the criterion is as follows:
(1) if S1 is 2S 2, judging that the sampling resistor works normally;
(2) if S1 ≠ 2 × S2, judging that the sampling resistance is abnormal, and further analyzing the type of the abnormal sampling resistance:
(a) if both S1 and S2 are zero, determining that at least one sampling resistor is open;
(b) if S1 is equal to S2, judging that the sampling resistor with two ends not grounded is short-circuited;
(c) if S1 is not zero and S2 is zero, judging that the sampling resistor with one end grounded is short-circuited;
(d) if S1 > 2 × S2 or S1 < 2 × S2, it is determined that the resistance value of at least one sampling resistor has changed.
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| CN202010643451.2A CN111900697A (en) | 2020-07-06 | 2020-07-06 | Double sampling circuit for electric power secondary equipment |
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| CN202010643451.2A CN111900697A (en) | 2020-07-06 | 2020-07-06 | Double sampling circuit for electric power secondary equipment |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115459772A (en) * | 2022-11-08 | 2022-12-09 | 江苏天合储能有限公司 | Current analog signal sampling calibration device and calibration method thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202471796U (en) * | 2012-02-10 | 2012-10-03 | 浙江中控技术股份有限公司 | A self-detection circuit of a sampling resistor of current signal |
| CN207353825U (en) * | 2017-10-13 | 2018-05-11 | 南京国电南自电网自动化有限公司 | A kind of hand-held reactor protection device |
-
2020
- 2020-07-06 CN CN202010643451.2A patent/CN111900697A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202471796U (en) * | 2012-02-10 | 2012-10-03 | 浙江中控技术股份有限公司 | A self-detection circuit of a sampling resistor of current signal |
| CN207353825U (en) * | 2017-10-13 | 2018-05-11 | 南京国电南自电网自动化有限公司 | A kind of hand-held reactor protection device |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115459772A (en) * | 2022-11-08 | 2022-12-09 | 江苏天合储能有限公司 | Current analog signal sampling calibration device and calibration method thereof |
| CN115459772B (en) * | 2022-11-08 | 2023-02-28 | 江苏天合储能有限公司 | Current analog signal sampling calibration device and calibration method thereof |
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Application publication date: 20201106 |