CN113325358A - Method and system for rapidly detecting residual current of intelligent electric meter - Google Patents

Method and system for rapidly detecting residual current of intelligent electric meter Download PDF

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Publication number
CN113325358A
CN113325358A CN202110494978.8A CN202110494978A CN113325358A CN 113325358 A CN113325358 A CN 113325358A CN 202110494978 A CN202110494978 A CN 202110494978A CN 113325358 A CN113325358 A CN 113325358A
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current
waveform
value
residual current
algorithm
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CN113325358B (en
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张本松
周尚礼
何恒靖
张鑫
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Zhejiang Reallin Electron Co ltd
Southern Power Grid Digital Grid Research Institute Co Ltd
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Zhejiang Reallin Electron Co ltd
Southern Power Grid Digital Grid Research Institute Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
    • G01R35/04—Testing or calibrating of apparatus covered by the other groups of this subclass of instruments for measuring time integral of power or current
    • 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
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • 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
    • G01R19/32—Compensating for temperature change
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

The invention discloses a method and a system for rapidly detecting residual current of an intelligent ammeter, which are characterized by comprising the steps of obtaining 1/4 waveform current instantaneous values through sampling and obtaining residual current effective values IE through a rapid waveform sorting algorithm. The quick waveform arrangement method comprises the steps of arranging current instantaneous values of 1/4 waveforms into full-cycle waveforms, calculating effective values Ie through an effective value algorithm, obtaining residual current effective values Ie, performing temperature compensation on Ie, and outputting. Calculating an effective value based on the 1/4 waveform, and improving the alarm speed of the residual current; and the accuracy of residual current detection is improved through a symmetric algorithm, a maximum judgment and an effective value algorithm. The temperature compensation current is detected and calculated for the environment temperature, and is compensated to the effective value of the residual current, so that the temperature adaptability is improved, and the alarm accuracy is further improved.

Description

Method and system for rapidly detecting residual current of intelligent electric meter
Technical Field
The invention relates to the field of electric detection alarm, in particular to a method and a system for rapidly detecting residual current of an intelligent ammeter.
Background
The residual current is the current with the sum of phase current vectors of all phases in the distribution line being not zero, and is caused by the electric leakage of equipment or lines under most conditions, and the electric equipment or lines can be burnt out when the electric leakage is serious, so that fire is caused. Therefore, residual current detection and residual current operated protectors are installed in the low-voltage power grid, and the protection device is an effective protection measure for preventing personal electric shock, electric fire and damage of electric equipment. The residual current monitoring method in the prior art respectively obtains effective values of live wire current and zero line through a metering chip, and the effective values are subtracted to obtain the effective values of residual current. And monitoring the data of the live wire and the zero line of the user by comparing the electricity consumption time periods, acquiring a plurality of groups of effective data points, calculating the difference value and the ratio of the live wire and the zero line, judging the change rate of the current of the live wire and the zero line of the electricity consumption of the user, and judging the approximate range of the residual current.
For example, a "electric energy meter capable of measuring residual current" disclosed in chinese patent literature, whose publication number CN204154810U includes the utility model provides an electric energy meter capable of measuring residual current, which comprises a casing, a terminal block, a phase line, a zero line, a relay, a phase line current sampling resistor, a residual current transformer and a circuit device; the relay, the phase line current sampling resistor and the residual current transformer are all arranged in the shell; the phase line and the zero line penetrate through the residual current transformer; the circuit device comprises a voltage sampling module, a signal processing module, an A/D conversion module, an electric energy metering module, a single chip microcomputer processing module, a relay control module, a communication module, an LCD display module, a key module and a power supply module. However, the scheme has the problems of low detection efficiency, low accuracy of the output current value because the output value of the common mutual inductor is used for estimating the residual current value, and the problem that the accuracy of an alarm system is influenced because the current is cut off by false alarm due to the influence of the external environment.
Disclosure of Invention
The invention provides a method and a system for rapidly detecting the residual current of an intelligent ammeter, which are high in detection precision, alarming speed and accuracy, and aims to solve the problems that a plurality of whole waves need to be detected, the metering speed is low, an effective value is obtained through a comparison method, and the alarming accuracy is influenced.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for rapidly detecting the residual current of an intelligent ammeter is characterized by comprising the steps of sampling to obtain 1/4 waveform current instantaneous values; obtaining residual current effective value I through rapid waveform sorting algorithmE. By using the 1/4 waveform to obtain the effective value, the detection efficiency improved by the original calculation method which at least needs to detect the whole cycle wave is improved by 75%.
Preferably, the rapid waveform arrangement method comprises arranging the current instantaneous value of 1/4 waveform into a full-circle waveform, and calculating an effective value I by an effective value algorithme。
Preferably, the method for arranging the current instantaneous value of 1/4 waveform into the full-circle waveform lattice by the rapid waveform arranging algorithm comprises a symmetrical algorithm.
Preferably, the symmetric algorithm comprises the steps of:
step S1: the current instantaneous value of 1/4 waveform is converted into the current absolute value i of 1/4 waveform1,i2,i3,…iN/4(ii) a Wherein N is the number of sampling points in a current period;
step S2: converting an absolute value of the current transient of the 1/4 waveform to a current value transient of the 1/2 waveform;
step S3: comparing and obtaining 1/2 current instantaneous values of the waveform, obtaining the maximum value I in the current instantaneous valuesMAXAnd 1/2 waveform currentMinimum value I of instantaneous valuesMIN；
Step S4: the current transient of the 1/2 waveform is copied and the full-cycle waveform is obtained by a symmetric algorithm.
Preferably, the effective value algorithm comprises a most value judgment: calculating the maximum deviation DeltaI ═ I1-Imax|-|IN/2-IminIf Δ I is 0, then ImaxIs a maximum value ofminIs the minimum value. If the delta I is not equal to 0, the sampling current is the fault current, the waveform is re-sampled, the problem of inaccurate metering caused by zero drift due to environmental factors is solved, the accuracy and the applicability of residual current measurement are improved, and the residual current measurement is accurate.
Preferably, the residual current effective value I is obtainedEAlso includes a pair ofeAnd outputting after temperature compensation. The adaptability of the residual current monitoring system to the temperature is improved, the situation that misstatement of an alarm is caused due to season introduction or environmental influence is prevented, and the precision of the residual current detection system is improved.
Preferably, the temperature compensation includes: detecting the environment temperature T of the intelligent ammeter, wherein the effective value of the current after temperature compensation is IE：IE＝Ie+1*T+2*T2+…+N*TN；
Wherein, T is the current temperature information, and N is the number of sampling points in a current period.
A method for rapidly detecting residual current of an intelligent ammeter is characterized by comprising the step of judging an effective value IEIf the threshold value is larger than the threshold value, alarming.
The utility model provides a quick detecting system of smart electric meter residual current, characterized by, includes main control unit, current transformer, temperature detecting system and alarm system, current transformer, temperature detecting system, alarm system are connected with main control unit respectively.
Preferably, the zero line and the phase line of the current transformer flow oppositely. The current transformer penetrates the L-phase current from the upper end to the lower end, and penetrates the N-phase current from the lower end to the upper end, so that the current transformer is equivalent to the vector sum difference value of the L and the N. Because the vector sum is directly sampled, the basic characteristic requirement of quick leakage current calculation can be completed.
Therefore, the invention has the following beneficial effects: (1) calculating an effective value based on the 1/4 waveform, and improving the alarm speed of the residual current; (2) and the accuracy of residual current detection is improved through a symmetric algorithm, a maximum judgment and an effective value algorithm. (3) The temperature compensation current is detected and calculated for the environment temperature, and is compensated to the effective value of the residual current, so that the temperature adaptability is improved, and the alarm accuracy is further improved.
Drawings
Fig. 1 is a schematic structural diagram of a residual current detection system according to an embodiment of the present invention.
Fig. 2 is a flowchart of a method for detecting residual current according to an embodiment of the present invention.
FIG. 3 is a waveform diagram illustrating 1/2 according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a full-cycle waveform according to an embodiment of the present invention.
In the figure: 1. the device comprises a main controller 2, a current transformer 3, a zero line 4 and a phase line.
Detailed Description
The invention is further described with reference to the following detailed description and accompanying drawings.
Example (b):
the method and the system for rapidly measuring the residual current as shown in the figures 1-4 comprise a current transformer, a main controller, a temperature sensor and an alarm, wherein the current transformer, the temperature sensor and the alarm are all connected with the main controller, the main controller comprises a relay and a metering chip, the current transformer penetrates L-phase current from the upper end to the lower end, and N-phase current penetrates from the lower end to the upper end, so that the current transformer is equivalent to measuring vectors and difference values of L and N. Because the vector sum is directly sampled, the basic characteristic requirement of quick leakage current calculation can be completed; the temperature sensor acquires temperature information around the residual current detection device and transmits the temperature information to the singlechip; the metering chip has wide dynamic range and high sampling speed and supports waveform output function.
The detection method adopted by the residual current detection system comprises the following steps:
after the detection device is powered on, the metering chip is initialized, DMA (direct memory access) is started, namely, direct memory access transmission is carried out, chip sampling is set, AD (analog-digital) is set to 64 points of each cycle sampling, the DMA is started to obtain waveform data, two points near the 0 point are taken as marks, 16 points are sampled, when the 16 points of waveform data are sampled, a rapid waveform sorting algorithm is started, the rapid waveform sorting method comprises the steps of sorting the current instantaneous value of 1/4 waveform into a whole cycle waveform, and then calculating an effective value I through an effective value algorithme. The method comprises the following steps:
step S1: the current instantaneous value of 1/4 waveform is converted into the current absolute value i of 1/4 waveform1,i2,i3,…i16(ii) a Wherein N is the number of sampling points in a current period;
step S2: converting an absolute value of the current transient of the 1/4 waveform to a current value transient of the 1/2 waveform;
step S3: comparing and obtaining 1/2 current instantaneous values of the waveform, obtaining the maximum value I in the current instantaneous valuesMAXAnd 1/2 minimum value of instantaneous value of currentMIN；
Step S4: the current transient of the 1/2 waveform is copied and the full-cycle waveform is obtained by a symmetric algorithm.
Judging the maximum value and the minimum value obtained and the removed full-wave data through the maximum value: calculating the maximum deviation DeltaI ═ I1-Imax|-|I32-IminIf Δ I is 0, then ImaxIs a maximum value ofminIs the minimum value. If the delta I is not equal to 0, the sampling current is the fault current, the waveform is re-sampled, the problem of inaccurate metering caused by zero drift due to environmental factors is solved, the accuracy and the applicability of residual current measurement are improved, and the residual current measurement is accurate. To obtain ImaxIs a maximum value ofminCarrying out effective value operation on the minimum value to obtain an effective value I of the residual currente。
The temperature sensor detects the ambient temperature T of the intelligent ammeter, converts the temperature value into a compensation current and compensates the compensation current to IeThe effective value of the current after temperature compensation is IE：IE＝Ie+1*T+2*T2+…+N*T64(ii) a Wherein T is the current temperature information. The temperature adaptability is improved, and the alarm accuracy is further improved.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Although the terms current transformer, effective value, instantaneous value, etc. are used more often herein, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.

Claims (10)

1. A method for rapidly detecting the residual current of an intelligent ammeter is characterized by comprising the steps of sampling to obtain 1/4 waveform current instantaneous values; obtaining residual current effective value I through rapid waveform sorting algorithmE。
2. The method as claimed in claim 1, wherein the fast waveform sorting method comprises sorting 1/4 waveform current instantaneous values into full-cycle waveforms, and calculating effective value I by effective value algorithme。
3. The method as claimed in claim 2, wherein the method for arranging 1/4 waveform current instantaneous values into a full-cycle waveform lattice by the fast waveform arranging algorithm comprises a symmetrical algorithm.
4. The method as claimed in claim 3, wherein the symmetric algorithm comprises the following steps:
step S1: for current transient of 1/4 waveformThe time value is converted into 1/4 waveform current absolute value i1,i2,i3,…iN/4(ii) a Wherein N is the number of sampling points in a current period;
step S2: converting an absolute value of the current transient of the 1/4 waveform to a current value transient of the 1/2 waveform;
step S3: comparing and obtaining 1/2 current instantaneous values of the waveform, obtaining the maximum value I in the current instantaneous valuesMAXAnd 1/2 minimum value of instantaneous value of currentMIN；
Step S4: the current transient of the 1/2 waveform is copied and the full-cycle waveform is obtained by a symmetric algorithm.
5. The method as claimed in claim 4, wherein the effective value algorithm comprises a most-valued decision: calculating the maximum deviation DeltaI ═ I1-Imax|-|IN/2-IminIf Δ I is 0, then ImaxIs a maximum value ofminIs the minimum value.
6. The method as claimed in claim 5 or 2, wherein the obtaining of the residual current effective value I is characterized in thatEAlso includes a pair ofeAnd outputting after temperature compensation.
7. The method for rapidly detecting the residual current of the smart meter as claimed in claim 6, wherein the temperature compensation comprises: detecting the environment temperature T of the intelligent ammeter, wherein the effective value of the current after temperature compensation is IE：IE＝Ie+1*T+2*T2+…+N*TN；
Wherein, T is the current temperature information, and N is the number of sampling points in a current period.
8. The method as claimed in claim 7, wherein the step of rapidly detecting the residual current of the smart meter comprises determining the effective value IEIf the threshold value is larger than the threshold value, alarming.
9. The utility model provides a quick detecting system of smart electric meter residual current, characterized by, includes main control unit, current transformer (2), temperature detecting system and alarm system, current transformer, temperature detecting system, alarm system are connected with main control unit respectively.
10. The system for rapidly detecting the residual current of the intelligent ammeter according to the claim 9, wherein the current transformer has a zero line (3) and a phase line (4) which are opposite in flow direction.
CN202110494978.8A 2021-05-07 2021-05-07 Rapid detection method and system for residual current of intelligent ammeter Active CN113325358B (en)

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Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0437899A (en) * 1990-06-04 1992-02-07 Nec Corp Digital tone generator
US20030011355A1 (en) * 2000-01-06 2003-01-16 Skerritt Robert Charles Current detector and current measuring apparatus including such detector with temperature compensation
CN1727906A (en) * 2005-07-28 2006-02-01 泰州苏源集团科电有限公司 Cycle sampling method in quality of power supply in electrical network
JP2008032660A (en) * 2006-07-31 2008-02-14 Chugoku Electric Power Co Inc:The Device and method for measuring leakage current
CN101149403A (en) * 2007-10-26 2008-03-26 辽宁工业大学 Method for sensing and measuring current through electric-thermal conversion and dedicated electric-thermal conversion sensor
EP2846432A1 (en) * 2013-09-05 2015-03-11 Siemens Aktiengesellschaft Residual current detection method and device
CN105094116A (en) * 2015-07-01 2015-11-25 西北工业大学 AC solid state power controller rapid arc fault detection data pre-processing method
CN105846697A (en) * 2016-05-05 2016-08-10 苏州汇川技术有限公司 PWM rectification control method under low switching frequency and PWM rectification control system thereof
CN108711822A (en) * 2018-05-23 2018-10-26 浙江中凯科技股份有限公司 A kind of guard method of residual current, device and residual current operated protective device
CN109975597A (en) * 2019-04-19 2019-07-05 常熟开关制造有限公司(原常熟开关厂） Residual current detection method, apparatus and intelligent electrical apparatus release
CN111044769A (en) * 2019-12-05 2020-04-21 国创新能源汽车智慧能源装备创新中心(江苏)有限公司 Integral residual current measuring method and integrated system
CN111596228A (en) * 2020-07-24 2020-08-28 宁波均联智行科技有限公司 Electric leakage detection method and device
CN112147403A (en) * 2020-09-16 2020-12-29 国创新能源汽车智慧能源装备创新中心(江苏)有限公司 Method and system for improving temperature adaptability of residual current detection device
CN112582978A (en) * 2019-09-30 2021-03-30 国创新能源汽车能源与信息创新中心(江苏)有限公司 Leakage protection method and device and charging pile

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0437899A (en) * 1990-06-04 1992-02-07 Nec Corp Digital tone generator
US20030011355A1 (en) * 2000-01-06 2003-01-16 Skerritt Robert Charles Current detector and current measuring apparatus including such detector with temperature compensation
CN1727906A (en) * 2005-07-28 2006-02-01 泰州苏源集团科电有限公司 Cycle sampling method in quality of power supply in electrical network
JP2008032660A (en) * 2006-07-31 2008-02-14 Chugoku Electric Power Co Inc:The Device and method for measuring leakage current
CN101149403A (en) * 2007-10-26 2008-03-26 辽宁工业大学 Method for sensing and measuring current through electric-thermal conversion and dedicated electric-thermal conversion sensor
EP2846432A1 (en) * 2013-09-05 2015-03-11 Siemens Aktiengesellschaft Residual current detection method and device
CN105094116A (en) * 2015-07-01 2015-11-25 西北工业大学 AC solid state power controller rapid arc fault detection data pre-processing method
CN105846697A (en) * 2016-05-05 2016-08-10 苏州汇川技术有限公司 PWM rectification control method under low switching frequency and PWM rectification control system thereof
CN108711822A (en) * 2018-05-23 2018-10-26 浙江中凯科技股份有限公司 A kind of guard method of residual current, device and residual current operated protective device
CN109975597A (en) * 2019-04-19 2019-07-05 常熟开关制造有限公司(原常熟开关厂） Residual current detection method, apparatus and intelligent electrical apparatus release
CN112582978A (en) * 2019-09-30 2021-03-30 国创新能源汽车能源与信息创新中心(江苏)有限公司 Leakage protection method and device and charging pile
CN111044769A (en) * 2019-12-05 2020-04-21 国创新能源汽车智慧能源装备创新中心(江苏)有限公司 Integral residual current measuring method and integrated system
CN111596228A (en) * 2020-07-24 2020-08-28 宁波均联智行科技有限公司 Electric leakage detection method and device
CN112147403A (en) * 2020-09-16 2020-12-29 国创新能源汽车智慧能源装备创新中心(江苏)有限公司 Method and system for improving temperature adaptability of residual current detection device

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