CN109596934B - Secondary circuit multipoint grounding double-clamp meter measuring method - Google Patents

Secondary circuit multipoint grounding double-clamp meter measuring method Download PDF

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CN109596934B
CN109596934B CN201811460282.8A CN201811460282A CN109596934B CN 109596934 B CN109596934 B CN 109596934B CN 201811460282 A CN201811460282 A CN 201811460282A CN 109596934 B CN109596934 B CN 109596934B
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branch
secondary circuit
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CN109596934A (en
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张冬容
谢春杨
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Guangzhou Gexingquan Electric Power Technology Co ltd
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    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract

The invention discloses a secondary circuit multipoint grounding double-clamp meter measuring method, firstly, a system detector clamp meter is used for detecting a secondary circuit N line, a secondary circuit N line earth impedance value R is obtained through calculation, then the system detector automatically obtains a conclusion according to the judgment whether R is larger than 200 ohm, whether a multipoint ground fault exists in an N600 system or not, if the multipoint ground fault exists, the system detector converts the R value impedance into a curve and sends a curve signal to a feeder line detector, then a feeder line detector clamp meter is used for detecting a branch circuit, the branch circuit impedance value R obtained by the feeder line detector detecting the branch circuit forms curve comparison with the R value sent by the system detector, and finally, whether the branch circuit has a ground fault point or not is obtained according to the condition that whether the R is more than 0.9R and less than 1.1R or not, and if the R is not, the other branch circuit is continuously detected; the secondary circuit multipoint grounding double-clamp meter measuring method has the advantages that wires do not need to be disconnected, and external resistors are not needed.

Description

Secondary circuit multipoint grounding double-clamp meter measuring method
Technical Field
The invention relates to a secondary circuit multipoint grounding double-clamp meter measuring method.
Background
According to the stipulations in the key points of measures for relay protection of power system and anti-accident of safety automatic device: the secondary loops of several groups of voltage transformers communicated through a control room zero-phase small bus (N600) are only required to ground one point of the N600 in the control room, and secondary neutral points of all the voltage transformers are required to be disconnected at a switch field ground point; in order to ensure reliable grounding, the neutral line of each voltage transformer must not be connected with a breaker or a contactor and the like which can be disconnected.
When the N600 is grounded in a switch field or a control room respectively, if a system fails and a transformer substation grounding grid flows large fault current, potential difference appears at two ends of the N600, which causes voltage phase shift of a neutral point and further influences amplitude values and phases of phase voltage and zero sequence voltage. Thus possibly causing distance protection, zero sequence direction protection to be refused or mistaken. If the N600 contact is poor, the voltage phase of the neutral point can be shifted. Therefore, the neutral wires of the voltage transformers cannot be connected with a circuit breaker or a contactor which can be disconnected, and the grounding of the secondary winding must be connected to the grounding copper bars of the screen cabinet by leading wires on the voltage transformer switching screen of the control room, so that the serial connection method cannot be adopted.
The existing N600 ground fault detection method comprises a resistance method, a shunt method and a voltage method.
Resistance method: the method comprises the steps of manually connecting a switchable resistance with a slide wire and a switchable grounding wire, then disconnecting one point of a grounding connecting wire of a control room, measuring the current on the slide resistor, analyzing the current on the slide wire resistance, and indicating that two-point (or multi-point) grounding exists in a PT secondary circuit N600 when the current changes. The detection method needs to be externally connected with a resistance circuit and a switch and disconnect a connecting wire which is originally grounded at one point of a control room, so that safety risk exists; analysis of the current data after testing requires a skilled technician.
A flow splitting method: injecting a direct current signal into two ends of one point grounding, measuring the current of one point grounding by using a direct current clamp meter, comparing the measured value with the injected current value, if the measured value is the same as the injected current value, indicating that only one point is grounded, and if the deviation is larger, indicating that two points (or multiple points) are grounded. Compared with a resistance method, the method can find out the grounding condition more quickly, but the dangerous condition that system misoperation can be caused by injecting an external signal into the N600 is adopted, and meanwhile, a direct current clamp meter is adopted, and the opening radian of the high-precision direct current clamp meter in the market at present is difficult to meet the measurement requirement.
Voltage method: the voltage method is that the voltage value of each N600 line to ground is measured by a multimeter on the basis of the resistance method, and if the voltage of the N600 line to ground at a certain position is 0 volt or a few millivolts, the ground can be preliminarily judged to have an N600 grounding point.
Disclosure of Invention
In view of the above, the present invention aims to provide a secondary circuit multipoint grounding double-clamp meter measurement method without disconnecting wires and external resistors.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a secondary circuit multipoint grounding double clamp meter measuring method is characterized in that whether a PT secondary circuit has multipoint grounding faults or not is judged by self-comparison of double clamp meter measuring data, and which group of PT secondary circuits has multipoint grounding is identified, and in order to achieve the purpose, the measuring method comprises the following steps:
firstly, detecting N lines of a one-point grounding secondary circuit of the N600 system by using a system detector clamp meter;
secondly, the system detector sends a modulation frequency modulation sine signal to the N line of the one-point grounding secondary circuit of the N600 system through the clamp meter CT coil;
thirdly, generating induced electromotive force E by modulating a point grounding secondary circuit N line of the frequency modulation sinusoidal signal N600 system;
detecting N lines of the one-point grounding secondary circuit of the N600 system by using a feeder detector clamp meter, and measuring current I (Ie + I50+ I1);
extracting a current value Ie through fast Fourier digital filtering;
sixthly, calculating the resistance R of the N line of the secondary loop to the ground according to the ohm law, the induced electromotive force E and the extracted current value Ie to obtain E/Ie;
seventhly, judging whether the resistance R of the secondary loop N line to the ground resistor meets R & gt 200 omega;
if the impedance R of the secondary loop N line to the ground resistor does not meet R & gt 200 omega, the N600 system has no multipoint ground fault;
ninthly, if the resistance R of the N line to the ground of the secondary loop meets R & gt 200 omega, the N600 system has a multipoint ground fault;
the system detector sends the detected R value signal to the feeder line detector through the communication module;
Figure BDA0001888511010000031
meanwhile, detecting the branch circuit by using a feeder detector clamp meter, and measuring the current I as (Ie + I50+ I1);
Figure BDA0001888511010000032
extracting a current value Ie by fast Fourier digital filtering;
Figure BDA0001888511010000033
according to ohm's law, inductionThe electromotive force E and the extracted current value Ie can be calculated to obtain branch resistance to ground R as E/Ie; meanwhile, the system and the R value signal sent by the system detector form curve comparison;
Figure BDA0001888511010000034
judging whether the branch impedance R is more than 0.9R and less than 1.1R;
Figure BDA0001888511010000035
if it satisfies the following
Figure BDA0001888511010000036
Judging the condition of the point indicates that the N600 system has a ground fault point;
Figure BDA0001888511010000037
if not satisfied the second
Figure BDA0001888511010000038
And the judging condition of the point continues to search for other branch fault points.
Furthermore, Ie in the step (iv) refers to a current measured after the system detector sends out a signal; i50 refers to the original current of the N line of the one-point grounding secondary circuit of the N600 system; i1 refers to other spurious interference currents.
Further, the steps
Figure BDA0001888511010000039
Ie in (1) refers to the current measured after the system detector sends out a signal; i50 refers to the original current of the N600 system branch; i1 refers to other spurious interference currents.
The technical effects of the invention are mainly reflected in the following aspects: the measuring method comprises the steps that firstly, a system detector clamp meter is used for detecting a secondary loop N line, a secondary loop N line ground impedance value R is obtained through calculation, then the system detector automatically obtains a conclusion according to the fact that whether R is larger than 200 ohms or not, whether multipoint ground faults exist in an N600 system or not, if the multipoint ground faults exist, the system detector converts R value impedance into a curve, the curve signal is sent to a feeder line detector, then a feeder line detector clamp meter is used for detecting branches, the branch impedance value R obtained by the feeder line detector through detecting the branches forms curve comparison with the R value sent by the system detector, according to the fact that whether the condition R satisfies the condition that R is larger than 0.9R and smaller than 1.1R or not, whether the branch has the ground fault point or not is finally obtained, and if not; the secondary circuit multipoint grounding double-clamp meter measuring method has the advantages that wires do not need to be disconnected, and external resistors are not needed.
Drawings
FIG. 1 is a flow chart of a secondary circuit multipoint grounding double clamp meter measurement method of the present invention;
FIG. 2 is a diagram of an N600 system device test of the present invention.
Detailed Description
A secondary loop multipoint grounding double clamp meter measuring method, as shown in fig. 1. Whether multipoint grounding faults exist in the PT secondary circuits or not is judged rapidly through self comparison of measured data of the double clamp gauges, and which group of PT secondary circuits are multipoint grounded is identified, and in order to achieve the purpose, the measuring method comprises the following steps:
firstly, detecting N lines of a one-point grounding secondary circuit of the N600 system by using a system detector clamp meter;
secondly, the system detector sends a modulation frequency modulation sine signal to the N line of the one-point grounding secondary circuit of the N600 system through the clamp meter CT coil;
thirdly, generating induced electromotive force E by modulating a point grounding secondary circuit N line of the frequency modulation sinusoidal signal N600 system;
detecting N lines of the one-point grounding secondary circuit of the N600 system by using a feeder detector clamp meter, and measuring current I (Ie + I50+ I1);
extracting a current value Ie through fast Fourier digital filtering;
sixthly, calculating the resistance R of the N line of the secondary loop to the ground according to the ohm law, the induced electromotive force E and the extracted current value Ie to obtain E/Ie;
seventhly, judging whether the resistance R of the secondary loop N line to the ground resistor meets R & gt 200 omega;
if the impedance R of the secondary loop N line to the ground resistor does not meet R & gt 200 omega, the N600 system has no multipoint ground fault;
ninthly, if the resistance R of the N line to the ground of the secondary loop meets R & gt 200 omega, the N600 system has a multipoint ground fault;
the system detector sends the detected R value signal to the feeder line detector through the communication module;
Figure BDA0001888511010000051
meanwhile, detecting the branch circuit by using a feeder detector clamp meter, and measuring the current I as (Ie + I50+ I1);
Figure BDA0001888511010000052
extracting a current value Ie by fast Fourier digital filtering;
Figure BDA0001888511010000053
calculating to obtain branch circuit ground resistance R branch as E/Ie branch according to ohm's law, induced electromotive force E and extracted current value Ie; meanwhile, the system and the R value signal sent by the system detector form curve comparison;
Figure BDA0001888511010000054
judging whether the branch impedance R is more than 0.9R and less than 1.1R;
Figure BDA0001888511010000055
if it satisfies the following
Figure BDA0001888511010000056
Judging the condition of the point indicates that the N600 system has a ground fault point;
Figure BDA0001888511010000057
if not satisfied the second
Figure BDA0001888511010000058
And the judging condition of the point continues to search for other branch fault points.
In this embodiment, Ie in the step (iv) refers to a current measured after the system detector sends out a signal; i50 refers to the original current of the N line of the one-point grounding secondary circuit of the N600 system; i1 refers to other spurious interference currents.
In this embodiment, the steps are
Figure BDA0001888511010000061
Ie in (1) refers to the current measured after the system detector sends out a signal; i50 refers to the original current of the N600 system branch; i1 refers to other spurious interference currents.
As shown in figure 2, the voltage generator and the current amplifier are sent to the tested grounding loop or the cable, the alternating current constant voltage of 2.35KHz is provided, the current generated by the voltage of only 2.35KHz in the current detection of the system detector is detected, and the impedance of the secondary loop N line to the ground can be calculated through fast Fourier digital filtering extraction, so that whether the secondary loop has multi-point faults or not and the fault magnitude can be distinguished. In the current detection of the branch detector, only the current generated by the voltage of 2.35KHz is detected, and the impedance of the branch to the ground can be calculated through fast Fourier digital filtering extraction. Because of this, the tiny current on the ground wire caused by the commercial alternating current and the high-frequency noise generated by the commercial alternating current and the self-contained device is eliminated, so that the accurate measurement result can be obtained, and the measurement advantage is achieved.
The technical effects of the invention are mainly reflected in the following aspects: the measuring method comprises the steps that firstly, a system detector clamp meter is used for detecting a secondary loop N line, a secondary loop N line ground impedance value R is obtained through calculation, then the system detector automatically obtains a conclusion according to the fact that whether R is larger than 200 ohms or not, whether multipoint ground faults exist in an N600 system or not, if the multipoint ground faults exist, the system detector converts R value impedance into a curve, the curve signal is sent to a feeder line detector, then a feeder line detector clamp meter is used for detecting branches, the branch impedance value R obtained by the feeder line detector through detecting the branches forms curve comparison with the R value sent by the system detector, according to the fact that whether the condition R satisfies the condition that R is larger than 0.9R and smaller than 1.1R or not, whether the branch has the ground fault point or not is finally obtained, and if not; the secondary circuit multipoint grounding double-clamp meter measuring method has the advantages that wires do not need to be disconnected, and external resistors are not needed.
The above are only typical examples of the present invention, and besides, the present invention may have other embodiments, and all the technical solutions formed by equivalent substitutions or equivalent changes are within the scope of the present invention as claimed.

Claims (1)

1. The utility model provides a secondary circuit multiple spot ground connection double clamp table measurement method which characterized in that: whether multipoint grounding faults exist in the PT secondary circuits or not is judged rapidly through self comparison of measured data of the double clamp gauges, and which group of PT secondary circuits are multipoint grounded is identified, and in order to achieve the purpose, the measuring method comprises the following steps:
firstly, detecting N lines of a one-point grounding secondary circuit of the N600 system by using a system detector clamp meter;
secondly, the system detector sends a modulation frequency modulation sine signal to the N line of the one-point grounding secondary circuit of the N600 system through the clamp meter CT coil;
thirdly, generating induced electromotive force E by modulating a point grounding secondary circuit N line of the frequency modulation sinusoidal signal N600 system;
detecting N lines of the one-point grounding secondary circuit of the N600 system by using a feeder detector clamp meter, and measuring current I (Ie + I50+ I1), wherein Ie refers to the current measured after the system detector sends out a signal; i50 refers to the original current of the N line of the one-point grounding secondary circuit of the N600 system; i1 refers to other clutter interference currents;
extracting a current value Ie through fast Fourier digital filtering;
calculating the resistance R of the secondary loop N line to the ground according to the ohm law, the induced electromotive force E and the extracted current value Ie;
seventhly, judging whether the resistance R of the secondary loop N line to the ground resistor meets R & gt 200 omega;
if the impedance R of the secondary loop N line to the ground resistor does not meet R & gt 200 omega, the N600 system has no multipoint ground fault;
ninthly, if the resistance R of the N line to the ground of the secondary loop meets R & gt 200 omega, the N600 system has a multipoint ground fault;
the system detector sends the detected R value signal to the feeder line detector through the communication module;
Figure FDA0002894651460000021
meanwhile, detecting the branch circuit by using a feeder detector clamp meter, and measuring the current I (Ie + I50+ I1), wherein Ie refers to the current measured after the system detector sends a signal; i50 refers to the original current of the N600 system branch; i1 refers to other clutter interference currents;
Figure FDA0002894651460000022
extracting a current value Ie by fast Fourier digital filtering;
Figure FDA0002894651460000023
calculating to obtain branch circuit ground resistance R branch as E/Ie branch according to ohm's law, induced electromotive force E and extracted current value Ie; meanwhile, the system and the R value signal sent by the system detector form curve comparison;
Figure FDA0002894651460000024
judging whether the branch impedance R is more than 0.9R and less than 1.1R;
Figure FDA0002894651460000025
if it satisfies the following
Figure FDA0002894651460000026
Judging the condition of the point indicates that the N600 system has a ground fault point;
Figure FDA0002894651460000027
if not satisfied the second
Figure FDA0002894651460000028
And the judging condition of the point continues to search for other branch fault points.
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CN111505533A (en) * 2020-05-06 2020-08-07 南京四联共创电气工程有限公司 Ground wire test terminal and system and ground wire test method under uninterrupted power supply working condition
CN111856179A (en) * 2020-06-24 2020-10-30 国网天津市电力公司电力科学研究院 Transformer substation secondary grounding monitoring device and method

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