CN111308398A - Method and device for judging polarity of zero sequence current transformer in transformer substation - Google Patents
Method and device for judging polarity of zero sequence current transformer in transformer substation Download PDFInfo
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- CN111308398A CN111308398A CN202010234704.0A CN202010234704A CN111308398A CN 111308398 A CN111308398 A CN 111308398A CN 202010234704 A CN202010234704 A CN 202010234704A CN 111308398 A CN111308398 A CN 111308398A
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- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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Abstract
The invention provides a method for judging the polarity of a zero sequence current transformer in a transformer substation. The method comprises the step S1 of collecting phase current I of a 10kV outgoing line by using zero sequence voltage detected by a voltage transformer on a busAAnd zero sequence current I0(ii) a Step S2, judging that single-phase earth fault and fault phase occur through the change of zero sequence voltage and phase voltage; and step S3, judging the polarity of the zero sequence current transformer by utilizing the similarity of the zero sequence current and the fault phase current. After the single-phase earth fault occurs, the small-current line selection device judges that the single-phase earth fault and the fault phase occur according to the change of the zero-sequence voltage and the change of the phase voltage.
Description
Technical Field
The invention relates to the field of electric power automation, in particular to a method and a device for judging the polarity of a zero sequence current transformer in a transformer substation.
Background
At present, a neutral point of a transformer 10kV side in a transformer substation generally adopts an ungrounded mode or an operation mode of grounding through an arc suppression coil, when a single-phase grounding fault occurs, the fault current ratio is small, a system can operate for 2 hours with the fault, and therefore the single-phase grounding fault is also called as a low-current grounding fault. A10 kV bus of the transformer substation is generally provided with a voltage transformer and can detect 3 phase voltages and zero sequence voltages. The single-phase earth fault is judged through the zero sequence voltage, and the fault phase can be judged through the change of the phase voltage. The 10kV outgoing line is generally only provided with 1 phase current transformer and 1 zero sequence current transformer. The polarity of the phase current transformer is generally not connected reversely, and the zero sequence current transformer is very small in zero sequence current, easy to connect reversely and difficult to judge because the power system works normally. When a single-phase earth fault occurs, the selection of the fault line is often dependent on the polarity of the zero-sequence current. Therefore, the polarity of the zero sequence current transformer is connected to the forward direction to cause line misjudgment, and the accuracy of single-phase earth fault judgment is reduced.
When a single-phase earth fault occurs in a 10kV line, the power frequency component of the zero-sequence current is small, but the transient component (300-3000 Hz) is large, the amplitude can reach more than 20A, the transient component can be used as a fault detection component, and meanwhile, the polarity of the transient component of the zero-sequence current can be used as the judgment of the fault line. Meanwhile, the single-phase grounding can also cause the change of the phase current, and the transient component of the phase current has stronger correlation with the transient component of the zero-sequence current. The polarity of the zero-sequence current can be judged by utilizing the correlation, and the reliability and the sensitivity of single-phase earth fault detection are improved.
Disclosure of Invention
The technical problem to be solved by the embodiments of the present invention is to provide a method and an apparatus for judging the polarity of a zero sequence current transformer in a transformer substation, so as to solve the technical problems of low accuracy of single-phase ground fault judgment and poor reliability and sensitivity of single-phase ground fault detection.
In one aspect of the present invention, a method for determining a polarity of a zero sequence current transformer in a transformer substation is provided, including:
step S1, collecting phase current I of 10kV outgoing line by using zero sequence voltage detected by a voltage transformer on a busAAnd zero sequence current I0；
Step S2, judging that single-phase earth fault and fault phase occur through the change of zero sequence voltage and phase voltage;
and step S3, judging the polarity of the zero sequence current transformer by utilizing the similarity of the zero sequence current and the fault phase current.
Further, in step S1, the phase current I of the 10kV outgoing line is collectedAAnd zero sequence current I0Specifically, phase current I from the time of fault occurrence to 5ms after fault occurrence is acquiredAAnd zero sequence current I0And after filtering, extracting the numerical value with the frequency range of 300 Hz-3000 Hz.
Further, in step S2, the occurrence of the single-phase ground fault and the fault phase is determined according to the change of the zero-sequence voltage and the phase voltage, specifically, the following formula is used for calculating:
wherein, IAPhase current for 10kV outgoing line, I0The zero sequence current of the 10kV outgoing line, i is the mark value of the acquisition time.
Further, in step S3, the specific process of determining the polarity of the zero-sequence current transformer includes, when k is greater than 0.7, if the fault phase is the same as the collected current, determining that the polarity of the zero-sequence current is correct; and if the fault phase is not in phase with the collected current, the polarity of the zero sequence current is considered to be wrong.
Further, the specific process for judging the polarity of the zero-sequence current transformer comprises that when k is less than 0.3, if the fault phase is in phase with the collected current, the polarity of the zero-sequence current is considered to be wrong; and if the fault phase is out of phase with the collected current, the polarity of the zero sequence current is considered to be correct.
Further, the specific process for judging the polarity of the zero sequence current transformer comprises judging by using a zero sequence current polarity method when k is greater than or equal to 0.3 and less than or equal to 0.7.
On the other hand, the invention also provides a polarity judgment device for the zero sequence current transformer in the transformer substation, which is used for realizing the following method:
step S1, collecting phase current I of 10kV outgoing line by using zero sequence voltage detected by a voltage transformer on a busAAnd zero sequence current I0；
Step S2, judging that single-phase earth fault and fault phase occur through the change of zero sequence voltage and phase voltage;
step S3, the similarity of the zero sequence current and the fault phase current is utilized to judge the polarity of the zero sequence current transformer;
the device includes: the small-current grounding line selection device is used for detecting 3 phase voltages and zero sequence voltages of a bus, detecting A phase currents and zero sequence currents of all 10kV outgoing lines on the bus, performing single-phase grounding fault line selection and installing the small-current grounding line selection device in a transformer substation;
voltage transformer on bus for detecting 3 phase voltages and zero sequence voltage V of bus0The transformer substation bus is arranged on a transformer substation bus;
a current transformer on 10kV line for detecting A-phase current I of the lineAThe transformer substation is arranged on a 10kV line in a transformer substation;
zero sequence current transformer for detecting zero sequence current I of line0And is arranged on a 10kV line in a transformer substation.
Further, the 3 phase voltages of the bus include a phase current VAPhase V of current BBAnd C phase current VC。
Further, the A-phase current and the zero-sequence current of the 10kV outgoing line and the 3-phase voltage and the zero-sequence voltage V of the bus0The current signal acquisition range of the power supply is 300 Hz-3000 Hz.
In summary, the embodiment of the invention has the following beneficial effects:
according to the method and the device for judging the polarity of the zero sequence current transformer in the transformer substation, after a single-phase ground fault occurs, the small current line selection device judges that the single-phase ground fault and a fault phase occur according to the change of the zero sequence voltage and the change of the phase voltage.
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 will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a schematic main flow diagram of a method for judging the polarity of a zero sequence current transformer in a transformer substation provided by the invention.
Fig. 2 is a logic schematic diagram of the polarity determination method for the zero sequence current transformer in the transformer substation provided by the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
The method for judging the polarity of the zero sequence current transformer in the transformer substation provided by the application is a schematic diagram of an embodiment of the method for judging the polarity of the zero sequence current transformer in the transformer substation provided by the invention, as shown in fig. 1 and 2. In this embodiment, the method comprises the steps of:
step S1, collecting phase current I of 10kV outgoing line by using zero sequence voltage detected by a voltage transformer on a busAAnd zero sequence current I0；
In a specific embodiment, the phase current I of the 10kV outgoing line is collectedAAnd zero sequence current I0Specifically, phase current I from the time of fault occurrence to 5ms after fault occurrence is acquiredAAnd zero sequence current I0And after filtering, extracting the numerical value with the frequency range of 300 Hz-3000 Hz.
Step S2, judging that single-phase earth fault and fault phase occur through the change of zero sequence voltage and phase voltage;
in a specific embodiment, the single-phase ground fault and the fault phase are determined to occur according to the change of the zero-sequence voltage and the phase voltage, specifically, the calculation is performed according to the following formula:
wherein, IAPhase current for 10kV outgoing line, I0The zero sequence current of the 10kV outgoing line, i is the mark value of the acquisition time.
Step S3, the similarity of the zero sequence current and the fault phase current is utilized to judge the polarity of the zero sequence current transformer;
in a specific embodiment, in the specific process of judging the polarity of the zero-sequence current transformer, when k is greater than 0.7, if the fault phase is in phase with the collected current, the polarity of the zero-sequence current is considered to be correct; if the fault phase is out of phase with the collected current, the polarity of the zero sequence current is considered to be wrong; when k is less than 0.3, if the fault phase is in phase with the collected current, the polarity of the zero-sequence current is considered to be wrong; if the fault phase is out of phase with the collected current, the polarity of the zero sequence current is considered to be correct; and when k is more than or equal to 0.3 and less than or equal to 0.7, judging by using a zero-sequence current polarity method.
Specifically, if the fault phase is the same as the collected current phase, and if k is greater than 0.7, the zero-sequence current is considered to have correct polarity; if k is less than 0.3, the polarity of the zero-sequence current is considered to be wrong; if k is more than or equal to 0.3 and less than or equal to 0.7, the judgment cannot be carried out;
if the fault phase is not in phase with the collected current, if k is greater than 0.7, the polarity of the zero-sequence current is considered to be wrong; if k is less than 0.3, the polarity of the zero-sequence current is correct; if k is not less than 0.3 and not more than 0.7, the judgment cannot be made.
On the other hand, the invention also provides a polarity judgment device for the zero sequence current transformer in the transformer substation, which is used for realizing the following method:
step S1, collecting phase current I of 10kV outgoing line by using zero sequence voltage detected by a voltage transformer on a busAAnd zero sequence current I0；
Step S2, judging that single-phase earth fault and fault phase occur through the change of zero sequence voltage and phase voltage;
and step S3, judging the polarity of the zero sequence current transformer by utilizing the similarity of the zero sequence current and the fault phase current.
The device includes: the small-current grounding line selection device is used for detecting 3 phase voltages and zero sequence voltages of a bus, detecting A phase currents and zero sequence currents of all 10kV outgoing lines on the bus, performing single-phase grounding fault line selection and installing the small-current grounding line selection device in a transformer substation;
voltage transformer on bus for detecting 3 phase voltages and zero sequence voltage V of bus0The sampling frequency is 10 kHz;
a current transformer on 10kV line for detecting A-phase current I of the lineAThe transformer substation is arranged on a 10kV line in a transformer substation;
zero sequence current transformer for detecting zero sequence current I of line0The transformer substation is arranged on a 10kV line in a transformer substation;
in a specific embodiment, the 3 phase voltages of the bus include a phase current VAPhase V of current BBAnd C phase current VC(ii) a The A-phase current and the zero sequence current of the 10kV outgoing line and the 3-phase voltage and the zero sequence voltage V of the bus0The current signal acquisition range of the power supply is 300 Hz-3000 Hz.
Specifically, when a single-phase earth fault occurs on a 10kV line, the low-current earth line selection device determines that the single-phase earth fault occurs by detecting the change of the zero sequence voltage of the bus, and determines the phase of the fault by determining the change of 3 phase voltages. According to the principle, the polarity of the zero sequence current can be judged.
In summary, the embodiment of the invention has the following beneficial effects:
according to the polarity judgment method of the zero sequence current transformer in the transformer substation, after a single-phase ground fault occurs, the small current line selection device judges that the single-phase ground fault and a fault phase occur according to the change of the zero sequence voltage and the change of the phase voltage.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (9)
1. A method for judging the polarity of a zero sequence current transformer in a transformer substation is characterized by comprising the following steps:
step S1, collecting phase current I of 10kV outgoing line by using zero sequence voltage detected by a voltage transformer on a busAAnd zero sequence current I0；
Step S2, judging that single-phase earth fault and fault phase occur through the change of zero sequence voltage and phase voltage;
and step S3, judging the polarity of the zero sequence current transformer by utilizing the similarity of the zero sequence current and the fault phase current.
2. The method of claim 1, wherein in step S1, the phase current I of the 10kV outgoing line is collectedAAnd zero sequence current I0Specifically, phase current I from the time of fault occurrence to 5ms after fault occurrence is acquiredAAnd zero sequence current I0And after filtering, extracting the numerical value with the frequency range of 300 Hz-3000 Hz.
3. The method according to claim 2, wherein in step S2, the single-phase earth fault and the fault phase are determined to have occurred through the change of the zero sequence voltage and the phase voltage, specifically according to the following formula:
wherein, IAPhase current for 10kV outgoing line, I0The zero sequence current of the 10kV outgoing line, i is the mark value of the acquisition time.
4. The method according to claim 3, wherein in step S3, the specific procedure for determining the polarity of the zero-sequence current transformer includes, when k is greater than 0.7, if the fault phase is in phase with the collected current, determining that the polarity of the zero-sequence current is correct; and if the fault phase is not in phase with the collected current, the polarity of the zero sequence current is considered to be wrong.
5. The method according to claim 4, wherein the specific process of judging the polarity of the zero sequence current transformer comprises that when k is less than 0.3, if the fault phase is in phase with the collected current, the polarity of the zero sequence current is considered to be wrong; and if the fault phase is out of phase with the collected current, the polarity of the zero sequence current is considered to be correct.
6. The method according to claim 5, wherein the specific process of judging the polarity of the zero sequence current transformer comprises judging by using a zero sequence current polarity method when k is greater than or equal to 0.3 and k is less than or equal to 0.7.
7. A device for determining the polarity of a zero sequence current transformer in a substation, which is used for implementing the method as claimed in any one of claims 1 to 6, and which comprises:
the small-current grounding line selection device is used for detecting 3 phase voltages and zero sequence voltages of a bus, detecting A phase currents and zero sequence currents of all 10kV outgoing lines on the bus, performing single-phase grounding fault line selection and installing the small-current grounding line selection device in a transformer substation;
voltage transformer on bus for detecting 3 phase voltages and zero sequence voltage V of bus0The transformer substation bus is arranged on a transformer substation bus;
a current transformer on 10kV line for detecting A-phase current I of the lineAThe transformer substation is arranged on a 10kV line in a transformer substation;
zero sequence current transformer for detecting zero sequence current I of line0And is arranged on a 10kV line in a transformer substation.
8. The apparatus of claim 7, wherein the 3 phase voltages of the bus include a-phase current VAPhase V of current BBAnd C phase current VC。
9. The apparatus of claim 8, wherein the a-phase current, zero sequence current of the 10kV outlet line and the 3 phase voltage, zero sequence voltage V of the bus bar0The current signal acquisition range of the power supply is 300 Hz-3000 Hz.
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Cited By (5)
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| CN116031842A (en) * | 2022-10-09 | 2023-04-28 | 重庆卓智软件开发有限公司 | Low-current grounding line selection protection method |
| CN117169800A (en) * | 2023-10-25 | 2023-12-05 | 华中科技大学 | Knowledge-based current transformer online monitoring method and device |
| CN117849446A (en) * | 2024-03-07 | 2024-04-09 | 国网山东省电力公司莱芜供电公司 | Transformer substation ground current detection system, method, electronic equipment and medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114200354A (en) * | 2022-02-16 | 2022-03-18 | 广东电网有限责任公司肇庆供电局 | Zero sequence CT polarity online detection method, system and equipment |
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| CN115566646A (en) * | 2022-09-22 | 2023-01-03 | 国网江苏省电力有限公司无锡供电分公司 | Distribution line single-phase grounding section positioning method and device based on information fusion |
| CN115566646B (en) * | 2022-09-22 | 2024-02-23 | 国网江苏省电力有限公司无锡供电分公司 | Distribution line single-phase grounding section positioning method and device based on information fusion |
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| CN117169800B (en) * | 2023-10-25 | 2024-02-06 | 华中科技大学 | Knowledge-based current transformer online monitoring method and device |
| CN117849446A (en) * | 2024-03-07 | 2024-04-09 | 国网山东省电力公司莱芜供电公司 | Transformer substation ground current detection system, method, electronic equipment and medium |
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Application publication date: 20200619 |