CN107942203B - Low-current grounding line selection method for enhancing fault characteristics - Google Patents
Low-current grounding line selection method for enhancing fault characteristics Download PDFInfo
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- CN107942203B CN107942203B CN201810021388.1A CN201810021388A CN107942203B CN 107942203 B CN107942203 B CN 107942203B CN 201810021388 A CN201810021388 A CN 201810021388A CN 107942203 B CN107942203 B CN 107942203B
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- G—PHYSICS
- 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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- 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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Abstract
The invention discloses a small current grounding line selection method for enhancing fault characteristics. The method solves the problem of low line selection accuracy caused by small electric fault amount of the current steady state line selection method utilizing fault steady state quantity, and has the advantages that after a single-phase earth fault occurs in a low-current grounding system, the fault current steady state component is obviously increased when a bus sectionalized circuit breaker is closed or a capacitor is switched on and off, so that the sensitivity of line selection and positioning protection based on the fault steady state quantity is improved, and the purposes of reliable line selection and positioning are achieved, and the structure is as follows: the bus comprises a bus of a protected power distribution system, wherein a capacitor increasing aid is arranged on the bus, a bus section switch adopts a circuit breaker, the capacitor increasing aid and the circuit breaker are connected with a measurement and control device, the measurement and control device is connected with a voltage transformer, and the voltage transformer is connected with the bus; the measurement and control device detects whether the small current grounding system has single-phase grounding fault or not and increases the grounding current by controlling the states of the capacitor and the breaker.
Description
Technical Field
The invention relates to a ground fault detection technology in an electric power system, in particular to a low-current ground line selection method for enhancing fault characteristics.
Background
At present, the 6-35kV power distribution network in China mainly adopts a low-current grounding mode. In the fault of the low-current grounding system, the probability of the single-phase grounding fault is the highest, so the single-phase grounding fault line selection is still a big problem in relay protection.
Through years of research, various line selection criteria are published and put into use on site, but most line selection principles are based on smaller fault characteristic quantity as the criteria, and the line selection accuracy is not high when a high-transition resistance fault occurs. At present, the principle of small current ground fault line selection mainly comprises 4 types: the method mainly utilizes the steady-state fault amount during single-phase earth fault as a criterion, is simple, but has small fault characteristic amount and is difficult to detect. And secondly, based on a transient fault quantity low-current earth fault line selection principle, the method mainly uses the transient fault quantity during single-phase earth fault as a criterion, and the transient fault quantity is larger than a steady-state fault characteristic quantity, but has short duration and is difficult to detect. And thirdly, a low-current grounding fault line selection principle based on an external diagnosis principle breaks through the conventional line selection principle that only a fault signal of a line is used as a line selection criterion, and a special signal is injected into a fault phase by using an injection device, but the injection signal is small under the influence of distributed capacitance and transition resistance, and the cost is increased because the injection device needs to be added. And the line selection criterion is based on a signal fusion technology, and combines various line selection principles based on steady-state and transient-state fault characteristic quantities, so that the line selection accuracy is improved to a certain extent, but each line selection criterion still uses a smaller characteristic quantity as the criterion, so that the line selection accuracy is low when a high-transition resistance fault occurs, and the problem of low line selection accuracy is not fundamentally solved.
Disclosure of Invention
The invention aims to solve the problem that the current steady-state line selection method based on fault steady-state quantity has low electrical fault quantity and causes low line selection accuracy, and provides a small-current grounding line selection method for enhancing fault characteristics, wherein when a single-phase grounding fault of a small-current grounding system occurs, if a bus sectional breaker (the circuit breakers are all bus sectional breakers) before the fault is in an open state, the bus sectional breaker is closed by a measurement and control device after the fault occurs; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault. The zero sequence current of a fault line is increased in a short time when a single-phase earth fault occurs in a system, and the zero sequence current of a non-fault line is still the capacitance current of the line, so that the difference of the zero sequence current between the fault line and the non-fault line is enlarged, and the accuracy of line selection is improved.
In order to achieve the purpose, the invention adopts the following technical scheme.
A small current grounding line selection method for enhancing fault characteristics comprises a bus of a protected power distribution system, wherein a capacitor increase assisting device is installed on the bus, a bus section switch adopts a circuit breaker, the capacitor increase assisting device and the circuit breaker are connected with a measurement and control device, the measurement and control device is connected with a voltage transformer, and the voltage transformer is connected with the bus; the measurement and control device monitors whether the small current grounding system has single-phase grounding fault, and when the single-phase grounding fault occurs, if the circuit breaker is in an open state before the fault, the measurement and control device closes the circuit breaker after the fault; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault. The zero sequence current of a fault line is increased in a short time when a single-phase earth fault occurs in a system, and the zero sequence current of a non-fault line is still the capacitance current of the line, so that the difference of the zero sequence current between the fault line and the non-fault line is enlarged, and the accuracy of line selection is improved.
The measurement and control device is composed of a three-phase voltage and zero-sequence voltage acquisition module, a circuit breaker state detection module, a circuit breaker switch driving module, a capacitor fling-cut switch driving module, a man-machine conversation module and a CPU, and is used for monitoring the three-phase voltage and the zero-sequence voltage of the small-current grounding system to judge whether the system has a single-phase grounding fault or not, so that the actions of the circuit breaker and the capacitor fling-cut switch are controlled. The three-phase voltage and zero sequence voltage acquisition module consists of a voltage transmitter, an RC low-pass filter, a preprocessing circuit consisting of an operational amplifier and an A/D conversion circuit; the circuit breaker state detection module consists of a circuit breaker auxiliary contact and a detection circuit; the circuit breaker switch driving module and the capacitor switching switch driving module are composed of a relay driving circuit and a control relay; the man-machine conversation module consists of a key and a liquid crystal display module; the CPU is composed of an STC12C5A60S2 singlechip, and mainly realizes the functions of judging whether a single-phase grounding fault occurs or not according to three-phase voltage and zero-sequence voltage, storing the state of the circuit breaker before the fault is acquired by the circuit breaker state detection module, sending switch opening and closing instructions to the circuit breaker switch driving module and the capacitor switching switch driving module when the single-phase grounding fault occurs, selecting a fault line and realizing man-machine conversation.
The capacitor boosting device comprises at least one capacitor arranged on each phase of the bus, the capacitors form a capacitor group, one end of each capacitor is respectively connected with each switching switch in series, and the other end of each capacitor is grounded.
A low-current grounding line selection method for enhancing fault characteristics comprises the following steps,
(1) when the low-current grounding system normally operates, the circuit breaker is opened or closed according to the requirement of an operation mode, and the measurement and control device monitors the three-phase voltage, the zero-sequence voltage and the state of the circuit breaker of the system in real time and judges whether the system has a single-phase grounding fault or not;
(2) when no single-phase earth fault occurs, repeating the step (1); when a single-phase earth fault occurs, if the circuit breaker is in an open state before the fault, the circuit breaker is closed by a measurement and control device after the fault, then a fault line is selected, and the circuit breaker is opened after the line selection is finished; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault, then the fault line is selected, and after the line selection is finished, the capacitor switching switch is disconnected;
(3) continuously monitoring the bus voltage and the zero sequence voltage of the system, and judging whether the single-phase earth fault is removed;
(4) if the fault is not removed, continuing to perform the operation of the step (3);
(5) and (5) if the fault is relieved, returning to the step (1) to perform the operation again.
The working process of the invention is as follows: for the operating low-current grounding system, the three-phase voltage, the zero-sequence voltage and the state of the circuit breaker of the system are monitored in real time by the measurement and control device, and whether the system has a single-phase grounding fault or not is judged in real time. When the system normally operates, the circuit breaker is switched off or switched on according to the requirement of an operation mode, the capacitor fling-cut switch is switched off, and the capacitor boosting device is not put into use. When a single-phase earth fault occurs, if the circuit breaker is in an open state before the fault, the circuit breaker is closed by the measurement and control device after the fault; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault. The method aims to increase the zero sequence current of a fault line when a fault occurs, and the zero sequence current of a non-fault line is still the capacitance current of the line, so that the difference of the zero sequence current between the fault line and the non-fault line is enlarged, and the accuracy of line selection is improved. After the line selection is finished, the circuit breaker is restored to the state required by the original work, and the capacitor switching switch is immediately switched off, so that adverse effects on the operation of the system are avoided.
The invention has the beneficial effects that: (1) after a single-phase earth fault occurs in a low-current earth system, the zero-sequence current of a fault line is increased for a short time through the circuit breaker or the capacitor boosting device, and the zero-sequence current of a non-fault line is still the capacitance current of the line, so that the difference of the zero-sequence current between the fault line and the non-fault line is enlarged, and the steady-state line selection and the positioning protection based on the fault steady-state quantity are more accurate. (2) The invention improves the anti-transition resistance capability of the steady state line selection and the positioning protection based on the fault steady state quantity, and enhances the fault degree of the fault point and correspondingly improves the anti-transition resistance capability because the zero sequence current is added.
In a word, the invention can effectively improve the accuracy of steady-state line selection and positioning protection based on fault steady-state quantity.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a functional block diagram of the measurement and control device.
FIG. 3 is a flow chart of the method of the present invention.
The system comprises a bus 1, a bus I section, a bus segmented circuit breaker 2, a capacitor fling-cut switch 3, a capacitor fling-cut switch 4, a capacitor, a measuring and controlling device 5, a three-phase voltage and zero-sequence voltage acquisition module 6, a circuit breaker state detection module 7, a circuit breaker switch driving module 8, a capacitor fling-cut switch driving module 9, a capacitor fling-cut switch driving module 10, a man-machine conversation module 11, a CPU 12, a voltage transformer and a circuit connected with the bus II section 13.
Detailed Description
In fig. 1, a capacitor 4 is installed on each phase of a section I bus 1 of a protected low-current grounding system, a bus section switch adopts a breaker 2, and the other end of the bus section switch is connected with a line 13 connected with a section ii bus. The measurement and control device 5 is used for monitoring whether a single-phase earth fault occurs in the low-current earth system, so as to control the actions of the circuit breaker 2 and the capacitor fling-cut switch 3, as shown in fig. 2. The measurement and control device 5 is composed of a three-phase voltage and zero-sequence voltage acquisition module 6, a circuit breaker state detection module 7, a circuit breaker switch driving module 8, a capacitor switching switch driving module 9, a man-machine conversation module 10 and a CPU 11, and is used for monitoring the three-phase voltage and the zero-sequence voltage of the low-current grounding system to judge whether the system has a single-phase grounding fault or not, so that the action of the circuit breaker 2 and the capacitor switching switch 3 is controlled. The three-phase voltage and zero sequence voltage acquisition module 6 is composed of a voltage transmitter, an RC low-pass filter, a preprocessing circuit composed of an operational amplifier and an A/D conversion circuit; the breaker state detection module 7 is composed of the breaker auxiliary contact and a detection circuit; the circuit breaker switch driving module 8 and the capacitor switching switch driving module 9 are composed of a relay driving circuit and a control relay; the man-machine conversation module 10 is composed of a key and a liquid crystal display module; the CPU 11 is composed of an STC12C5a60S2 single chip microcomputer, and mainly realizes the functions of determining whether a single-phase ground fault occurs or not according to the three-phase voltage and the zero-sequence voltage, storing the state of the circuit breaker 2 before the fault is collected by the circuit breaker state detection module 7, and issuing a switch opening and closing instruction to the circuit breaker switch driving module 8 and the capacitor on-off switch driving module 9 when the single-phase ground fault occurs, selecting a fault line, and performing a man-machine conversation. The measurement and control device 5 is further connected with a voltage transformer 12, and one end of the voltage transformer 12 is connected with the I-section bus 1.
The method of the invention is shown in figure 3:
(1) when the low-current grounding system normally operates, the circuit breaker is opened or closed according to the requirement of an operation mode, and the measurement and control device monitors the three-phase voltage, the zero-sequence voltage and the state of the circuit breaker of the system in real time and judges whether the system has a single-phase grounding fault or not;
(2) when no single-phase earth fault occurs, repeating the step (1); when a single-phase earth fault occurs, if the circuit breaker is in an open state before the fault, the circuit breaker is closed by a measurement and control device after the fault, then a fault line is selected, and the circuit breaker is opened after the line selection is finished; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault, then the fault line is selected, and after the line selection is finished, the capacitor switching switch is disconnected;
(3) continuously monitoring the bus voltage and the zero sequence voltage of the system, and judging whether the single-phase earth fault is removed;
(4) if the fault is not removed, continuing to perform the operation of the step (3);
(5) and (5) if the fault is relieved, returning to the step (1) to perform the operation again.
In fig. 1, it is assumed that a single-phase earth fault occurs in phase C of line ii. If the circuit breaker 2 is in an open state before the fault, the measurement and control device 5 closes the circuit breaker after the fault; if the circuit breaker 2 is in a closed state before the fault, the capacitor switching switch 3 is closed by the measurement and control device after the fault. The method aims to increase the zero sequence current of a fault line in a short time when a single-phase earth fault occurs in a system, and the zero sequence current of a non-fault line is still the capacitance current of the line, so that the difference of the zero sequence current between the fault line and the non-fault line is enlarged, and the judgment accuracy of steady state line selection and positioning protection by utilizing fault steady state quantity can be improved.
Claims (3)
1. A small current grounding line selection method for enhancing fault characteristics comprises a bus of a protected power distribution system, wherein a capacitor increase assisting device is installed on the bus, a bus section switch adopts a circuit breaker, the capacitor increase assisting device and the circuit breaker are connected with a measurement and control device, the measurement and control device is connected with a voltage transformer, and the voltage transformer is connected with the bus; the capacitor boosting device comprises at least one capacitor arranged on each phase of the bus, the capacitors form a capacitor group, one end of each capacitor is respectively connected with each switching switch in series, and the other end of each capacitor is grounded; the measurement and control device monitors whether the small current grounding system has single-phase grounding fault, and when the single-phase grounding fault occurs, if the circuit breaker is in an open state before the fault, the measurement and control device closes the circuit breaker after the fault; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault; the zero sequence current of a fault line is increased in a short time when a single-phase earth fault occurs in a system, and the zero sequence current of a non-fault line is still the capacitance current of the line, so that the difference of the zero sequence current between the fault line and the non-fault line is enlarged, and the accuracy of line selection is improved.
2. The small current grounding line selection method for enhancing fault characteristics as claimed in claim 1, wherein: the measurement and control device consists of a three-phase voltage and zero-sequence voltage acquisition module, a circuit breaker state detection module, a circuit breaker switch driving module, a capacitor fling-cut switch driving module, a man-machine conversation module and a CPU (central processing unit), and is used for monitoring the three-phase voltage and the zero-sequence voltage of the small-current grounding system to judge whether the system has a single-phase grounding fault or not so as to control the actions of the circuit breaker and the capacitor fling-cut switch; the three-phase voltage and zero sequence voltage acquisition module consists of a voltage transmitter, an RC low-pass filter, a preprocessing circuit consisting of an operational amplifier and an A/D conversion circuit; the circuit breaker state detection module consists of a circuit breaker auxiliary contact and a detection circuit; the circuit breaker switch driving module and the capacitor switching switch driving module are composed of a relay driving circuit and a control relay; the man-machine conversation module consists of a key and a liquid crystal display module; the CPU is composed of an STC12C5A60S2 singlechip, and mainly realizes the functions of judging whether a single-phase grounding fault occurs or not according to three-phase voltage and zero-sequence voltage, storing the state of the circuit breaker before the fault is collected by the circuit breaker state detection module, sending a switch on-off instruction to the circuit breaker switch driving module and the capacitor switching switch driving module when the single-phase grounding fault occurs, selecting a fault line and performing man-machine interaction.
3. The small current grounding line selection method for enhancing fault characteristics as claimed in claim 1, wherein: the method comprises the following steps of,
(1) when the low-current grounding system normally operates, the circuit breaker is opened or closed according to the requirement of an operation mode, and the measurement and control device monitors the three-phase voltage, the zero-sequence voltage and the state of the circuit breaker of the system in real time and judges whether the system has a single-phase grounding fault or not;
(2) when no single-phase earth fault occurs, repeating the step (1); when a single-phase earth fault occurs, if the circuit breaker is in an open state before the fault, the circuit breaker is closed by a measurement and control device after the fault, then a fault line is selected, and the circuit breaker is opened after the line selection is finished; if the circuit breaker is in a closed state before the fault, the capacitor switching switch is closed by the measurement and control device after the fault, then the fault line is selected, and after the line selection is finished, the capacitor switching switch is disconnected;
(3) continuously monitoring the bus voltage and the zero sequence voltage of the system, and judging whether the single-phase earth fault is removed;
(4) if the fault is not removed, continuing to perform the operation of the step (3);
(5) and (5) if the fault is relieved, returning to the step (1) to perform the operation again.
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| CN108152683A (en) * | 2018-01-10 | 2018-06-12 | 济南大学 | Based on the earth fault line selection method for helping increasing principle |
| CN110535116A (en) * | 2019-09-10 | 2019-12-03 | 北京华电瑞通电力工程技术有限公司 | A kind of arc extinction cabinet and small current neutral grounding system |
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| CN205248782U (en) * | 2015-12-25 | 2016-05-18 | 安徽工程大学 | Little electric wire netting based on feeder automation system |
| CN106154118A (en) * | 2016-09-29 | 2016-11-23 | 武汉科技大学 | A kind of Single-phase Earth-fault Selection in Distribution Systems and positioner and method |
| CN106370961A (en) * | 2016-08-17 | 2017-02-01 | 积成电子股份有限公司 | Capacitance load injection based transformer station small current grounding fault line selecting method |
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| JP2006136158A (en) * | 2004-11-08 | 2006-05-25 | Mitsubishi Heavy Ind Ltd | Apparatus coping with ground fault |
| CN100511908C (en) * | 2007-05-10 | 2009-07-08 | 济南大学 | Stable status zero-sequence current increase and assistance device and method |
| CN101598761B (en) * | 2009-07-29 | 2011-01-26 | 江苏省电力公司常州供电公司 | Fault line selection method for small electric current grounding system of distribution network |
| US8810979B2 (en) * | 2010-03-09 | 2014-08-19 | Siemens Industry, Inc. | Method and apparatus for supervisory circuit for ground fault circuit interrupt device |
| CN102288875B (en) * | 2011-07-12 | 2013-06-12 | 国网电力科学研究院 | Low-current grounding wire-selecting method |
| CN104678260A (en) * | 2015-03-25 | 2015-06-03 | 南京南瑞继保电气有限公司 | System and method for single-phase grounding line selection of small current grounding system |
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| CN205248782U (en) * | 2015-12-25 | 2016-05-18 | 安徽工程大学 | Little electric wire netting based on feeder automation system |
| CN106370961A (en) * | 2016-08-17 | 2017-02-01 | 积成电子股份有限公司 | Capacitance load injection based transformer station small current grounding fault line selecting method |
| CN106154118A (en) * | 2016-09-29 | 2016-11-23 | 武汉科技大学 | A kind of Single-phase Earth-fault Selection in Distribution Systems and positioner and method |
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