CN102004205A - Judging methods of single phase-to-earth fault and resonance overvoltage fault in small current grounding system - Google Patents
Judging methods of single phase-to-earth fault and resonance overvoltage fault in small current grounding system Download PDFInfo
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Abstract
The invention relates to judging methods of the single phase-to-earth fault and the resonance overvoltage fault in a small current grounding system. When the system has a single phase-to-earth fault, the voltage of the earthed phase is reduced, the voltage of the non-earthed phase is increased; if the earth point is metallic grounded, the voltage of the earthed phase is zero, the voltages of the other two phases are increased to the line voltage and the brightness of a harmonic elimination lamp arranged on a PT open-delta winding is higher than 10% of the brightness under the rated voltage; when the system has a resonance fault, the voltages of the three phases are higher than the line voltage and change irregularly and the harmonic elimination lamp has different brightnesses according to different harmonic degrees; and if the voltage of one phase is reduced, the voltages of the other two phases are not higher than the line voltage and the line voltage is normal, the system is judged to have a single phase-to-earth fault; and when the voltmeter has an irregular swinging phenomenon, the system has a resonance overvoltage fault. By using the methods, the common faults of the small current system can be judged easily and practically; and the methods are accurate, reliable, convenient and practical.
Description
Technical field
The present invention relates to the method for discrimination of singlephase earth fault and resonance overvoltage fault in power equipment the grounding system fault method of discrimination, particularly small current neutral grounding system.
Background technology
Small current neutral grounding system all shows as residual voltage and raises when single-phase earthing and resonant condition take place, and system's imbalance of three-phase voltage has ground signalling to take place, and phenomenon is closely similar.Therefore, make operation power dispatcher false judgment fault type.And cause corresponding error to be handled, seriously jeopardize electric power netting safe running.
Summary of the invention
The purpose of this invention is to provide the method for discrimination of singlephase earth fault and resonance overvoltage fault in a kind of small current neutral grounding system, with accurate judgement fault type, is singlephase earth fault or resonance overvoltage fault on earth.
Purpose of the present invention is achieved in that the method for discrimination of singlephase earth fault and resonance overvoltage fault in a kind of small current neutral grounding system, and its method of discrimination is as follows:
Described singlephase earth fault shows as:
Difference according to the ground connection situation, ground connection is divided into metallic earthing and nonmetal character ground connection again: porcelain vase, lightning arrester puncture, when the substation transformer winding insulation punctures class one phase metallic short circuit ground connection, the phase voltage feature is that the fault phase voltage is zero, non-fault phase voltage is increased to line voltage, neutral point displacement voltage is a phase voltage, and the open delta winding voltage equals 100V; When electric arc, tree bamboo, high resistance, transition resistance class one phase nonmetal character short circuit ground connection, the phase voltage feature is that the fault phase voltage is low, and less than phase voltage, non-fault phase-to-ground voltage raises greater than zero, less than line voltage, the open delta winding voltage is less than 100V greater than phase voltage; Along with the variation of transition resistance, fluctuation by a relatively large margin takes place in each phase voltage, surpasses line voltage sometimes.Two phase voltages of non-ground connection are generally unequal;
The resonance overvoltage fault shows as:
According to the difference of resonance frequency, resonance is divided into first-harmonic resonance, high-frequency resonant and low-frequency resonant again;
First-harmonic resonance: superpotential is generally less than and equals 3 times of phase voltages, and a phase voltage reduces but is not 0, and two phase voltages raise greater than line voltage in addition, and neutral-point displacement is outside voltage triangle, and PT open delta winding voltage is sent ground signalling greater than 100V; PT is an electromagnetic potential transformer;
High-frequency resonant: superpotential is generally less than and equals 3.5 times of phase voltages, and three phase-to-ground voltages raise simultaneously, and greater than line voltage, neutral-point displacement is outside voltage triangle, and PT open delta winding voltage is sent ground signalling greater than 100V;
Low-frequency resonant: superpotential is generally less than and equals 2 times of phase voltages, and three phase-to-ground voltages raise in turn according to phase sequence, produces the frequency wobbles phenomenon, and neutral-point displacement is in voltage triangle, and PT open delta winding voltage is generally less than 100V, sends ground signalling;
The method of discrimination of above-mentioned resonance overvoltage fault and singlephase earth fault is: during system generation single-phase earthing, the ground connection phase voltage reduces, and non-ground connection phase voltage raises; If earth point is the direct ground connection of metallicity, the ground connection phase voltage is 0, and other two-phases raise and are line voltage, and the harmonic elimination lamp brightness that PT open delta winding is installed is very high, above 10% of brightness under the rated voltage; When resonance took place, three-phase voltage can surpass line voltage, the irregular variation of three-phase voltage, and the harmonic elimination lamp is the brightness difference with resonance degree difference; If it is a lot of that phase voltage has two-phase to raise, surpass line voltage, PT open delta winding voltage is greater than 30V, or no current on the arc suppression coil, then is judged to be resonance; If a phase voltage reduces, other is no more than line voltage at the rising of two phase voltages and line voltage is normal, and decidable is system's single-phase earthing; It is resonance that voltage table has the irregular dancing decidable of low frequency.
The invention has the beneficial effects as follows:
1, changes by the value of mensuration phase voltage, line voltage and the brightness of variation and PT triangle winding voltage and PT open delta winding harmonic elimination lamp thereof, can accurately judge fault type fast, actually or singlephase earth fault resonance overvoltage fault.
2, the present invention has proposed the method for discrimination of singlephase earth fault and resonance overvoltage fault according to network system voltage fluctuation rule, and is simple, accurately and reliably, convenient and practical to differentiating small current system most common failure type.The present invention helps the dispatching of power netwoks personnel when voltage fluctuation, rapidly accurate failure judgement place, thereby fast processing fault.Powerful guarantee the safe operation of electrical network.
Embodiment
In order to make the traffic control personnel can be when system's generation voltage fluctuation according to the voltage fluctuation rule, accurate failure judgement type, the fast processing fault, ensure electric power netting safe running, respectively with regard to the different signs of most common failures such as resonance overvoltage, single-phase earthing and circuit broken string, classification analysis is as follows below:
Fault signature:
1, singlephase earth fault
According to the difference of ground connection situation, ground connection is divided into metallic earthing and nonmetal character ground connection again.One phase metallicity (punctures as porcelain vase, lightning arrester, substation transformer winding insulation punctures etc.) during short circuit ground connection, the phase voltage feature is that the fault phase voltage is zero, and non-fault phase voltage is increased to line voltage, neutral point displacement voltage is a phase voltage, and the open delta winding voltage equals 100V; During one phase nonmetal character (through transition resistance, as electric arc, tree bamboo, high resistance etc.) short circuit ground connection, the phase voltage feature is that the fault phase voltage is low, greater than zero and less than phase voltage, non-fault phase-to-ground voltage raises, and less than line voltage, the open delta winding voltage is less than 100V greater than phase voltage.Along with the variation of transition resistance, fluctuation by a relatively large margin takes place in each phase voltage, surpasses line voltage sometimes.Two phase voltages of non-ground connection are generally unequal.
2, resonance overvoltage
According to the difference of resonance frequency, resonance is divided into first-harmonic resonance, high-frequency resonant and low-frequency resonant again.
First-harmonic resonance: superpotential is generally less than and equals 3 times of phase voltages, and a phase voltage reduces (not being 0), and two phase voltages raise greater than line voltage in addition.Neutral-point displacement is outside voltage triangle, and PT open delta winding voltage is sent ground signalling greater than 100V.
High-frequency resonant: superpotential is generally less than and equals 3.5 times of phase voltages, and three phase-to-ground voltages raise simultaneously, greater than line voltage.Neutral-point displacement is outside voltage triangle, and PT open delta winding voltage is sent ground signalling greater than 100V.
Low-frequency resonant: superpotential is generally less than and equals 2 times of phase voltages.Three phase-to-ground voltages raise in turn according to phase sequence, produce the frequency wobbles phenomenon.Neutral-point displacement is in voltage triangle, and PT open delta winding voltage is generally less than 100V, sends ground signalling.
3, disconnection fault
When a certain broken string mutually of system high pressure side, the phase voltage feature is an imbalance of three-phase voltage, sends ground signalling sometimes.Broken string phase voltage and neutral point voltage raise, and non-broken string two phase voltages equate and reduce.
4, bus PT fuse failure
During PT one phase high-voltage wire iron-melting fusing, voltage characteristic reduces significantly for the fusing phase voltage, and two phase voltages are constant in addition, and two relevant line voltage indications then can reduce.PT open delta winding voltage is sent ground signalling greater than 30V.During the fusing of PT one phase low-tension fuse, voltage characteristic is similar to the high-voltage wire iron-melting fusing situation, but the output of PT open delta winding no-voltage, no ground signalling is sent.
Fault distinguishing:
Resonance, broken string and PT high pressure fuse melting accident all may be sent ground signalling, are referred to as " illusory ground connection ".But tangible distinguishing characteristic is arranged with singlephase earth fault.
The difference of PT one phase high pressure fuse melting and singlephase earth fault: during earth fault, the fault phase-to-ground voltage reduces, and non-fault phase-to-ground voltage raises, line voltage is constant, and during PT one phase high pressure fuse melting, voltage-to-ground one reduces mutually, two phase voltages are constant in addition, and the indication of line voltage then can reduce.
In sum, small current neutral grounding system most common failure Practical Criteria is as shown in the table.Facts have proved, use the Practical Criteria table, simple, accurately and reliably, convenient and practical to distinguishing small current system most common failure character.To the fast processing fault, ensure electric power netting safe running, have important practical significance.
Small current neutral grounding system most common failure Practical Criteria table
Claims (2)
1. the method for discrimination of singlephase earth fault and resonance overvoltage fault in the small current neutral grounding system, it is characterized in that: its method of discrimination is as follows:
Described singlephase earth fault shows as:
According to the difference of ground connection situation, ground connection is divided into metallic earthing and nonmetal character ground connection again; When a phase metallic short circuit ground connection, the phase voltage feature is that the fault phase voltage is zero, and non-fault phase voltage is increased to line voltage, and neutral point displacement voltage is a phase voltage, and the open delta winding voltage equals 100V; When a phase nonmetal character short circuit ground connection, the phase voltage feature is that the fault phase voltage is low, and less than phase voltage, non-fault phase-to-ground voltage raises greater than zero, and less than line voltage, the open delta winding voltage is less than 100V greater than phase voltage; Along with the variation of transition resistance, fluctuation by a relatively large margin takes place in each phase voltage, surpasses line voltage sometimes.Two phase voltages of non-ground connection are generally unequal;
The resonance overvoltage fault shows as:
According to the difference of resonance frequency, resonance is divided into first-harmonic resonance, high-frequency resonant and low-frequency resonant again;
First-harmonic resonance: superpotential is generally less than and equals 3 times of phase voltages, and a phase voltage reduces but is not 0, and two phase voltages raise greater than line voltage in addition, and neutral-point displacement is outside voltage triangle, and PT open delta winding voltage is sent ground signalling greater than 100V; PT is an electromagnetic potential transformer;
High-frequency resonant: superpotential is generally less than and equals 3.5 times of phase voltages, and three phase-to-ground voltages raise simultaneously, and greater than line voltage, neutral-point displacement is outside voltage triangle, and PT open delta winding voltage is sent ground signalling greater than 100V;
Low-frequency resonant: superpotential is generally less than and equals 2 times of phase voltages, and three phase-to-ground voltages raise in turn according to phase sequence, produces the frequency wobbles phenomenon, and neutral-point displacement is in voltage triangle, and PT open delta winding voltage is generally less than 100V, sends ground signalling;
The method of discrimination of above-mentioned resonance overvoltage fault and singlephase earth fault is: during system generation single-phase earthing, the ground connection phase voltage reduces, and non-ground connection phase voltage raises; If earth point is the direct ground connection of metallicity, the ground connection phase voltage is 0, and other two-phases raise and are line voltage, and the harmonic elimination lamp brightness that PT open delta winding is installed is very high, above 10% of brightness under the rated voltage; When resonance took place, three-phase voltage can surpass line voltage, the irregular variation of three-phase voltage, and the harmonic elimination lamp is the brightness difference with resonance degree difference; If it is a lot of that phase voltage has two-phase to raise, surpass line voltage, PT open delta winding voltage is greater than 30V, or no current on the arc suppression coil, then is judged to be resonance; If a phase voltage reduces, other is no more than line voltage at the rising of two phase voltages and line voltage is normal, and decidable is system's single-phase earthing; It is resonance that voltage table has the irregular dancing decidable of low frequency.
2. according to the method for discrimination of singlephase earth fault and resonance overvoltage fault in the described small current neutral grounding system of claim 1, it is characterized in that: a described phase metallic earthing is: porcelain vase, lightning arrester or substation transformer winding insulation puncture ground connection; A described phase nonmetal character ground connection is: electric arc, tree bamboo, high resistance or transition resistance ground connection.
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Application publication date: 20110406 |