CN101340086B - Single-phase grounding fault determining, protecting method and system of neutral-point uneffective earthed electric grid - Google Patents
Single-phase grounding fault determining, protecting method and system of neutral-point uneffective earthed electric grid Download PDFInfo
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Abstract
The invention discloses a distinguishing, protective method and a protective system of single-phase grounding faults of a neutral point non-effectively grounded power network in view of the judgment wrong regions of the single-phase grounding faults of a neutral point non-effectively grounded system; wherein, the distinguishing method of the single-phase grounding faults distinguishes the fault phase according to the relationship between the zero sequence voltage and phase voltage as well as the relationship between the phase voltages to provide bases for right throwing and withdrawing of grounding protection, and the distinguishing method can particularly distinguish the weak signals of unobservable high resistance grounding faults to eliminate the faults in the bud; a grounding comprehensive protection method and a grounding comprehensive protection system combine a voltage limiting and bypass protection method which clamp the fault phase voltage and a current compensation protection method which uses inductance-current to compensate current of a grounding capacitor and so as to achieve the ideal effects of reliably eliminating the faults such as arc grounding without being influenced by ground current as well as reducing the grounding fault current without accurately tracing and adjusting the compensation current values. The method and the system have the advantages of strong practicality, simple measurement and control and reliable protection.
Description
Technical field
The present invention relates to a kind of neutral non-effective grounding electrical network to comprehensive differentiation of single phase ground fault, the comprehensive method of protection and the Integrated Protection System thereof of elimination fault, specifically a kind of neutral non-effective grounding electrical network is to differentiation, guard method and the system of single phase ground fault.
Background technology
In electric power system, single-phase earthing is the major failure form of operation of power networks, accounts for more than 60% of full electric network total failare, and quite a few phase fault is to be developed by single phase ground fault.The reliable degree of electric power system under the identical situation of other conditions, only depends on the working method of electric power system neutral point.The earthing mode of research electric power system neutral point mainly is correctly to be familiar with and to handle the single phase ground fault problem that this is seen at most.
The type of single phase ground fault can be divided into: arc grounding, high resistance ground and metal ground connection.According to the statistics of electric power system, the single phase ground fault of the overwhelming majority is arc grounding and high resistance ground.The harm maximum of single-phase arc grounding, high resistance ground is the most common, extension as the branch in the overhead transmission line bumps, the cable insulation in the broken string, cable line makes moist, aging or the like, all present the feature of high resistance ground, and the arc grounding fault develops from high resistance earthing fault mostly also.
The earth resistance excursion of high resistance ground is big, unstable, and malfunction is the most complicated, and after earth resistance arrived to a certain degree greatly, fault signature was different from common feature, and fault message is very faint, so that become a difficult problem in protection and the route selection.So; when high resistance earthing fault takes place owing to report is arranged during the accident that protection malfunction or tripping cause: breaking to fall as transmission line causes loss of life or personal injury in cement flooring protection tripping, and broken string falls to protect tripping in the mountain and forest region and cause that fire, cable blow out or the like.Most protection product all exists erroneous judgement, malfunction or tripping to high resistance earthing protecting, and its reason is except fault message is faint, and main is the mistaken ideas that exist on the understanding.Because the voltage analysis during usually to isolated neutral system generation single-phase earthing all is to analyze by typical metal ground connection, this moment, the ground connection phase voltage was zero, the non-phase voltage that connects is upgraded to line voltage, and neutral point excursion is to earth point, and residual voltage equals the phase voltage before the opposite fault of direction.So that produce a kind of generally conclusion of approval: ground connection is the minimum phase of amplitude in the three-phase voltage mutually, the overwhelming majority is that the earth fault protection product of criterion also all is to differentiate the ground connection phase by this conclusion with voltage.In fact this is correct in the scope of earth resistance less than certain critical value, and when earth resistance during greater than this critical value, this conclusion is wrong.In other words, in the scope of high resistance ground, arrive to a certain degree when earth resistance is big, ground connection is not the minimum phase of voltage magnitude mutually.Defend tenaciously aforementioned conclusion, must cause erroneous judgement, the malfunction protected in the high resistance earthing fault.In addition, be the earth fault protection product of criterion with the electric current, zero-sequence current is very little during owing to high resistance ground, and tripping; The route selection product also therefore and can't route selection.
Arc suppression coil is modal a kind of protection equipment of eliminating single phase ground fault; it is connected between neutral point of electric network and the ground; when single phase ground fault takes place; it produces the capacity current that inductance current is offset fault; fault current is reduced in the scope of regulation, to eliminate arc grounding or to suppress other earth fault.This just requires the capacitance current of measuring system exactly, and the inductance value of accurately regulating arc suppression coil is complementary with the capacitance current that needs to offset, otherwise does not just reach the purpose of protection.
Because the trend that the capacity of transformer station has the process that substep puts in place and continues to enlarge, this just make the capacity of arc suppression coil often be in non-little be big awkward condition: little, then be operated in the undercompensation state, be easy to generate resonance during system excision circuit; Big, cause the idleness of equipment to damage easily and waste.Even the heap(ed) capacity of arc suppression coil meets the needs of current system, because the size of the capacitance current of system changes with the change of system operation mode, make the arc suppression coil measure and control device very complicated, operating difficulties, calculating and accuracy of measurement that capacitance current is changed are not enough, in actual motion, be difficult to operate in best gear, particularly cause resonance in order to avoid compensation, often make the residual flow in compensation backarc road still bigger, being still within the bounds of possibility of resume combustion after the zero passage finally causes the extinguishing arc failure.And arc suppression coil compensation only is the power frequency capacitance current, and actual electric current by earth point not only has the power frequency capacitance current, but also include a large amount of high-frequency currents and current in resistance property, the sustained combustion that only high-frequency current and current in resistance property just can pilot arcs when serious, particularly the high frequency oscillation current amplitude of cable circuit is bigger, decay is slow, so that high-frequency current still has big amplitude when the power current zero passage, can not accomplish complete blow-out.
In addition, arc suppression coil can cause neutral point displacement voltage to raise unusually, can not reduce maximum of arcing ground over-voltage or the like, and suchlike drawback so that arc suppression coil is not high at many local operational percentages, causes significant wastage, and interruption of service has report also the time.And arc suppression coil the complete sets of equipment assembly is many, cost is high, take up an area of greatly, and operation maintenance complexity, bad adaptability, along with the development of current power, the increase-volume of electrical network, many arc suppression coils are faced with superseded.
Summary of the invention
At existing single phase ground fault is differentiated have mistaken ideas; easily cause the erroneous judgement of high resistance earthing fault or fail to judge and effective protection problem can't be provided, invent differentiation, guard method and the system of a kind of neutral non-effective grounding electrical network single phase ground fault.
Technical scheme of the present invention is:
One, method of discrimination
A kind of differentiation and guard method of single phase ground fault phase of neutral non-effective grounding electrical network is characterized in that: is fault signature district 1 with residual voltage greater than 1/2 normal phase voltage, and declaring the minimum of three-phase voltage in this zone is the fault phase mutually; Equaling 1/2 normal phase voltage with residual voltage is fault signature district 2, and the phase voltage of declaring 90 ° of hysteresis residual voltages in this zone is the fault phase; Is fault signature district 3 with residual voltage less than 1/2 normal phase voltage, and declaring the inferior low of three-phase voltage in this zone is the fault phase mutually; After judging that fault mutually, on fault phase bus, drop into ground protection (ground protection can be by reactor ground connection, or alternate manner ground connection).
The present invention is by concluding the rule of isolated neutral system single phase ground fault, established the Mathematical Modeling of earth resistance and phase voltage, neutral point displacement voltage relation, creatively design the foundation of failure judgement: after single-phase earthing takes place, size according to residual voltage, fault coverage is divided into three characteristic areas, is fault signature district 1 with residual voltage greater than 1/2 normal phase voltage, and declaring the minimum of three-phase voltage in this zone is the fault phase mutually; Equaling 1/2 normal phase voltage with residual voltage is fault signature district 2, and the phase voltage of declaring 90 ° of hysteresis residual voltages in this zone is the fault phase; Is fault signature district 3 with residual voltage less than 1/2 normal phase voltage, and declaring the inferior low of three-phase voltage in this zone is the fault phase mutually; This shows,, can both accurately judge fault and fault mutually, thereby high resistance earthing fault is implemented effectively protection, will be difficult to discover fault in the past and eliminate in bud no matter how grounding resistance changes.
Two, guard method
The present invention is directed to the technological deficiency of existing elimination single phase ground fault, a kind of neutral non-effective grounding electrical network is eliminated the guard method of single phase ground fault, it is characterized in that: after single-phase earthing taking place and judging that fault mutually, (ground protection can be by reactor L ground connection earlier fault phase bus to be dropped into ground protection, or alternate manner ground connection), its effect is: clamp down on the fault phase voltage, shift fault current, make the fault point insulation recovery, eliminate earth fault, will delay time then this phase bus is withdrawed from ground connection; If earthing capacitance current is less than 20A, only throwing-move back ground connection at fault phase bus finishes protection; Otherwise after fault phase bus dropped into ground protection, the neutral point with three phase mains dropped into reactor Ln ground connection again, and the capacitance current of the inductive current compensation of ground fault that is produced by Ln makes it less than 20A; Then, ground protection withdraws from from the fault phase delay, and is normal if system voltage recovers, and then withdraws from reactor Ln at neutral point, finishes protection; Otherwise, keep reactor Ln in the neutral point input, once more fault is dropped into ground protection mutually, through the several seconds time-delay, withdraw from again for the second time; If still have fault, then be judged to the continuous earth fault, still keep dropping into reactor Ln at neutral point, continue once more in the congenial ground protection of fault, until the excision faulty line, ground protection withdraws from from fault phase bus and power supply neutral point.
Under the control of microcomputer control device, reactor L cooperatively interacts to the pressure limiting of fault phase bus, the ground protection of bypass and the current compensation protection that reactor Ln produces, and realizes a kind of ideal protection effect of eliminating single phase ground fault.
Three, protection system
A kind of neutral non-effective grounding electrical network is eliminated the single phase ground fault protection system; it is characterized in that: mainly by microcomputer control device, reactor (L), reactor (Ln), voltage transformer (TV), current transformer (CT1, CT2), four monopolar high-voltage switches (Ko, Ka; Kb Kc) forms.The power supply neutral point is connected with monopolar high-voltage switch (Ko) upper contact head, and the following contact of monopolar high-voltage switch (Ko) is connected with an end of reactor (Ln), and the other end of reactor (Ln) passes ground connection behind the winding of current transformer (CT2); The power supply three-phase bus respectively with monopolar high-voltage switch (Ka, Kb, Kc) the upper contact head of often opening main contacts separately is corresponding to link to each other, after interconnecting, their following contact links to each other with the end of reactor L, the other end of reactor (L) passes ground connection behind the winding of current transformer (CT1), four monopolar high-voltage switch (Ko, Ka, Kb, Kc) be subjected to the control of the output switching terminal of microcomputer control device, the end points of voltage transformer (TV) secondary winding links to each other with the corresponding voltage input of microcomputer control device respectively, current transformer (CT1, the secondary terminals (I of secondary terminals CT2) and system's feeder line zero sequence current mutual inductor
01..., I
0n) link to each other with the corresponding current input terminal of microcomputer control device respectively.Microcomputer control device wherein can adopt conventional microcomputer to add software and realize.
Beneficial effect of the present invention:
The present invention has disclosed the rule of isolated neutral system single phase ground fault; various features and the differentiation and the protection guard method of high resistance earthing fault have been found out; no matter how earth resistance and fault signature change, and can both accurately differentiate fault and fault mutually, implement effectively protection.
The present invention has realized the isolated neutral system single phase ground fault is implemented FR effective protection, especially can differentiate the small-signal that is difficult to discover high resistance earthing fault, and fault is eliminated in bud.
The present invention combines the guard method of pressure limiting, bypass and the guard method of current compensation; the two advantage is separately given full play to, and the two shortcoming is separately remedied mutually, and is practical; observing and controlling is simple and reliable, has realized a kind of desirable approach of single phase ground fault of eliminating.
Description of drawings
Fig. 1 is differentiation of the present invention and guard method flow chart.
Fig. 2 is the electric structure principle chart of protection system of the present invention.
Fig. 3 is the theory diagram of microcomputer control system of the present invention.
Among Fig. 2: Ko, Ka, Kb, Kc are high-voltage switch gear, and TV is a voltage transformer, and CT1, CT2 are current transformer, and L, Ln are different reactors.
Embodiment
Below in conjunction with drawings and Examples this present invention is further described.
One, single phase ground fault phase method of discrimination
A kind of method of discrimination of single phase ground fault phase of neutral non-effective grounding electrical network, with reference to figure 1: when single phase ground fault takes place, be fault signature district 1 with residual voltage greater than 1/2 normal phase voltage, that declares three-phase voltage in this zone minimumly is the fault phase mutually; Equaling 1/2 normal phase voltage with residual voltage is fault signature district 2, and the phase voltage of declaring 90 ° of hysteresis residual voltages in this zone is the fault phase; Is fault signature district 3 with residual voltage less than 1/2 normal phase voltage, and declaring the inferior low of three-phase voltage in this zone is the fault phase mutually.
Two, eliminate the comprehensive method of protection of single phase ground fault
A kind of neutral non-effective grounding electrical network is eliminated the guard method of single phase ground fault; with reference to figure 1, Fig. 2; it is characterized in that: microcomputer control device is set respectively on electrical network and is used to eliminate the reactor L of fault and arc-suppression reactor Ln etc. forms protection system; zero-sequence current value when haveing with fault by three-phase voltage, the residual voltage of microcomputer control device detection of grid, carry out fault as follows and eliminate:
Microcomputer control device has detected single phase ground fault, and at first the failure judgement phase satisfies the condition in fault signature district 1 as if residual voltage, and declaring voltage minimum is the fault phase mutually; If residual voltage satisfies the condition in fault signature district 2, the voltage of declaring 90 ° of hysteresis residual voltages is the fault phase mutually; If residual voltage satisfies the condition in fault signature district 3, declare the inferior low fault phase that is mutually of voltage; If ground connection zero-sequence current value is less than 20A, protection is only finished by throwing-move back reactor L, and process is as follows: 1) microcomputer control device driving malfunction phase high-voltage switch gear closure, this is passed through reactor L ground connection mutually, to clamp down on the fault phase voltage, shift fault current, make the fault point insulation recovery, eliminate earth fault, drive this high-voltage switch gear time-delay disjunction then, withdraw from reactor L, normal if system voltage recovers, then protection is finished; 2) if fault still exists, then repeat above process, for the second time fault congenial-move back reactor L; 3) if still have fault, then be judged to the continuous earth fault, continue for the third time,, reactor L is withdrawed from until the faulty line excision at the congenial reactor L of fault.
Microcomputer control device has detected single phase ground fault, and at first the failure judgement phase satisfies the condition in fault signature district 1 as if residual voltage, and declaring voltage minimum is the fault phase mutually; If residual voltage satisfies the condition in fault signature district 2, the voltage of declaring 90 ° of hysteresis residual voltages is the fault phase mutually; If residual voltage satisfies the condition in fault signature district 3, declare the inferior low fault phase that is mutually of voltage; If ground connection zero-sequence current value is greater than 20A, protection is by throwing-move back reactor L and throwing-move back reactor Ln to finish jointly, process is as follows: 1) microcomputer control device is earlier at the congenial reactor L of fault, then drive high-voltage switch gear Ko closure, the power supply neutral point is passed through reactor Ln ground connection, the capacitance current of the inductive current compensation of ground fault that Ln produces, make it less than 20A, because L is to the pressure limiting of fault phase, the bypass effect has guaranteed not to be subjected to the influence of earth current size, single phase ground faults such as reliable elimination arc grounding, thereby, needn't accurately pursue the current compensation degree, make observing and controlling become simple to electric current, the two combination of L and Ln realizes the ideal effect of protecting; Then, reactor L is moved back in the high-voltage switch gear of fault phase time-delay disjunction; At this moment, normal if system voltage recovers, then disjunction high-voltage switch gear Ko withdraws from reactor Ln, finishes protection; 2) if fault still exists, keep reactor Ln to drop at the power supply neutral point, for the second time fault congenial-move back reactor L, 3) if still have fault, then be judged to the continuous earth fault, keep reactor Ln equally, for the third time at the congenial reactor L of fault and lasting in power supply neutral point input, until the faulty line excision, make reactor L and coil Ln withdraw from, reset again.
Three, eliminate the Integrated Protection System of single phase ground fault
A kind of neutral non-effective grounding electrical network is eliminated the Integrated Protection System of single phase ground fault; with reference to figure 2, Fig. 3; it is mainly by microcomputer control device, reactor L, reactor Ln, voltage transformer TV, current transformer (CT1; CT2), four monopolar high-voltage switch (Ko; Ka; Kb, Kc) and form.The power supply neutral point is connected with monopolar high-voltage switch (Ko) upper contact head, and the following contact of monopolar high-voltage switch (Ko) is connected with the end of reactor Ln, and the other end of reactor Ln passes ground connection behind the winding of current transformer CT2; The power supply three-phase bus respectively with monopolar high-voltage switch (Ka, Kb, Kc) the upper contact head of often opening main contacts separately is corresponding to link to each other, after interconnecting, their following contact links to each other with the end of reactor L, the other end of reactor L passes ground connection behind the winding of current transformer CT1, four monopolar high-voltage switch (Ko, Ka, Kb, Kc) be subjected to the control of the output switching terminal of microcomputer control device, the end points of voltage transformer TV secondary winding links to each other with the corresponding voltage input of microcomputer control device respectively, current transformer CT1, the secondary terminals (I of the secondary terminals of CT2 and system's feeder line zero sequence current mutual inductor
01..., I
0n) link to each other with the corresponding current input terminal of microcomputer control device respectively.
Microcomputer control device wherein can adopt conventional microcomputer to add software and be realized, its hardware is formed as shown in Figure 3.
Described high-voltage switch gear is monopolar high-voltage vacuum switch or high-tension electricity electronic switch.
Example 1.
When 6kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 2kV, and this system's normal phase voltage is 3.6kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 1, therefore, can declare and minimum one be the fault phase mutually in the three-phase voltage this moment, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 2.
When 6kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 1.8kV, and this system's normal phase voltage is 3.6kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 2, therefore, that phase voltage that can declare 90 ° of the residual voltages of lagging behind this moment is the fault phase, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 3.
When 6kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 1.2kV, and this system's normal phase voltage is 3.6kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 3, therefore, can declare in three-phase voltage this moment time low one and be the fault phase mutually, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 4.
When 10kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 4kV, and this system's normal phase voltage is 6kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 1, therefore, can declare and minimum one be the fault phase mutually in the three-phase voltage this moment, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 5.
When 10kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 3kV, and this system's normal phase voltage is 6kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 2, therefore, that phase voltage that can declare 90 ° of the residual voltages of lagging behind this moment is the fault phase, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 6.
When 10kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 2kV, and this system's normal phase voltage is 6kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 3, therefore, can declare in three-phase voltage this moment time low one and be the fault phase mutually, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 7.
When 35kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 12kV, and this system's normal phase voltage is 21kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 1, therefore, can declare and minimum one be the fault phase mutually in the three-phase voltage this moment, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 8.
When 35kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 10.5kV, and this system's normal phase voltage is 21kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 2, therefore, that phase voltage that can declare 90 ° of the residual voltages of lagging behind this moment is the fault phase, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
Example 9.
When 35kV neutral non-effective grounding network system generation single-phase earthing, recording residual voltage is 9kV, and this system's normal phase voltage is 21kV, can find out by described method of discrimination, this single phase ground fault satisfies the condition of characteristic area 3, therefore, can declare in three-phase voltage this moment time low one and be the fault phase mutually, (ground protection can be by reactor L ground connection to drop into ground protection immediately on this phase bus, or alternate manner ground connection), if fault current less than 20A, does not then drop into reactor Ln, only finish protection by throwing-move back reactor L; If it is greater than 20A, then reactor Ln is measured current value adjustment to suitable position according to CT2, drive high-voltage switch gear Ko closure, by reactor Ln ground connection, the inductive current compensation of ground fault current that is produced by Ln is less than 20A with the power supply neutral point; For transient fault, after the above-mentioned protection time-delay several seconds, withdraw from reactor L, whether eliminate according to the system voltage failure judgement then, then withdraw from Ln if eliminate; Otherwise, keep reactor Ln in the neutral point input, make fault mutually by reactor L ground connection once more, through the several seconds time-delay, withdraw from reactor L more for the second time; If still have fault, then be judged to the continuous earth fault, still keep reactor Ln in the neutral point input, continue once more at the congenial reactor L of fault, until according to prior selection, or by artificial tripping operation disengagement failure circuit, or by device tripping operation case action disengagement failure circuit, involution reactor L and reactor Ln.
The part that the present invention does not relate to prior art that maybe can adopt all same as the prior art is realized.
Claims (2)
1. the differentiation and the guard method of the single phase ground fault phase of a neutral non-effective grounding electrical network is characterized in that:
Method of discrimination is: is fault signature district 1 with residual voltage greater than 1/2 normal phase voltage, and declaring the minimum of three-phase voltage in this zone is the fault phase mutually; Equaling 1/2 normal phase voltage with residual voltage is fault signature district 2, and the phase voltage of declaring 90 ° of hysteresis residual voltages in this zone is the fault phase; Is fault signature district 3 with residual voltage less than 1/2 normal phase voltage, and declaring the inferior low of three-phase voltage in this zone is the fault phase mutually; After judging that fault mutually, on fault phase bus, drop into ground protection;
Earthing protecting method is: after single-phase earthing taking place and judging that fault mutually, earlier fault phase bus is dropped into ground protection, its effect is: clamp down on the fault phase voltage, shift fault current, make the fault point insulation recovery, eliminate earth fault, time-delay withdraws from this phase bus from ground connection then; If earthing capacitance current is less than 20A, only throwing-move back ground connection at fault phase bus finishes protection; Otherwise after fault phase bus dropped into ground protection, the neutral point with three phase mains dropped into second reactor (Ln) ground connection again, and the capacitance current of the inductive current compensation of ground fault that is produced by second reactor (Ln) makes it less than 20A; Then, ground protection withdraws from from the fault phase delay, and is normal if system voltage recovers, and then withdraws from second reactor (Ln) at neutral point, finishes protection; Otherwise, keep second reactor (Ln) in the neutral point input, once more fault is dropped into ground protection mutually, through the several seconds time-delay, withdraw from again for the second time; If still have fault, then be judged to the continuous earth fault, still keep dropping into second reactor (Ln) at neutral point, continue once more in the congenial ground protection of fault, until the excision faulty line, ground protection withdraws from from fault phase bus and power supply neutral point.
2. system that realizes the described method of claim 1, it is characterized in that: mainly by microcomputer control device, first reactor (L), second reactor (Ln), voltage transformer (TV), first current transformer (CT1), second current transformer (CT2), the first monopolar high-voltage switch (Ko), the second monopolar high-voltage switch (Ka), the 3rd monopolar high-voltage switch (Kb) and the 4th monopolar high-voltage switch (Kc) are formed, the power supply neutral point is connected with first monopolar high-voltage switch (Ko) upper contact head, the following contact of the first monopolar high-voltage switch (Ko) is connected with an end of second reactor (Ln), and the other end of second reactor (Ln) passes ground connection behind the winding of second current transformer (CT2); The power supply three-phase bus respectively with the second monopolar high-voltage switch (Ka), the upper contact head of often opening main contacts separately of the 3rd monopolar high-voltage switch (Kb) and the 4th monopolar high-voltage switch (Kc) is corresponding to link to each other, the second monopolar high-voltage switch (Ka), after interconnecting, the following contact of the 3rd monopolar high-voltage switch (Kb) and the 4th monopolar high-voltage switch (Kc) links to each other with an end of first reactor (L), the other end of first reactor (L) passes ground connection behind the winding of first current transformer (CT1), the first monopolar high-voltage switch (Ko), the second monopolar high-voltage switch (Ka), the 3rd monopolar high-voltage switch (Kb) and the 4th monopolar high-voltage switch (Kc) are subjected to the control of the output switching terminal of microcomputer control device, the end points of voltage transformer (TV) secondary winding links to each other with the corresponding voltage input of microcomputer control device respectively, the secondary terminals of first current transformer (CT1) and second current transformer (CT2) and the secondary terminals (I of system's feeder line zero sequence current mutual inductor
01..., I
0n) link to each other with the corresponding current input terminal of microcomputer control device respectively.
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| CN2008101303773A CN101340086B (en) | 2008-01-21 | 2008-07-11 | Single-phase grounding fault determining, protecting method and system of neutral-point uneffective earthed electric grid |
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| CN2008101303773A CN101340086B (en) | 2008-01-21 | 2008-07-11 | Single-phase grounding fault determining, protecting method and system of neutral-point uneffective earthed electric grid |
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| CN2008101303773A Active CN101340086B (en) | 2008-01-21 | 2008-07-11 | Single-phase grounding fault determining, protecting method and system of neutral-point uneffective earthed electric grid |
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