CN104111403A - Microcomputer integrated protection line-selection method for low-current earthed power system - Google Patents
Microcomputer integrated protection line-selection method for low-current earthed power system Download PDFInfo
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Abstract
The invention discloses a microcomputer integrated protection line-selection method for a low-current earthed power system. when a neutral point is low-current earthed or a single-phase earth fault happens to the insulated power system, cabinet voltage small generatrix signal and a zero-sequence current signal are used as input signals, magnitude and angle of a zero sequence voltage signal are calculated, and magnitude and angle of a same zero sequence current signal are also calculated. A zero sequence voltage value U0 being greater than or equal to 30V is used as a first criterion, a measured zero sequence current value being greater than or equal to 0.85 times of a calculated zero sequence current value of the line is used as a second criterion, and frequencies of the zero-sequence current of the line are strictly used as a third criterion. If the three criteria come into existence simultaneously, single-phase earth faults happen to the system, and system earthing is reported. A measured zero sequence current value being greater than or equal to 1.15 times of the calculated zero sequence current value is used as a fifth criterion and a power direction element is used as a fourth criterion. If the five criteria are satisfied simultaneously, the line is earthed and is used for displaying or tripping. Thus, automation level of the system is improved, and stability and high-quality operation of a power grid are protected.
Description
Technical field
The present invention relates to 3-63KV intermediate voltage electric power system, the electric system of neutral point insulation or large impedance earth mode, when there is singlephase earth fault, whether be the method for faulty line, relate in particular to a kind of small current neutral grounding electric system microcomputer complex protection selection method if accurately judging this circuit.
Background technology
The factors such as the electric pressure of Neutral Grounding Modes of Power System and this system, the size of single-phase-to-ground current, overvoltage level and protective device are closely related.The conventional earthing mode of electric system has system with effectively earthed neutral and the large class of system with non-effectively earthed neutral two, the kind of concrete ground connection has: neutral-point solid ground, neutral point are through four kinds of arc suppression coil (arc) ground connection, Neutral Grounding through Resistance in Electrical, isolated neutral, wherein, neutral point, through resistance-grounded system, is divided into again high resistance ground and low-impedance earthed system by ground current size.Therefore, by ground current size, be divided into again large earthed system: comprise neutral-point solid ground and low-impedance earthed system; Small current neutral grounding system: comprise neutral by arc extinction coil grounding, high resistance ground; Isolated neutral system, i.e. isolated neutral system.Some western countries adopt large earthed system, the intermediate voltage electric power system of China adopts small current neutral grounding system or isolated neutral system, in the different periods of history, proportion is different separately with region, twenty or thirty before year isolated neutral system be main flow, afterwards, along with the research and development of arc suppression coil, perfect, popularization, progressively turn to and take small current neutral grounding system as main.
Every kind of earthing mode of electric system, corresponding electric pressure, the method for operation, moving law difference, the relative merits of system self are also different.General, in China's electric system, 63KV adopts large earthed system above, and object is effectively to avoid system overvoltage to bring too high operating cost and initial investment to the insulating material in electric system.3～63KV system is called medium voltage network, general neutral point small current neutral grounding mode or the neutral point insulation mode of adopting, object is to guarantee reliability and the power supply continuity of system, the large earthed system of the general employing of the low-pressure systems such as the following system of 3KV (especially 380V system), because its transformer capacity is little, have the function that can excise rapidly faulty line, coverage is little, safe, stable.The following system of 3KV also has small current neutral grounding or isolated neutral system, distinguishes very not strict.In some western countries, medium voltage network also adopts large earthing mode, and what this mode was sacrificed is system continuity, reliability, and what obtain is that the excision of system failure point is rapid, has ensured the safe and stable operation of non-fault line.In fact, no matter which kind of earthing mode, has relative merits, and key is how to maximize favourable factors and minimize unfavourable ones, and needs the consideration of comprehensive, system and selects earthing mode.
In neutral point insulation and small current neutral grounding electric system, at present the most difficult be as how the fastest speed, the highest precision, accurately the circuit that singlephase earth fault has occurred is screened and is judged.If realize accurate route selection, just can realize computer integrated protection and directly act on tripping operation, can promptly and accurately excise faulty line, can within the shortest time, recover the reliable and stable operation of whole electric system again, to guaranteeing reliability, the continuity of electric power system, guarantee power grid quality, prevent that because of singlephase earth fault, expanding as other accidents (as line to line fault, three-phase shortcircuit etc.) has very important meaning, to promoting the automatization level of electric system to have positive effect; Also can avoid the tripping operation expanded range because having adopted large earthed system to cause, power failure range expands, the problems such as causality loss increase.
It is that route selection hit rate is low that line selection device for low current has a variety of, maximum problems in the market, and the highest also only have 75% left and right; The basic reason that hit rate or accuracy rate are low is to be subject to the not high factor puzzlement of the precision of uncertainty, line selection apparatus of electric system itself own, also has the factor puzzlements such as zero sequence current mutual inductor, zero sequential potential transformer wiring be lack of standardization.Electric system itself exists multichannel to allot, operation and the stoppage in transit of allotting circuit are subject to user's request and line security, the impact of the factors such as maintenance, there is the possibility that puts into operation at any time or stop transport on any road, it is erratic that this throwing is moved back, do not predict, it is a kind of unordered stochastic process, and it is this unordered, do not have the variation of rule directly to have influence on the size of capacitance current in electric system, the size of regular link capacitance current depends on the form of allotting circuit, cross section, length, the factors such as load characteristic, the size of capacitance current that the circuit of single-phase earthing occurs be all line capacitance electric currents of same electrical network and, therefore, only depend on the size variation of capacitance current to be difficult to clear and definite Shi Na mono-tunnel fault, simultaneously, existence due to Harmonic in Power System, also there is randomness in harmonic wave capacitance current, changing at any time, because these variations do not have rule, more can not be described by mathematical model, to single-phase grounding selecting, increased difficulty, line selection apparatus neither one when design is stable, accurate index is as the criterion of singlephase earth fault, this is also the not high reason of the precision of line selection apparatus own, add the strict demand of direction power component butted line correctness: the strict correct wiring of each connection terminal that must guarantee zero sequential potential transformer and zero sequence current mutual inductor, in real work, the power directional element often lack of standardization of this wiring moves inaccurate key, and the people often lack of standardization of the wiring conflict psychology low to route selection accuracy rate, also has a reason: zero sequential potential transformer and zero sequence current mutual inductor, sense, the capacitive size disunity, uncertain of signal transmission component sent in the change that comprises line selection apparatus itself, make residual voltage waveform and zero-sequence current waveform in electric system difficult by comparison, can only do trend judgement, be difficult to precise quantification.
Summary of the invention
Object of the present invention provides a kind of small current neutral grounding electric system microcomputer complex protection selection method with regard to being in order to address the above problem.
In order to achieve the above object, the present invention has adopted following technical scheme:
A kind of small current neutral grounding electric system microcomputer complex protection selection method, in this method, input signal is 4, wherein voltage signal is 3, Ua, the Ub, the Uc that by power system voltage mutual inductor (PT) secondary, are provided, one of current signal, by zero sequence current mutual inductor (zero sequence CT) secondary, provided, enter following determining step:
The first criterion: residual voltage criterion, to combine and protect the direct input that hardware does not have residual voltage, residual voltage is calculated through software by Ua, Ub, Uc input quantity, comprises effective value and phase place.Residual voltage setting valve is adjusted as U by < < handbook > > latest edition
0>=30V;
Second Criterion: zero-sequence current effective value criterion, zero-sequence current adopts syllogic determining method, and this is that feature by small current neutral grounding system or isolated neutral system determines.Meet I0, the criterion that the system that can be used as has single-phase earthing to occur;
The 3rd criterion: zero-sequence current and residual voltage frequency invariance, now the frequency of residual voltage and zero-sequence current can not directly be measured in fact, adopts sampled point determining method between peak value to be judged, and this is the unique distinction of this method;
Above three criterions are set up simultaneously, sentence " system earth " message and show; If only have the first criterion to set up, be likely that PT insurance is disconnected; If only have Second Criterion set up,, be likely that out-of-balance current or the harmonic current of system causes; If 1st, 2 criterions are set up simultaneously, this is also the traditional method of decision-making system ground connection, but thunder and lightning has the possibility that causes the 1st, 2 criterions simultaneously to be set up, also have a phase PT broken string to have harmonic current to exist simultaneously, only have when first, second, third criterion is set up simultaneously, just can judge " system earth ", otherwise system earth necessarily have above 3 presentations simultaneously;
The 4th criterion: power direction determining method, both the electric current and the residual voltage that had flow through this circuit zero sequence current mutual inductor carry out phase place judgement, leading residual voltage 0～90 degree of equidirectional both zero-sequence currents, not this line-to-ground, otherwise, both zero-sequence current hysteresis residual voltage 0～90 degree, was this line-to-ground;
The 5th criterion: zero-sequence current value method is judged,, a circuit, no matter be cable line or overhead transmission line, once circuit and load are determined, the single-phase capacitive earth current of this circuit is just determined in fact, this current value is to calculate or to come out, as the normally zero-sequence current value over the ground of single line, and when unbalanced earth fault capacitance current is normal operation 3 times of phase line capacitive earth current;
Fourth, fifth criterion is to determine the whether sufficient and necessary condition of ground connection of this circuit, and evidence, once i.e. this circuit generation singlephase earth fault must be that the first to the 5th criterion is set up simultaneously, indispensable mutually.
The computing method of circuit unbalanced earth fault capacitance current comprise:
1. for load, be the circuit of synchronous motor, must calculate the single-phase capacitive earth current of synchronous motor;
2. other load is not considered single-phase capacitive earth current, and its value is very little, negligible;
3. for the building-out capacitor in current transformer downstream, due to wye connection, neutral ground, with the ratings 3 times of calculating in ground of single-phase capacitance electric current.
The calculation procedure of circuit unbalanced earth fault capacitance current,
1. the unbalanced earth fault capacitance current of cable line is calculated as follows:
6kv cable line
10kv cable line
The single-phase earthing electric capacity of cable line, electric current can also be estimated by following formula (this formula is applicable to each electric pressure)
I
c＝0.1U
rlA
With s in above formula---the nominal section mm2 of cable core
U
r---circuit rated line voltage kv
L---line length km
I
c---earthing capacitance current A
2. overhead transmission line unbalanced earth fault capacitance current is calculated as follows
Without aerial earth wire single loop I
c=2.7U
rl * 10
-3a
There is aerial earth wire single loop I
c=3.3U
rl * 10
-3a
The unbalanced earth fault capacitance current of overhead transmission line can also be estimated by following formula (this formula is applicable to each electric pressure)
The mean value unit of the every km unbalanced earth fault capacitance current of overhead transmission line and cable line: A/KM
The impact of residual voltage, zero-sequence current during some special circumstances, comprising:
1. thunder and lightning: all can install lightning arrester in accordance with regulations in medium-pressure electricity supply system, system overvoltage is during higher than lightning arrester threshold values, lightning arrester can shorted to earth, now may occur that single-phase large electric current or single-phase voltage-to-ground are zero.That is: the situation that residual voltage and zero-sequence current all satisfy condition, at this moment frequency ratio definition and necessity just appears suddenly out.
2. the single-phase-to-ground current of the large earthed system of adjacent lines impact: medium voltage network itself is generally isolated neutral system or small current neutral grounding mini system.If circuit is parallel with large earthed system circuit, large earthed system, once occur earth fault, can induce certain electromotive force because line mutual-inductance acts on adjacent lines, therefore also likely induces zero-sequence current, now has two measures to filter it.The one,, residual voltage value >=30V; The 2nd, I03 time delay >=2 second of adjusting.Once because ground fault occurs large earthed system, can be at short notice cutly go out electrical network, can not continue again impact.
Take three WV signal Ua, Ub, Uc in each high voltage power distributing cabinet is input signal; the zero sequence current mutual inductor signal I0 in machine of take is zero-sequence current input signal; take computer integrated protection unit as signals collecting; signal operation, logic judgement, demonstration and node output carrier, first gather input signal.Meet 1,2,3 criterion, i.e. U simultaneously
0>=30V, the program I that adjusts
03>=0.85I
0, I
0value is by manually calculating, by 0.85I
0i adjusts
03, same I
01>=1.15I
0also by manually calculating, manual entry is adjusted.
Beneficial effect of the present invention is:
The present invention is a kind of small current neutral grounding electric system microcomputer complex protection selection method, when neutral point is the electric system generation singlephase earth fault of small current neutral grounding or insulation, take WV signal and zero sequence current signal in cabinet is input signal, draw as calculated size and the angle of residual voltage signal, same zero sequence current signal also calculates size and angle, with residual voltage value U
0>=30V is the first criterion, take and measure zero-sequence current value and be more than or equal to that to calculate 0.85 times of this circuit zero sequence current value be Second Criterion, the frequency strict conformance of this circuit zero-sequence current of take is the 3rd criterion, these three criterions are set up simultaneously, in system, there is singlephase earth fault to occur, report " system earth " be take and measured zero-sequence current value and be more than or equal to that to calculate 1.15 times of this circuit zero sequence current value be the 5th criterion, take power directional element as the 4th criterion, if meet 5 criterions simultaneously, this line-to-ground, and for showing or tripping operation, improve the automatization level of this system, to stablizing of this electrical network, guaranteeing role is played in high-quality operation.
Accompanying drawing explanation
Fig. 1 is the structured flowchart of a kind of small current neutral grounding electric system of the present invention microcomputer complex protection selection method;
Fig. 2 is a kind of embodiment schematic diagram of the present invention;
Fig. 3 is another kind of embodiment schematic diagram of the present invention.
Embodiment
Below in conjunction with instantiation, the invention will be further described:
Below in conjunction with accompanying drawing and specific embodiment, the invention will be further described, in illustrative examples and the explanation of this invention, is used for explaining the present invention, but not as a limitation of the invention.
Small current neutral grounding system single channel is combined the five criterion methods of guarantor
(1) applicable system: this method is applicable to middle pressure neutral point small current neutral grounding system, voltage range is generally in 3～63kv system, small current neutral grounding system refers to that neutral point in electric power system is through grounding through arc or large resistance eutral grounding, this method is equally applicable to isolated neutral system, is also applicable to small current neutral grounding system and isolated neutral system in low pressure range.
(2) single channel is combined and is protected concept: this method is applicable to originally allot in small current neutral grounding and neutral point insulation electric system the single-phase earthing judgement of circuit, for the concentrated route selection of whole distribution system, be referred to as single channel and combine protect five criterion ground connection determining methods, judgement object is only limited to this circuit and as other, does not allot the criterion of circuit.
(3) five criterion methods: this method adopts five criterion methods, is different from other route selection, determining method.4 of this method input signals, wherein voltage signal is 3, Ua, the Ub, the Uc that by power system voltage mutual inductor (PT) secondary, are provided, one of current signal, is provided by zero sequence current mutual inductor (zero sequence CT) secondary.It is that phase sequence is correct that the wiring of Ua, Ub, Uc is required, and the benefit of doing is like this without residual voltage signal.It is that zero sequence current mutual inductor position, direction are placed correctly that the wiring of zero-sequence current I0 is required, press the correctly installation of zero sequence current mutual inductor mounting list, correct wiring and be correctly connected with the comprehensive connection terminal of protecting, correct to guarantee the directivity of zero-sequence current, the ground wires such as armature of cable, shielding, grounded screen can not be with cable core together through zero sequence CT center pit, be outside CT independent grounding.
As shown in Figure 2:
When in like manner, overhead transmission line adopts three-phase CT differential to be zero sequence CT, can not there is ground wire to pass CT hole.
The first criterion: residual voltage criterion, to combine and protect the direct input that hardware does not have residual voltage, residual voltage is calculated through software by Ua, Ub, Uc input quantity, comprises effective value and phase place.Residual voltage setting valve is adjusted as U by < < handbook > > latest edition
0>=30V.
Second Criterion: zero-sequence current effective value criterion, zero-sequence current adopts syllogic determining method, and this is that feature by small current neutral grounding system or isolated neutral system determines.Meet I0, the criterion that the system that can be used as has single-phase earthing to occur.
The 3rd criterion: zero-sequence current and residual voltage frequency invariance, now the frequency of residual voltage and zero-sequence current can not directly be measured in fact, adopts sampled point determining method between peak value to be judged, and this is the unique distinction of this method.
Above three criterions are set up simultaneously, sentence " system earth " message and show.If only have the first criterion to set up, be likely that PT insurance is disconnected; If only have Second Criterion set up,, be likely that out-of-balance current or the harmonic current of system causes; If fruit the 1st, 2 criterions are set up simultaneously, this is also the traditional method of decision-making system ground connection, but thunder and lightning has the possibility that causes the 1st, 2 criterions simultaneously to be set up, also have a phase PT broken string to have harmonic current to exist simultaneously, only have when first, second, third criterion is set up simultaneously, just can judge " system earth ", otherwise system earth necessarily have above 3 presentations simultaneously.
The 4th criterion: power direction determining method, both the electric current and the residual voltage that had flow through this circuit zero sequence current mutual inductor carry out phase place judgement, leading residual voltage 0～90 degree of equidirectional both zero-sequence currents, not this line-to-ground, otherwise, both zero-sequence current hysteresis residual voltage 0～90 degree, was this line-to-ground.
The 5th criterion: the judgement of zero-sequence current value method, no matter a circuit, be cable line or overhead transmission line, once circuit and load are definite, the single-phase capacitive earth current of this circuit is just determined in fact.This current value is to calculate or to come out, as the normally zero-sequence current value over the ground of single line, and when unbalanced earth fault capacitance current is normal operation 3 times of phase line capacitive earth current.This circuit single-phase-to-ground current calculates and statistical method is shown in appendix 1.
Fourth, fifth criterion is to determine the whether sufficient and necessary condition of ground connection of this circuit, and evidence, once i.e. this circuit generation singlephase earth fault must be that the first to the 5th criterion is set up simultaneously, indispensable mutually.
(4) calculating of circuit unbalanced earth fault capacitance current
1. for load, be the circuit of synchronous motor, must calculate the single-phase capacitive earth current of synchronous motor.
2. other load is not considered single-phase capacitive earth current, and its value is very little, negligible.
3. for the building-out capacitor that is positioned at zero sequence current mutual inductor downstream, due to wye connection, neutral ground, with the ratings 3 times of calculating in ground of single-phase capacitance electric current.
As shown in Figure 3:
To the circuit of building-out capacitor isolated neutral, due to electric capacity, Y connects, isolated neutral, ground connection is fault, with electrical network simultaneously ground connection be small probability event, do not consider.The situation of dihedral connection, uneven capacitance current value is not considered.
4. for example: a line voltage distribution grade is 10kv, first through 100m cable, then through 3km pole line, then through 50m cable, drag a 4000kw non-salient pole synchronous motor.
So, the single-phase capacitive earth current of this circuit is exactly 150 meters of cables, 3 km pole lines and synchronous motor separately unbalanced earth fault capacitance current and.
That is: I0 total=I01 cable+I02 cable+I0 pole line+I0 synchrodyne
(5) setting principle of I01, I02, I03
The single-phase capacitive earth current of a certain routine calculation and be I0
I03=0.85I0
Because:
1. I0 value itself is exactly more accurate estimated value, has its coarse composition.
2. the error that the factors such as type selecting of zero sequence current mutual inductor cause is in 10% left and right.
3. consider systematic error 5%.
4. comprehensive taking into account system error superimposed factor, considers by 15%, thus I03=0.85I0, can be causing that the various errors of I0 are included, zero-sequence current value I0 reality >=I03, system has ground connection possible.
I02＝I0
I0 value is the value going out as calculated, is more accurate calculated value, on this basis, is used as threshold criterion.
I01＝1.15I0
Because:
I01 is as one of criterion of this road ground connection, and its actual ground current value is bound to be greater than I0.Reason:
The external capacitive electric current of i, consideration distribution system 15%～18%, getting it little is also 15%.
Ii, consider the over-compensation factor through grounding through arc, be also greater than 15%, so, judge the setting valve of this road ground current, with composition error and arc suppression coil over-compensation factor, get 1.15 times of I0
(6) impact of residual voltage, zero-sequence current during some special circumstances
1. thunder and lightning
In medium-pressure electricity supply system, all can install lightning arrester in accordance with regulations, system overvoltage is during higher than lightning arrester threshold values, and lightning arrester can shorted to earth, now may occur that single-phase large electric current or single-phase voltage-to-ground are zero.That is: the situation that residual voltage and zero-sequence current all satisfy condition, at this moment frequency ratio definition and necessity just appears suddenly out.
The impact of the single-phase-to-ground current impact of the large earthed system of adjacent lines and line to line fault, three-phase shortcircuit electric current:
Medium voltage network itself is generally isolated neutral system or small current neutral grounding mini system.If circuit is parallel with large earthed system circuit, large earthed system, once occur earth fault, can induce certain electromotive force because line mutual-inductance acts on adjacent lines, therefore also likely induces zero-sequence current, now has two measures to filter it.The one,, residual voltage value >=30V; The 2nd, I03 time delay >=2 second of adjusting.Once because ground fault occurs large earthed system, can be at short notice cutly go out electrical network, can not continue again impact.
Appendix 1: circuit single-phase-to-ground current computing method
Appendix 2: the unbalanced earth fault capacitance current computing method of synchronous motor
Appendix 1
The calculating of unbalanced earth fault capacitance current
Unbalanced earth fault capacitance current in electrical network is comprised of power circuit and the two-part capacitance current of power equipment (synchronous generator, large capacity synchronous motor and transformer etc.).
(1) unbalanced earth fault capacitance current of cable line is calculated as follows:
6kv cable line
10kv cable line
The single-phase earthing electric capacity of cable line, electric current can also be estimated by following formula (this formula is applicable to each electric pressure)
I
c＝0.1U
rlA
With s in above formula---the nominal section mm2 of cable core
U
r---circuit rated line voltage kv
L---line length km
I
c---earthing capacitance current A
(2) overhead transmission line unbalanced earth fault capacitance current is calculated as follows
Without aerial earth wire single loop I
c=2.7U
rl * 10
-3a
There is aerial earth wire single loop I
c=3.3U
rl * 10
-3a
The unbalanced earth fault capacitance current of overhead transmission line can also be estimated by following formula (this formula is applicable to each electric pressure)
The mean value unit of the every km unbalanced earth fault capacitance current of overhead transmission line and cable line: A/KM
The mean value unit of the every km unbalanced earth fault capacitance current of overhead transmission line and cable line: A/KM
Note: bracket inner digital is for there being the overhead transmission line of aerial earth wire
The earthing capacitance current value that electric substation increases
Unbalanced earth fault capacitance current for synchronous motor calculates by existing computing formula.
Unbalanced earth fault capacitance current for synchronous motor calculates by existing computing formula.
For asynchronous motor, the calculating of the unbalanced earth fault capacitance current of transformer, the unbalanced earth fault capacitance current of asynchronous motor and transformer has certainly, because as long as wire has distribution just to have capacitance current on space length, the capacitance current of asynchronous machine and transformer and space size own, winding sectional area, distribution are spatially relevant, voltage is even variation on winding, separate with the differential equation.More complicated, again because its value is very little, during for concrete circuit, can ignore.
Unbalanced earth fault capacitance current (6-10KV) computing method of appendix 2 step motor
The unbalanced earth fault capacitance current of 1 synchronous motor
The capacitance current of implicit-pole synchronous motor
S in formula
rM---the rated capacity MVA of motor
U
rM---the rated voltage V of motor
Angular velocity omega=2 π the f of ω---motor, ω=314 when f=50HZ
K---be decided by the coefficient of the class of insulation, when temperature is 15-20 ℃ of k=0.0187
(2) capacitance current of salient-pole synchronous motor
In formula:
S
rM---the rated capacity kVA of motor
U
rM---the rated voltage V of motor
Angular velocity omega=2 π the f of ω---motor, ω=314 when f=50HZ
The rotating speed r/min of n---motor
K---be decided by the coefficient of the class of insulation, for B-class insulation when 25 ℃ of the temperature, k ≈ 40
The electric capacity of above synchronous motor calculates only for 6-10KV system.
5, implementation:
Take three WV signal Ua, Ub, Uc in each high voltage power distributing cabinet is input signal, and the zero sequence current mutual inductor signal I0 in machine of take is zero-sequence current input signal.Take computer integrated protection unit as signals collecting, signal operation, logic judgement, demonstration and node output carrier.First input signal is gathered.
Meet 1,2,3 criterion, i.e. U simultaneously
0>=30V, the program I that adjusts
03>=0.85I
0, I
0value is by manually calculating, by 0.85I
0i adjusts
03.Same I
01>=1.15I
0also by manually calculating, manual entry is adjusted.
One, this patent is in middle pressure or part low-voltage power system, the electric system of small current neutral grounding and neutral insulation.Voltage transformer secondary voltage signal Ua, Ub, the Uc easily getting in cabinet of take is voltage signal input, and calculate according to this size and the angle of residual voltage, the zero sequence current signal of correct wiring of take is input signal, totally 4 input quantities, and according to this for the singlephase earth fault on this route road of criterion carries out in good time criterion judgement.
Two, except 1,2 criterions are traditional criterion, adopt the 3rd criterion of residual voltage frequency and zero-sequence current frequency strict conformance, object is the erroneous judgement that the assorted frequency signals such as filtering thunder and lightning cause.
Three, the method for residual voltage frequency and zero-sequence current strict conformance is, with or or some points, remove to divide equally a cycle of residual voltage at 32 at 24, such as dividing equally with 32,32 points are constant, along with the change of residual voltage frequency, the interval between 32 shops changes thereupon.According to this characteristic, counted and counted in the same interval in cycle of zero-sequence current simultaneously, count consistent synchronously with residual voltage, residual voltage is consistent with zero-sequence current frequency, otherwise inconsistent.
Four, except still adopting direction power component to carry out zero-sequence current direction detection, the method that adopts zero-sequence current size to compare with this routine calculation of zero-sequence current value, zero-sequence current measured value is greater than calculated value, as a criterion---the 5th criterion of this circuit generation single-phase earthing.
Five, adopt five criterion methods, system ensemble the electric system at this circuit and this circuit place is judged, five is condition altogether, and evidence, indispensable mutually, lacks criterion and means there is erroneous judgement possibility.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within being all included in protection scope of the present invention.
Claims (5)
1. the microcomputer complex protection selection method of a small current neutral grounding electric system, it is characterized in that: in this method, input signal is 4, wherein voltage signal is 3, Ua, the Ub, the Uc that by power system voltage mutual inductor (PT) secondary, are provided, one of current signal, by zero sequence current mutual inductor (zero sequence CT) secondary, provided, enter following determining step:
(1) first criterion: residual voltage criterion, to combine and protect the direct input that hardware does not have residual voltage, residual voltage is calculated through software by Ua, Ub, Uc input quantity, comprises effective value and phase place.Residual voltage setting valve is adjusted as U by < < handbook > > latest edition
0>=30V;
(2) Second Criterion: zero-sequence current effective value criterion, zero-sequence current adopts syllogic determining method, and this is that feature by small current neutral grounding system or isolated neutral system determines.Meet I0, the criterion that the system that can be used as has single-phase earthing to occur;
(3) the 3rd criterions: zero-sequence current and residual voltage frequency invariance, now the frequency of residual voltage and zero-sequence current can not directly be measured in fact, adopts sampling number determining method between peak value to be judged, and this is the unique distinction of this method;
(4) above three criterions are set up simultaneously, sentence " system earth " message and show; If only have the first criterion to set up, be likely that PT insurance is disconnected; If only have Second Criterion set up,, be likely that out-of-balance current or the harmonic current of system causes; If 1st, 2 criterions are set up simultaneously, this is also the traditional method of decision-making system ground connection, but thunder and lightning has the possibility that causes the 1st, 2 criterions simultaneously to be set up, also likely a phase PT broken string has harmonic current to exist simultaneously, only have when first, second, third criterion is set up simultaneously, just can judge " system earth ", otherwise system earth necessarily have above 3 presentations simultaneously;
(5) the 4th criterions: power direction determining method, both the electric current and the residual voltage that had flow through this circuit zero sequence current mutual inductor carry out phase place judgement, leading residual voltage 0～90 degree of equidirectional both zero-sequence currents, not this line-to-ground, otherwise, both zero-sequence current hysteresis residual voltage 0～90 degree, was this line-to-ground;
(6) the 5th criterions: zero-sequence current value method is judged,, a circuit, no matter be cable line or overhead transmission line, once circuit and load are determined, the single-phase capacitive earth current of this circuit is just determined in fact, this current value is to calculate or to come out, as the normally zero-sequence current value over the ground of single line, and when unbalanced earth fault capacitance current is normal operation 3 times of phase line capacitive earth current;
(7) fourth, fifth criterions are to determine the whether sufficient and necessary condition of ground connection of this circuit, and evidence, once i.e. this circuit generation singlephase earth fault must be that the first to the 5th criterion is set up simultaneously, indispensable mutually.
2. a kind of small current neutral grounding electric system microcomputer complex protection selection method according to claim 1, is characterized in that, the computing method of circuit unbalanced earth fault capacitance current comprise:
1. for load, be the circuit of synchronous motor, must calculate the single-phase capacitive earth current of synchronous motor;
2. other load is not considered single-phase capacitive earth current, and its value is very little, negligible;
3. for the building-out capacitor that is positioned at zero sequence current mutual inductor downstream, due to wye connection, neutral ground, with the ratings 3 times of calculating in ground of single-phase capacitance electric current.
3. a kind of small current neutral grounding electric system microcomputer complex protection selection method according to claim 2, is characterized in that, the calculation procedure of circuit unbalanced earth fault capacitance current,
1. the unbalanced earth fault capacitance current of cable line is calculated as follows:
6kv cable line
10kv cable line
The single-phase earthing electric capacity of cable line, electric current can also be estimated by following formula (this formula is applicable to each electric pressure)
I
c＝0.1U
rlA
With s in above formula---the nominal section mm2 of cable core
U
r---circuit rated line voltage kv
L---line length km
I
c---earthing capacitance current A
2. overhead transmission line unbalanced earth fault capacitance current is calculated as follows
Without aerial earth wire single loop I
c=2.7U
rl * 10
-3a
There is aerial earth wire single loop I
c=3.3U
rl * 10
-3a
The unbalanced earth fault capacitance current of overhead transmission line can also be estimated by following formula (this formula is applicable to each electric pressure)
The mean value unit of the every km unbalanced earth fault capacitance current of overhead transmission line and cable line: A/KM.
4. a kind of small current neutral grounding electric system microcomputer complex protection selection method according to claim 1, is characterized in that, the impact of residual voltage, zero-sequence current while effectively eliminating some special circumstances, comprising:
1. thunder and lightning: all can install lightning arrester in accordance with regulations in medium-pressure electricity supply system, system overvoltage is during higher than lightning arrester threshold values, lightning arrester can shorted to earth, now may occur that single-phase large electric current or single-phase voltage-to-ground are zero.That is: the situation that residual voltage and zero-sequence current all satisfy condition, at this moment frequency ratio meaning and necessity just appears suddenly out.
2. the single-phase-to-ground current impact of the large earthed system of adjacent lines and two-phase and three-phase shortcircuit current affects: medium voltage network itself is generally isolated neutral system or small current neutral grounding mini system.If circuit is parallel with large earthed system circuit, large earthed system, once occur earth fault, can induce certain electromotive force because line mutual-inductance acts on adjacent lines, therefore also likely induces zero-sequence current, now has two measures to filter it.The one,, residual voltage value >=30V; The 2nd, I03 time delay >=2 second of adjusting.Once because ground fault occurs large earthed system, can be at short notice cutly go out electrical network, can not continue again impact.
5. a kind of small current neutral grounding electric system microcomputer complex protection selection method according to claim 1; it is characterized in that; take three WV signal Ua, Ub, Uc in each high voltage power distributing cabinet is input signal; the zero sequence current mutual inductor signal I0 in machine of take is zero-sequence current input signal; take computer integrated protection unit as signals collecting, signal operation, logic judgement, demonstration and node output carrier, first input signal is gathered.Meet 1,2,3 criterion, i.e. U simultaneously
0>=30V, the program I that adjusts
03>=0.85I
0, I
0value is by manually calculating, by 0.85I
0i adjusts
03, same I
01>=1.15I
0also by manually calculating, manual entry is adjusted.
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Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104977499A (en) * | 2015-07-23 | 2015-10-14 | 中国电力科学研究院 | Small current grounding system single-phase grounding fault line selection method |
| CN105203909A (en) * | 2015-10-22 | 2015-12-30 | 宁波三星医疗电气股份有限公司 | Hardware criterion circuit for single-phase grounding protection line selection |
| CN108196167A (en) * | 2018-03-08 | 2018-06-22 | 云南电网有限责任公司电力科学研究院 | Low current fault wire selection system based on piezoelectric ceramics voltage acquisition |
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| CN109324260A (en) * | 2018-09-17 | 2019-02-12 | 国网新疆电力有限公司经济技术研究院 | Small current earthing wire-selecting method and device |
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| CN111103501A (en) * | 2018-10-09 | 2020-05-05 | 长沙理工大学 | Method and system for measuring ground insulation parameters of ungrounded neutral point power distribution network |
| CN111157835A (en) * | 2018-11-07 | 2020-05-15 | 国网电力科学研究院武汉南瑞有限责任公司 | Power grid single-phase earth fault judgment method |
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| CN112649694A (en) * | 2019-10-12 | 2021-04-13 | 南京南瑞继保电气有限公司 | Method for judging single-phase earth fault of small-current grounding system |
| CN112684288A (en) * | 2020-12-10 | 2021-04-20 | 国网陕西省电力公司西咸新区供电公司 | Method for realizing small-current single-phase grounding line selection by utilizing three-phase fault signal current |
| CN112684286A (en) * | 2020-12-10 | 2021-04-20 | 国网陕西省电力公司西咸新区供电公司 | Method for realizing small-current single-phase grounding line selection |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1397807A (en) * | 2002-08-16 | 2003-02-19 | 华中科技大学 | Method for positioning grounding failure region of feed line in low-current grounding system |
| CN101539607A (en) * | 2009-04-09 | 2009-09-23 | 北京市天利自动化设备研究所 | Method for grounding and selecting lines of low-current grounding system and device |
| CN101951010A (en) * | 2010-08-23 | 2011-01-19 | 南京弘毅电气自动化有限公司 | Ground protection method for small-current ground system |
| CN102608483A (en) * | 2012-02-22 | 2012-07-25 | 北京航空航天大学 | Direction diagnosing system of grounded fault of small current grounded distribution system |
| CN102788936A (en) * | 2012-09-03 | 2012-11-21 | 安徽理工大学 | Low current grounding fault circuit selection method |
| CN103474980A (en) * | 2013-09-02 | 2013-12-25 | 昆明理工大学 | Transient-power-direction-based single-phase grounding protection method for power distribution network |
-
2014
- 2014-04-24 CN CN201410167013.8A patent/CN104111403A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1397807A (en) * | 2002-08-16 | 2003-02-19 | 华中科技大学 | Method for positioning grounding failure region of feed line in low-current grounding system |
| CN101539607A (en) * | 2009-04-09 | 2009-09-23 | 北京市天利自动化设备研究所 | Method for grounding and selecting lines of low-current grounding system and device |
| CN101951010A (en) * | 2010-08-23 | 2011-01-19 | 南京弘毅电气自动化有限公司 | Ground protection method for small-current ground system |
| CN102608483A (en) * | 2012-02-22 | 2012-07-25 | 北京航空航天大学 | Direction diagnosing system of grounded fault of small current grounded distribution system |
| CN102788936A (en) * | 2012-09-03 | 2012-11-21 | 安徽理工大学 | Low current grounding fault circuit selection method |
| CN103474980A (en) * | 2013-09-02 | 2013-12-25 | 昆明理工大学 | Transient-power-direction-based single-phase grounding protection method for power distribution network |
Non-Patent Citations (3)
| Title |
|---|
| 王中荣: "《中性点不直接接地系统的电容电流》", 《天津电力》 * |
| 郝建成: "《配电网电容电流测量分析》", 《东北电力技术》 * |
| 陈立军: "《10kv配电网单相接地电容电流的工程计算法探讨》", 《继电器》 * |
Cited By (24)
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| CN105203909B (en) * | 2015-10-22 | 2018-04-17 | 宁波三星医疗电气股份有限公司 | A kind of hardware criterion circuit of one-phase ground protection route selection |
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