CN101915884B - Identification method of ground fault phases in three-phase ungrounded system and identification device thereof - Google Patents
Identification method of ground fault phases in three-phase ungrounded system and identification device thereof Download PDFInfo
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- CN101915884B CN101915884B CN2010102525059A CN201010252505A CN101915884B CN 101915884 B CN101915884 B CN 101915884B CN 2010102525059 A CN2010102525059 A CN 2010102525059A CN 201010252505 A CN201010252505 A CN 201010252505A CN 101915884 B CN101915884 B CN 101915884B
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Abstract
The invention relates to an identification method of ground fault phases in a three-phase ungrounded system and an identification device thereof. The identification method comprises the following steps: firstly selecting any line voltage in the three-phase ungrounded system as reference voltage, determining value domains of phase difference between theoretical zero-sequence voltage of the fault phases and the reference voltage when a ground fault occurs on each phase aiming at the reference voltage, and carrying out real-time online acquisition of the actually measured zero-sequence voltage; if the actually measured zero-sequence voltage is zero, judging no ground fault occurs; and if the actually measured zero-sequence voltage is not zero, calculating the phase difference between the actually measured zero-sequence voltage and the reference voltage, and judging which value domain the phase difference falls into so as to judge that the ground fault occurs on the phase corresponding to the value domain. The identification method can rapidly judge the ground fault occurs on A phase or B phase or C phase in the three-phase ungrounded system and directly point out the ground fault phases while finding out the fault, thus reducing troubleshooting time, being beneficial to eliminate faults timely, and guaranteeing safe operation of the system.
Description
Technical field
The present invention relates to adopt in electric system and the special-purpose distribution system in the method for operation of isolated neutral, to method and the identification device that earth fault is differentiated mutually takes place.
Background technology
Electric system and special-purpose distribution system have the method for operation of a lot of employing substation transformer isolated neutrals; When single-phase earthing (rigidity or arc grounding) fault takes place; Because line voltage still remains unchanged; So the user is worked on influence not quite,, thereby has improved the power supply reliability of system greatly so regulation allows the short time to operate with failure (being generally maximum two hours) in the electric power rules.
But when isolated neutral system generation singlephase earth fault (as shown in Figure 1, fault is the C phase mutually), the voltage-to-ground of non-fault phase can be elevated to line voltage or more than the line voltage by normal phase voltage; When single-phase arc grounding fault took place, intermittent superpotential reached as high as 3.5 times of normal phase voltage; Also have data to show, when single-phase arc grounding took place cable line, the superpotential of non-fault phase can reach 4～71 times, and equipment, circuit and electric rotating machine etc. have been caused serious threat.
In view of above reason; On-line real time monitoring bus insulation against ground resistance is found fault early, is fixed a breakdown, and is one of effective precautionary measures that ensure the isolated neutral system safe operation; And when finding fault, directly point out the earth fault phase; To reducing the investigation time, fix a breakdown rapidly, particularly necessary.
The existing at present real-time monitoring device that is used for the online resistance to earth of isolated neutral system, its electric principle is as shown in Figure 2, and wherein, u is for measuring the insulation against ground resistance R
SSignal source, its externally voltage signal of output can be direct current also can be low-frequency alternating; R is for isolating the repeating resistance of holding concurrently; R is the internal resistance of source of system under test (SUT); U0 is a measurement output signals.Can find out through circuit analysis: the size of U0 is by u, R, r, R
SThe separate common decision of value and earth fault, when the value of u, R, r was confirmed, the size of U0 depended on earth fault phase R
SValue and internal resistance of source value sum, consider the safety of metering circuit self in the practice and do not influence the operate as normal of system under test (SUT) that the value of isolating the repeating resistance R that holds concurrently must be big (generally will reach hundreds of kilo-ohm); And the internal resistance of source r of system under test (SUT) all very little under direct current and low frequency (generally have only several Europe even less than an Europe), so no matter which phase the reduction of insulation against ground resistance R s occurs in, all distinguish is come out on measurement output signals U0.That is to say that this technology can't identify the earth fault phase.
Shown in Figure 3 is another kind of insulation resistance TT&C system, and it only is applicable to the isolated neutral system of multiple branch circuit through microcomputerized control.Ultimate principle is on each branch road, to establish a zero sequence current mutual inductor LT, and when a certain branch road, when for example a certain phase line insulation against ground resistance R s on j road diminished, the zero sequence current mutual inductor LTj on this branch road just had signal output.Therefore, this technology can only detect and differentiate the branch road that earth fault takes place, but can not further find out the fault phase again.
Summary of the invention
The present invention seeks to provide for the deficiency that overcomes prior art a kind of can identify concrete which the discrimination method and the identification device of earth fault appear mutually.
For achieving the above object, the technical scheme that the present invention adopts is: identification method of ground fault phases in a kind of three-phase isolated neutral system, it comprises the steps:
(a), choose that arbitrary line voltage is as reference voltage in the three-phase isolated neutral system, this reference voltage is a vector voltage;
When (b), confirming that to this reference voltage each mutually earth fault takes place; The codomain of phase differential between the mutually theoretical residual voltage of each fault and this reference voltage, described theoretical residual voltage are defined as any one issuable residual voltage vector when mutually earth fault taking place;
(c), real-time online collection actual measurement residual voltage, if the actual measurement residual voltage is zero, then judges earth fault do not take place; If the actual measurement residual voltage is non-vanishing, then get into step (d);
(d), calculate the phase differential between actual measurement residual voltage and the said reference voltage, judge this phase differential falls into which codomain of step (b), can judge and the corresponding earth fault that takes place mutually of this codomain.
Further; In the step (b), in the step (b), described theoretical residual voltage confirms that with respect to the codomain of phase differential between the reference voltage method is: after reference voltage is selected; When setting certain and mutually earth fault taking place, its theoretical residual voltage is θ with respect to the phase angle change initial angle of reference voltage
i, then this corresponding codomain that breaks down mutually is θ
i～θ
i+ 120 °, described variation initial angle θ
iThe reverse vector of phase voltage that is defined as this phase is with respect to the angle of this reference voltage.Be that the A corresponding codomain scope that breaks down mutually is θ
A～θ
A+ 120 °; The B corresponding codomain scope that breaks down mutually is θ
B～θ
B+ 120 °; The C corresponding codomain that breaks down mutually is θ
C～θ
C+ 120 °.
In the step (d), phase differential obtained through the mistiming between the pulse of calculating each voltage over zero between actual measurement residual voltage and the reference voltage.
The present invention also provides earth fault phase identification device in a kind of three-phase isolated neutral system; It comprises the residual voltage Acquisition Circuit that is used to gather residual voltage, the reference voltage Acquisition Circuit that is used to gather any two phase top-stitching voltages, with described residual voltage Acquisition Circuit voltage output end and the voltage treatment circuit that is connected with reference voltage Acquisition Circuit voltage output end; Described voltage treatment circuit receives and calculates the phase differential between residual voltage Acquisition Circuit output voltage and the reference voltage Acquisition Circuit output voltage; And with preset fault mutually codomain compare, separate with the fault of judging actual generation earth fault correspondence.
According to such scheme in the enforcement further optimized; Described residual voltage Acquisition Circuit comprises the connection resistance that is electrically connected respectively mutually with each power supply, respectively is connected the sample resistance that resistance is in series with described; Described reference voltage Acquisition Circuit is the sampling transformer with two input links, described voltage treatment circuit comprise first pulse producer that is connected with the sampling transformer output terminal, with sample resistance be in parallel second pulse producer that is connected, and the processor that is electrically connected of the first pulse producer output terminal and the second pulse producer output terminal.
Described voltage treatment circuit also comprises being connected with the processor output terminal and is used to show concrete fault display screen mutually.
Because the utilization of technique scheme; The present invention compared with prior art has advantage: the present invention when residual voltage is non-vanishing, further carries out analytical calculation with detected residual voltage and selected datum line voltage through the real-time detecting system residual voltage; Draw the phase differential between actual measurement residual voltage and the reference voltage; Thereby can judge apace in the three-phase isolated neutral system specifically be A phase, B mutually or earth fault takes place C mutually, promptly when finding fault, can directly point out the earth fault phase, reduced the investigation time; Help discharging early fault, guaranteed the safe operation of system.
Description of drawings
Accompanying drawing 1 is for three-phase isolated neutral system wiring diagram and C phase ground connection synoptic diagram occurs;
Accompanying drawing 2 is that a kind of earth fault is differentiated schematic diagram in the prior art;
Accompanying drawing 3 is that another kind of earth fault is differentiated schematic diagram in the prior art;
Accompanying drawing 4 is that earth fault residual voltage acquisition principle figure takes place in the three-phase isolated neutral system;
The voltage vector graph of a relation of accompanying drawing 5 for utilizing discrimination method of the present invention to detect;
Accompanying drawing 6 is earth fault phase identification device of the present invention;
Wherein: wherein: 1, residual voltage Acquisition Circuit;
2, normal voltage collector;
3, voltage treatment circuit; 31, first pulse producer; 32, second pulse producer; 33, processor; 34, display screen;
Embodiment
Below in conjunction with accompanying drawing, specify particular content of the present invention for example:
A, B, the C three-phase of drawing with cable in the three-phase isolated neutral system have been shown among Fig. 1, when one mutually earth fault takes place, between this fault and ground, have formed a stake resistance R
SShown in figure for A ground connection is taken place mutually; We adopt respectively through drawing a residual voltage sample circuit from A, B, C three-phase, being specially that resistance R 1 is connected with A, resistance R 2 is connected with B, resistance R 3 is connected with C, and then sample resistance R0 is connected with resistance R 1, R2, R3 jointly; Like this, the voltage on the sample resistance R0 is residual voltage.When three-phase voltage balance and A, B, the insulation against ground of C three-phase are all good, stake resistance Rs=∞, residual voltage U0=0.When arbitrary one breaks down mutually, stake resistance Rs ≠ ∞, U0 ≠ 0.Under the certain situation of resistance R 1=R2=R3 and R0 value, the mould of U0 | U0| increases along with reducing of stake resistance Rs value, its phasing degree by stake resistance Rs and system over the ground the capacitor value of distributed capacitance Cs determine jointly.
So when the earth fault of generation is arranged; The vector correlation of each line voltage and residual voltage is as shown in Figure 5, and the residual voltage vector has an angle Δ θ with respect to each line voltage vector, when a selected certain line voltage; Corresponding different earth fault phases, Δ θ has clear and definite and different spans.
Above-mentioned the principle of the invention is introduced, will the method for discrimination of earth fault phase of the present invention be described below:
At first, choose that arbitrary line voltage is as reference voltage in the three-phase isolated neutral system, this reference voltage is a vector voltage, and the phase angle of supposing this reference voltage is θ
0
Then; When earth fault takes place in mutually to this reference voltage setting; The codomain of phase differential between the mutually theoretical residual voltage of each fault and this reference voltage, described theoretical residual voltage are defined as arbitrary issuable residual voltage vector when mutually earth fault taking place.When earth fault takes place in different voltages mutually; Size in conjunction with concrete system ground capacitance and stake resistance; The codomain of phase differential confirms that method is between the mutually theoretical residual voltage of fault and this reference voltage: after the reference voltage vector is selected; When certain mutually earth fault took place, its theoretical residual voltage was set at θ with respect to the phase angle change initial angle of reference voltage
i, then this corresponding codomain scope that breaks down mutually is θ
i～θ
i+ 120 °, above-mentioned variation initial angle θ
iBe defined as: with the reverse vector of this fault phase phase voltage vector angle with respect to reference voltage.Particularly, then the A corresponding codomain scope that breaks down mutually is θ
A～θ
A+ 120 °; The B corresponding codomain scope that breaks down mutually is θ
B～θ
B+ 120 °; The C corresponding codomain that breaks down mutually is θ
C～θ
C+ 120 °;
Confirm the codomain scope of good above-mentioned phase differential, get final product this three-phase isolated neutral system of on-line real time monitoring, the residual voltage of real-time acquisition system if the actual measurement residual voltage is zero, is then judged earth fault is not taken place; If the actual measurement residual voltage is non-vanishing, then can judges earth fault has taken place;
In case the actual measurement residual voltage is non-vanishing; Then further which earth fault being appeared at analyzes mutually; Concrete grammar is the phase differential that calculates between actual measurement residual voltage and the said reference voltage, and this account form can obtain through the mistiming of calculating between this actual measurement residual voltage zero crossing pulse and the pulse of reference voltage zero crossing.After obtaining both phase differential, judge this phase differential falls into which codomain of setting, falls into which codomain, then can confirm separate break down corresponding with this codomain.
According to above-mentioned discrimination method; The present invention also provides earth fault phase identification device in a kind of three-phase isolated neutral system; As shown in Figure 6; It comprises residual voltage Acquisition Circuit 1, reference voltage Acquisition Circuit 2, voltage treatment circuit 3, and wherein, described residual voltage Acquisition Circuit 1 can be connected the sample resistance R0 realization that resistance R 1, R2, R3 are in series by the connection resistance R 1 that is electrically connected respectively mutually with each voltage, R2, R3, with each.Reference voltage Acquisition Circuit 2 is a transformer, and it has two input links, can be directly from two alternate acquisition line voltages with as reference voltage.Voltage treatment circuit 3 comprise first pulse producer 31 that is connected with the sampling transformer output terminal, with sample resistance R0 be in parallel second pulse producer 32 that is connected, the processor 33 that is electrically connected with first pulse producer, 31 output terminals and second pulse producer, 32 output terminals and be used to show fault display screen 34 mutually; The transformer of reference voltage Acquisition Circuit 2 with the voltage of gathering after suitable conversion; Input to first pulse producer 31; Described first pulse producer 31 is gathered the pulse of reference voltage zero crossing and is inputed to processor 33; Second pulse producer 32 obtains residual voltage from sample resistance Rs; And the pulse of gathering its zero crossing inputs to processor 33; Processor 33 receives and calculates the residual voltage gathered and the phase differential between the reference voltage, and with preset fault mutually codomain compare, thereby judge and show the actual corresponding voltage phase of earth faults that takes place through display screen 34.
Adopt fault phase discrimination method of the present invention and identification device, can when finding earth fault, directly point out the earth fault phase, guarantee the rapid eliminating of fault, ensured the safe operation of three-phase isolated neutral system.
Claims (3)
1. identification method of ground fault phases in the three-phase isolated neutral system is characterized in that: it utilizes in the three-phase isolated neutral system earth fault phase identification device to differentiate,
In the described three-phase isolated neutral system earth fault phase identification device comprise the residual voltage Acquisition Circuit (1) that is used to gather residual voltage, the reference voltage Acquisition Circuit (2) that is used to gather any two-phase top-stitching voltage, with described residual voltage Acquisition Circuit (1) voltage output end and the voltage treatment circuit (3) that is connected with reference voltage Acquisition Circuit (2) voltage output end; Described voltage treatment circuit (3) receives and calculates the phase difference between residual voltage Acquisition Circuit (1) output voltage and reference voltage Acquisition Circuit (2) output voltage; And with preset fault mutually codomain compare; With the phase of judging that actual generation earth fault is corresponding
Described residual voltage Acquisition Circuit (1) comprises the connection resistance (R1 that is electrically connected respectively mutually with each voltage; R2; R3); With the described resistance (R1 that respectively is connected; R2; R3) sample resistance that is in series (R0); Described reference voltage Acquisition Circuit (2) is for having the sampling transformer of two input links; Described voltage treatment circuit (3) comprises first pulse producer (31) that is connected with the sampling transformer output terminal; Second pulse producer (32) that is in parallel and is connected with sample resistance (R0); The processor (33) that is electrically connected with first pulse producer (31) output terminal and second pulse producer (32) output terminal; Be connected with processor (33) output terminal and be used to show concrete fault display screen (34) mutually
This discrimination method comprises the steps:
(a), choose that arbitrary line voltage is as reference voltage in the three-phase isolated neutral system, this reference voltage is a vector voltage;
(b), to this reference voltage; Confirm when each mutually earth fault takes place the codomain of phase differential between the mutually theoretical residual voltage of this fault and this reference voltage, described theoretical residual voltage is defined as any one issuable residual voltage vector when mutually earth fault taking place;
(c), real-time online collection actual measurement residual voltage, if the actual measurement residual voltage is zero, then judges earth fault do not take place; If the actual measurement residual voltage is non-vanishing, then get into step (d);
(d), calculate the phase differential between actual measurement residual voltage and the said reference voltage, judge this phase differential falls into which codomain of step (b), can judge and the corresponding earth fault that takes place mutually of this codomain.
2. identification method of ground fault phases in the three-phase isolated neutral system according to claim 1; It is characterized in that: in the step (b); Described theoretical residual voltage confirms that with respect to the codomain of phase differential between the reference voltage method is: after reference voltage is selected; When setting certain and mutually earth fault taking place, its theoretical residual voltage is θ with respect to the phase angle change initial angle of reference voltage
i, then this corresponding codomain is θ
i～θ
i+ 120 °, described variation initial angle θ
iThe reverse vector of phase voltage that is defined as this earth fault phase is with respect to the angle of this reference voltage.
3. identification method of ground fault phases in the three-phase isolated neutral system according to claim 1 is characterized in that: in the step (d), phase differential can obtain through the mistiming between the pulse of calculating each voltage over zero between actual measurement residual voltage and the reference voltage.
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| CN101915884B true CN101915884B (en) | 2012-05-23 |
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| EP3524985A1 (en) * | 2018-02-09 | 2019-08-14 | Bender GmbH & Co. KG | Apparatus and method for insulation monitoring with detection of defective outer conductor in an unearthed 3-phase power supply system |
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