CN105974173A - Current detection method of one-phase inversion grounding device - Google Patents
Current detection method of one-phase inversion grounding device Download PDFInfo
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- CN105974173A CN105974173A CN201510584530.XA CN201510584530A CN105974173A CN 105974173 A CN105974173 A CN 105974173A CN 201510584530 A CN201510584530 A CN 201510584530A CN 105974173 A CN105974173 A CN 105974173A
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Abstract
The present invention discloses a current detection method of a one-phase inversion grounding device. The main body of the device is a one-phase inverter which is connected between the neutral point of a power distribution network and the ground. In the condition of the normal operation of an electric system, two power frequency current with the same injection amplitude and different phase angles are injected into the neutral point of the power distribution network at different times through an inversion circuit, the neutral point voltage value when the current is injected twice is measured in real time, and the power distribution network grounding parameters (power distribution network equivalent impedance and equivalent electromotive force) are calculated, so that the amplitudes and the phases of the power distribution network fault arc extinguishing and the three-phase imbalance compensation current. The current is injected to the neutral point to inhibit the grounding fault arc and maintain the three-phase voltage balance. The current detection method of the one-phase inversion grounding device can be enforced when the system is normally operated so as to effectively avoid the influence of the transient process on the detection precision at the occurrence of the grounding fault; and moreover, the current detection method of the one-phase inversion grounding device only needs to inject current into the neutral point twice to realize the current detection, with high timeliness and simple realization.
Description
Technical field
The present invention relates to the electric current detecting method of a kind of single-phase inversion type grounding device, be particularly well-suited to the association area such as one-phase earthing failure in electric distribution network and three-phase imbalance Overvoltage suppressing.
Background technology
Power distribution network is in the terminal of power system, and structure is complicated and changeable, and contacts closely with user, is easily caused the generation of all kinds of fault.Singlephase earth fault is the fault occurred most frequently in power distribution network, can produce arc light when fault current is excessive, and arc burning will bring the significant damage such as fire, equipment damage；Three-phase imbalance voltage is the difficult problem being difficult to thoroughly solve of the medium-term and long-term existence of power distribution network; the existence of three-phase imbalance overvoltage can affect power distribution network single-phase load properly functioning, jeopardize line insulation; and bring difficulty to fault detect, even result in protection device misoperation, cause electric power accident.
For solving the problems referred to above of power distribution network, earth-fault current and uneven overvoltage are limited by domestic and international power distribution network commonly used change neutral grounding mode, experienced by isolated neutral through grounding through arc through development courses such as low resistance groundings.Isolated neutral system remains to operate with failure 1 ~ 2 hour after there is singlephase earth fault, and power supply reliability is high, but each insulation mutually need to be by phase voltageDesign, higher to insulating requirements again；Neutral by arc extinction coil grounding system can reduce earth-fault current effectively, but can only compensate the fault current of power frequency, and the access of arc suppression coil can causing trouble route selection difficulty；Through small resistance grounding system when there is earth fault, short circuit current is very big, and protective relaying device can excise faulty line in instant of failure action, but also reduce the power supply reliability of which simultaneously.
For meeting the service requirement of the various state of power distribution network comprehensively, make up the defect of different earthing mode, the advantage comprehensively utilizing various earthing mode, and select earthing mode flexibly according to the running status of electrical network, it is proposed that a kind of novel Grounding Mode of Distribution Network.Single-phase inversion device is i.e. used to be connected between neutral point and the earth, replace traditional neutral non-effective grounding mode, controlled electric current is injected to power network neutral point by inverter, regulate and control amplitude and the phase place of this electric current, thus reach the residual voltage of control system, it is achieved suppression fault and the purpose of uneven overvoltage.
Summary of the invention
The singlephase earth fault often occurred for power distribution network and three-phase imbalance overvoltage, the present invention proposes the electric current detecting method of a kind of single-phase inversion type grounding device, by twice when power system is properly functioning to neutral point injection current, be calculated the parameter over the ground of system, by this parameter injection current amplitude in the case of different faults and phase place.The present invention solves the technical scheme of above-mentioned technical problem and comprises the following steps:
1) in the case of power distribution network is properly functioning, it is connected to the new type grounding device twice between neutral point and the earth to neutral point injection current, is respectively I i1、 I i2, record and record corresponding neutral point voltage U N1、 U N2；
2) utilize I i1、 I i2、 U N1、 U N2Calculate distribution line equivalence earth impedanceZ eqAnd power distribution network three phase mains equivalent potential E eq；
3) when power distribution network generation singlephase earth fault, according to step 2) gainedZ eqAnd E eqCalculate corresponding injection current amplitude and phase place, and be injected into power network neutral point, the generation of suppression fault electric arc；
4) when power distribution network produces three-phase imbalance overvoltage, according to step 2) gainedZ eqAnd E eqCalculate corresponding injection current amplitude and phase place, and be injected into power network neutral point, maintain three-phase equilibrium.
The invention has the beneficial effects as follows:
1) when power distribution network is properly functioning, twice injection current calculates line-to-ground parameter, it is not necessary to reinjecting Current calculation after fault occurs, when can eliminate fault, the impact on measurement result of the transient state parameter, significantly improves current detection accuracy；
2) the method only needs to inject two primary currents to neutral point and can realize fault crowbar currents and the detection of three-phase imbalance compensation electric current, has high real-time and realizes easy advantage.
The present invention is further illustrated below in conjunction with the accompanying drawings.
Accompanying drawing explanation
Fig. 1 is a kind of single-phase inversion type grounding device topological diagram.
Fig. 2 is single-phase inversion type earthed system equivalent circuit diagram.
Fig. 3 is twice injected value of current of three-phase imbalance and power distribution network parameter value of calculation.
Fig. 4 is three-phase imbalance Overvoltage suppressing dynamic waveform figure.
Fig. 5 is twice injected value of current of singlephase earth fault and power distribution network parameter value of calculation.
Fig. 6 is that singlephase earth fault voltage suppresses dynamic waveform figure.
Detailed description of the invention
Fig. 1 is the topological diagram of a kind of single-phase inversion type grounding device,、、It is the three phase mains of distribution system,、、、、、Represent three-phase resistance to earth and electric capacity respectively,R dRepresent earth resistance when there is singlephase earth fault,U NFor system neutral voltage.This single-phase inversion type earthed system is through an active inverter ground connection, and inverter is by DC sourceU DCPower supply, produces, by PWM inversion, the injection current that amplitude is controlled with phase place I iInjecting neutral point, T represents injection transformer.
Fig. 2 is new type grounding device and power distribution network equivalent circuit diagram.Owing to active-inverter is fully controllable, therefore can be equivalent to a controlled current source, and power distribution network three phase mains is equivalent to electromotive force,(wherein,,)；Three-phase earth impedance is equivalent to impedance,。
On the basis of A, B phases line voltage, by twice of injection current source to power network neutral point injection current I i1、 I i2, wherein, and.It is implanted sequentially I i1、 I i2And record corresponding neutral point voltage respectively U N1、 U N2After, superposition theorem know that neutral point voltage is represented by:
(1)
Two formulas are subtracted each other can obtain power distribution network equivalence earth impedance, equivalent potential。
Meanwhile, the relation understood between injection current and neutral point voltage and power distribution network equivalent potential, impedance according to Fig. 2 is:
(2)
Separately below with regard to three-phase imbalance situation and the value of singlephase earth fault analysis injection current:
( 1 )Power distribution network generation three-phase imbalance:
Described new type grounding device is by clamping down on neutral point voltage to zero to power distribution network injection current, it is achieved the suppression of three-phase imbalance, now controls target, bringing injection current knowable to formula (2) into is:
(3)
Neutral point voltage can be suppressed to zero the injection of electric current shown in formula (3) neutral point, it is achieved that the suppression of three-phase imbalance.
Fig. 3 show when power distribution network exists three-phase imbalance twice neutral point voltage value corresponding to injection current, and corresponding power distribution network parameter, injection current reference value.Fig. 4 show three-phase imbalance Overvoltage suppressing dynamic waveform figure.
( 2 )Power distribution network generation singlephase earth fault:
If distribution system equivalent source is after fault, equiva lent impedance is.Inverter is by forcing faulted phase voltage to be zero to neutral point injection current, and to realize the purpose of fault extinguishing arc, now controlling target is(setting fault to occur in C phase), and,, bringing injection current knowable to formula (2) into is:
(4)
The injection of electric current shown in formula (4) neutral point can be realized the opposite number that neutral point voltage is faulted phase voltage, and simultaneous faults phase voltage is suppressed to zero, it is achieved that singlephase earth fault extinguishing arc.
Fig. 5 show system properly functioning time neutral point voltage value corresponding to twice injection current, and corresponding power distribution network parameter, injection current reference value.Fig. 6 show singlephase earth fault voltage suppression dynamic waveform figure.
Claims (2)
1. an electric current detecting method for single-phase inversion type grounding device, comprises the steps:
1) in the case of power distribution network is properly functioning, to neutral point timesharing, the single-phase inversion type grounding device being connected between neutral point with the earth injects that amplitude is equal, phase angle two power currents not etc., is designated as respectively I i1、 I i2, record and record corresponding neutral point voltage U N1、 U N2；
2) utilize I i1、 I i2、 U N1、 U N2Calculate distribution line equivalence earth impedanceZ eqAnd power distribution network three phase mains equivalent potential E eq；
3) when power distribution network generation singlephase earth fault, according to step 2) gainedZ eqAnd E eqCalculate corresponding injection current amplitude and phase place, and be injected into power network neutral point, the generation of suppression fault electric arc；
When power distribution network produces three-phase imbalance overvoltage, according to step 2) gainedZ eqAnd E eqCalculate corresponding injection current amplitude and phase place, and be injected into power network neutral point, maintain three-phase equilibrium.
The electric current detecting method of a kind of single-phase inversion type grounding device the most according to claim 1, described step 3) in injection current amplitude with phase calculation method be: if there is singlephase earth fault, injection current is(set fault to occur in C phase,E cFor faulted phase voltage)；If generation three-phase imbalance, then injection current is。
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| CN107332227A (en) * | 2017-09-05 | 2017-11-07 | 国网湖南省电力公司 | The singlephase earth fault voltage arc extinguishing method and system of isolated neutral system |
| CN112350293A (en) * | 2020-10-30 | 2021-02-09 | 西安工程大学 | Active arc extinction method for single-phase earth fault of power distribution network with secondary injection current |
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| CN112350293A (en) * | 2020-10-30 | 2021-02-09 | 西安工程大学 | Active arc extinction method for single-phase earth fault of power distribution network with secondary injection current |
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