中壓電網(wǎng)中性點(diǎn)接地方式及消除單相接地故障技術(shù)
摘  要
中壓電網(wǎng)中性點(diǎn)接地方式的選擇是一個(gè)綜合性的技術(shù)問題，它涉及到供電可靠性、人身及設(shè)備安全、絕緣、過電壓、繼電保護(hù)、通信（電磁環(huán)境）、接地裝置等各個(gè)方面。它具有理論研究與實(shí)際經(jīng)驗(yàn)密切結(jié)合的特點(diǎn)，是電力系統(tǒng)實(shí)現(xiàn)安全與經(jīng)濟(jì)運(yùn)行的技術(shù)基礎(chǔ)和系統(tǒng)工程。
論文介紹了我國6~66kV中壓電網(wǎng)中性點(diǎn)主要的接地方式及其各自的優(yōu)缺點(diǎn)，論述了一種應(yīng)用于中性點(diǎn)不接地系統(tǒng)消除單相接地故障及選線、消除鐵磁性諧振的新方法以及實(shí)現(xiàn)這種方法的智能綜合保護(hù)裝置。
論文的主要?jiǎng)?chuàng)新之處：1）采用新的電壓消弧法：用電抗器鉗制故障相的電壓，有效地防止接地電弧的重燃，消除弧光接地過電壓，保證供電可靠性；2）歸納不接地系統(tǒng)單相接地故障的規(guī)律，確立其接地電阻與相電壓、中性點(diǎn)位移電壓關(guān)系的數(shù)學(xué)模型，提出判斷故障相的依據(jù)、創(chuàng)造性地設(shè)計(jì)了相應(yīng)的判斷和保護(hù)程序，不論接地電阻值如何變化，都能夠準(zhǔn)確對高阻接地故障提供有效的保護(hù)，將以往難以察覺故障消滅在萌芽狀態(tài)。3）采用新的消諧方法：當(dāng)諧振發(fā)生時(shí)，直接在一相母線與地之間并接電抗器，使回路遠(yuǎn)離諧振點(diǎn)，并限制諧振過電壓。
論文所述的保護(hù)裝置通過了國家相關(guān)檢驗(yàn)機(jī)構(gòu)的全面、嚴(yán)格的電氣性能和環(huán)境型式試驗(yàn)、電磁兼容試驗(yàn)、10kV電網(wǎng)的現(xiàn)場接地故障試驗(yàn)、并在多個(gè)變電站10kV電網(wǎng)系統(tǒng)掛網(wǎng)運(yùn)行等，證實(shí)了這種新方法及裝置的可靠性與實(shí)用性。該裝置已獲國家級新產(chǎn)品鑒定, 鑒定結(jié)論為：“裝置的設(shè)計(jì)思路新穎，保護(hù)性能良好，其消弧、消諧的方法、對高阻接地故障的判別和保護(hù)處于國內(nèi)領(lǐng)先水平”。

關(guān)鍵詞：中性點(diǎn)接地方式、弧光接地 高阻接地 選線 鐵磁諧振 智能綜合保護(hù)裝置

 
Neutral-poin grounding mode in medium voltage network
and Technique to eliminate single-phase ground fault
Abstract
It is comprehensive technological issue for medium voltage network to choose its neutral-point grounding mode. This issue will involve reliability of power supply; the safety of person and equipment; insulation; overvoltage; protective relay; communication (mangnetic environment); earthing device and so on. It has characteristic of combining theory with practice, meanwhile it is also technological basis and system engineering for power system to operate economically and safely.
This paper introduces main neutral-point grounding modes in 6-66KV medium voltage network in our country and its advantages and disadvantages in some cases. And present a kind of new method of eliminating single-phase ground fault; ferro-resonance and checking up line troubled in neutral-point non-ground system. At same time ,in this paper also describe a comprehensive intelligence device that implements these techniques.
The major innovation in this paper includes:1) developing a new voltage method that eliminates electric arc by a reactor that limit overvoltage between faulty phase and the ground. This reactor can effectually prevent electric arc from reigniting; and eliminate arc-grounding overvoltage in order to accomplish reliability of power supply.2) find a single-phase faulty rules in non-grounded system and a mathematical mode that relate to relationship between earthing resistance and phase voltage, neutral-point displacement voltage. As a result, we got a criterion that can judge faulty phase, according to this criterion we design protective program that can effectually protect network from high-resistance ground faulty(HRGF)no matter how resistance change, as a result we can destroy the single-phase faulty while it just right form..3)using a new method to suppress resonance: when resonance just happened, directly adding a reactor in parallel between a phase bus and ground in order to apart circuit from resonance point so as to limit resonance overvoltage.
Our protective device as described above has passed a series of tests conducted by relevant government inspection agencies. These tests include an extensive and rigorous electrical performance test; an environmental type test; an electromagnetic compatibility test; and operation in many 10KV substations. This new technique and protective device are shown to be reliable and practical. A national-level new product appraisal was completed and a certification was granted. It is stated in the certificate that:” the design of this device is new style, protective performance good, the method for eliminating electric are, resonance; criterion and protection identifying HRGF are first class in China.”
Key words: neutral-point grounding mode, electric arc grounding, high-resistance grounding, checking up line faulty, Ferro-resonance, comprehensive intelligence protective device
①發(fā)生單相接地故障時(shí)（例如A相），故障相的對地電容C0被短接；①When the single-phase earth trouble occurs (such as A phase), earth capacitance C0of fault phase is shorted;
②非故障線路3I01的大小等于本線路的接地電容電流，其電容性無功功率的方向?yàn)橛赡妇�流向線路；
②The size of non-fault line 3I01 is equal to the earth capacitive current of this line. The direction of inactive power of the capacitive character is to flow to the line from the bus bar;
③故障線路3I02的大小等于所有非故障線路的3I01之和，也就是所有非故障線路的接地電容電流之和；其電容性無功功率的方向?yàn)橛删�路流向母線；
③The size of non-fault line 3I02 is equal to the sum of all non-fault line 3I01, that is to say the sum of the earth capacitive current of all non-fault line; the direction of inactive power of the capacitive character is to flow to the line from the bus bar;
④若零序電流互感器的極性是以變電所母線流向線路為正方向，那么非故障線路的零序電流超前零序電壓90°，故障線路的零序電流滯后零序電壓90°，故障線路的零序電流與非故障線路的零序電流在相位上相差180°。
④If the polarity of the mutual inductor of zero sequence current calculates the positive direction by the flowing direction of the bus bar of transformer station, the advanced zero sequence voltage of zero sequence of non-fault line is about 90°. The delayed zero sequence current of zero sequence of fault line is about 90°. The phase difference of the phrase of the zero sequence of fault line and zero sequence of non-fault line is about 180°.
ZN05A裝置采用了零序電流群體比幅比相加零序電壓相位的選線原理：當(dāng)3U0大于整定值時(shí)，啟動對所有饋線的零序電流幅值排序，取幅值大的前2~4個(gè)電流比相，若某電流與其它電流方向相反，并滯后零序電壓相位90º，則判定該線路接地，否則為母線接地。

ZN05A device adopts the line selection principle of summing up the amplitude and phase-comparison of zero sequence current colony rate and phrase of zero sequence voltages: When 3U0 is greater than the setting value, start the amplitude arrangement of the zero sequence current of all the feeders, and take the first 2-4 greater amplitude of current phase-comparison. If the current is conversed with the other current direction and the phrase of the delayed zero sequence voltage is about 90º, it may be determined that it shall be line grounding, otherwise shall be bus bar grounding.
此種方法為多重判據(jù)（又稱3C方案），多重判據(jù)即為用二種及以上原理為判據(jù)，增加可靠性和抗干擾性能力，減少受系統(tǒng)運(yùn)行方式、長短線、接地電阻的影響。排序避免了設(shè)定值，具有設(shè)定值隨動的“水漲船高”的優(yōu)點(diǎn)。它既可以避免單一判據(jù)帶來的局限性，也可以相對縮短選線的時(shí)間，是較理想的方式。
This method shall be multiple criteria decision (is also called 3C scheme). The multiple criteria decision applies two types and above principle as the criteria. Increases the dependability and interference resistance, and reduces the effect of operation mode, line size and earth resistance of system. The arrangement process avoids the setting value, which has the advantage of “the rising tide raising all boats”. It can avoid the limitation that the single criterion brought, and may shorten the time to select the line relatively as well. It is a better ideal mode.
裝置具有高速采樣、高速數(shù)據(jù)處理和快速傅氏變換及諧波分析能力，在故障發(fā)生40ms內(nèi)，就完成了32路零序電流選線，此時(shí)采集的故障電流信息未受到任何保護(hù)動作的影響，保證了以零序電流基波為基礎(chǔ)的比幅比相選線原理應(yīng)用的準(zhǔn)確性，當(dāng)饋線二次側(cè)零序電流不小于20mA時(shí)，裝置就能準(zhǔn)確采樣和選線。
The device is featured by high speed sampling, high-speed data processing, high speed fourier transform and harmonic analysis. In 40ms when fault occurred, this device is capable to finish 32 zero sequence lines selection. At this moment, the collected information of fault current does not effect by any protective movement, therefore, guarantee the accuracy of the application of line selection which based on the amplitude and phase-comparison of the fundamental wave of zero sequence current. When the side zero sequence current of the No.2 feeder is smaller than 20mA（the primary side shall be 0.8A）, the device may sample and select the line accurately.

4消諧新方法及原理
4 New method and principle of harmonic elimination
4.1常見的消除鐵磁諧振產(chǎn)品的原理及缺陷
4.1Principle and defect of common products of ferromagnetic resonance elimination
鐵磁諧振是由于系統(tǒng)中的電壓互感器、變壓器、消弧線圈等非線性電感受激而產(chǎn)生磁路飽和，引發(fā)持續(xù)的振蕩。在正常運(yùn)行條件下，電路的初始感抗大于容抗（ωL 0 > 1/ωC），電路不具備諧振條件，當(dāng)電路受到擾動（如，電網(wǎng)的突然合閘、單相接地故障的發(fā)生和消除）使電感兩端電壓升高而導(dǎo)致鐵芯飽和時(shí)，感抗隨之減小，當(dāng)ωL = 1/ωC時(shí)即滿足諧振條件，在電感、電容兩端形成過電壓，并產(chǎn)生勵(lì)磁涌流，形成持久不衰減的分頻、工頻或倍頻諧振，其破壞力很大，輕則燒壞元件，重則燒毀設(shè)備。
Ferromagnetic resonance is the consistent oscillation due to the saturation of the stimulated nonlinear inductance such as potential transformer, transformer and arc-suppression coil, etc. Under the normal operating condition, the initial induction reactance of the line shall be greater than the capacitive reactance （ωL 0 > 1/ωC）. The line does not possess the resonance condition. When the lines are disturbed (for instance, the occurrence and elimination of sudden gate closing and the fault of single-phase grounding) and made the voltage of both ends of the inductance rise and cause the saturation of iron core, and the induction reactance is reduced as well. When ωL = 1/ωC meet resonance condition, both ends of inductance and electric capacity shall form the excess voltage, produce the magnetizing inrush current, and form the lasting frequency division, work frequency or frequency doubling, which shall burn out component or destroy the equipment when it is serious.
 
圖9 串聯(lián)諧振電路
Fig. 9 Series resonant circuit
對于電網(wǎng)中性點(diǎn)不接地系統(tǒng)，鐵磁諧振的產(chǎn)生回路可簡化為最簡單的串聯(lián)諧振電路（見圖9）。電阻在回路中起限流作用，消耗諧振能量，減小諧振范圍。通常國內(nèi)的一次或二次消諧產(chǎn)品，就是在電壓互感器的一次中性點(diǎn)或二次開口三角處加電阻，以電阻的耗能作用，阻尼和消除諧振。但是所有這些消諧產(chǎn)品均有消諧死區(qū)，消諧效果不理想，并且它們只能針對加裝消諧電阻的電壓互感器產(chǎn)生的諧振起作用，對系統(tǒng)母線上其它設(shè)備或操作等產(chǎn)生的諧振無能為力，以至系統(tǒng)中因諧振引起的事故時(shí)有發(fā)生。上述電阻消諧存在的缺陷原因可從能量的觀點(diǎn)來闡明，見圖10。
As to the ungrounding system of neutral-point of electric network, the circuit produced by the ferromagnetic resonance can be simplified for the simplest series connection resonance circuit (see Fig. 9). The resistance plays a current limiting role in the circuit. It may consume resonance energy and reduce the resonance range. Usually the domestic primary or secondary harmonic elimination product is to add increase the resistance at the primary neutral-points or secondary triangular area of the open vent of potential transformer. Apply the dissipation energy of the resistance to damp and eliminate the resonance. But all these harmonic elimination products all have the dead space of harmonic elimination. It is unsatisfactory to achieve the idea result of harmonic elimination. And they can only operate to the resonance produced by the potential transformer with additional installed harmonic elimination resistance. It is powerless to operate to the resonance of the bus bar of system or other operating equipments. Therefore, the accident caused by resonance is occurred occasionally in the system. The reason of the defect of above-mentioned harmonic elimination resistance may be illustrated from the view of energy. See Fig. 10.
圖中縱坐標(biāo)W代表能量，橫坐標(biāo)A代表諧振頻率的幅值，WR為阻尼電阻的損耗能量，WL為電源通過非線性電感所引進(jìn)回路的能量。在圖10（a）中只要有稍微輕微的“擾動”就可以產(chǎn)生一個(gè)微小的振蕩幅值，由于引進(jìn)能量大于損耗能量，幅值就可以自發(fā)的持續(xù)上升，直至穩(wěn)定點(diǎn)A0為止，這就是自激現(xiàn)象，亦稱為“軟激發(fā)”。在圖10（b）中則不同，在0~A1的幅值范圍內(nèi)，WL不足以抵償損耗WR，故起始的振蕩就會衰減消失；若初始幅值超過A1，振蕩就可以一直發(fā)展到幅值A(chǔ)2，建立其穩(wěn)定的諧振，這是外激而產(chǎn)生的，又稱硬激發(fā)。由此可見，電阻的耗能范圍是一定的，它們的消諧范圍也就是有限的。而系統(tǒng)的運(yùn)行狀態(tài)是變化的，電容、電感參數(shù)也隨之改變，固定的電阻根本不能滿足這些變化的需要，也就是說特定阻值的電阻只對特定范圍的諧振有作用，對于超出這個(gè)范圍諧振無能為力。所以電阻消諧效果不理想，存在消諧死區(qū)。
Ordinate W represents the energy; abscissa a represents the amplitude of resonance frequency; WR is the loss energy of the damping resistance; WL is the power switch-in from the circuit of the non-linear inductance introduces. In Fig. 10 (a) the slight “Disturb” may produce small amplitude of vibration. Because the inducing energy is greater than the losing energy, the amplitude raises spontaneously until reach a steady point A0. This is self-excitation phenomena, and is also called “Soft exciting”. It is quite different in Fig. 10 (b), within the amplitude range of 0-A1, WL is not sufficient to compensate the loss of WR, so the initial vibration shall decay and disappear; if the initial amplitude exceeds A1, the oscillation may reach to amplitude A2, and sets up its steady resonance. This is defied and produced from outside and also called hard exciting. Therefore, dissipation energy of resistance range is constant. And their harmony range is limited. The systematic operation state is changed constantly, and the electric capacity and inductance parameter is changed as well. The regular resistance can't meet demands of these changes at all. That is to say, the resistance of the resistance with specific value is to only operate to the specific range of resonance. As fro the resonance beyond this range shall be powerless. Therefore, the result of harmonic elimination of resistance is unsatisfactory and has the dead space of harmonic elimination.

 
軟激發(fā)soft exciting     硬激發(fā)：hard exciting
圖10 激發(fā)鐵磁諧振的能量曲線
Fig. 10 Energy curves of excited ferromagnetic resonance
4.2 ZN05A裝置消諧方法及原理
4.2 Method and principle of harmonic elimination of ZN05A device
從以上的分析可知，當(dāng)諧振發(fā)生時(shí)ωL = 1/ωC，此時(shí)只要改變電感L的參數(shù)，使ωL ≠ 1/ωC，就能破壞諧振條件，消除鐵磁諧振。
The analysis of the above shows, when the resonance occurred, ωL = 1/ωC. At this moment, changing the parameter of inductance L and make ωL ≠ 1/ωC may destroy the resonance condition and eliminate the ferromagnetic resonance.
 
裝置消諧原理：harmonic elimination principle
等效電路：equivalent circuit
圖11 消諧新方法及原理
Fig. 11 New method and principle of harmonic elimination

ZN05A裝置消諧方法及原理如圖11所示，當(dāng)系統(tǒng)中發(fā)生諧振時(shí)，閉合開關(guān)K’,將電感L’并聯(lián)到產(chǎn)生磁路飽和的那相母線和地之間(見圖11(a))，這就改變回路電感參數(shù)，使ωL ≠ 1/ωC破壞了諧振條件，使系統(tǒng)自然脫諧(見圖11(b))；同時(shí)旁路了產(chǎn)生了飽和的那相電感，提供了泄放勵(lì)磁涌流的通路，并且鉗制諧振過電壓小于線電壓，保護(hù)系統(tǒng)的元件和設(shè)備免遭諧振的摧毀。該消諧方法能滿足系統(tǒng)各種運(yùn)行方式的變化，對系統(tǒng)任何條件下產(chǎn)生的諧振都能夠消諧。
The method and principle of harmonic elimination of ZN05A device see Fig. 11. When the resonance is occurred in the system, close switch K’and connect the inductance L’the circuit between saturated bus bar and ground (see Fig. 11 (a )). And it may change the inductance parameter of the circuit, and make ωL ≠ 1/ωC so as to destroy resonance condition. Therefore, the system is in a state of out-of-resonance naturally (see Fig. 11 (b)); at the same time the bypass produced the saturated inductance, which may offer the discharged passage of magnetizing inrush current, and the limited resonance voltage is smaller than the voltage of circuit. So as to protect systematic component and equipment exempt from the destroying of resonance. This method of harmonic elimination may meet the changes of different operation mode of system. And may eliminate the resonance produced to the system under all conditions.
通過三相10kV實(shí)驗(yàn)室的試驗(yàn)完全證實(shí)了上述論點(diǎn)：LXQ消諧器是目前國內(nèi)廣泛使用的一次消諧產(chǎn)品之一，它加在電壓互感器（PT）一次中性點(diǎn)與地之間如圖11（a）虛框所示，圖12是使用LXQ消諧器，發(fā)生諧振時(shí)的錄波圖。
The test of three phases 10kV laboratory have totally proved above-mentioned arguments: LXQ harmonic elimination device is one of the primary harmonic elimination product used extensively in our country at present. It is installed between the location neutral-point and ground of potential transformer (PT). See Fig. 11 (a). Fig. 12 is the wave-recorded diagram when the resonance occurred for the application of the harmonic elimination device of LXQ.

 
圖12消諧器LXQ無法消除的諧振
Fig. 12 The resonance that can't be eliminated by the LXQ device

波形表明：a時(shí)刻，單相接地發(fā)生；c時(shí)刻，接地消失，激發(fā)諧振；c~d時(shí)段，諧振持續(xù)穩(wěn)定存在，即該消諧器對此種諧振無能為力。
The wave form shows: at a moment, single-phase grounding may occur; at c moment, the grounding may disappear and excite the resonance; at c-d moment, the resonance exists continually and steadily. It means that this harmonic elimination device is powerless for the resonance of this type.
 
圖13 ZN05A裝置可靠消除LXQ無法消除的諧振
The Fig. 13 The resonance that can be eliminated by the ZN05A device while can't be eliminated by the LXQ

圖13是在與圖5-4完全相同的條件下，使用消諧新方法的錄波圖，b~d時(shí)段：諧振發(fā)生區(qū)；d~e時(shí)段：裝置消諧保護(hù)動作區(qū)；e時(shí)刻后：消諧完畢，系統(tǒng)恢復(fù)正常。該圖證明：ZN05A裝置能夠消除前述LXQ消諧器不能消除的諧振，對系統(tǒng)提供無死區(qū)的消諧保護(hù)。
Fig. 13 is the application of new method for wave-recorded diagram of harmonic elimination under the same condition of Fig.5-4. At b-d moment: the area of the resonance occurs; at d-e period: operating area of the harmonic elimination protection of the device; at e moment: After the harmonic elimination process is finished, the system returns to normal. This picture proves: ZN05A device can eliminate resonance that can be eliminated by the ZN05A device while can't be eliminated by the above-mentioned LXQ, and provide harmonic elimination protection without dead area.
5.ZN05A智能型綜合保護(hù)裝置性能驗(yàn)證
5. Performance verification of ZN05A comprehensive intelligence grounding protection device
不接地電網(wǎng)系統(tǒng)發(fā)生單相接地是一個(gè)復(fù)雜的動態(tài)過渡過程，國內(nèi)外的歷史實(shí)踐經(jīng)驗(yàn)證實(shí)：計(jì)算機(jī)仿真不能替代現(xiàn)場試驗(yàn)，只利用低電壓在產(chǎn)品的二次端進(jìn)行單相接地的模擬試驗(yàn)，完全沒有意義，不僅不利于提高產(chǎn)品制造質(zhì)量，而且對電網(wǎng)的安全運(yùn)行也十分有害。為了真實(shí)的、客觀的驗(yàn)證智能綜合保護(hù)裝置的技術(shù)、安全性能等各項(xiàng)指標(biāo)，廣州寧志電力科技公司建立了三相10kV系統(tǒng)接地故障試驗(yàn)室，配備了具有國際領(lǐng)先水平的多通道示波記錄儀，對裝置進(jìn)行了大量反復(fù)的弧光接地、高阻接地、金屬接地、鐵磁諧振等試驗(yàn)；在國家繼電器檢測中心對控制器通過了型式試驗(yàn)和電磁兼容試驗(yàn)；在廣東省電力行業(yè)高低壓電工產(chǎn)品檢測中心對裝置整體性能進(jìn)行了型式試驗(yàn)；在南方電網(wǎng)佛山供電局110kV祿堂站用一條10kV饋線ZN05A裝置進(jìn)行了現(xiàn)場（弧光、高阻、金屬）接地試驗(yàn)；在廣東佛山、清遠(yuǎn)、肇慶等地區(qū)電網(wǎng)ZN05A裝置掛網(wǎng)運(yùn)行多年。通過這一系列的型式試驗(yàn)、現(xiàn)場試驗(yàn)和掛網(wǎng)運(yùn)行我們?nèi)〉昧嗽S多珍貴的、客觀的、全面的單相接地故障數(shù)據(jù)和運(yùn)行經(jīng)驗(yàn)，并對這些數(shù)據(jù)和經(jīng)驗(yàn)加以理論上的分析總結(jié)，設(shè)計(jì)出了符合實(shí)際的，高效安全的智能型接地綜合保護(hù)裝置。該裝置通過了中國機(jī)械聯(lián)合會和南方電網(wǎng)公司的新產(chǎn)品鑒定，鑒定結(jié)論為：裝置的設(shè)計(jì)思路新穎、保護(hù)性能良好，其消弧、消蝎的方法，對高阻接地故障判斷和保護(hù)水平處于國內(nèi)領(lǐng)先水平。
The single-phase connection of the ungrounding network system is a complicated dynamic transition process. The historical experience and practice both at home and abroad proves: the emulation of the computer can't substitute the field test. It only utilizes low-voltage to carry on the single-phase grounding simulation test on the secondary terminal of products, which is totally meanness. It is not only unfavorable to improving the quality of products, but also very harmful to the safety operation of network system. For achieving the indexes such as technology of the intellectual comprehensive protector of verification and security performance, etc. in fairness and objectiveness, the Guangzhou Ningzhi Electric Science and Technology Co., Ltd has established three-phase 10kV systematic ground trouble testing laboratory. These labs equips with the multi-channel electrographic recording device, which takes a lot of repeated trial such as electric arc grounding, high-resistance grounding, metal grounding and ferromagnetic resonance, etc.; the National Relay Testing Center has carried out the modeling test and electromagnetic compatibility test for the controller. The high voltage and low voltage electric products testing center of Power Industry of Guangdong Province has carried out the modeling test and electromagnetic compatibility test for the complete unit; The Lutang station of Southern Network Foshan Power Supply Bureau has carried out the field grounding test of the 10kV feeder (electric arc, high and metal grounding) ; verifies the protective performance of 110kV ZN05A device; the ZN05A device has applied in the network of Foshan, Qingyuan and Zhaoqing of Guangdong ,etc. for many years. We has obtained a lot of precious, objective and overall fault data and operating experience of single-phase grounding through a series modeling test, field test and operation in network. We also analysis and summarize these data and experience, therefore, designed the practical, high-efficient and safe comprehensive protecting device of intelligent grounding. This device is approved by Mechanical Federation and Southern Network Corporation of China。 The conclusion is: The device has a novel design and good protective performance. The method of arc suppressing, arc extinguishing, judgment of the fault condition of high-resistance grounding and protective competence takes a leading state in our country.
6.結(jié)束語
6. Conclusion
通過對電網(wǎng)中性點(diǎn)各種接地方式的綜合比較，在科學(xué)研究和大量反復(fù)的嚴(yán)謹(jǐn)試驗(yàn)的基礎(chǔ)上，廣州寧志電力科技公司獨(dú)創(chuàng)性地取得了對高阻接地故障保護(hù)動作的判據(jù)，使ZN05A智能型接地綜合保護(hù)裝置能夠捕捉微弱的故障信息，對饋線斷線、絕緣老化等高阻故障提供準(zhǔn)確的保護(hù)；同時(shí)驗(yàn)證了在故障相母線上投電抗器接地的保護(hù)方式是安全可靠的，它既保留了中性點(diǎn)不接地方式的優(yōu)點(diǎn)：接地電流小，供電可靠性高，又彌補(bǔ)了不接地方式的單相接地電弧易重燃，內(nèi)部過電壓倍數(shù)高等缺點(diǎn)。當(dāng)諧振發(fā)生時(shí)，直接在一相母線與地之間并接電抗器，能夠使系統(tǒng)自然脫離諧振，并限制諧振過電壓。在選線方面采用多重判據(jù)的選線原理和高速DSP能夠保證小電流接地選線的高準(zhǔn)確率�？傊�本論文論述的接地綜合保護(hù)方法和裝置比中性點(diǎn)直接接地，小電阻接地的大電流接地方式利用變電站的接地網(wǎng)更為安全，其消弧性能、以及對弧光過電壓和諧振過電壓的限制比消弧線圈更為有效，并且結(jié)構(gòu)簡單可靠，占地面積小，綜合成本低，是一種值得推廣應(yīng)用的接地保護(hù)方法和裝置。
Through the comprehensive comparing of the various grounding method of neutral-point of network, on the basis of scientific research and a large number of repeated rigorous tests, the Guangzhou Ningzhi Electric Science and Technology Co., Ltd. has obtained the criterion of the protecting movement of the fault of the high-resistance grounding originally, which enable ZN05A comprehensive intelligence grounding protection device of intelligent grounding may catch the faint fault information and provide the accurate protection for the high-resistance fault of broken feeder and aged circuit, etc. At the same time, it may verify that the protecting method of applying the reactor grounding on the fault bus bar is safety and relied. It kept the advantage of the ungrounding neutral-point type : the ground current is small, reliability of power supply is high, and made up the defect of easy restriking of the arc of single-phase grounding and high multiple of internal over-voltage of ungrounding device. When the resonance occurred, connecting the reactor between a phase bus bar and ground directly can isolate the system from the resonance naturally, and limit the over-voltage of resonance as well. The multiple criterions of circuit selection and high speed DSP in circuit selection principle can guarantee high rate of accuracy of circuit selection of small current. In general, this thesis illustrate the comprehensive protective method of ground and direct ground device of neutral-point and large current grounding of low resistance grounding which use the grounding network of transformer substation is safer. The arc performance, the restriction of over-voltage of arc and resonance of over-voltage is more effective than arc coil. The unit has a feature of simple construction, reliable operation, small floor coverage and low comprehensive cost, which is worthy of promotion and application.

 武漢翻譯公司

2012.10.26