CN1209634C - Method for positioning grounding failure region of feed line in low-current grounding system - Google Patents

Abstract

The present invention discloses a method for positioning the grounding failure section of feed lines in a low-current grounding system, which has the steps 1. zero sequence voltage and zero sequence current of each power distribution switch point on feed lines are monitored; 2. if the zero sequence voltage is larger than the setting value, then the system is judged as failure; 3. the zero sequence current variation which flows through each switch is calculated before and after the failure, and the section zero sequence current which flows from each section switch of a section is found out; 4. the feed line failure state is judged according to the amplitude value and phase characteristics of each section zero sequence current which flows from the feed lines into the sections, and the failure sections are positioned. The zero sequence current and the zero sequence voltage of each section switch point on only one feed line are measured by the present invention, and the failure judgement and the section positioning of the single-phase grounding are realized. The method of the present invention is suitable for various small current grounding systems. The present invention adopts the principle that all the switches are mutually communicated, and thus, the present invention conforms to the development requirement from the power distribution automation to the distributed control.

Description

Small current neutral grounding system feeder line earth fault section localization method

Technical field

The present invention relates to distribution system fault section location isolation technology and relay protection of power system technology, specifically is exactly a kind of small current neutral grounding system feeder line earth fault section localization method.

Background technology

Though small current neutral grounding system generation singlephase earth fault does not form short-circuit loop, the possibility that causes serious secondary accident is arranged, must promptly find out fault section.Traditional automatic circuit, sectionaliser isolated fault section can't solve the fault isolation of single-phase earthing of small current earthing system.Existing protective relaying device also can only be discerned faulty line (being microcomputer single-phase grounding selecting device) from many outlets in power station.

Open, application number provided a kind of " earthing protection method for small current earthing system " for 0114452.9 application for a patent for invention on 09 06th, 2000, the steps include: the residual voltage of 1. monitoring system, the zero-sequence current of each feeder line, select each phase voltage of monitoring and each feeder line zero-sequence current; 2. residual voltage is greater than setting valve decision-making system fault then; 3. calculate fault each feeder line negative-sequence current variable quantity of front and back takes place; When 4. certain feeder line negative-sequence current variable quantity is greater than accurate working current, can judge this line fault according to negative-sequence current size, direction or energy function respectively.Above-mentioned patented claim and existing one-phase ground protection only are grounded the function of failure line selection; generally need to gather and compare the information about power of each outlet; the singlephase earth fault circuit could be determined, the demand for development that the feeder automation fault section is discerned isolation automatically can not be adapted to.

Summary of the invention

The object of the present invention is to provide a kind of small current neutral grounding system feeder line earth fault section localization method,, realize the quick identification and the isolation of fault section to overcome above-mentioned the deficiencies in the prior art.

A kind of small current neutral grounding system feeder line earth fault section localization method comprises the steps:

(1) goes out the residual voltage and the zero-sequence current at wiretap and each block switch place on feeder line of on-line monitoring;

When (2) residual voltage was greater than setting valve, the decision-making system fault constantly was that fault takes place constantly with the residual voltage sudden change;

(3) calculate the fault front and back and flow through wiretap and each block switch zero-sequence current variable quantity, and calculate each section zero-sequence current of inflow;

(4) maximal value of each section zero-sequence current amplitude of inflow is I on the note feeder line _0MAX, I _0MAXWith the ratio of the mean value that flows into other section zero-sequence current amplitudes on the feeder line be K _M, the longest section length of this feeder line and the ratio of other section length mean values are D _MIf K _M＞K _KD _M, judge singlephase earth fault point on this feeder line, the section that satisfies this condition is a fault section, K in the following formula _KBe safety factor, value is 3.

Above-mentioned steps (4) is: the maximal value that flows into each section zero-sequence current amplitude on the note feeder line is I _0MAX, flow into I _0MAXThe zero-sequence current of respective segments and residual voltage angle are φ; In isolated neutral system, if singlephase earth fault point is judged on this feeder line in sin φ＞0, the section that satisfies this condition is a fault section; In neutral point resistance grounded system and neutral by arc extinction coil grounding system, if singlephase earth fault point is judged on this feeder line in cos φ＜0, the section that satisfies this condition is a fault section.

The present invention only need measure the zero-sequence current and the residual voltage at each block switch place on the feeder line, can realize this feeder line singlephase earth fault is judged and the section location.The zero-sequence current that flows into fault section is about earth-fault current, and both directions are identical; The zero-sequence current that flows into non-fault section is very little, leading residual voltage 90 degree.Adopt the inventive method to carry out ground protection, the protection precision is only relevant with residue current of ground fault in electrical (ground connection steady-state current), so the inventive method is applicable to various small current neutral grounding systems.Simultaneously, this method adopts the principle of each switch mutual communication, has met the requirement of power distribution automation to distributed control development.

Description of drawings

Fig. 1 is the structural representation of distribution network system zero sequence equivalent network;

Fig. 2 is the structural representation of feeder line M upper curtate b single-phase earthing emulation (R=5 Ω).

Embodiment

The basis of this method is that each block switch all has the three-phase voltage current sensor on the feeder line, and the communication channel contact is arranged each other.Its total thinking is: 1) residual voltage and the zero-sequence current at each panel switches place on the monitoring feeder line; 2) residual voltage is greater than setting valve decision-making system fault then; 3) calculate the zero-sequence current variable quantity that each switch is flow through in the fault front and back, obtain the zero-sequence current that flows into this section by each block switch of section; 4) according to the amplitude, this feeder fault state of phase characteristic decidable and the fault location section that flow into each section zero-sequence current on the feeder line.

Little distribution network system with two outlets is an example, and two outlets are divided into three sections.Each block switch of record section flows into the zero-sequence current of this section for flowing into the section zero-sequence current.Single-phase earthing takes place, zero sequence equivalent network such as Fig. 1 in the e section somewhere c that unites that sets up departments mutually.Node 1,4 is the outlet isolating switch among the figure, and node 2,3,5,6 is the line sectionalizing switch; Z _NFor neutral ground element equiva lent impedance (for isolated neutral system Z _N=∞), R is the earth point transition resistance; Be the system zero sequence voltage, ${\stackrel{\·}{I}}_{0j}(j=1,2,\mathrm{3,4,5,6})$ For flowing through the zero-sequence current of each switch, ${\stackrel{\·}{I}}_{0\mathrm{ci}}(i=a,b,c,d,e,f)$ For flowing through the electric current of the single-phase ground capacitance of each section,

For flowing into the zero-sequence current of trouble spot.Flow into each section zero-sequence current ${\stackrel{\·}{I}}_{0i}(i=a,b,c,d,e,f)$ For:

${\stackrel{\·}{I}}_{0a}={\stackrel{\·}{I}}_{01}-{\stackrel{\·}{I}}_{02}-{\stackrel{\·}{I}}_{03}={\stackrel{\·}{I}}_{0\mathrm{ca}}$

${\stackrel{\·}{I}}_{0b}={\stackrel{\·}{I}}_{02}={\stackrel{\·}{I}}_{0\mathrm{cb}}$

${\stackrel{\·}{I}}_{0c}={\stackrel{\·}{I}}_{03}={\stackrel{\·}{I}}_{0\mathrm{cc}}$

${\stackrel{\·}{I}}_{0d}={\stackrel{\·}{I}}_{04}-{\stackrel{\·}{I}}_{05}={\stackrel{\·}{I}}_{0\mathrm{cd}}$

${\stackrel{\·}{I}}_{0e}={\stackrel{\·}{I}}_{05}-{\stackrel{\·}{I}}_{06}={\stackrel{\·}{I}}_{0\mathrm{ce}}-{\stackrel{\·}{I}}_{F0}$

${\stackrel{\·}{I}}_{0f}={\stackrel{\·}{I}}_{06}={\stackrel{\·}{I}}_{0\mathrm{cf}}$

Flow into the fault section zero-sequence current and be about earth-fault current, both directions are identical; It is very little to flow into non-fault section zero-sequence current, leading residual voltage 90 degree.Adopt said method to carry out ground protection, the protection precision is only relevant with residue current of ground fault in electrical, so said method is applicable to various small current neutral grounding systems.

Below 3 10kV systems that adopt different earthing modes are analyzed, each system description is as follows:

Each system neutral earth element equiva lent impedance is designated as Z _NAll outlets of system are all converted and are pole line, and wherein an overhead outlet M is divided into three section La=2km, Lb=3km, and Lc=1km then according to each section length of feeder line M, gets D _M=2.

(1) system 1 is isolated neutral mode (Z _N=∞), the overhead outlet length overall is 18km.

(2) system 2 is the neutral point high grounding, Z _N=R _N=2000 Ω, the overhead outlet length overall is 81km.

(3) system 3 is the neutral by arc extinction coil grounding mode, Z _N=6000+j345.4 Ω, the overhead outlet length overall is 506km.

Singlephase earth fault takes place in the section b to feeder line M in the system 1, and the situation emulation of earth point transition resistance R=5 Ω flows into each section zero-sequence current such as Fig. 2.Flow into fault section b zero-sequence current i among the figure _0bPerfect section zero-sequence current i with inflow _0a, i _0cThe amplitude obvious difference, phase place is opposite.

Singlephase earth fault in the system 1,2,3 is occurred in the b section of circuit M, the situation of R=5 Ω, the situation of R=2000 Ω; Singlephase earth fault occurs in the situation of All other routes and carries out emulation, and all simulation results gather as table 1.I in the table _0aFor flowing into the zero-sequence current of section a, I _0bFor flowing into the zero-sequence current of section b, I _0cFor flowing into the zero-sequence current of section c, φ _bFor flowing into the angle of section b zero-sequence current and residual voltage.As shown in Table 1, under the situation of earth point transition resistance R=5 Ω and R=2000 Ω, K _MAnd I _0MAXCorresponding φ _bSubtle change is only arranged, and utilization flows into amplitude, the phase characteristic of section zero-sequence current can accurately judge the singlephase earth fault section, and said method has very strong anti-ground connection transition resistance ability.

This method can realize the accurate location of small current neutral grounding system feeder line earth fault section, has overcome that traditional small current neutral grounding system ground protection need be gathered and the information about power of each outlet relatively, and only can be grounded the deficiency of failure line selection.

Table 1 single-phase earthing simulation result gathers

	System 1 (NUG)				System 2 (NRG)				System 3 (NEG)
													Earth fault	Feeder line M upper curtate b		Not on feeder line M		Feeder line M upper curtate b		Not on feeder line M		Feeder line M upper curtate b		Not on feeder line M
Earth point transition resistance R/ Ω	5	2000	5	2000	5	2000	5	2000	5	2000	5	2000
													3I 0a/A	0.0924	0.0905	0.0924	0.0904	0.0922	0.0420	0.0922	0.0420	0.0922	0.0690	0.0922	0.0690
3I 0b/A	0.6928	0.6788	0.1386	0.1357	5.4371	2.4751	0.1383	0.0630	1.4131	1.0575	0.1384	0.1033
													3I 0c/A	0.0462	0.0452	0.0462	0.0452	0.0461	0.0210	0.0461	0.0210	0.0461	0.0345	0.0461	0.0345
K M	9.7951	10.0044	2.0000	2.00015	78.6276	78.5746	2.0000	2.0000	20.4352	20.4348	2.0014	2.0019
													sinφ b	0.9990	1.0000	-1.0000	-1.0000
cosφ b					-0.7490	-0.7495	0.0000	0.0000	-0.9845	-0.9707	0.0000	0.0000
													The fault section location, (K kD M＝6)	K M＞6，I 0MAX＝I 0b sinφ bGreater than 0 section b fault		K M＜6 feeder line M are sound		K M＞6，I 0MAX＝I 0bcosφ bLess than 0 section b fault		K M＜6 feeder line M are sound		K M＞6，I 0MAX＝I 0bcosφ bLess than 0, section b fault		K M＜6 feeder line M are sound

Claims (2)

1. a small current neutral grounding system feeder line earth fault section localization method comprises the steps:

(1) goes out the residual voltage and the zero-sequence current at wiretap and each block switch place on feeder line of on-line monitoring;

When (2) residual voltage was greater than setting valve, the decision-making system fault constantly was that fault takes place constantly with the residual voltage sudden change;

(3) calculate the fault front and back and flow through wiretap and each block switch zero-sequence current variable quantity, and calculate each section zero-sequence current of inflow;

(4) maximal value of each section zero-sequence current amplitude of inflow is I on the note feeder line _0MAX, I _0MAXWith the ratio of the mean value that flows into other section zero-sequence current amplitudes on the feeder line be K _M, the longest section length of this feeder line and the ratio of other section length mean values are D _MIf K _M＞K _KD _M, judge singlephase earth fault point on this feeder line, the section that satisfies this condition is a fault section, K in the following formula _KBe safety factor, value is 3.

2. a kind of small current neutral grounding system feeder line earth fault section localization method according to claim 1, it is characterized in that: step (4) is: the maximal value that flows into each section zero-sequence current amplitude on the note feeder line is I _0MAX, flow into I _0MAXThe zero-sequence current of respective segments and residual voltage angle are φ; In isolated neutral system, if singlephase earth fault point is judged on this feeder line in sin φ＞0, the section that satisfies this condition is a fault section; In neutral point resistance grounded system and neutral by arc extinction coil grounding system, if singlephase earth fault point is judged on this feeder line in cos φ＜0, the section that satisfies this condition is a fault section.

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