CN105244853A - Substation DC power supply system with grounding inspection line selection checking mechanism - Google Patents
Substation DC power supply system with grounding inspection line selection checking mechanism Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
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- Y04S10/20—Systems supporting electrical power generation, transmission or distribution using protection elements, arrangements or systems
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Abstract
The invention provides a substation DC power supply system with a grounding inspection line selection checking mechanism, relating to a DC power supply which supplies power to the relay protection and automatic device and the telecontrol communication device of a substation and the protection of the system. The invention especially relates to the substation DC power supply system with the grounding inspection line selection checking mechanism. The system comprises an online monitoring automatic inspection control module and a group of inspection function modules. The inspection function modules comprise a DC bus detection module, a balanced bridge detection module, an unbalanced bridge detection module, a fault branch determination module and a line selection checking module. According to the state quantities of current voltage before and after a fault and the calculation amount of a grounding resistor and the electrical association among the three members, the fault feature recognition is carried out, an automatic inspection mode based on logic event driving is employed, a line selection checking function is integrated into the substation DC power supply system with the grounding inspection line selection checking mechanism, an unbalanced bridge mode is called through logic judgment to identify zero drift and fault branches, and the wrong selection or missed selection of a DC grounding inspection device is quickly identified.
Description
Technical field
The present invention relates to the DC power system and protection thereof of powering for the relaying protection of transformer station and automatics, telecontrol communication device, particularly relate to a kind of transforming plant DC power-supply system possessing earth fault automatic inspection function.
Background technology
DC power system is one of three large concealed works in transformer station; DC power supply is as the important component part of electric power system; for some important conventional loads, relaying protection and automatics, telecontrol communication device provide uninterruption power source, and provide emergency lighting power supply.DC power system generation one point earth, can not produce short circuit current, and system can continue to run.But; earth point must be searched in time and eliminate earth fault as early as possible; otherwise when there is another one point earth; just likely cause signalling, relaying protection and automatics, the misoperation of circuit breaker or miss operation; likely cause DC power supply short circuit, cause fuse blows, or fast independent power source switch disconnects; make equipment lose operating power, cause electric power system catastrophe failure and even accident.Therefore, do not allow DC power system long-play under Grounding on one point, on-line monitoring must be carried out to DC power system, realize rapid failure diagnosis and state estimation, search rapidly and get rid of earth fault, stopping the electric power system fault caused because of DC power system ground connection.DC power system is carried out to the fault line selection method of on-line monitoring, be mainly divided into alternating current method and Using Direct Current Bridge Method.Alternating current method is also referred to as Low frequency signal injection method, and the ac current signal that alternating current method utilizes AC signal and instrument transformer to measure calculates branch insulation resistance value, can not locate negative or positive electrode ground connection; In addition, Low frequency signal injection method can be falsely dropped because system distributed capacitance is excessive, and branch road can be caused during looped network mode to there is harmonic circulating current, is mainly used in portable grounding resistance tester at present.Chinese invention patent " the DC power system earth-fault detecting method of high anti-jamming capacity " (patent of invention number: ZL201310063104.2 Authorization Notice No.: CN103091606B) discloses a kind of detection method adopting AC signal injection method to monitor the earth fault of DC power system, comprise the following steps: step one, at set intervals, between DC power system bus and the earth, injected frequency is lower than the low-frequency ac electric current signal of power frequency, step 2, the fault branch determined is measured and obtains current signal, utilize harmonic extraction unit, and adopt windowed interpolation method to obtain the signal of each frequency component in current signal, step 3, the signal of each frequency component of the low-frequency ac electric current signal that comparison step one is injected and the current signal that step 2 obtains, determine the place that the low-frequency ac signal respective frequencies component signal injected disappears, this place is fault point.
Using Direct Current Bridge Method does not affect by distributed capacitance, and detection sensitivity is higher, is extensively adopted by microcomputer insulation tester.Chinese invention patent application " a kind of DC power system insulated monitoring method and equipment thereof " (application for a patent for invention number: 201310063104.2 publication numbers: CN103018614A) discloses a kind of DC power system insulated monitoring method and equipment thereof, for solve the DC power system existed in prior art monitoring in the process of Branch-circuit check greatly consuming time, thus the problem of fault branch can not be detected in time.The DC power system insulated monitoring method of the embodiment of the present invention comprises: when determining that bus breaks down, and determines the pole to be detected of the branch road be connected with the bus broken down; Wherein, the insulating resistance value of the bus be connected with the pole to be detected of branch road is not more than first threshold; The pole to be detected of branch road is detected.The embodiment of the present invention is when bus breaks down, the pole to be detected of the branch road be connected by the bus determined with break down, and detect to determine fault branch to the pole to be detected of this branch road, avoid each when busbar fault, all need all to patrol and examine the positive pole of each branch road and negative pole, thus substantially reduce the time of detection failure branch road.
But technique scheme does not all relate to the route selection that transforming plant DC ground connection patrols and examines and checks, lack the check to multiple branch circuit insulation decline information, cannot exclusive PCR information, may falsely drop during differentiation or leak choosing.
Summary of the invention
The object of this invention is to provide and a kind ofly possess the transforming plant DC power-supply system that ground connection patrols and examines route selection Checking Mechanism, make full use of the advantage of balanced bridge pattern and unbalanced bridge mode computation earth resistance, according to the quantity of state of the forward and backward current/voltage of fault and the amount of calculation of earth resistance, and the electrical link of three, carry out fault signature identification, identify drift branch road and ground connection branch road, reduction to absurdity is adopted to check earth resistance computational process, overcoming while earth fault falsely drops, leaks choosing, improve the seek rate of fault branch.
The present invention solves the problems of the technologies described above adopted technical scheme:
A kind of possess the transforming plant DC power-supply system that ground connection patrols and examines route selection Checking Mechanism, for providing uninterrupted power supply for the important conventional load of transformer station, relaying protection and automatics, telecontrol communication device, described transforming plant DC power-supply system comprises positive bus-bar and negative busbar, and connects some direct current branch of conventional load, relaying protection and automatics, telecontrol communication device and devices for emergency illumination; It is characterized in that:
Described transforming plant DC power-supply system also comprises one group of direct-current bridge element for system on-line monitoring, and described direct-current bridge element comprises the balance bridge resistance that the identical standard resistor of two resistances is formed; The test resistor bridge that the standard resistor that two resistances are identical is formed; Two control the relay diverter switch of testing resistor bridge on-state; And the on-Line Monitor Device for patrolling and examining the insulation against ground state of transforming plant DC power-supply system;
The voltage detecting input of described on-Line Monitor Device, be connected to positive bus-bar and the negative busbar of transforming plant DC power-supply system, the branch road leakage current test input of described on-Line Monitor Device, be connected to the DC leakage flow sensor of each direct current branch, the leakage current of each branch road is sampled;
Described on-Line Monitor Device comprises on-line monitoring automatic detecting control module and one group of inspection function module; Described inspection function module comprises DC bus detection module, balanced bridge detection module, unbalanced bridge detection module, and module is checked in fault branch determination module and route selection;
Described automatic detecting control module, by controlling the operation of each inspection function module, performs the event driven automatic detecting pattern of logic-based;
The event driven automatic detecting pattern of described logic-based comprises the following steps:
S100: adopt unbalanced bridge mode detection to calculate busbar grounding resistance;
S200: adopt balanced bridge pattern to carry out grounding and patrol and examine;
S220: judge whether leakage current changes, if leakage current is unchanged, judges that this branch road has drift fault-free; Otherwise order performs step S240;
S240: judge leakage current whether monotone variation, if leakage current is not monotone variation, starts unbalanced bridge pattern; Otherwise order performs step S260;
S260: fault after-current deducts PRE-FAULT CURRENT, then calculates earth resistance, judges whether to meet branch trouble criterion, if meet branch trouble criterion, judges that this branch road is as fault branch; Otherwise, start unbalanced bridge pattern.
Of the present invention possess the one preferably technical scheme that ground connection patrols and examines the transforming plant DC power-supply system of route selection Checking Mechanism, it is characterized in that described route selection is checked module and also comprised reduction to absurdity check submodule, described wrong method is checked submodule and is connected to DC bus detection module, patrol and examine the busbar grounding resistance of trying to achieve in route selection process according to DC earthing, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong.
The better technical scheme of one of the route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined, it is characterized in that described wrong method is checked submodule and is also connected to fault branch determination module, the positive and negative bus resistance to earth of each branch road of trying to achieve is patrolled and examined in route selection process according to DC earthing, calculate negative busbar and positive bus-bar all-in resistance over the ground, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong.
The invention has the beneficial effects as follows:
The route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined, according to the quantity of state of the forward and backward current/voltage of fault and the amount of calculation of earth resistance, and the electrical link of three, carry out fault signature identification, adopt the event driven automatic detecting pattern of logic-based, effectively can take into account the rapidity of balanced bridge and the fault-tolerance of unbalanced bridge, improve seek rate and fault tolerance level, realize quick diagnosis and fix a breakdown, both improve the operating efficiency of engineering site, again reduce the risk of blindly drawing road to bring.
The route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined practical, only route selection need be checked function i ntegration patrols and examines in the transforming plant DC power-supply system of route selection Checking Mechanism to possessing ground connection, identification drift and fault branch is come by Logic judgment dynamic call unbalanced bridge pattern, the automatic detecting pattern of unbalanced bridge pattern is called relative to existing timing, falsely dropping or leaking choosing of DC earthing inspection device can be identified fast, under the prerequisite not increasing hardware cost, improve the performance of inspection device.
Accompanying drawing explanation
Fig. 1 is the unbalanced bridge mode detection schematic diagram of busbar grounding resistance;
Fig. 2 is the bus insulation resistance measuring circuit figure of K1 closure state;
Fig. 3 is the bus insulation resistance measuring circuit figure of K2 closure state;
Fig. 4 is DC detection method branch road Cleaning Principle figure;
Fig. 5 is the single spur track ground connection equivalent circuit diagram based on balanced bridge pattern;
Fig. 6 is the single spur track ground connection equivalent circuit diagram based on unbalanced bridge pattern;
Fig. 7 is the control flow chart of the event driven automatic detecting pattern of logic-based;
Fig. 8 is the equivalent circuit diagram of multiple branch circuit ground connection;
Fig. 9 is the structural representation of transforming plant DC power-supply system insulation against ground on-Line Monitor Device.
Embodiment
In order to technique scheme of the present invention can be understood better, describe in detail further below in conjunction with drawings and Examples.
Of the present invention possess the transforming plant DC power-supply system that ground connection patrols and examines route selection Checking Mechanism, for providing uninterrupted power supply for the important conventional load of transformer station, relaying protection and automatics, telecontrol communication device, described transforming plant DC power-supply system comprises positive bus-bar+KM and negative busbar-KM, and connects some direct current branch of conventional load, relaying protection and automatics, telecontrol communication device and devices for emergency illumination; As shown in Figure 1, described transforming plant DC power-supply system also comprises one group of direct-current bridge element for system on-line monitoring, and described direct-current bridge element comprises balance bridge resistance Rb1, Rb2 that the identical standard resistor of two resistances is formed; Test resistor bridge RL1, RL2 that the standard resistor that two resistances are identical is formed; Two control the relay diverter switch K1, the K2 that test resistor bridge on-state; And the on-Line Monitor Device 1 for patrolling and examining the insulation against ground state of transforming plant DC power-supply system, i.e. inspection device.As shown in Figure 4, the voltage detecting input of described on-Line Monitor Device 1, be connected to positive bus-bar+KM and the negative busbar-KM of transforming plant DC power-supply system, the branch road leakage current test input of described on-Line Monitor Device 1, be connected to DC leakage flow sensor I1, the I2 (being called for short direct current transducer or instrument transformer) of each direct current branch, the leakage current of each branch road is sampled.
The structure of the on-Line Monitor Device 1 of described transforming plant DC power-supply system as shown in Figure 9, comprises on-line monitoring automatic detecting control module 10 and one group of inspection function module; Described inspection function module comprises DC bus detection module 11, balanced bridge detection module 12, unbalanced bridge detection module 13, and module 15 is checked in fault branch determination module 14 and route selection;
Described on-line monitoring automatic detecting control module 10 is connected to described each inspection function module, by controlling the operation of each inspection function module, performs the event driven automatic detecting pattern of logic-based;
Described DC bus detection module 11 adopts unbalanced bridge pattern, by detection computations positive and negative DC bus insulation against ground resistance, carries out on-line monitoring to the earth fault of positive bus-bar or negative busbar;
Described balanced bridge detection module 12 adopts balanced bridge pattern, by detection computations branch insulation resistance, searches DC ground fault branch road;
Described unbalanced bridge detection module 13 adopts unbalanced bridge pattern, and change positive and negative DC bus voltage to earth and the total leakage current of branch road by switching test resistor bridge, each branch insulation resistance of detection computations, searches DC ground fault branch road;
Described fault branch determination module 14, for the insulation resistance testing result of more each branch road, selects the fault branch determining earth fault occurs;
Module 15 is checked in described route selection, carries out fault signature identification, avoid falsely dropping or leaking choosing of fault branch for the correlation logic according to the voltage before and after fault, electric current and resistance.
Busbar grounding resistance detection principle adopts bridge method, and its principle as shown in Figure 1.Wherein U
p, U
nfor positive bus-bar and negative busbar voltage; R
b1, R
b2for balance bridge resistance, they are standard resistors that resistance is identical, are separately fixed at DC bus two ends; R
l1, R
l2for test resistor bridge, they are standard resistors that resistance is identical, by relay switching on DC bus; The maximum detectability choosing power and the electricity leakage sensor will considering bus bar resistance of balance bridge resistance and test resistor bridge numerical value.R
x, R
yfor grounding resistance to be measured; In figure, geodetic point voltage is zero potential, meets formula:
U
n/R
b1+U
p/R
b2+U
n/R
L1+U
p/R
L2+U
n/R
x+U
p/R
y＝0；
By diverter switch K1, the turning on and off of K2 during measurement, thus calculate DC bus insulation against ground resistance according to measuring Un and Up obtained.
When K1 closes, equivalent electric circuit as shown in Figure 2.Can obtain according to Fig. 2:
U
n1/R
b1+U
p1/R
b2+U
n1/R
L1+U
n1/R
x+U
p1/R
y＝0(1)
When K2 closes, equivalent electric circuit as shown in Figure 3.From circuit formulation:
U
n2/R
b1+U
p2/R
b2+U
p2/R
L2+U
n2/R
x+U
p2/R
y＝0(2)
Combined by formula 1,2 and obtain Rx and Ry
R
x＝(U
n1*U
p2-U
n2*U
p1)/(A*U
p2-B*U
p1)(3)
R
y＝(U
n2*U
p1-U
n1*U
p2)/(A*U
n2-B*U
n1)(4)
Wherein: A=-(U
n1/ R
b1+ U
p1/ R
b2+ U
n1/ R
l1), B=-(U
n2/ R
b1+ U
p2/ R
b2+ U
p2/ R
l2).
From above formula, affect R
xand R
yfactor be measuring voltage U
n1, U
n2, U
p1, U
p2with fixed resistance R
b1, R
b2, R
l1, R
l2.As long as so consider that measuring voltage is on the impact of earth resistance.Because direct voltage value is comparatively large, less absolute value measured deviation can not cause larger relative quantity change, and it is higher that it measures confidence level opposite branches.
Using Direct Current Bridge Method utilizes bus positive pole+KM voltage to earth, bus negative pole-KM voltage to earth and branch road DC leakage stream calculation branch road both positive and negative polarity insulation against ground grounding resistance, then carries out route selection in conjunction with branch insulation warning setting value.
Direct current branch Cleaning Principle as shown in Figure 4, the wherein corresponding 1# branch road of I1, I2 and the total leakage current of 2# branch road.
Bridge balance measurement method:
During DC balance electric bridge mode computation branch insulation resistance, first judge the direction of the total leakage current of branch road, location branch road negative or positive electrode insulation reduces, and then calculates grounding resistance with positive bus-bar voltage to earth or negative busbar voltage to earth.Composition graphs 1 and Fig. 4 can draw single spur track ground connection based on balanced bridge pattern equivalent electric circuit as shown in Figure 5, wherein I
0for the total leakage current of branch road, direction shown in figure is reference direction.Positive and negative busbar resistance to earth value can be tried to achieve according to Fig. 5:
I
0be negative: positive bus-bar resistance to earth value is infinity,
Negative busbar resistance to earth value R
n=U
n/ I
0(5),
I
0for just: positive bus-bar resistance to earth value R
p=U
p/ I
0(6),
Negative busbar resistance to earth value is infinitely great.
Unbalanced bridge mensuration:
During direct current unbalanced bridge mode computation branch insulation resistance, the total leakage current measurement of same use positive bus-bar voltage to earth, negative busbar voltage to earth, branch road direct current calculates, but needs to change positive bus-bar voltage to earth, negative busbar voltage to earth and the total leakage current of branch road by switching test resistor bridge.
Closed K2 (drops into R
l2) time, branch road equivalent electric circuit as shown in Fig. 6 (a), now U
p, U
n, I
0value U respectively
p1, U
n1, I
1.Closed K1 (drops into R
l1) time, branch road equivalent electric circuit as shown in Fig. 6 (b), now U
p, U
n, I
0value U respectively
p2, U
n2, I
2.Outflow of bus current node A is positive direction, R
yand R
xbe respectively positive bus-bar insulation against ground resistance value and the negative busbar insulation against ground resistance value of certain branch road.
Can obtain according to Fig. 6 (a):
I
1-U
n1/R
x-U
p1/R
y＝0(7)
Can obtain according to Fig. 6 (b):
I
2-U
n2/R
x-U
p2/R
y＝0(8)
Association type (7) and formula (8) solve:
R
x＝(U
p1U
n2-U
p2U
n1)/(U
p1I
2-U
p2I
1)(9)
R
y＝(U
p2U
n1-U
p1U
n2)/(U
n1I
2-U
n2I
1)(10)
If R
yfor infinity, namely the insulation against ground of negative busbar one pole reduces, by (7) and (8) simplified formula formula:
R
x＝(U
n2-U
n1)/(I
2-I
1)(11)
If R
xfor infinity, namely the insulation against ground of positive bus-bar one pole reduces, by (7) and (8) simplified formula formula:
R
y＝(U
p2-U
p1)/(I
2-I
1)(12)
When certain pole ground connection, an other pole can be reported by mistake according to formula 11 and 12 and also there is identical earth resistance.
DC leakage flow sensor (instrument transformer) is contactless sensing, and rely on magnetic induction loop induction test, measuring object signal is small, easily by extraneous interference (as geomagnetic noise, instrument transformer is placed different, and null offset is also different); DC leakage flow sensor magnetic coil remanent magnetism; DC leakage current sensor detection circuit as amplifier etc. drift (temperature drift, time drift etc.) be direct current, after long-play, make current sensor there is drift problem, so calculate branch insulation grounding resistance according to formula 9 and 10, easily produce wrong report branch road.The state analyzed route selection wrong report by the following examples or fail to report, describes the route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined in detail:
(1) DC leakage current sensor fluctating is on the impact calculating grounding resistance.If Fig. 4 is when actual 220V system, do not measure U under switching test resistor bridge
p, U
nbe respectively 176V ,-44V, it is as follows that balancing method calculates grounding resistance:
1# branch road drift I
10=2mA; R
y1=176/2=88K Ω
1# branch road drift I
10=-2mA; R
x1=-44/ (-2)=22K Ω
2# branch road drift I
20=-2mA, namely actual measurement is-6.4mA, R
x2=6.875K Ω
Unbalanced bridge pattern eliminates drift impact by difference component.
(2) the magnetic coil remanent magnetism in DC leakage flow sensor, signal disturbing, sample circuit instability occurs measuring current-jump.Such as certain power station is run down certain branch road DC leakage flow sensor all the year round and is detected the value saltus step that actual DC leakage current has 0.5mA, and branch insulation resistance does not also reach alarming value simultaneously.Be decided to be 220V system (branch insulation is reported to the police as 50K Ω) for Fig. 4 to be analyzed as follows:
The negative busbar insulation against ground of 1# branch road is reduced to 60K, now U
p, U
nbe respectively 180V ,-40V, I
1may be-0.667mA ,-1.167mA; Namely negative busbar insulation against ground resistance value corresponds to 60K Ω and 34K Ω, and 2# branch road negative busbar has a 10K Ω resistance over the ground, directly reports to the police, and the insulation simultaneously may taking 1# branch road out of reduces.
Identical condition, use unbalanced bridge to calculate, falsely drop due to the sampled value saltus step of 1# branch road DC leakage flow sensor, multiselect goes out 1# branch road.
By above two point analysis, the drift of DC leakage current sensor sample can be solved by unbalanced bridge pattern, but for common DC leakage current sensor sample saltus step, even unbalanced bridge pattern also cannot solve.In addition, balanced bridge pattern can't detect the situation that positive and negative busbar insulating resistance declines simultaneously, namely there is operating dead zone problem.
The signature analysis of fault branch:
DC bus earth resistance calculates precision higher than branch road, and its priority is the highest.
When carrying out route selection after calculating ground fault, not only consider the absolute value of earth resistance, also will consider the relative variation of the quantity of states such as current/voltage before and after fault---electric current and voltage change direction and change size meet true ground connection.Namely according to the consecutive variations of voltage swing and leakage current size, analyze resistance and voltage, the correlation logic of electric current checks.Derived by circuit, following feature can be drawn:
(1) when certain branch road exists drift electric current or sample rate current saltus step, namely before fault, drift electric current is leakage current, before and after fault, leakage current is constant, its earth resistance and the linear change of voltage, earth resistance may be caused to diminish and meet earth resistance threshold value because voltage reduces, but should to get rid of this branch road be fault branch.
(2), there is less leakage current in the branch road that insulation is lower, during other groundings, voltage reduces, but corresponding branch current also reduces, and can not falsely drop.
(3) when not having the branch road earth fault of drift, leakage current increases, and voltage to earth reduces, and earth resistance is along with voltage acceleration change.
(4) when certain branch road exists leakage current, leakage current monotonic increase before and after fault, be then homopolarity insulation decline before and after fault, but there is the possibility of falsely dropping.
(5) when certain branch road exists leakage current, before and after fault, leakage current is non-monotonic increases progressively, then whether there is electric leakage one pole earth resistance situation of change after a failure before Water demand fault to analyze leakage current is drift.If not drift, be then that ground connection occurs another pole of this branch road.If drift, then need to do difference stream, avoid Lou selecting.
(6) for the situation that positive and negative busbar insulating resistance declines simultaneously, under current time identification, be the sequencing can distinguishing the two poles of the earth ground connection.Its individual features in the balanced mode first reports a certain pole ground connection, then do not report fault earthing again.Search earth resistance under now just needing to switch to uneven pattern, avoid Lou selecting.
Under normal circumstances, be that the little leakage current cannot distinguishing (1) and (2) causes because of drift or because insulation reduces.So leakage current can not be there is according to branch road judge this branch road generation drift.
By above analysis, the quantity of state of the present invention according to the forward and backward current/voltage of fault and the amount of calculation of earth resistance, and the electrical link of three, carry out fault signature identification, proposes the event driven automatic detecting pattern of logic-based.Of the present invention possess ground connection and patrol and examine an embodiment of the route selection check method flow process of the transforming plant DC power-supply system of route selection Checking Mechanism as shown in Figure 7, comprises the following steps:
S100: adopt unbalanced bridge mode detection to calculate busbar grounding resistance;
S200: adopt balanced bridge pattern to carry out grounding and patrol and examine;
S220: judge whether leakage current changes, if leakage current is unchanged, judges that this branch road has drift fault-free; Otherwise order performs step S240;
S240: judge leakage current whether monotone variation, if leakage current is not monotone variation, starts unbalanced bridge pattern; Otherwise order performs step S260;
S260: fault after-current deducts PRE-FAULT CURRENT, then calculates earth resistance, judges whether to meet branch trouble criterion, if meet branch trouble criterion, judges that this branch road is as fault branch; Otherwise, start unbalanced bridge pattern.
Check based on reduction to absurdity:
Fault-tolerant ability according to bridge method is mathematically analyzed known:
1) balanced bridge pattern is equivalent to known 2 variablees of root, according to 1 equation (5) or formula (6), solves 1 unknown quantity.As long as when 2 known quantities have 1 to make mistakes, then solving result mistake, the data according to discontinuity surface time single cannot be fault-tolerant.
2) unbalanced bridge pattern is equivalent to known 6 known quantities, according to 2 equations (7) and formula (8), solves 2 unknown quantitys.When wherein 1 unknown quantity is infinitely great (during one pole ground connection), be equivalent to decrease 1 unknown quantity; If now there is drift, be equivalent to the unknown quantity that increase by 1 is new, now become again and solve 2 unknown quantitys, still have solution.If but there is the two poles of the earth ground connection, when having again drift, be equivalent to 2 equation solutions, 3 unknown quantitys, unbalanced bridge pattern is without solution simultaneously.
The embodiment that ground connection patrols and examines the transforming plant DC power-supply system of route selection Checking Mechanism is possessed according to of the present invention, described route selection is checked module 15 and is also comprised reduction to absurdity check submodule, described wrong method is checked submodule and is connected to DC bus detection module 11, patrol and examine the busbar grounding resistance of trying to achieve in route selection process according to DC earthing, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong.Described reduction to absurdity checks the step that submodule performs the check of following reduction to absurdity:
S270: patrol and examine the busbar grounding resistance R tried to achieve in route selection process according to DC earthing
xand R
y, oppositely calculate the estimated value U' of positive and negative busbar voltage
pand U'
n;
S272: the positive and negative busbar voltage estimated value U' of gained will be calculated
pand U'
n, with corresponding positive and negative busbar voltage measured value U
pand U
ncompare, if U'
pand U'
namong any one be different from its measured value, then judge to exist in the branch road of trying to achieve in route selection process the special circumstances that bridge method cannot accurately calculate, described on-Line Monitor Device sends the wrong information warning of route selection result.
The preferred embodiment that ground connection patrols and examines the transforming plant DC power-supply system of route selection Checking Mechanism is possessed according to of the present invention, described wrong method is checked submodule and is also connected to fault branch determination module 14, the positive and negative bus resistance to earth of each branch road of trying to achieve is patrolled and examined in route selection process according to DC earthing, calculate negative busbar and positive bus-bar all-in resistance over the ground, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong.Further comprising the steps of after described step S272:
S274: according to the positive and negative bus resistance to earth R of the branch road i tried to achieve in route selection process
yiand R
xi, calculate negative busbar all-in resistance R over the ground
x Σ=R
x1//R
x2... .R
xm//R
b1, positive bus-bar is all-in resistance R over the ground
y Σ=R
y1//R
y2... .R
ym//R
b2, wherein, i is the integer from 1 to m, and m is the total circuitry number of transforming plant DC power-supply system;
S276: according to negative busbar all-in resistance R over the ground
x Σwith positive bus-bar all-in resistance R over the ground
y Σ, oppositely calculate the estimated value U of positive and negative busbar voltage "
pwith U "
n:
U"
p＝U*R
yΣ/(R
xΣ+R
yΣ)(13)
U"
n＝-U*R
xΣ/(R
xΣ+R
yΣ)(14)
Wherein, U "
pfor the estimated value of positive bus-bar voltage, U "
nfor the estimated value of negative busbar voltage, U is DC bus-bar voltage, R
x Σfor negative busbar all-in resistance over the ground, R
y Σfor positive bus-bar all-in resistance over the ground;
S278: the positive and negative busbar voltage estimated value U of gained will be calculated "
pwith U "
n, with corresponding positive and negative busbar voltage measured value U
pand U
ncompare, if U "
pwith U "
namong any one be different from its measured value, then judge in the m bar branch road of trying to achieve in route selection process, the special circumstances having at least a road to there is bridge method cannot accurately to calculate, described on-Line Monitor Device sends the wrong information warning of route selection result.
Adopt reduction to absurdity to carry out the principle of checking, first suppose that all grounding resistance calculations values are true, then calculated the estimated value U' of the positive and negative busbar voltage participating in many ground connection branch road by the earth resistance calculated
p, U'
n, U "
pwith U "
n.If calculate value U'
p, U'
n, U "
pwith U "
nwith measured value U
pand U
ndifference, then illustrate that bridge method fails correctly to process drift electric current.From formula (13) and formula (14), the earth resistance mistake in computation of any one branch road in m branch road, all by different from the busbar voltage of actual measurement for the busbar voltage causing calculating, thus the special circumstances that there is balanced bridge pattern or unbalanced bridge pattern and cannot accurately calculate are described in these branch roads, need to adopt additive method to carry out manual intervention to route selection result further.
Embodiment effect analysis
Within 2006, build up the analysis of operating direct current 220V system monitoring to Shanghai transformer station, virtual voltage 243.5V, use the microcomputer insulating monitor WJY3000A of Shenzhen special fast power equipment difficult to understand, DC power system separates 48 tunnels and feeds out loop.Select 4 road branch roads to analyze, select branch road to be respectively:
1# branch road direct current sampling circuit is normal, without drift, and sampled result good stability, good insulating;
4# branch road direct current sampling circuit is normal, without drift, and sampled result good stability, negative busbar insulating resistance value reduces;
17# road direct current sampling circuit is normal, has drift, sampled result good stability, and negative busbar insulating resistance value reduces;
33# road direct current sampling circuit is normal, and without drift, the saltus step of sampled result stability is large, and negative busbar insulating resistance value reduces.
Adopt route selection Checking Mechanism, carry out data record as shown in table 1 to table 3 to fielded system, table 4 and table 5 are regular inspection experimental data, wherein, table 4 is the experimental data that 1# branch road negative busbar connects 10K ohmic load over the ground, and table 5 is the directly grounded experimental data of 1# branch road negative busbar.In table 1 ~ table 5: R
bpand R
bnbe respectively balance bridge method calculate just over the ground with negative resistance to earth value, R
npand R
nnbe respectively uneven bridge method calculate just over the ground with negative resistance to earth value, unit K Ω.
Table 12014 day entry data in year June 10
Table 22014 day entry data in year July 11
Table 32014 day entry data in year August 10
Table 42014 day entry data in year September 10 (regular inspection test 1# is negative meets 10K)
Table 52014 day entry data in year September 10 (the direct ground connection experiment of regular inspection test 1# negative busbar)
By table 1 ~ table 5 analysis of experimental data, the route selection of table 4 data is 1# and 33#, because the direct current transducer sampling instability of 33# causes multiselect; The result that table 5 is same with table 4.
Use the data of route selection Checking Mechanism associative list 1 ~ table 5, reduce because 4#, 17#, 33# branch road has existed insulation, use mathematical statistics Algorithm Analysis variation tendency, what rate of change was large is preferential information.So his-and-hers watches 4 point out 1# branch road to be the preferential branch road investigated; And same analytical table 5,1# branch road is also the branch road of preferential investigation.And route selection check method of the present invention is to the data analysis before and after fault and logical derivation, can analyzes and find out the large direct current transducer 17# of CT drift.Based on route selection check method of the present invention to the data analysis after fault and derivation, 33# branch road can be picked out and there is sampling saltus step.After check completes, being formed and check report accordingly, inform that operation maintenance personnel 17# exists drift, there is sampling saltus step in 33#.
Those of ordinary skill in the art will be appreciated that; above embodiment is only used to technical scheme of the present invention is described; and be not used as limitation of the invention; any the above embodiment is done based on connotation of the present invention change, modification, all will drop in the protection range of claim of the present invention.
Claims (3)
1. possess the transforming plant DC power-supply system that ground connection patrols and examines route selection Checking Mechanism, for transforming plant DC power-supply system insulation against ground on-line monitoring, comprise on-line monitoring automatic detecting control module and one group of inspection function module; It is characterized in that:
Described inspection function module comprises DC bus detection module, balanced bridge detection module, unbalanced bridge detection module, and module is checked in fault branch determination module and route selection;
Described on-line monitoring automatic detecting control module is connected to described each inspection function module, by controlling the operation of each inspection function module, performs the event driven automatic detecting pattern of logic-based;
Described DC bus detection module adopts unbalanced bridge pattern, by detection computations positive and negative DC bus insulation against ground resistance, carries out on-line monitoring to the earth fault of positive bus-bar or negative busbar;
Described balanced bridge detection module adopts balanced bridge pattern, by detection computations branch insulation resistance, searches DC ground fault branch road;
Described unbalanced bridge detection module adopts unbalanced bridge pattern, and change positive and negative DC bus voltage to earth and the total leakage current of branch road by switching test resistor bridge, each branch insulation resistance of detection computations, searches DC ground fault branch road;
Described fault branch determination module, for the insulation resistance testing result of more each branch road, selects the fault branch determining earth fault occurs;
Module is checked in described route selection, carries out fault signature identification, avoid falsely dropping or leaking choosing of fault branch for the correlation logic according to the voltage before and after fault, electric current and resistance;
The event driven automatic detecting pattern of described logic-based comprises the following steps:
S100: adopt unbalanced bridge mode detection to calculate busbar grounding resistance;
S200: adopt balanced bridge pattern to carry out grounding and patrol and examine;
S220: judge whether leakage current changes, if leakage current is unchanged, judges that this branch road has drift fault-free; Otherwise order performs step S240;
S240: judge leakage current whether monotone variation, if leakage current is not monotone variation, starts unbalanced bridge pattern; Otherwise order performs step S260;
S260: fault after-current deducts PRE-FAULT CURRENT, then calculates earth resistance, judges whether to meet branch trouble criterion, if meet branch trouble criterion, judges that this branch road is as fault branch; Otherwise, start unbalanced bridge pattern.
2. according to claim 1 possess the transforming plant DC power-supply system that ground connection patrols and examines route selection Checking Mechanism, it is characterized in that described route selection is checked module and also comprised reduction to absurdity check submodule, described wrong method is checked submodule and is connected to DC bus detection module, patrol and examine the busbar grounding resistance of trying to achieve in route selection process according to DC earthing, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong.
3. according to claim 2 possess the transforming plant DC power-supply system that ground connection patrols and examines route selection Checking Mechanism, it is characterized in that described wrong method is checked submodule and is also connected to fault branch determination module, the positive and negative bus resistance to earth of each branch road of trying to achieve is patrolled and examined in route selection process according to DC earthing, calculate negative busbar and positive bus-bar all-in resistance over the ground, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong and it is characterized in that described wrong method is checked submodule and is also connected to fault branch determination module, the positive and negative bus resistance to earth of each branch road of trying to achieve is patrolled and examined in route selection process according to DC earthing, calculate negative busbar and positive bus-bar all-in resistance over the ground, oppositely calculate the estimated value of positive and negative busbar voltage; According to the difference of the measured value of described estimated value and corresponding voltage, infer that route selection result is wrong.
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| CN112946340A (en) * | 2019-12-10 | 2021-06-11 | 通用汽车环球科技运作有限责任公司 | Method and apparatus for monitoring isolation of a power bus |
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