CN105242163A - Wire selection checking method of substation DC grounding inspection - Google Patents
Wire selection checking method of substation DC grounding inspection Download PDFInfo
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- CN105242163A CN105242163A CN201510418985.4A CN201510418985A CN105242163A CN 105242163 A CN105242163 A CN 105242163A CN 201510418985 A CN201510418985 A CN 201510418985A CN 105242163 A CN105242163 A CN 105242163A
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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
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- 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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- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention provides a wire selection checking method of substation DC grounding inspection, relating to a method for detecting an electric fault in a cable, transmission wire or network, and particularly relates to a method for detecting a substation DC system grounding fault. The method comprises the a step of using an electric bridge method to carry out bus or branch grounding inspection, a step of carrying out fault characteristic recognition according to the state amounts of current voltage before and after a fault and the calculation amount of a grounding resistor and the electrical contact of the above three amounts, an automatic inspection mode based on logic event driving is employed, the rapidness of a balance electric bridge and the fault tolerance of an unbalanced electric bridge, the search speed and a fault tolerance level are improved, and the rapid diagnosis and troubleshooting are realized. A wire selection checking function is integrated into a substation DC grounding inspection device, an unbalanced electric bridge mode is called through a logic judgment to identify a zero drift and a fault branch, the wrong selection or missed selection of the DC grounding inspection device is rapidly identified, and the performance of the inspection device is improved under the premise of not increasing hardware cost.
Description
Technical field
The present invention relates to the method for electric fault in exploration cable, transmission line or network, particularly relating to a kind of method for detecting transformer station direct current system earth fault, and use device or the system of the method.
Background technology
DC power system is one of three large concealed works in transformer station; direct supply is as the important component part of electric system; for some important conventional loads, relay protection and aut.eq., 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 telltale, relay protection and aut.eq., the misoperation of isolating switch or miss operation; likely cause direct supply short circuit, cause fuse blows, or fast independent power source switch disconnects; make equipment lose operating power, cause electric system catastrophic 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 AC method and Using Direct Current Bridge Method.AC method is also referred to as Low frequency signal injection method, and the ac current signal that AC method utilizes AC signal and mutual inductor 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 trouble spot.
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 bus-bar 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 the route selection check method that a kind of transforming plant DC ground connection is patrolled and examined, make full use of the advantage of balanced bridge pattern and unbalanced bridge mode computation stake resistance, according to the quantity of state of the forward and backward current/voltage of fault and the calculated amount of stake 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 stake resistance computation 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:
The route selection check method that transforming plant DC ground connection is patrolled and examined, for transforming plant DC power-supply system insulation against ground on-Line Monitor Device, is characterized in that comprising 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 non-fault; 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 stake 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.
The one preferably technical scheme of the route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined, characterized by further comprising the step that following employing reduction to absurdity carries out checking:
S270: patrol and examine the busbar grounding resistance of trying to achieve in route selection process according to DC earthing, oppositely calculates the estimated value of positive and negative busbar voltage;
S272: the positive and negative busbar voltage estimated value of gained will be calculated, compare with corresponding positive and negative busbar voltage measured value, if any one among positive and negative busbar voltage estimated value is different from its measured value, then there are the special circumstances that bridge method cannot accurately calculate in judgement route selection process, described on-Line Monitor Device sends the wrong information warning of route selection result.
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, is characterized in that after described step S272 further comprising the steps of:
S274: according to the positive and negative bus resistance to earth of each branch road of trying to achieve in route selection process, calculates negative busbar and positive bus-bar all-in resistance over the ground;
S276: according to negative busbar and positive bus-bar all-in resistance over the ground, oppositely calculates the estimated value of positive and negative busbar voltage:
S278: the positive and negative busbar voltage estimated value of gained will be calculated, compare with corresponding positive and negative busbar voltage measured value, if any one among positive and negative busbar voltage estimated value is different from its measured value, then judge in the 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.
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 calculated amount of stake 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 work 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 in transforming plant DC ground connection inspection device, 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.
The route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined, for transforming plant DC power-supply system insulation against ground on-Line Monitor 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, relay protection and aut.eq., 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 measuring resistance of two resistances is formed; Test resistor bridge RL1, RL2 that the measuring resistance that two resistances are identical is formed; Two control the relay change-over 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 end 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 end 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 mutual inductor) of each direct current branch, the leakage current of each branch road is sampled.The structure of transforming plant DC power-supply system insulation against ground on-Line Monitor Device 1 as shown in Figure 9, comprises on-line monitoring automatic detecting control module 10, for controlling the operation of each functional module, performs the event driven automatic detecting pattern of logic-based; DC bus detection module 11, for 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; Balanced bridge detection module 12, for detection computations branch insulation resistance, adopts balanced bridge pattern to search DC ground fault branch road; Unbalanced bridge detection module 13, changes positive and negative DC bus voltage-to-ground and the total leakage current of branch road, each branch insulation resistance of detection computations by switching test resistor bridge, adopts unbalanced bridge pattern to search DC ground fault branch road; 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 14 is checked in 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 measuring resistances that resistance is identical, are separately fixed at DC bus two ends; R
l1, R
l2for test resistor bridge, they are measuring resistances 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 change-over 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 electrical 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 electrical 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 stake resistance.Because DC 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-ground, bus negative pole-KM voltage-to-ground 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 valve.
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-ground or negative busbar voltage-to-ground.Composition graphs 1 and Fig. 4 can draw single spur track ground connection based on balanced bridge pattern equivalent electrical 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-ground, negative busbar voltage-to-ground, branch road direct current calculates, but needs to change positive bus-bar voltage-to-ground, negative busbar voltage-to-ground and the total leakage current of branch road by switching test resistor bridge.
Closed K2 (drops into R
l2) time, branch road equivalent electrical 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 electrical 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 dirction, 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 stake resistance.
DC leakage flow sensor (mutual inductor) is contactless sensing, and rely on magnetic induction loop induction test, measuring object signal is small, easily by extraneous interference (as geomagnetic noise, mutual inductor is placed different, and zero point drift 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 analysiss, 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 stake 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 stake 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 stake resistance and the linear change of voltage, stake resistance may be caused to diminish and meet stake 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-ground reduces, and stake resistance is along with voltage acceleration change.
(4) when certain branch road exists leakage current, leakage current monotone increasing 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 stake 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 ground again.Search stake 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 calculated amount of stake resistance, and the electrical link of three, carry out fault signature identification, proposes the event driven automatic detecting pattern of logic-based.An embodiment of the route selection check method that transforming plant DC ground connection of the present invention is patrolled and examined 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 non-fault; 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 stake 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.
An embodiment of the route selection check method that transforming plant DC ground connection according to the present invention is patrolled and examined, also comprises the step that following employing reduction to absurdity carries out checking:
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.
A preferred embodiment of the route selection check method that transforming plant DC ground connection according to the present invention is patrolled and examined, 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 stake 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 stake resistance miscount 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 domain of claim of the present invention.
Claims (3)
1. a transforming plant DC ground connection route selection check method of patrolling and examining, for transforming plant DC power-supply system insulation against ground on-Line Monitor Device, is characterized in that comprising 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 non-fault; 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 stake 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. the transforming plant DC ground connection according to claim 1 route selection check method of patrolling and examining, characterized by further comprising the step that following employing reduction to absurdity carries out checking:
S270: patrol and examine the busbar grounding resistance of trying to achieve in route selection process according to DC earthing, oppositely calculates the estimated value of positive and negative busbar voltage;
S272: the positive and negative busbar voltage estimated value of gained will be calculated, compare with corresponding positive and negative busbar voltage measured value, if any one among positive and negative busbar voltage estimated value is different from its measured value, then there are the special circumstances that bridge method cannot accurately calculate in judgement route selection process, described on-Line Monitor Device sends the wrong information warning of route selection result.
3. the transforming plant DC ground connection according to claim 2 route selection check method of patrolling and examining, is characterized in that after described step S272 further comprising the steps of:
S274: according to the positive and negative bus resistance to earth of each branch road of trying to achieve in route selection process, calculates negative busbar and positive bus-bar all-in resistance over the ground;
S276: according to negative busbar and positive bus-bar all-in resistance over the ground, oppositely calculates the estimated value of positive and negative busbar voltage:
S278: the positive and negative busbar voltage estimated value of gained will be calculated, compare with corresponding positive and negative busbar voltage measured value, if any one among positive and negative busbar voltage estimated value is different from its measured value, then judge in the 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.
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