CN105182148A - Substation direct-current power source system - Google Patents
Substation direct-current power source system Download PDFInfo
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- CN105182148A CN105182148A CN201510419366.7A CN201510419366A CN105182148A CN 105182148 A CN105182148 A CN 105182148A CN 201510419366 A CN201510419366 A CN 201510419366A CN 105182148 A CN105182148 A CN 105182148A
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Abstract
The invention relates to a direct-current power source system for supplying power for the relay protection, automatic device and remote communication device of a substation and protection of the direct-current power source system, in particular, a substation direct-current power source system with a grounding fault automatic inspection function. The substation direct-current power source system includes an inspection control module, a direct-current busbar detection module connected with the output end of the inspection and control module, a direct-current branch detection module and a line selection verification module; fault feature identification is carried out according to the state quantity of current before and after a fault, the state quantity of voltage before and after the fault and the calculation quantity of grounding resistance, and electrical connections among the state quantity of current, the state quantity of voltage and the calculation quantity of grounding resistance; a line selection verification function is integrated onto the substation direct-current power source system with a grounding inspection line selection verification mechanism through adopting a logical event driving-based automatic inspection mode; and zero drift and fault branches can be identified through calling an unbalanced bridge mode and based on logical judgment, and therefore, wrong selection or missed selection of direct-current grounding inspection devices can be fast identified.
Description
Technical field
The present invention relates to the DC power system and protection thereof of powering for the relay protection of transformer station and aut.eq., telecontrol communication device; be specifically related to a kind of transforming plant DC power-supply system, particularly 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; 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 a kind of transformer dc source system, the quantity of state of described DC power system 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, identify drift branch road and ground connection branch road, overcoming while earth fault falsely drops, leaks choosing, improve the seek rate of fault branch.
For achieving the above object, the solution of the present invention is: a kind of transformer dc source system, described transforming plant DC power-supply system comprises positive bus-bar and negative busbar, for connecting some direct current branch of conventional load, relay protection and aut.eq., telecontrol communication device and devices for emergency illumination, for one group of direct current bridge element of system on-line monitoring, and the on-Line Monitor Device for patrolling and examining the insulation against ground state of transforming plant DC power-supply system, each direct current branch is provided with DC leakage flow sensor;
The voltage detecting input end of described on-Line Monitor Device, connect positive bus-bar and the negative busbar of transforming plant DC power-supply system, the branch road leakage current test input end of described on-Line Monitor Device, connect the DC leakage flow sensor of each direct current branch, the leakage current of each direct current branch is sampled;
Described on-Line Monitor Device comprises patrols and examines control module, and with the described DC bus detection module of patrolling and examining control module output terminal and being connected, module is checked in direct current branch detection module and route selection, described patrols and examines control module for controlling DC bus detection module, the operation of module is checked in direct current branch detection module and route selection, described DC bus detection module is used for the direct current bridge element by switching DC power system, detection computations just, the insulation against ground resistance of negative DC bus, on-line monitoring is carried out to the earth fault of positive bus-bar or negative busbar, described direct current branch detection module is used for the insulation resistance of each direct current branch of detection computations, and the insulation resistance testing result of more each branch road, select the fault branch determining earth fault occurs, described route selection is checked module and is used for carrying out fault signature identification according to the correlation logic of the voltage before and after fault, electric current and resistance, avoids falsely dropping or leaking choosing of fault branch.
According to transforming plant DC power-supply system of the present invention, described direct current bridge element comprises two balance bridge resistance, two test resistor bridges, and the relay change-over switch of two described test resistor bridge on-states of control, two described balance bridge resistance are separately fixed at DC bus two ends, and described test resistor bridge passes through relay change-over switch switching on DC bus.
According to transforming plant DC power-supply system of the present invention, busbar grounding resistance detection adopts bridge method, and 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
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; R
l1, R
l2for test resistor bridge, they are measuring resistances that resistance is identical; 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.
According to transforming plant DC power-supply system of the present invention, turning on and off by relay change-over switch when measuring busbar grounding resistance, according to measuring the U obtained
p, U
ncalculate the insulation against ground resistance R of DC bus
x, R
y, that is: two each self-closings of relay change-over switch, obtain respectively:
U
n1/R
b1+U
p1/R
b2+U
n1/R
L1+U
n1/R
x+U
p1/R
y＝0
U
n2/R
b1+U
p2/R
b2+U
p2/R
L2+U
n2/R
x+U
p2/R
y＝0
Thus calculate R
x, R
yvalue.
According to transforming plant DC power-supply system of the present invention, described direct current branch detection module comprises balanced bridge detecting unit, unbalanced bridge detecting unit and fault branch identifying unit, described balanced bridge detecting unit adopts balanced bridge pattern, by detection computations branch insulation resistance, search DC ground fault branch road; Described unbalanced bridge detecting unit adopts unbalanced bridge pattern, and change positive and negative DC bus voltage-to-ground 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 identifying unit, for the insulation resistance testing result of more each branch road, selects the fault branch determining earth fault occurs.
According to transforming plant DC power-supply system of the present invention, during described balanced bridge mode detection grounding resistance, first the direction of the total leakage current of direct current branch is judged, the insulation of positioning DC branch road negative or positive electrode reduces, then according to positive bus-bar voltage-to-ground or negative busbar voltage-to-ground, calculate grounding resistance, be specially:
If judge the total leakage current I of direct current branch
0be negative, then direct current branch positive bus-bar resistance to earth value is infinitely great, direct current branch negative busbar resistance to earth value Rn=Un/I
0;
If judge the total leakage current I of direct current branch
0for just, then direct current branch positive bus-bar resistance to earth value Rp=Up/I
0, direct current branch negative busbar resistance to earth value is infinitely great.
According to transforming plant DC power-supply system of the present invention, during described unbalanced bridge mode detection branch insulation resistance, need 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, drop into R
l2time, U
p, U
n, I
0value U respectively
p1, U
n1, I
1; Drop into R
l1time, U
p, U
n, I
0value U respectively
p2, U
n2, I
2, outflow of bus current node 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; Thus have:
I
1-U
n1/R
x-U
p1/R
y＝0
I
2-U
n2/R
x-U
p2/R
y＝0
Obtain:
R
x＝(U
p1U
n2-U
p2U
n1)/(U
p1I
2-U
p2I
1)
R
y＝(U
p2U
n1-U
p1U
n2)/(U
n1I
2-U
n2I
1)
According to transforming plant DC power-supply system of the present invention, the specific works process that module is checked in described route selection is:
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 beneficial effect that the present invention reaches: DC power system of the present invention can according to the calculated amount of the quantity of state of the forward and backward current/voltage of fault and stake resistance, and the electrical link of three, carry out fault signature identification, adopt automatic detecting pattern, 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.
Route selection only need be checked function i ntegration and be patrolled and examined in the transforming plant DC power-supply system of route selection Checking Mechanism to possessing ground connection by the present invention, 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.
Transforming plant DC power-supply system of the present invention; for providing uninterrupted power supply for the important conventional load of transformer station, relay protection and aut.eq., telecontrol communication device; as shown in Figure 1; described transforming plant DC power-supply system comprises positive bus-bar+KM and negative busbar-KM; connect some direct current branch of conventional load, relay protection and aut.eq., telecontrol communication device and devices for emergency illumination; one group of direct current bridge element; 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 1, 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.
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 the online inspection device 1 of described transforming plant DC power-supply system as shown in Figure 9, comprise and patrol and examine control module 10, and with the described DC bus detection module 11 of patrolling and examining control module output terminal and being connected, module 15 is checked in direct current branch detection module and route selection, described online inspection device comprises patrols and examines control module, and with the described DC bus detection module of patrolling and examining control module output terminal and being connected, module is checked in direct current branch detection module and route selection, described patrols and examines control module for controlling DC bus detection module, the operation of module is checked in direct current branch detection module and route selection, described DC bus detection module is used for the direct current bridge element by switching DC power system, detection computations just, the insulation against ground resistance of negative DC bus, on-line monitoring is carried out to the earth fault of positive bus-bar or negative busbar, described direct current branch detection module is used for the insulation resistance of each direct current branch of detection computations, and the insulation resistance testing result of more each branch road, select the fault branch determining earth fault occurs, described route selection is checked module and is used for carrying out fault signature identification according to the correlation logic of the voltage before and after fault, electric current and resistance, avoids falsely dropping or leaking choosing of fault branch.
Described direct current branch detection module comprises balanced bridge detecting unit 12, unbalanced bridge detecting unit 13 and fault branch identifying unit 14.Described balanced bridge detecting unit 12 adopts balanced bridge pattern, by detection computations branch insulation resistance, searches DC ground fault branch road; Described unbalanced bridge detecting unit 13 adopts unbalanced bridge pattern, and change positive and negative DC bus voltage-to-ground 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 identifying unit 14, for the insulation resistance testing result of more each branch road, selects the fault branch determining earth fault occurs.
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
n
Be 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
n
Be 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.The route selection of transforming plant DC power-supply system of the present invention checks an embodiment of module specific works flow process 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.
According to an embodiment of transforming plant DC power-supply system of the present invention, described route selection is checked module 15 and is also comprised reduction to absurdity check submodule, described reduction to absurdity 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 reduction to absurdity is checked submodule and is also connected to fault branch identifying unit 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 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 (8)
1. a transforming plant DC power-supply system, it is characterized in that: described transforming plant DC power-supply system comprises positive bus-bar and negative busbar, for connecting some direct current branch of conventional load, relay protection and aut.eq., telecontrol communication device and devices for emergency illumination, for one group of direct current bridge element of system on-line monitoring, and the on-Line Monitor Device for patrolling and examining the insulation against ground state of transforming plant DC power-supply system, each direct current branch is provided with DC leakage flow sensor;
The voltage detecting input end of described on-Line Monitor Device, connect positive bus-bar and the negative busbar of transforming plant DC power-supply system, the branch road leakage current test input end of described on-Line Monitor Device, connect the DC leakage flow sensor of each direct current branch, the leakage current of each direct current branch is sampled;
Described on-Line Monitor Device comprises patrols and examines control module, and with the described DC bus detection module of patrolling and examining control module output terminal and being connected, module is checked in direct current branch detection module and route selection, described patrols and examines control module for controlling DC bus detection module, the operation of module is checked in direct current branch detection module and route selection, described DC bus detection module is used for the direct current bridge element by switching DC power system, detection computations just, the insulation against ground resistance of negative DC bus, on-line monitoring is carried out to the earth fault of positive bus-bar or negative busbar, described direct current branch detection module is used for the insulation resistance of each direct current branch of detection computations, and the insulation resistance testing result of more each branch road, select the fault branch determining earth fault occurs, described route selection is checked module and is used for carrying out fault signature identification according to the correlation logic of the voltage before and after fault, electric current and resistance, avoids falsely dropping or leaking choosing of fault branch.
2. transforming plant DC power-supply system according to claim 1, it is characterized in that, described direct current bridge element comprises two balance bridge resistance, two test resistor bridges, and the relay change-over switch of two described test resistor bridge on-states of control, two described balance bridge resistance are separately fixed at DC bus two ends, and described test resistor bridge passes through relay change-over switch switching on DC bus.
3. transforming plant DC power-supply system according to claim 2, is characterized in that, busbar grounding resistance detection adopts bridge method, and 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
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; R
l1, R
l2for test resistor bridge, they are measuring resistances that resistance is identical; 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.
4. transforming plant DC power-supply system according to claim 3, is characterized in that, turning on and off by relay change-over switch when measuring busbar grounding resistance, according to measuring the U obtained
p, U
ncalculate the insulation against ground resistance R of DC bus
x, R
y, that is: two each self-closings of relay change-over switch, obtain respectively:
U
n1/R
b1+U
p1/R
b2+U
n1/R
L1+U
n1/R
x+U
p1/R
y＝0
U
n2/R
b1+U
p2/R
b2+U
p2/R
L2+U
n2/R
x+U
p2/R
y＝0
Thus calculate R
x, R
yvalue.
5. transforming plant DC power-supply system according to claim 4, it is characterized in that, described direct current branch detection module comprises balanced bridge detecting unit, unbalanced bridge detecting unit and fault branch identifying unit, described balanced bridge detecting unit adopts balanced bridge pattern, by detection computations branch insulation resistance, search DC ground fault branch road; Described unbalanced bridge detecting unit adopts unbalanced bridge pattern, and change positive and negative DC bus voltage-to-ground 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 identifying unit, for the insulation resistance testing result of more each branch road, selects the fault branch determining earth fault occurs.
6. transforming plant DC power-supply system according to claim 5, it is characterized in that, during described balanced bridge mode detection grounding resistance, first the direction of the total leakage current of direct current branch is judged, the insulation of positioning DC branch road negative or positive electrode reduces, then according to positive bus-bar voltage-to-ground or negative busbar voltage-to-ground, calculate grounding resistance, be specially:
If judge the total leakage current I of direct current branch
0be negative, then direct current branch positive bus-bar resistance to earth value is infinitely great, direct current branch negative busbar resistance to earth value Rn=Un/I
0;
If judge the total leakage current I of direct current branch
0for just, then direct current branch positive bus-bar resistance to earth value Rp=Up/I
0, direct current branch negative busbar resistance to earth value is infinitely great.
7. transforming plant DC power-supply system according to claim 5, it is characterized in that, during described unbalanced bridge mode detection branch insulation resistance, need 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, drop into R
l2time, U
p, U
n, I
0value U respectively
p1, U
n1, I
1; Drop into R
l1time, U
p, U
n, I
0value U respectively
p2, U
n2, I
2, outflow of bus current node 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; Thus have:
I
1-U
n1/R
x-U
p1/R
y＝0
I
2-U
n2/R
x-U
p2/R
y＝0
Obtain:
R
x＝(U
p1U
n2-U
p2U
n1)/(U
p1I
2-U
p2I
1)
R
y＝(U
p2U
n1-U
p1U
n2)/(U
n1I
2-U
n2I
1)。
8. transforming plant DC power-supply system according to claim 1, is characterized in that, the specific works process that module is checked in described route selection is:
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.
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