CN102570431B - Method for limiting short circuit current of power grid - Google Patents
Method for limiting short circuit current of power grid Download PDFInfo
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Abstract
The invention discloses a method for limiting a short circuit current of a power grid. Specific to a conventional 3/2 connection mode of a transformer substation, the method comprises the following steps: limiting the short circuit current and limiting the maximum short circuit current passing through a fault clearance switch to be not more than a rated breaking current; under the condition of out-of-limit short circuit current level, after fixation is broken or in fault during normal running, selectively tripping off one or more switches in a plant in turn by performing relaying protection; and isolating certain branch fault currents so as to reduce the to-be-cut-off maximum short circuit current of the fault clearance switch, till the maximum short circuit current is lower than the rated breaking current, thereby ensuring the successful trip of the switch and isolating the fault. According to the method provided by the invention, the short circuit current is limited while the power transmission of the power grid during the normal running process is not influenced, the cost is low and the engineering implementation is easily performed.
Description
Technical field
The present invention relates to a kind of method for limiting short circuit current of power grid, belong to the T & D Technology field.
Background technology
Rapid growth along with Electricity Demand, the scale expanding day of electric power system, power supply and electrical network be crypto set more, and the partial electric grid short circuit current level also rises thereupon, part plant stand short circuit current approaches or surpasses the specified breaking current of switch, to safe operation of power system, threatens.Therefore, finding cost-effective short-circuit current limiting measure, is one of significant challenge of facing of power network development.
Method for limiting short circuit current of power grid commonly used mainly contains following five kinds at present:
One of method is to improve the rupturing capacity of switch.The method is that the existing switch of plant stand is replaced by the switch that specified breaking current is larger, the switch that is for example 50kA by the original specified breaking current of 500kV electric pressure is replaced by the switch that specified breaking current is 63kA, the method is obviously a kind of directly effective solution, but the transformer station out-of-limit due to short circuit current is generally load-center substation, need the number of switches of replacing a lot, therefore required investment is large, long in time limit, buying new switch needs substantial contribution on the one hand, can only be progressively to change during engineering construction on the other hand, make the electrical network load-center substation for a long time in the abnormal running state, as long as and have a switch not change complete, the out-of-limit danger caused of short circuit current just exists always.
Two of method is to adjust electric network composition, booster tension grade.The operation of next stage power system delamination and subarea is divided into some districts by the network of primary voltage grade, the more higher leveled electrical network of Radiation access, and capacity power plant directly accesses in more higher leveled electrical network greatly, and the short circuit current of original electric pressure electrical network will decrease.On the basis of high one-level electric pressure power network development, low-voltage-grade power system delamination and subarea operation is the most direct effective method of limiting short-circuit current, but has equally the problem of the aspect such as less economical and long in time limit.
Three of method is that electric substation adopts the bus section operation to open busbar sectional izing switch.The method is implemented convenient, makes the bus fanout operation, can increase system impedance, effectively reduces short circuit current level, but, by the electrical link of impair system, reduces system safety nargin and operational flexibility, likely causes that bus load distributes simultaneously unbalanced.
Four of method is to install the little reactance of transformer neutral point additional.Install little reactance additional at transformer neutral point; the method construction is convenient; invest less; but only larger to the effect that reduces electrical network regional area single-phase short circuit current; invalid for the short circuit current that alleviates three phase short circuit fault; but also to consider the Overvoltage and insulation coordination of system and transformer neutral point, the relay protection setting of system is also had a certain impact.
Five of method is to adopt series reactor.But the method increases system impedance, to System Reactive Power, voltage, loss and stability, can impact, although researched and developed at present the controlled series reactor, while making its normal operation, impedance is zero, only at fault current, surpass when it sets threshold values and seal in current-limiting impedance with limiting short-circuit current, but current required expense is higher, operating experience is not enough, remain practice test and popularization.
Summary of the invention
The objective of the invention is 3/2 mode of connection commonly used for transformer station provides a kind of method for limiting short circuit current of power grid, relatively existing method for limiting short circuit current of power grid, and the method expense is cheap and be easy to engineering construction.
The object of the present invention is achieved like this: the method for limiting short circuit current of power grid under a kind of 3/2 mode of connection of 500kV electric pressure, and described comprising:
The branch current of A, calculating plant stand busbar short-circuit electric current and the branch road that is connected;
B, determine the branch road of branch current minimum and the string at place thereof;
Whether C, relatively more definite busbar short-circuit electric current and a way outlet short circuit current be out-of-limit, if the busbar short-circuit electric current is out-of-limit, disconnects the middle switch that at least one is not main transformer place string; If a way outlet short circuit current is out-of-limit, at least one limit switch that is positioned at the offside bus bar side that go here and there at the open-circuit line place; If busbar short-circuit electric current and a way outlet short circuit current are simultaneously out-of-limit, disconnect one is not the middle switch of main transformer place string and the limit switch or staggered two the limit switches that are positioned at different strings and different bus bar side that disconnect that are positioned at the offside bus bar side of circuit place string simultaneously.
When in described disconnection, switch limits the busbar short-circuit electric current, preferential selection provides the middle switch of the string of short circuit current maximum.
During switch restraining line, described disconnection limit way outlet short circuit current, the preferential limit switch that is positioned at the offside bus bar side of selecting to provide the circuit place string of short circuit current minimum.
In described disconnection, the mode of switch and limit switch disconnects or realizes that by relaying protection the selectivity order tripping operation disconnects for fixing.
Compared with prior art, the advantage of the method for limiting short circuit current of power grid under 3/2 mode of connection of a kind of 500kV electric pressure of the present invention is: 3/2 mode of connection of commonly using for current 500kV plant stand, neither change switch and also do not reduce the short circuit current of short dot, but by the out-of-limit problem of short circuit current specific to the switch in plant stand, disconnect at least one switch or a plurality of switch in plant stand during normal operation, make plant stand in non-full mode of connection operation, do not need to increase primary equipment, just can isolated part branch, short-circuit electric current, thereby reduce in process of fault isolation to flow through the short circuit current of switch, reach the purpose that reduces the short circuit current that switch need to cut-off, until lower than the specified breaking current of switch, guarantee the switch isolated fault of successfully tripping.The required investment of method for limiting short circuit current of power grid provided by the invention is very low, good in economic efficiency, and enforcement is convenient, the duration is short.
The accompanying drawing explanation
Fig. 1 is switch schematic diagram in fixing disconnection or selectivity order tripping;
Fig. 2 is fixing the disconnection or selectivity order tripping limit switch schematic diagram;
Fig. 3 is switch and limit switch schematic diagram in fixing disconnection or selectivity order tripping;
Fig. 4 is fixing staggered the disconnection or the staggered tripping of selectivity order limit switch schematic diagram.
In figure, the Filled Rectangle piece is denoted as closed switch, and the hollow rectangle piece is denoted as the switch of disconnection; K12, K22, K32, K42, K52 are denoted as middle switch; K11, K21, K31, K41, K51 and K13, K23, K33, K43, K53 are denoted as the limit switch; 13X, 33X, 43X, 53X and 21X, 31X, 41X, 51X are denoted as respectively 13 branch lines, 33 branch lines, 43 branch lines, 53 branch lines and 21 branch lines, 31 branch lines, 41 branch lines, 51 branch lines; MX1 and MX2 are denoted as respectively a bus and No. two buses; ZB1 and ZB2 are denoted as respectively a main transformer branch line and No. two main transformer branch lines.
Embodiment
It is example that the present embodiment be take the transformer station with five complete strings.Understand and realize the present invention now describing by reference to the accompanying drawings embodiments of the invention for the ease of persons skilled in the art.
In order to realize the present invention, described comprising the following steps:
Steps A: according to studied target plant stand and boundary condition, calculate plant stand busbar short-circuit electric current and the branch current of the branch road that is connected.
Step B: according to the result of calculation of steps A, each branch current compared and sorts according to ascending, determining the branch road of branch current minimum and the string at place thereof.
Step C: relatively determine that whether busbar short-circuit electric current and a way outlet short circuit current be out-of-limit.This step specifically minute three kinds of situations compares and limits.
The first situation: the busbar short-circuit electric current is out-of-limit relatively reaches restriction.If the busbar short-circuit electric current surpasses the specified breaking current of switch, disconnect the middle switch that at least one is not main transformer place string.The specified breaking current of busbar short-circuit Current calculation value and all limits switch is compared, and when the busbar short-circuit electric current is less than the specified breaking current of limit switch, the busbar short-circuit electric current is not out-of-limit, does not need to take current limiting measures.Otherwise the busbar short-circuit electric current is out-of-limit, need to take current limiting measures.If need to stay certain margin of safety,, when busbar short-circuit electric current and margin of safety sum are less than the specified breaking current of limit switch, the busbar short-circuit electric current is safe, does not need to take current limiting measures.Otherwise the busbar short-circuit electric current is dangerous, need to take current limiting measures.When not of uniform size the causing of specified breaking current of limit switch, for example have plenty of 50kA, have plenty of 60kA, get minimum specified breaking current and compare.
The non-full wiring operational mode current-limiting method of restriction busbar short-circuit electric current can have multiple, and according to the size of the out-of-limit amount of short circuit current, the mode difference of non-full wiring, need the number of switches of disconnection also different.Specifically be divided into following three steps:
The first step: disconnect the middle switch that at least one is not main transformer place string, generally disconnect one or two middle switches, the present embodiment selects to disconnect a middle switch.When in disconnection, switch limits the busbar short-circuit electric current, from short-circuit current limitation effect angle, consider, preferential selection provides the middle switch of the string of short circuit current maximum, the maximum short circuit current that in the time of can reducing busbar short-circuit to greatest extent, switch need cut-off, but be not suitable for selecting to disconnect the middle switch of main transformer place string, also can distribute and the stable operation situation in conjunction with system load flow after fault, considered and select.
Second step: analyze in disconnecting the maximum short circuit current that while after switch, the busbar short-circuit fault occurring, switch need to cut-off.Referring to Fig. 1, if K switch 42 in disconnecting, so when a bus MX1 short circuit, each limit K switch 11, K21, K31, K41 and K51 that protection action tripping is connected with bus MX1, having and only have two kinds of situation: the one, K41 is not last disconnection, the short circuit current maximum that in K11, K21, K31 and K51, last that switch disconnected need to cut-off, its value is the busbar short-circuit electric currents of 41 branch lines from this plant stand is deviate from, owing to having lacked a loop line, the busbar short-circuit electric current reduces in the time of must be than full wiring; The 2nd, K41 is last disconnection, the maximum short circuit current maximum that the switch that in K11, K21, K31 and K51, penultimate disconnects need to cut-off, and its value is that a bus MX1 short circuit current deducts the short circuit current that 41 branch lines provide.The risk of measure is that 41 branch lines are accompanied and stopped, and after can excising by fault bus, recovers 41 branch lines operations to the K42 that closes in during this period of time before recovering.During No. two bus MX2 short circuits, the current limliting situation is identical therewith.
The 3rd step: relatively determine whether the maximum short circuit current that switch need cut-off is less than its specified breaking current, if so, disconnecting the non-full wiring operational mode of switch in this is the method for restriction busbar short-circuit electric current.
If the out-of-limit amount of short circuit current is larger, the connected branch road of general this plant stand is more, needs to disconnect one and can repeat the first step to the three steps with upper switch, until the maximum short circuit current that switch need cut-off is less than its specified breaking current.
The second situation: way outlet short circuit current is out-of-limit relatively reaches restriction.When a way outlet short circuit current is out-of-limit, at least one limit switch that is positioned at the offside bus bar side that go here and there at the open-circuit line place.For each branch road be connected with bus, comprise circuit and transformer etc., deduct branch current with the busbar short-circuit electric current respectively, if this difference is less than the middle switch that is connected with this branch road and the specified breaking current of limit switch, this way outlet short circuit current is not out-of-limit, does not need to take current limiting measures, if this difference is greater than the middle switch that is connected with this branch road or the specified breaking current of limit switch, this way outlet short circuit current is out-of-limit, need to take current limiting measures.If need to stay certain margin of safety, when this difference and margin of safety sum are less than the specified breaking current of the middle switch that is connected with this branch road and limit switch, this way outlet short circuit current is safe, do not need to take current limiting measures, otherwise, this way outlet short circuit current is dangerous, need to take current limiting measures.When not of uniform size the causing of specified breaking current of the middle switch be connected with branch line and limit switch, for example have plenty of 50kA, have plenty of 60kA, get minimum specified breaking current and compare.
The non-full wiring operational mode current-limiting method of a restriction way outlet short circuit current can have multiple, and according to the size of an out-of-limit amount of way outlet short circuit current, the mode difference of non-full wiring, need the number of switches of disconnection also different.Concrete minute two steps:
The first step: at least one limit switch of the branch road offside that disconnected branches outlet short circuit current is out-of-limit generally disconnects one or two limit switches, referring to Fig. 2.
Second step: the maximum short circuit current that while after analysis disconnection opposite side switch, the branch road outlet short circuit occurring, switch need to cut-off.Referring to Fig. 2, after disconnecting the limit K switch 13 of branch road offside of a main transformer ZB1, when connecting the way outlet short circuit of a main transformer ZB1, protection action tripping K11 and K12, have and only have two kinds of situations: the one, K12 disconnects prior to K11, K12 only need disconnect the short circuit current that 13 branch lines provide, after this short circuit current that K11 need to cut-off is that the busbar short-circuit electric current of 13 branch lines from plant stand is deviate from deducts now the short circuit current that main transformer ZB1 provides, 13 branch lines deviate to reduce the maximum short circuit current that the K11 switch need to cut-off; The 2nd, K11 disconnects prior to K12, and the short circuit current that K11 need to cut-off is that the busbar short-circuit electric current deducts the short circuit current that short circuit current that the circuit that connects a main transformer ZB1 provides and 13 branch lines provide, and the K12 switch only need cut-off the short circuit current that 13 branch lines provide.The risk of measure is that 13 branch lines are accompanied and stopped, and after can excising by fault branch, recovers 13 branch lines operations to the K13 that closes in during this period of time before recovering.
When other way outlet short circuit current is out-of-limit, current-limiting method is identical therewith.
The third situation: busbar short-circuit electric current and the simultaneously out-of-limit restriction of a way outlet short circuit current.When the busbar short-circuit electric current and way outlet short circuit current when simultaneously out-of-limit, can disconnect middle switch and at least one limit switch or staggered two the limit switches that are positioned at different strings and different bus bar side that disconnect that at least one is not main transformer place string simultaneously.This kind of situation be the method in Combination application the first situation and the second situation namely.
Fig. 3 is switch and the combination that disconnects the limit switch in disconnecting, the maximum short circuit current that during by the 42 restriction busbar short-circuit of K switch in disconnecting, switch need cut-off, the maximum short circuit current that while by disconnecting 13 restrictions of limit K switch, propping up the way outlet short circuit, switch need cut-off, in disconnecting after K switch 42 and limit K switch 13, the maximum short circuit current that when bus and way outlet short circuit, switch need cut-off all is lowered simultaneously.
In addition, disconnect the effect that the limit switch also can play the maximum short circuit current that while limiting the offside busbar short-circuit, switch need cut-off simultaneously.For example, after disconnecting K13, when a bus MX1 is short-circuited fault, if K11 is not last disconnection, the short circuit current maximum that the limit switch of a last disconnection of bus MX1 side need to cut-off, its value is the busbar short-circuit electric current of the 1st string from plant stand goes out string; If K11 is last disconnection, the short circuit current maximum that the switch that bus MX1 side penultimate disconnects cut-offs, its value deducts for bus MX1 short circuit current the short circuit current that 13 branch lines and main transformer ZB1 branch line provide.K11 only need cut-off the short circuit current that 13 branch lines in two kinds of situations and main transformer ZB1 branch line provide.
If two bus bar side respectively has a limit switch be positioned on different strings to be disconnected, the staggered limit K switch 51 of a bus MX1 and the limit K switch 13 of No. two bus MX2 of disconnecting for example, the maximum short circuit current that in the time of can limiting two way outlet short circuits, switch need cut-off, the maximum short circuit current that simultaneously switch need cut-off during two busbar short-circuits also is lowered, thereby reaches the purpose that simultaneously limits bus and a way outlet short circuit current.Fig. 4 is the example of this staggered disconnection limit method of switching.
By parity of reasoning can learn, disconnects with two a string limit switches and makes this string deviate from from transformer station the specific combination situation that (going out string) is disconnection limit switch current-limiting method.
The inventive method is tested at Central China Power Grid 500kV Xiaogan Substation, and the main wiring diagram of this transformer station as shown in Figure 1.Test is carried out according to the following steps:
Steps A: the Xiaogan Substation 500kV bus three-phase shortcircuit electric current calculated according to running mode data is 51.81kA, and can obtain each branch current, as shown in the table simultaneously:
Step B: the ascending order of each branch current is: the branch line branch current that connects No. one and No. two main transformer is respectively 1.61kA and 2.34kA, 41 branch lines and 51 branch line branch currents and is 4.30kA, 21 branch lines and 31 branch line branch currents and is that 4.94kA, 13 branch lines and 33 branch line branch currents are respectively 6.79kA and 6.82kA, 43 branch lines and 53 branch line branch currents are 8.17kA.The branch road of branch current minimum is the branch road that connects a main transformer, is positioned at the first string.
Step C: relatively determine that whether busbar short-circuit electric current and a way outlet short circuit current be out-of-limit.This step specifically minute three kinds of situations compares and limits.
The first situation: the busbar short-circuit electric current is out-of-limit relatively reaches restriction.Xiaogan Substation 500kV busbar short-circuit electric current is 51.81kA, and it is 50kA that the specified breaking current of part switch is arranged, so the busbar short-circuit electric current is out-of-limit.Now short-circuit current limitation method provided by the invention is divided three steps:
The first step: disconnect the middle switch that at least one is not main transformer place string.For Xiaogan Substation, referring to Fig. 1, in all branch roads that are connected with the plant stand bus, the short circuit current minimum that the branch line of a main transformer ZB1 of connection provides, next is to connect the short circuit current that the branch line of No. two main transformer ZB1 provides, that the 4th string is similar with the situation of the 5th string again, the short circuit current maximum that the 3rd string provides.When three phase short circuit fault occurs in a bus MX1, the 1st string and the 2nd is serially connected with main transformer, be not suitable for selecting to disconnect the middle switch of place string, the 4th string is similar with the situation of the 5th string, can select to disconnect middle K switch 42 or the K52 of place string, consider the 4th string plan transformation, the present embodiment selects to disconnect K42 simultaneously.
Second step: analyze in disconnecting the maximum short circuit current that while after switch, the busbar short-circuit fault occurring, switch need to cut-off.Referring to Fig. 1, if disconnect, it not the middle K switch 42 of main transformer place string, so when a bus MX1 short circuit, if K41 is not last disconnection, the short circuit current maximum that in K11, K21, K31 and K51, last that switch disconnected need to cut-off, its value is the busbar short-circuit electric currents of 41 branch lines from this plant stand is deviate from, and result of calculation is 48.85kA; If K41 is last disconnection, the maximum short circuit current maximum that the switch that in K11, K21, K31 and K51, penultimate disconnects need to cut-off, its value is that a bus MX1 short circuit current deducts the short circuit current that 41 lines provide, and is 51.81-4.30=47.51kA.
The 3rd step: relatively determine whether the maximum short circuit current that switch need cut-off is less than its specified breaking current.According to second step, no matter K41 with which kind of order disconnects, and because middle K switch 42 has disconnected, K41 only need cut-off above-mentioned two kinds of short circuit currents that different situations 41 branch lines provide, and the short circuit current that the wall scroll branch line provides is generally much smaller than the specified breaking current of switch.Therefore the short circuit current that all limits switch need to cut-off all is less than the specified breaking current of its 50 kilo-ampere, and during a bus MX1 short circuit, switch can effectively cut-off, thus isolated fault.
During No. two bus MX2 short circuits, the current limliting situation is identical during with a bus MX1 short circuit, and the maximum short circuit current that now switch need to cut-off is that 48.79kA(K43 is not last disconnection) or 51.81-8.17=43.64kA(K43 finally disconnect); K43 only need cut-off the short circuit current that under two kinds of different situations, 43 branch lines provide.
In sum, in disconnection, after K switch 42, the maximum short circuit current that during the Xiaogan Substation busbar short-circuit, switch need cut-off is as shown in the table:
Therefore, in disconnection after K switch 42, no matter Xiaogan Substation bus MX1 short circuit or No. two bus MX2 short circuit, the short circuit current that all switches need to cut-off all is less than its specified breaking current, and switch can effectively cut-off, thus isolated fault.
The second situation: way outlet short circuit current is out-of-limit relatively reaches restriction.In all connected branch roads of Xiaogan Substation 500kV bus, the branch road that the branch current minimum is provided is the branch road ZB1 that connects a main transformer, its short circuit current provided is 1.61kA, therefore when connecting the line outlet generation three-phase shortcircuit of a main transformer ZB1, the maximum short circuit current that switch need cut-off is 51.81-1.61=50.20kA, surpasses the specified breaking current 50kA of switch.In like manner known other way outlet short circuit current is not out-of-limit.Now short-circuit current limitation method provided by the invention is divided two steps:
The first step: at least one limit switch of the branch road offside that disconnected branches outlet short circuit current is out-of-limit, for Xiaogan Substation, referring to Fig. 2, in all branch roads that are connected with bus, the short circuit current minimum that the branch line of a main transformer ZB1 of connection provides, its way outlet short circuit current is out-of-limit, and therefore selection disconnects the limit K switch 13 of the branch line offside of a main transformer ZB1.
Second step: the maximum short circuit current that while after analysis disconnection opposite side switch, the branch road outlet short circuit occurring, switch need to cut-off.For Xiaogan Substation, after disconnecting limit K switch 13, when connecting the way outlet short circuit of a main transformer ZB1, if K12 disconnects prior to K11, K12 only need disconnect the short circuit current that 13 branch lines provide, after this short circuit current that K11 need to cut-off is that the busbar short-circuit electric current of 13 branch lines from plant stand is deviate from deducts now the short circuit current that main transformer ZB1 provides, the short circuit current calculated after 13 branch lines are deviate from is 48.12kA, the short circuit current that now ZB1 provides is 1.61kA, and the maximum short circuit current that K11 need cut-off is 48.12-1.61=46.51kA; If K11 disconnects prior to K12, the short circuit current that K11 need to cut-off is that the busbar short-circuit electric current deducts the short circuit current that short circuit current that main transformer ZB1 provides and 13 branch lines provide, be 51.81-1.61-6.79=43.41kA, the K12 switch only need cut-off the short circuit current that 13 branch lines provide.Therefore, which kind of situation no matter, the short circuit current that all switches need cut-off all is less than the specified breaking current of its 50kA, and switch can effectively cut-off, thus isolated fault.
The third situation: busbar short-circuit electric current and the simultaneously out-of-limit restriction of a way outlet short circuit current.For Xiaogan Substation, its busbar short-circuit electric current is out-of-limit with the line outlet short circuit current that is connected a main transformer ZB1, now selecting to disconnect is not middle K switch 42 and the limit K switch 13 of main transformer place string, as shown in Figure 3, according to noted earlier, the maximum short circuit current that during busbar short-circuit, switch need cut-off is limited to and is no more than 48.85kA, the maximum short circuit current that during way outlet short circuit, switch need cut-off is limited to and is no more than 46.51kA, all is limited to below the specified breaking current of switch 50kA.
For Xiaogan Substation, after disconnecting K13, when a bus MX1 is short-circuited fault, if K11 is not last disconnection, the short circuit current maximum that the last limit switch disconnected need to cut-off, its value is the busbar short-circuit electric current of the 1st string from plant stand goes out string, result of calculation is 47.61kA; If K11 is last disconnection, the short circuit current maximum that the switch that penultimate disconnects cut-offs, its value deducts for bus MX1 short circuit current the short circuit current that 13 branch lines and main transformer ZB1 branch line provide, be 51.81-6.79-1.61=43.41kA, K11 only need cut-off the short circuit current that 13 branch lines in two kinds of situations and main transformer ZB1 provide.Therefore disconnect the effect that the limit switch also can play the maximum short circuit current that while limiting the offside busbar short-circuit, switch need cut-off simultaneously.
The maximum short circuit current that while disconnecting limit K switch main transformer line outlet of 13 rear connections or a bus three-phase shortcircuit, switch need to cut-off is as shown in the table:
For Xiaogan Substation, if interlock again and disconnect a limit switch of a bus MX1 side in the limit K switch 13 that disconnects No. two bus MX2 sides, for example select K51, as shown in Figure 4, when No. two bus MX2 three-phase shortcircuits, if K53 is not last disconnection, the short circuit current maximum that the last limit switch disconnected need to cut-off, its value is the busbar short-circuit electric current of the 5th string from Xiaogan Substation goes out string, and result of calculation is 46.39kA; If K53 is last disconnection, the short circuit current maximum that the switch that penultimate disconnects need cut-off, its value deducts the short circuit current that 53 branch lines and 51 branch lines provide, i.e. 51.81-8.17-4.30=39.34kA for No. two bus MX2 short circuit currents; The K53 switch only need cut-off the short circuit current that in two kinds of situations, 53 branch lines and 51 branch lines provide, thereby the short circuit current that each limit switch need cut-off is all lower than the specified drop-out current of its 50kA.
Restriction in conjunction with 13 pairs of bus MX1 short circuit currents of aforementioned disconnection limit K switch is known, disconnect the limit K switch 51 of a bus MX1 of Xiaogan Substation and the limit K switch 13 of No. two bus MX2 if staggered, the maximum short circuit current that in the time of can limiting two way outlet short circuits, switch need cut-off, the maximum short circuit current that simultaneously switch need cut-off during two busbar short-circuits also is lowered, thereby reaches the purpose that simultaneously limits bus and a way outlet short circuit current.
Comprehensive the above, for Xiaogan Substation, the invention provides two kinds of short-circuit current limitation methods, the one, K switch 42 and limit K switch 13 in disconnecting, as shown in Figure 3, the 2nd, disconnect limit K switch 13 and limit K switch 51, as shown in Figure 4, these two kinds of methods can be simultaneously switch need cut-off during by bus and way outlet three-phase shortcircuit maximum short circuit current be restricted to below the specified breaking current of 50kA.In conjunction with the trend after short circuit malfunction and stability analysis, in disconnection, K switch 42 is relative with the method for limit K switch 13 more excellent, therefore as recommend method.
The switch disconnect mode can be fixing the disconnection, while normally moving, just switch is disconnected, and makes it in stand-by state, can be also the selectivity tripping operation, after short trouble occurs, by relaying protection, at first makes its tripping operation, and then relevant rest switch trips again.Because the selectivity tripping operation has extended trouble duration, under the present art condition, fixedly disconnect mode is more feasible.
Short-circuit current limitation method provided by the present invention is not limited to the quantity of the string that transformer station has and whether imperfect string is arranged, the string number of transformer station is not equal to five and/or imperfect string is arranged, and can implement similarly and apply short-circuit current limitation method provided by the present invention.
The inventive method is applicable to power plant and the transformer station of employing 3/2 mode of connection of 500kV electric pressure, be particularly useful for short circuit current surpass the specified breaking current of switch few or in the recent period short circuit current out-of-limit but short circuit current at a specified future date descends or due to relevant plant stand place or power system operating mode restriction, make conventional current limiting measures can't implement or the medium situation of switch replacing work progress under as a kind of interim current limiting measures, grid power transmission while can limiting short-circuit current not affecting again normal operation, with low cost and be easy to engineering construction.
Relevant data described herein and equipment are the specific embodiment of patent of the present invention, are illustrating that patent spirit of the present invention is done.Patent person of ordinary skill in the field of the present invention can make various modifications or supplements or adopt similar mode to substitute described specific embodiment, but can't depart from the spirit of patent of the present invention or surmount the defined scope of appended claims.
Claims (4)
1. the method for limiting short circuit current of power grid under 3/2 mode of connection of a 500kV electric pressure, is characterized in that comprising the steps:
The branch current of A, calculating plant stand busbar short-circuit electric current and the branch road that is connected;
B, determine the branch road of branch current minimum and the string at place thereof;
Whether C, relatively more definite busbar short-circuit electric current and a way outlet short circuit current be out-of-limit, if the busbar short-circuit electric current is out-of-limit, disconnects the middle switch that at least one is not main transformer place string; If a way outlet short circuit current is out-of-limit, at least one limit switch that is positioned at the offside bus bar side that go here and there at the disconnected branches place; If busbar short-circuit electric current and a way outlet short circuit current are simultaneously out-of-limit, disconnect one is not the middle switch of main transformer place string and the limit switch or staggered two the limit switches that are positioned at different strings and different bus bar side that disconnect that are positioned at the offside bus bar side of branch road place string simultaneously.
2. according to the method for limiting short circuit current of power grid under 3/2 mode of connection of the said a kind of 500kV electric pressure of claim 1, while it is characterized in that in described disconnection switch restriction busbar short-circuit electric current, can preferentially select to provide the middle switch of the string of short circuit current maximum.
3. according to the method for limiting short circuit current of power grid under 3/2 mode of connection of the said a kind of 500kV electric pressure of claim 1, while it is characterized in that described disconnection limit switch restriction way outlet short circuit current, can preferentially select to provide the limit switch that is positioned at the offside bus bar side of the branch road place string of short circuit current minimum.
4. according to the method for limiting short circuit current of power grid under 3/2 mode of connection of claim 1,2 or 3 said a kind of 500kV electric pressures, it is characterized in that the mode of switch in described disconnection or limit switch disconnects or realizes that by relaying protection the selectivity order tripping operation disconnects for fixing.
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| CN107579521B (en) * | 2017-10-19 | 2019-08-13 | 广西电网有限责任公司电力科学研究院 | A kind of PSD-SCCP500kV main transformer branch Analysis of Short-Circuit Current method of object-oriented |
| CN109599748B (en) * | 2018-10-31 | 2020-10-16 | 国网宁夏电力有限公司电力科学研究院 | Control method and device for short-circuit current of transformer substation, storage medium and processor |
| CN109962448B (en) * | 2019-02-02 | 2023-06-09 | 中国电力科学研究院有限公司 | Short-circuit current absorption branch input control method and device based on voltage characteristics |
| CN111244907B (en) * | 2020-01-17 | 2022-09-09 | 中国电力科学研究院有限公司 | On-off time sequence control method and system of breaker in transformer substation |
| CN111262227A (en) * | 2020-01-17 | 2020-06-09 | 华北电力大学 | Method and device for regulating system topology to limit breaker on-off short-circuit current |
| CN112736871B (en) * | 2020-12-24 | 2024-05-10 | 国网浙江省电力有限公司电力科学研究院 | Method and system for finely checking short-circuit current of transformer substation of 220kV and below |
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