CN108459233B - Equivalent circuit of main transformer high-voltage two-phase disconnection fault and identification method - Google Patents
Equivalent circuit of main transformer high-voltage two-phase disconnection fault and identification method Download PDFInfo
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Abstract
The invention provides an equivalent circuit of a main transformer high-voltage two-phase disconnection fault, which is equivalent to a circuit formed by a 220kV bus, a 110kV bus, a plurality of 220kV normal main transformers and 220kV fault main transformers, and the neutral point of the fault main transformer is grounded. The method specifically comprises a positive sequence network, a negative sequence network and a zero sequence network which are mutually connected in series; the positive sequence network comprises positive sequence equivalent buses and high, medium and low voltage side positive sequence impedance of each main transformer; the negative sequence network comprises a negative sequence equivalent bus and negative sequence impedance of each main transformer high and medium voltage side; the zero sequence network comprises a zero sequence equivalent bus and a neutral point grounded main transformer, and the high and medium voltage side negative sequence impedance is realized; the positive, negative and zero sequence impedances of the high-voltage side of the fault main transformer have currents with the same magnitude and direction, and the negative and zero sequence impedances of the medium-voltage side have currents with the same magnitude and direction. By implementing the method, the problems of insufficient processing experience, low efficiency and the like caused by the simultaneous tripping event of the main transformer due to the high-voltage two-phase disconnection of the 220kV main transformer can be solved.
Description
Technical Field
The invention relates to the technical field of power transmission and transformation of power systems, in particular to an equivalent circuit of a main transformer high-voltage two-phase disconnection fault and a recognition method.
Background
In 2017, after the overhaul work of the high switch of the No. 3 main transformer of a 220kV transformer substation is finished, power is transmitted, in the power transmission process, the high switch is turned on firstly, no abnormality exists, but after the power is turned on, the zero sequence overcurrent II section protection simultaneous action phenomenon occurs on the middle voltage side of the No. 3 main transformer and the running No. 1 main transformer, so that the two No. 3 main transformers and the No. 1 main transformer trip simultaneously. After deeply analyzing the fault waveform and the fault current amplitude, the worker confirms that the reason of the event is that the BC two-phase broken line of the No. 3 main transformer is high.
However, at present, no document is available for carrying out theoretical research on a two-phase broken line with a high 220kV main transformer, and the field lacks experience of handling broken line faults, so that the analysis time of the event is long, and the two main transformers cannot quickly re-supply power, thereby greatly influencing the power supply reliability and the safe and stable operation capability of a power grid.
Therefore, an equivalent circuit and an identification method for a main transformer high-phase disconnection fault are needed, and the problems of insufficient processing experience, low efficiency and the like caused by a main transformer and tripping event due to the fact that 220kV main transformer high-phase disconnection can be solved.
Disclosure of Invention
The technical problem to be solved by the embodiment of the invention is to provide an equivalent circuit and an identification method for a main transformer high two-phase disconnection fault, which can solve the problems of insufficient processing experience, lower efficiency and the like caused by a main transformer simultaneous tripping event due to 220kV main transformer high two-phase disconnection.
In order to solve the technical problems, the embodiment of the invention provides an equivalent circuit of a main transformer high-phase disconnection fault, which is equivalent to a circuit formed by a 220kV bus, a 110kV bus and a plurality of 220kV normal main transformers and a 220kV fault main transformer which are connected in parallel between the two, wherein the neutral point of the 220kV fault main transformer is grounded;
the equivalent circuit of the main transformer high-phase disconnection fault comprises a positive sequence network, a negative sequence network and a zero sequence network which are mutually connected in series; wherein,
the positive sequence network comprises a positive sequence equivalent bus of the 220kV bus, a corresponding equivalent power supply and an equivalent resistor thereof, a positive sequence equivalent bus of the 110kV bus, a corresponding equivalent load thereof, and high-voltage side positive sequence impedance, medium-voltage side positive sequence impedance and low-voltage side positive sequence impedance which are respectively corresponding to the plurality of 220kV normal main transformers and the 220kV fault main transformers; the equivalent power supply of the 220kV bus is connected in series with the input end of the positive sequence equivalent bus of the 220kV bus through an equivalent resistor of the 220kV bus; the equivalent load of the 110kV bus is connected in series with the output end of the positive sequence equivalent bus of the 110kV bus; each 220kV normal main transformer is used for butting one end of the corresponding high-voltage side positive sequence impedance, one end of the corresponding medium-voltage side positive sequence impedance and one end of the corresponding low-voltage side positive sequence impedance together, connecting the other end of the corresponding high-voltage side positive sequence impedance to the output end of the positive sequence equivalent bus of the 220kV bus, and connecting the other end of the corresponding medium-voltage side positive sequence impedance to the input end of the positive sequence equivalent bus of the 110kV bus; the 220kV fault main transformer is used for butting one end of the corresponding high-voltage side positive sequence impedance, one end of the corresponding medium-voltage side positive sequence impedance and one end of the corresponding low-voltage side positive sequence impedance together, connecting the other end of the corresponding medium-voltage side positive sequence impedance to the input end of the positive sequence equivalent bus of the 110kV bus, and connecting the other end of the corresponding high-voltage side positive sequence impedance to one end of the negative sequence network; the output end of the positive sequence equivalent bus of the 220kV bus is also connected to one end of the zero sequence network;
the negative sequence network comprises a negative sequence equivalent bus of the 220kV bus, a negative sequence equivalent bus of the 110kV bus, and high-voltage side negative sequence impedance and medium-voltage side negative sequence impedance corresponding to each of the 220kV normal main transformers and the 220kV fault main transformers; each 220kV normal main transformer connects one end of the corresponding high-voltage side negative sequence impedance and one end of the corresponding medium-voltage side negative sequence impedance in series, connects the other end of the corresponding high-voltage side negative sequence impedance to a negative sequence equivalent bus of the 220kV bus, and connects the other end of the corresponding medium-voltage side negative sequence impedance to a negative sequence equivalent bus of the 110kV bus; the 220kV fault main transformer connects one end of the corresponding high-voltage side negative sequence impedance and one end of the corresponding medium-voltage side negative sequence impedance in series, the other end of the corresponding medium-voltage side negative sequence impedance is connected with the negative sequence equivalent bus of the 110kV bus, and the other end of the corresponding high-voltage side negative sequence impedance is connected with the other end of the zero sequence network; the negative sequence equivalent bus of the 220kV bus is also connected with the other end of the positive sequence impedance of the high-voltage side of the 220kV fault main transformer in the positive sequence network;
the zero-sequence network comprises a zero-sequence equivalent bus of the 220kV bus, a zero-sequence equivalent bus of the 110kV bus, high-voltage side zero-sequence impedance and medium-voltage side zero-sequence impedance which are respectively corresponding to a 220kV main transformer with a grounded neutral point among the plurality of 220kV normal main transformers, and high-voltage side zero-sequence impedance and medium-voltage side zero-sequence impedance of the 220kV fault main transformer; wherein, each neutral point-grounded 220kV normal main transformer connects one end of each corresponding high-voltage side zero-sequence impedance and one end of each corresponding medium-voltage side zero-sequence impedance in series, and also connects the other end of each corresponding high-voltage side zero-sequence impedance to a zero-sequence equivalent bus of the 220kV bus, and also connects the other end of each corresponding medium-voltage side zero-sequence impedance to a zero-sequence equivalent bus of the 110kV bus; the 220kV fault main transformer connects one end of the corresponding high-voltage side zero-sequence impedance and one end of the corresponding medium-voltage side zero-sequence impedance in series, the other end of the corresponding medium-voltage side zero-sequence impedance is connected with the zero-sequence equivalent bus of the 110kV bus, and the other end of the corresponding high-voltage side zero-sequence impedance is connected with the output end of the positive-sequence equivalent bus of the 220kV bus in the positive-sequence network; the zero sequence equivalent bus of the 220kV bus is also connected with the other end of the negative sequence impedance of the high-voltage side of the 220kV fault main transformer in the negative sequence network;
the high-voltage side positive sequence impedance, the high-voltage side negative sequence impedance and the high-voltage side zero sequence impedance of the 220kV fault main transformer are equal in magnitude and same in direction;
and the medium-voltage side negative sequence impedance and the medium-voltage side zero sequence impedance of the 220kV fault main transformer have currents with the same magnitude and the same direction.
The voltages of the positive sequence equivalent bus, the negative sequence equivalent bus and the zero sequence equivalent bus of the 220kV bus are equal.
The voltages of the positive sequence equivalent bus, the negative sequence equivalent bus and the zero sequence equivalent bus of the 110kV bus are equal.
And the low-voltage side positive sequence impedances corresponding to the 220kV normal main transformers and the 220kV fault main transformers are equal in magnitude and same in direction.
The embodiment of the invention also provides a method for identifying the main transformer high two-phase disconnection fault, which is realized on the equivalent circuit of the main transformer high two-phase disconnection fault, and comprises the following steps:
s1, acquiring currents of high-voltage side positive sequence impedance, medium-voltage side positive sequence impedance and low-voltage side positive sequence impedance of a 220kV fault main transformer flowing through a positive sequence network, currents of high-voltage side negative sequence impedance and medium-voltage side negative sequence impedance of the 220kV fault main transformer flowing through a negative sequence network and currents of high-voltage side zero sequence impedance and medium-voltage side zero sequence impedance of the 220kV fault main transformer flowing through a zero sequence network from the equivalent circuit;
and step S2, when the current with the same magnitude and the same direction is detected on the high-voltage side positive sequence impedance, the high-voltage side negative sequence impedance and the high-voltage side zero sequence impedance of the 220kV fault main transformer, and the current with the same magnitude and the same direction is detected on the medium-voltage side negative sequence impedance and the medium-voltage side zero sequence impedance of the 220kV fault main transformer, determining that the 220kV fault main transformer is high and a two-phase disconnection fault occurs.
The embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, the actual parallel running main transformer circuit is converted into the equivalent circuit, and the current of the fault main transformer in the equivalent circuit is judged to rapidly determine the two-phase disconnection fault of the fault main transformer, so that the problems of insufficient processing experience, lower efficiency and the like caused by the simultaneous tripping event of the main transformer due to the high two-phase disconnection of the 220kV main transformer can be solved.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that it is within the scope of the invention to one skilled in the art to obtain other drawings from these drawings without inventive faculty.
Fig. 1 is a practical circuit diagram of a single 220kV main transformer provided by an embodiment of the present invention; wherein a is a 220kV main transformer with a neutral point grounded; b is 220kV main transformer with neutral point not grounded;
FIG. 2 is an equivalent circuit of FIG. 1 a;
FIG. 3 is an equivalent circuit of FIG. 1 b;
fig. 4 is an actual circuit diagram of a main transformer high two-phase disconnection fault provided by an embodiment of the present invention;
fig. 5 is an equivalent circuit diagram of a main transformer high two-phase disconnection fault provided by an embodiment of the present invention;
fig. 6 is an application scenario diagram of an equivalent circuit of a main transformer high two-phase disconnection fault provided by an embodiment of the present invention;
fig. 7 is a flowchart of a method for identifying a main transformer high two-phase broken line fault provided by an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent.
The inventor finds that the problems existing in the actual circuit can be rapidly analyzed by converting the actual circuit into the equivalent circuit and analyzing the equivalent circuit, thereby being beneficial to reducing the complexity of data analysis, improving the analysis efficiency and providing effective guarantee for actual fault treatment.
As shown in fig. 1, in the study of the two-phase disconnection in which the 220kV main transformer is high, the 220kV main transformer may be divided into a 220kV main transformer in which the neutral point is grounded (as shown in fig. 1 a) and a 220kV main transformer in which the neutral point is not grounded (as shown in fig. 1 b).
At this time, as shown in fig. 2, the 220kV main transformer with the neutral point grounded shown in fig. 1a is converted into an equivalent circuit including positive sequence, negative sequence and zero sequence. Wherein Z is H（1） 、Z H（2） 、Z H（0） The high-voltage side impedance of the 220kV main transformer which is grounded at the neutral point is in a positive sequence equivalent circuit, a negative sequence equivalent circuit and a zero sequence equivalent circuit respectively; z is Z M（1） 、Z M（2） 、Z M（0） Medium voltage side impedance in a positive sequence equivalent circuit, a negative sequence equivalent circuit and a zero sequence equivalent circuit of the 220kV main transformer respectively with a neutral point grounded; z is Z L（1） 、Z L（2） 、Z L（0） And the low-voltage side impedance in the positive sequence equivalent circuit, the negative sequence equivalent circuit and the zero sequence equivalent circuit of the 220kV main transformer with the neutral point grounded respectively.
As shown in fig. 3, the 220kV main transformer with the neutral point not grounded shown in fig. 1 b is converted into an equivalent circuit including a positive sequence and a negative sequence. Because the main transformer neutral point does not run in the ground, zero sequence current circulation cannot be formed, namely, only a positive sequence equivalent circuit and a negative sequence equivalent circuit are formed. Wherein Z is H（1） 、Z H（2） The high-voltage side impedance of the 220kV main transformer with the neutral point not grounded in a positive sequence equivalent circuit and a negative sequence equivalent circuit respectively; z is Z M（1） 、Z M（2） Medium voltage side impedance in a positive sequence equivalent circuit and a negative sequence equivalent circuit of the 220kV main transformer with the neutral point not grounded respectively; z is Z L（1） 、Z L（2） The low-voltage side impedance of the 220kV main transformer with the neutral point not grounded in a positive sequence equivalent circuit and a negative sequence equivalent circuit is respectively.
Therefore, according to the 220kV main transformer equivalent transformation process, the 220kV main transformer high-phase disconnection fault circuit can be subjected to equivalent transformation to determine the authenticity of the fault. As shown in fig. 4, the main transformer high two-phase disconnection fault circuit is formed by a 220kV busbar, a 110kV busbar, a plurality of 220kV normal main transformers (such as 220kV main transformers #1, #2, …, # N) and a 220kV fault main transformer (such as 220kV main transformer #n+1) which are connected in parallel, and a 220kV fault main transformer neutral point is grounded. It should be noted that the 220kV main transformer #1 to #N+1 are preliminarily determined, but the two-phase disconnection fault of the 220kV fault main transformer #N+1 is still undetermined.
Therefore, the inventor provides an equivalent circuit of a main transformer high-phase disconnection fault, and can rapidly judge the possibility of the main transformer to be disconnected faults of the two phases aiming at the main transformer high-phase disconnection fault circuit shown in fig. 4.
As shown in fig. 5, in the embodiment of the present invention, an equivalent circuit for a main transformer high-phase disconnection fault provided by the inventor specifically includes: a positive sequence network A, a negative sequence network B and a zero sequence network C which are mutually connected in series; wherein,
the positive sequence network A comprises a positive sequence equivalent bus A1 of the 220kV bus, a corresponding equivalent power supply Es and an equivalent resistor Zs, a positive sequence equivalent bus A2 of the 110kV bus, a corresponding equivalent load Zp, and high-voltage side positive sequence impedance Z corresponding to each of 220kV normal main transformers #1 to #N and 220kV fault main transformer #N+1 H（1） Positive sequence impedance Z of medium voltage side M（1） Low-voltage side positive sequence impedance Z L（1） The method comprises the steps of carrying out a first treatment on the surface of the The equivalent power supply Es of the 220kV bus is connected in series with the input end of the positive sequence equivalent bus A1 of the 220kV bus through an equivalent resistor Zs of the 220kV bus; the equivalent load Zp of the 110kV bus is connected in series to the output end of the positive sequence equivalent bus A2 of the 110kV bus; each 220kV normal main transformer #1 to #N respectively corresponds to the positive sequence impedance Z of the high voltage side H（1） One end, medium voltage side positive sequence impedance Z M（1） One end of (d) and low-side positive sequence impedance Z L（1） Is butted together and also respectively corresponds to the positive sequence impedance Z of the high voltage side H（1） The other end of the voltage transformer is connected with the output end of a positive sequence equivalent bus A1 of the 220kV bus, and the corresponding medium voltage side positive sequence impedance Z is also respectively connected with M（1） The other end of the bus is connected with the input end of a positive sequence equivalent bus A2 of the 110kV bus; 220kV fault main transformer #N+1 is used for leading corresponding high-voltage side positive sequence impedance Z H（1） One end, medium voltage side positive sequence impedance Z M（1） One end of (d) and low-side positive sequence impedance Z L（1） Is butted together and also has a corresponding medium-voltage side positive sequence impedance Z M（1） The other end of the positive sequence equivalent bus A2 is connected with the input end of the 110kV bus, and the corresponding positive sequence impedance Z of the high voltage side is also connected with the input end of the positive sequence equivalent bus A2 H（1） The other end of the negative sequence network B is connected with one end of the negative sequence network B; the output end of the positive sequence equivalent bus A1 of the 220kV bus is also connected to one end of the zero sequence network C;
the negative sequence network B comprises a negative sequence equivalent bus B1 of a 220kV bus, a negative sequence equivalent bus B2 of a 110kV bus, and high-voltage side negative sequence impedance Z corresponding to each of a plurality of 220kV normal main transformers #1 to #N and 220kV fault main transformers #N+1 H（2） Negative sequence impedance Z of medium voltage side M（2） The method comprises the steps of carrying out a first treatment on the surface of the Wherein each 220kV normal main transformer #1 to # N respectively corresponds to the high-voltage side negative sequence impedance Z H（2） One end of (d) and medium voltage side negative sequence impedance Z M（2） Is connected in series with one end of each other and respectively corresponds to the high-voltage side negative sequence impedance Z H（2） The other end of the bus is connected with a negative sequence equivalent bus B1 of the 220kV bus, and the corresponding medium-voltage side negative sequence impedance Z is also respectively connected with M（2） The other end of the bus is connected with a negative sequence equivalent bus B2 of the 110kV bus; 220kV fault main transformer #N+1 is used for leading corresponding high-voltage side negative sequence impedance Z H（2） One end of (d) and medium voltage side negative sequence impedance Z M（2） Is connected in series with one end of the capacitor, and the corresponding medium-voltage side negative sequence impedance Z M（2） The other end of the bus is connected with a negative sequence equivalent bus B2 of the 110kV bus, and the corresponding high-voltage side negative sequence impedance Z is also connected with the bus H（2） The other end of the zero sequence network C is accessed to the other end of the zero sequence network C; negative sequence equivalent bus B1 of 220kV bus is also connected with high-voltage side positive sequence impedance Z of 220kV fault main transformer #N+1 in positive sequence network A H（1） Is connected with the other end of the connecting rod;
the zero-sequence network C comprises a zero-sequence equivalent bus C1 of a 220kV bus, a zero-sequence equivalent bus C2 of a 110kV bus, and 220kV main transformers #K to #K+L (K+L) with grounded neutral points among a plurality of 220kV normal main transformers #1 to #N<N) the respective corresponding high-voltage side zero sequence impedance Z H（0） Zero sequence impedance Z of medium-voltage side M（0） High-voltage side zero-sequence impedance Z of 220kV fault main transformer #N+1 H（0） Zero sequence impedance Z of medium-voltage side M（0） The method comprises the steps of carrying out a first treatment on the surface of the Wherein each neutral point is grounded, and 220kV normal main transformers #K to #K+L respectively correspond to the high-voltage side zero sequence impedance Z H（0） One end and medium voltage side zero sequence impedance Z M（0） Is connected in series with one end of each other and respectively corresponds to the zero sequence impedance Z of the high voltage side H（0） Is arranged at the other end of (2)The zero sequence equivalent buses C1 of the 220kV buses are connected, and the corresponding medium-voltage side zero sequence impedance Z is also adopted M（0） The other end of the bus is connected with a zero sequence equivalent bus C2 of the 110kV bus; 220kV fault main transformer #N+1 is used for realizing corresponding high-voltage side zero sequence impedance Z H（0） One end and medium voltage side zero sequence impedance Z M（0） One end of the transformer is connected in series and the corresponding medium-voltage side zero sequence impedance Z is also used M（0） The other end of the bus is connected with a zero sequence equivalent bus C2 of the 110kV bus, and the corresponding high-voltage side zero sequence impedance Z is also connected with H（0） The other end of the bus is connected with the output end of a positive sequence equivalent bus A1 of the 220kV bus in the positive sequence network A; zero sequence equivalent bus C1 of 220kV bus is also connected with high-voltage side negative sequence impedance Z of 220kV fault main transformer #N+1 in negative sequence network B H（2） Is connected with the other end of the connecting rod;
wherein, 220kV fault main transformer #N+1 high-voltage side positive sequence impedance Z H（1） Negative sequence impedance Z at high voltage side H（2） High-voltage side zero sequence impedance Z H（0） The currents with the same magnitude and the same direction are simultaneously arranged on the two electrodes; for example, the high-side positive sequence impedance Z H（1） Is the current I of (2) 11 Negative sequence impedance Z at high voltage side H（2） Is the current I of (2) 21 Zero sequence impedance Z at high voltage side H（0） Is the current I of (2) 01 Equal in size and direction;
wherein, 220kV fault main transformer #N+1 medium-voltage side negative sequence impedance Z M（2） Zero sequence impedance Z of medium-voltage side M（0） With currents of equal magnitude and direction, e.g. medium-voltage side negative-sequence impedance Z M（2） Is the current I of (2) 22 Zero sequence impedance Z of medium-voltage side M（0） Is the current I of (2) 02 Equal in size and in the same direction.
It should be noted that, because the power grid has no negative sequence load, the winding of the main transformer low-voltage side does not generate negative sequence current in the equivalent circuit, the main transformer low-voltage side is in triangular connection, and the main transformer low-voltage side line current does not generate zero sequence current in the equivalent circuit, so that the low-voltage side of the 220kV fault main transformer #N+1 does not generate negative sequence current and zero sequence current. K. L, N are all positive integers.
It will be appreciated that once a 220kV faulty main transformer #n is detected+1 high-side positive-sequence impedance Z H（1） Negative sequence impedance Z at high voltage side H（2） High-voltage side zero sequence impedance Z H（0） The current with the same magnitude and direction is simultaneously provided, and the negative sequence impedance Z of the medium voltage side of the 220kV fault main transformer #N+1 M（2） Zero sequence impedance Z of medium-voltage side M（0） And meanwhile, the currents with the same magnitude and the same direction exist, so that the fault of the 220kV fault main transformer #N+1 is judged to be a two-phase broken line fault.
In the embodiment of the invention, the voltages of the positive sequence equivalent bus A1, the negative sequence equivalent bus B1 and the zero sequence equivalent bus C1 of the 220kV bus are equal and are 220kV.
In the embodiment of the invention, the voltages of the positive sequence equivalent bus A2, the negative sequence equivalent bus B2 and the zero sequence equivalent bus C2 of the 110kV bus are equal and are 110kV.
In the embodiment of the invention, a plurality of 220kV normal main transformers #1 to #N and 220kV fault main transformer #N+1 respectively correspond to low-voltage side positive sequence impedance Z L（1） Meanwhile, the currents with the same magnitude and the same direction are provided, and because the broken line fault of the power grid does not cause equipment damage, normal power supply can be maintained, and at the moment, the time from the broken line fault to main transformer tripping is only maintained for a few seconds, and the load requirement of a user is unchanged in the time. It should be noted that, because of the low-voltage side positive sequence impedance Z corresponding to each of the 220kV normal main transformers #1 to #N and 220kV fault main transformer #n+1 L（1） The current with the same magnitude and the same direction is simultaneously provided, and the load demand is unchanged and constant, so that the low-voltage side positive sequence impedance Z corresponding to each of the 220kV normal main transformers #1 to #N and 220kV fault main transformer #N+1 in the graph 5 L（1） May be omitted.
As shown in fig. 6, an application scenario of an equivalent circuit diagram of a main transformer high-phase disconnection fault in an embodiment of the present invention is further described, which specifically includes:
fig. 6 is an equivalent circuit of an actual circuit of the 4 220kV main transformer; wherein #1 to #3 are normal main transformers, #4 is a fault main transformer, #1 and #4 are neutral point grounded main transformers, and #2 to #3 are neutral point ungrounded main transformers; equivalent power supply E S The load current flowing into the positive sequence circuit A is denoted as I Hf The method comprises the steps of carrying out a first treatment on the surface of the #1- #4 main transformerThe 10kV side load current is recorded as I Lf1 、I Lf2 、I Lf3 、I 01 ；I Mf Equivalent load current of 110kV bus; i 1 、I 2 、I 0 Positive sequence, negative sequence and zero sequence currents in the sequence network circuit respectively.
At this time, the high-voltage side positive-sequence impedance Z of the #4 fault main transformer H（1） Is the current I of (2) 11 Negative sequence impedance Z at high voltage side H（2） Is the current I of (2) 21 Zero sequence impedance Z at high voltage side H（0） Is the current I of (2) 01 Equal in size and direction, and medium-voltage side negative sequence impedance Z M（2） Is the current I of (2) 22 Zero sequence impedance Z of medium-voltage side M（0） Is the current I of (2) 02 Equal in size and in the same direction.
Listing the voltage equation and ohm law equation of each node, and obtaining a zero sequence current formula (1) of the zero sequence circuit as follows:
（1）
let I before disconnection Hf =1200a, then we get；
At this time, the obtained 281A has little difference with the zero sequence current actually measured when the #4 fault main transformer is high and the two-phase broken line fault occurs, so that the correctness of the equivalent circuit is verified.
As shown in fig. 7, in the embodiment of the present invention, a method for identifying a main transformer high two-phase disconnection fault is provided, which is implemented on the equivalent circuit of the main transformer high two-phase disconnection fault, and the method includes:
s1, acquiring currents of high-voltage side positive sequence impedance, medium-voltage side positive sequence impedance and low-voltage side positive sequence impedance of a 220kV fault main transformer flowing through a positive sequence network, currents of high-voltage side negative sequence impedance and medium-voltage side negative sequence impedance of the 220kV fault main transformer flowing through a negative sequence network and currents of high-voltage side zero sequence impedance and medium-voltage side zero sequence impedance of the 220kV fault main transformer flowing through a zero sequence network from the equivalent circuit;
and step S2, when the current with the same magnitude and the same direction is detected on the high-voltage side positive sequence impedance, the high-voltage side negative sequence impedance and the high-voltage side zero sequence impedance of the 220kV fault main transformer, and the current with the same magnitude and the same direction is detected on the medium-voltage side negative sequence impedance and the medium-voltage side zero sequence impedance of the 220kV fault main transformer, determining that the 220kV fault main transformer is high and a two-phase disconnection fault occurs.
The embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, the actual parallel running main transformer circuit is converted into the equivalent circuit, and the current of the fault main transformer in the equivalent circuit is judged to rapidly determine the two-phase disconnection fault of the fault main transformer, so that the problems of insufficient processing experience, lower efficiency and the like caused by the simultaneous tripping event of the main transformer due to the high two-phase disconnection of the 220kV main transformer can be solved.
Those of ordinary skill in the art will appreciate that all or a portion of the steps in implementing the methods of the above embodiments may be implemented by a program to instruct related hardware, where the program may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc.
The foregoing disclosure is illustrative of the present invention and is not to be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (5)
1. The equivalent circuit is characterized by being equivalent to a circuit formed by a 220kV bus, a 110kV bus, a plurality of 220kV normal main transformers and a 220kV fault main transformer which are connected in parallel between the 220kV bus and the 110kV bus, and the neutral point of the 220kV fault main transformer is grounded;
the equivalent circuit of the main transformer high-phase disconnection fault comprises a positive sequence network, a negative sequence network and a zero sequence network which are mutually connected in series; wherein,
the positive sequence network comprises a positive sequence equivalent bus of the 220kV bus, a corresponding equivalent power supply and an equivalent resistor thereof, a positive sequence equivalent bus of the 110kV bus, a corresponding equivalent load thereof, and high-voltage side positive sequence impedance, medium-voltage side positive sequence impedance and low-voltage side positive sequence impedance which are respectively corresponding to the plurality of 220kV normal main transformers and the 220kV fault main transformers; the equivalent power supply of the 220kV bus is connected in series with the input end of the positive sequence equivalent bus of the 220kV bus through an equivalent resistor of the 220kV bus; the equivalent load of the 110kV bus is connected in series with the output end of the positive sequence equivalent bus of the 110kV bus; each 220kV normal main transformer is used for butting one end of the corresponding high-voltage side positive sequence impedance, one end of the corresponding medium-voltage side positive sequence impedance and one end of the corresponding low-voltage side positive sequence impedance together, connecting the other end of the corresponding high-voltage side positive sequence impedance to the output end of the positive sequence equivalent bus of the 220kV bus, and connecting the other end of the corresponding medium-voltage side positive sequence impedance to the input end of the positive sequence equivalent bus of the 110kV bus; the 220kV fault main transformer is used for butting one end of the corresponding high-voltage side positive sequence impedance, one end of the corresponding medium-voltage side positive sequence impedance and one end of the corresponding low-voltage side positive sequence impedance together, connecting the other end of the corresponding medium-voltage side positive sequence impedance to the input end of the positive sequence equivalent bus of the 110kV bus, and connecting the other end of the corresponding high-voltage side positive sequence impedance to one end of the negative sequence network; the output end of the positive sequence equivalent bus of the 220kV bus is also connected to one end of the zero sequence network;
the negative sequence network comprises a negative sequence equivalent bus of the 220kV bus, a negative sequence equivalent bus of the 110kV bus, and high-voltage side negative sequence impedance and medium-voltage side negative sequence impedance corresponding to each of the 220kV normal main transformers and the 220kV fault main transformers; each 220kV normal main transformer connects one end of the corresponding high-voltage side negative sequence impedance and one end of the corresponding medium-voltage side negative sequence impedance in series, connects the other end of the corresponding high-voltage side negative sequence impedance to a negative sequence equivalent bus of the 220kV bus, and connects the other end of the corresponding medium-voltage side negative sequence impedance to a negative sequence equivalent bus of the 110kV bus; the 220kV fault main transformer connects one end of the corresponding high-voltage side negative sequence impedance and one end of the corresponding medium-voltage side negative sequence impedance in series, the other end of the corresponding medium-voltage side negative sequence impedance is connected with the negative sequence equivalent bus of the 110kV bus, and the other end of the corresponding high-voltage side negative sequence impedance is connected with the other end of the zero sequence network; the negative sequence equivalent bus of the 220kV bus is also connected with the other end of the positive sequence impedance of the high-voltage side of the 220kV fault main transformer in the positive sequence network;
the zero-sequence network comprises a zero-sequence equivalent bus of the 220kV bus, a zero-sequence equivalent bus of the 110kV bus, high-voltage side zero-sequence impedance and medium-voltage side zero-sequence impedance which are respectively corresponding to a 220kV main transformer with a grounded neutral point among the plurality of 220kV normal main transformers, and high-voltage side zero-sequence impedance and medium-voltage side zero-sequence impedance of the 220kV fault main transformer; wherein, each neutral point-grounded 220kV normal main transformer connects one end of each corresponding high-voltage side zero-sequence impedance and one end of each corresponding medium-voltage side zero-sequence impedance in series, and also connects the other end of each corresponding high-voltage side zero-sequence impedance to a zero-sequence equivalent bus of the 220kV bus, and also connects the other end of each corresponding medium-voltage side zero-sequence impedance to a zero-sequence equivalent bus of the 110kV bus; the 220kV fault main transformer connects one end of the corresponding high-voltage side zero-sequence impedance and one end of the corresponding medium-voltage side zero-sequence impedance in series, the other end of the corresponding medium-voltage side zero-sequence impedance is connected with the zero-sequence equivalent bus of the 110kV bus, and the other end of the corresponding high-voltage side zero-sequence impedance is connected with the output end of the positive-sequence equivalent bus of the 220kV bus in the positive-sequence network; the zero sequence equivalent bus of the 220kV bus is also connected with the other end of the negative sequence impedance of the high-voltage side of the 220kV fault main transformer in the negative sequence network;
the high-voltage side positive sequence impedance, the high-voltage side negative sequence impedance and the high-voltage side zero sequence impedance of the 220kV fault main transformer are equal in magnitude and same in direction;
and the medium-voltage side negative sequence impedance and the medium-voltage side zero sequence impedance of the 220kV fault main transformer have currents with the same magnitude and the same direction.
2. The equivalent circuit for a main transformer high two-phase disconnection fault according to claim 1, wherein the voltages of a positive sequence equivalent bus, a negative sequence equivalent bus and a zero sequence equivalent bus of the 220kV bus are all equal.
3. The equivalent circuit for a main transformer high two-phase disconnection fault according to claim 2, wherein the voltages of a positive sequence equivalent bus, a negative sequence equivalent bus and a zero sequence equivalent bus of the 110kV bus are all equal.
4. The equivalent circuit for a main transformer high two-phase disconnection fault according to claim 3, wherein the low-voltage side positive sequence impedances corresponding to the 220kV normal main transformer and the 220kV fault main transformer have currents with the same magnitude and the same direction.
5. A method for identifying a main transformer high two-phase disconnection fault, which is realized on the equivalent circuit of the main transformer high two-phase disconnection fault according to any one of claims 1 to 4, and comprises the following steps:
s1, acquiring currents of high-voltage side positive sequence impedance, medium-voltage side positive sequence impedance and low-voltage side positive sequence impedance of a 220kV fault main transformer flowing through a positive sequence network, currents of high-voltage side negative sequence impedance and medium-voltage side negative sequence impedance of the 220kV fault main transformer flowing through a negative sequence network and currents of high-voltage side zero sequence impedance and medium-voltage side zero sequence impedance of the 220kV fault main transformer flowing through a zero sequence network from the equivalent circuit;
and step S2, when the current with the same magnitude and the same direction is detected on the high-voltage side positive sequence impedance, the high-voltage side negative sequence impedance and the high-voltage side zero sequence impedance of the 220kV fault main transformer, and the current with the same magnitude and the same direction is detected on the medium-voltage side negative sequence impedance and the medium-voltage side zero sequence impedance of the 220kV fault main transformer, determining that the 220kV fault main transformer is high and a two-phase disconnection fault occurs.
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