CN218940660U - Novel high-factory low-voltage side branch zero sequence overcurrent relay protection circuit - Google Patents
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Abstract
The utility model relates to a novel high-factory low-voltage side branch zero-sequence overcurrent relay protection circuit, which is characterized in that a branch switch position criterion is added to zero-sequence overcurrent I section protection logic, so that a zero-sequence I section acts on a jump branch switch and locks power supply switching of a factory, a zero-sequence overcurrent II section acts on complete stop and starts power supply switching of the factory, the effects that the zero-sequence I section returns when the branch switch jumps and signals of a locking quick-cutting device disappear are achieved, and the problem that quick-cutting cannot be started after the action of the branch zero-sequence II section is solved. According to the utility model, by adding the judgment condition that the branch switch is not in the split position, when the branch on the low-voltage side of a high-rise plant is grounded and the branch switch is tripped, the zero sequence I section does not meet the action condition and returns, and the quick switching outlet of the power supply for the plant is blocked and returns, so that the quick switching device of the power supply for the plant can receive the quick switching starting signal, and the fault processing time is reduced.
Description
Technical Field
The utility model relates to the technical field of power systems, in particular to a novel high-factory low-voltage side branch zero sequence overcurrent relay protection circuit.
Background
At present, relay protection equipment manufacturers pay attention to the cooperation of high-factory low-voltage side branch protection and a factory power supply fast switching device, and the problem is not considered when the logic design is protected. In engineering application, the high-low voltage side branch grounding protection of the factory is only configured with two sections of irrelevant zero sequence overcurrent protection, each section of the zero sequence overcurrent protection has one section of delay. The fault zero-sequence current entering the protection device is taken from the fault zero-sequence current at the neutral point resistor side, and the fault zero-sequence current cannot distinguish the bus faults for the high-voltage plant or the branch faults at the low-voltage side of the high-voltage plant, so that the problem of selectivity exists.
In order to solve the selectivity problem, two sections of zero sequence are generally put into the field, the section I of the zero sequence acts on the jump branch switch through a short delay time and is locked and cut quickly, and the section II of the zero sequence acts on the whole stop and starts and cut quickly through a long delay time. If the fault current disappears after the zero sequence I section action branch switch is tripped, the zero sequence II section does not act, which indicates that the fault is a high-voltage bus grounding fault for a plant, and at the moment, the power supply for the plant is blocked to quickly switch so as to prevent the starting and standby from being switched on the fault bus; if the zero sequence I section action branch switch is tripped, the fault current does not disappear, and the zero sequence II section also acts, which means that the transformer branch is grounded, the fault is completely stopped at the moment, and the quick switching of the station power supply is started to ensure the power supply of the station auxiliary equipment.
However, if the low-voltage side branch of the high-voltage plant is grounded, after the branch zero sequence I section acts, the protection outlet is blocked for quick switching of the power supply of the plant, the fault current continuously exists to cause the protection outlet not to return, the quick switching device of the power supply of the plant can always receive a blocking and quick switching signal from the protection outlet, and the quick switching device of the power supply of the plant is blocked and switched and waits for manual reset. Although the protection outlet starts the quick switching of the station service power after the branch zero sequence II section acts, the quick switching device cannot act and cannot complete the switching because of locking, and the high-voltage station bus loses power, so that the fault processing time is prolonged. Therefore, the cooperation of the zero sequence overcurrent protection of the low-voltage side branch of the high-voltage plant and the quick switching device of the power supply for the plant has defects in engineering application, so that the quick switching device of the power supply for the plant cannot be started correctly when the low-voltage side branch of the high-voltage plant fails.
Disclosure of Invention
The embodiment of the utility model provides a novel zero sequence overcurrent relay protection circuit for a low-voltage side branch of a high-voltage plant, which at least solves the problem that a quick switching device for a plant power supply cannot be started correctly when the low-voltage side branch of the high-voltage plant fails in the related art.
In a first aspect, the embodiment of the utility model provides a novel high-factory low-voltage side branch zero-sequence overcurrent relay protection circuit, wherein the protection circuit comprises zero-sequence overcurrent I-section protection logic and zero-sequence overcurrent II-section protection logic; the zero sequence overcurrent I section protection logic comprises a first AND gate and a first delayer; the zero sequence overcurrent II section protection logic comprises a second AND gate and a second delayer; wherein,,
the first input end and the second input end of the first AND gate are respectively connected with a branch switch and a first zero sequence current detection circuit, and the output end of the first AND gate is connected with the input end of the first delay device; the first input end of the second AND gate is connected with the second zero sequence current detection circuit, and the output end of the second AND gate is connected with the input end of the second delayer;
when the branch switch is in a closing state and the first zero sequence current detection circuit detects that the fault zero sequence current is greater than a first setting value, the first AND gate outputs a first protection outlet signal through a first delay; and when the second zero-sequence current detection circuit detects that the fault zero-sequence current is greater than a second setting value, the second AND gate outputs a second protection outlet signal through a second delay.
In a preferred embodiment, the zero sequence overcurrent I-section protection logic further comprises a first not gate connected between the branch switch and a first input of the first and gate; when the branch switch is not in a split state and the first zero sequence current detection circuit detects that the fault zero sequence current is greater than a first setting value, the first AND gate outputs a first protection outlet signal through a first delay.
In some of these embodiments, the first and gate further comprises a third input terminal, and the second and gate further comprises a second input terminal; the third input end of the first AND gate and the second input end of the second AND gate are connected with the branch zero sequence protection hard pressing plate.
Specifically, the first delayer comprises a first output end, a second output end and a third output end; the first output end of the first delayer is connected to the distributed control system, the second output end of the first delayer is connected to the station service fast switching device, and the third output end of the first delayer is connected to the branch switch.
Specifically, the second delayer comprises a first output end and a second output end; the first output end of the second delay device is connected to each switch of the power plant power generation group electric system, and the second output end of the second delay device is connected to the power plant power quick switching device.
In another preferred embodiment, the zero sequence over-current II segment protection logic further includes a third delay connected between the output of the second and gate and the input of the second delay.
Specifically, the third delayer includes three output terminals; the first output end of the third delayer is connected to the decentralized control system, the second output end of the third delayer is connected with the input end of the second delayer, and the third output end of the third delayer is connected to the station service quick switching device.
In another preferred embodiment, the protection circuit further includes a second not gate, the first and gate further includes a fourth input terminal, the fourth input terminal is connected to the output terminal of the second not gate, and the input terminal of the second not gate is connected to the output terminal of the second delay device.
Compared with the prior art, the novel high-factory low-voltage side branch zero-sequence overcurrent relay protection circuit provided by the embodiment of the utility model has the advantages that the branch switch position criterion is added to the zero-sequence overcurrent I section protection logic, so that the zero-sequence I section acts on the jump branch switch and locks the power supply switching of the plant, the zero-sequence overcurrent II section acts on the complete stop and starts the power supply switching of the plant, the effect that the zero-sequence I section returns when the branch switch jumps and the signal of the locking quick-cutting device disappears is achieved, and the problem that the quick-cutting cannot be started after the branch zero-sequence II section acts is solved. The utility model can start the switching of the power supply of the plant when the branch of the high plant breaks down, so that the switching of the power supply of the plant can be completed quickly, and the fault processing time is reduced.
Drawings
The accompanying drawings, which are included to provide a further understanding of the utility model and are incorporated in and constitute a part of this specification, illustrate embodiments of the utility model and together with the description serve to explain the utility model and do not constitute a limitation on the utility model. In the drawings:
FIG. 1 is a wiring diagram of a section of bus in a typical utility power system;
FIG. 2 is a schematic diagram of a novel high-factory low-voltage side branch zero sequence overcurrent relay protection circuit according to an embodiment of the utility model;
FIG. 3 is a schematic diagram of a novel high-factory low-voltage side branch zero sequence overcurrent relay protection circuit according to another embodiment of the utility model;
fig. 4 is a schematic diagram of a novel high-factory low-voltage side branch zero-sequence overcurrent relay protection circuit according to another embodiment of the utility model.
Detailed Description
The present utility model will be described and illustrated with reference to the accompanying drawings and examples in order to make the objects, technical solutions and advantages of the present utility model more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model. All other embodiments, which can be made by a person of ordinary skill in the art based on the embodiments provided by the present utility model without making any inventive effort, are intended to fall within the scope of the present utility model. Moreover, it should be appreciated that while such a development effort might be complex and lengthy, it would nevertheless be a routine undertaking of design, fabrication, or manufacture for those of ordinary skill having the benefit of this disclosure, and thus should not be construed as having the benefit of this disclosure.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the utility model. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is to be expressly and implicitly understood by those of ordinary skill in the art that the described embodiments of the utility model can be combined with other embodiments without conflict.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this utility model belongs. The terms "a," "an," "the," and similar referents in the context of the utility model are not to be construed as limiting the quantity, but rather as singular or plural. The terms "comprising," "including," "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, article, or apparatus that comprises a list of steps or modules (elements) is not limited to only those steps or elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. The terms "connected," "coupled," and the like in connection with the present utility model are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The term "plurality" as used herein means greater than or equal to two. "and/or" describes an association relationship of an association object, meaning that there may be three relationships, e.g., "a and/or B" may mean: a exists alone, A and B exist together, and B exists alone. The terms "first," "second," "third," and the like, as used herein, are merely distinguishing between similar objects and not representing a particular ordering of objects.
The embodiment of the utility model provides a novel high-factory low-voltage side branch zero-sequence overcurrent relay protection circuit which is mainly applied to a factory electrical system of a power plant, wherein fig. 1 is a wiring diagram of a bus of a certain section of a typical factory electrical system, when a unit normally operates, a working branch switch 1DL is in a closed position, a standby branch switch 3DL is in a split position, the factory bus is powered by a high-factory transformer, and a starting and standby high-voltage side switch 2DL is in a closed position to enable the starting and standby transformer to operate in a hot standby state. When the transformer group protection action or the high-power plant becomes faulty, the working branch switch 1DL is tripped, and meanwhile, the power plant quick switching device is started to close the standby branch switch 3DL, and the power plant bus is started to operate, so that power supply of auxiliary equipment is ensured.
The protection circuit provided by the utility model can be used for improving the action coordination of a quick switching device for station service in an electrical system and a working branch switch 1DL (simply called a branch switch) in fig. 1. Specifically, the protection circuit of the embodiment configures two sections of zero sequence overcurrent protection logic for the low-voltage side branch of the high-voltage plant: zero sequence overcurrent I section protection logic (zero sequence I section for short) and zero sequence overcurrent II section protection logic (zero sequence II section for short). As shown in fig. 2, the zero sequence overcurrent I-section protection logic includes a first and gate and a first delay T1; the zero sequence overcurrent II section protection logic comprises a second AND gate U2 and a second delayer T2. The first input end and the second input end of the first and gate U1 of the embodiment are respectively connected with a branch switch and a first zero sequence current detection circuit, and the output end of the first and gate U1 is connected with the input end of the first delay T1; the first input end of the second AND gate U2 is connected with the second zero sequence current detection circuit, and the output end of the second AND gate U2 is connected with the input end of the second delayer T2.
In this embodiment, the first zero-sequence current detection circuit and the second zero-sequence current detection circuit are both used to detect the fault zero-sequence current 3I in the electrical system 0 The difference is that the setting values of the two detection circuits (i.e. the protection device setting values) are different in size.
Wherein, for fault zero sequence current 3I 0 The neutral point of the low-voltage side of the high-power plant of most thermal power plants is grounded through a small resistor. The small resistor grounding mode can effectively limit the overvoltage level, when the system is in single-phase grounding, the sound phase voltage is short in rising duration, various overvoltage of the single-phase grounding can be reduced, and the equipment is facilitated. When single-phase grounding occurs, the zero sequence overcurrent protection has better sensitivity because of larger current flowing through the fault line, and the grounding line can be detected easily. The grounding resistance of the branch neutral point of the high-voltage plant is far larger than other impedances of the system, so that the single-phase grounding current (fault zero-sequence current 3I 0 ) Can be approximated by the following formula:
in the formula, 3I 0 Is a single-phase grounding current (fault zero-sequence current 3I 0 )，U N The voltage is rated for a high-voltage system for a factory, and R is the resistance value of a grounding resistor. In this way the calculation is carried out,the fault zero sequence current is 100A to 200A when the bus for the high-voltage plant of the general thermal power plant is in single-phase grounding fault, and compared with the load current, the zero sequence current is small, and the phase overcurrent protection is insensitive.
When the branch switch is in the closing state, the first zero-sequence current detection circuit detects the fault zero-sequence current 3I 0 3I greater than a first setting value 0g1 Time (3I) 0 ＞3I 0g1 ) The first AND gate U1 outputs a first protection outlet signal through a first delay T1; when the second zero-sequence current detection circuit detects the fault zero-sequence current 3I 0 Greater than a second setting value 3I 0g2 Time (3I) 0 ＞3I 0g2 ) The second and gate U2 outputs a second protection output signal through a second delay T2.
The first protection output signal output by the first delayer T1 through T1 delay is divided into three paths, referring to fig. 2 specifically, the first delayer T1 includes a first output end, a second output end and a third output end; the first output end of the first delay T1 is connected to a distributed control system, and a first protection outlet signal is sent to a DCS (distributed control system), a fault wave recording system and the like; the second output end of the first delay T1 is connected to a station service quick switching device (quick switching device for short), and the quick switching device is locked after receiving the first protection outlet signal; the third output end of the first delay T1 is connected to the branch switch, and the branch switch receives the first protection outlet signal to trip.
The second protection output signal output by the second delayer T2 through T2 (wherein T2 is greater than T1) is divided into two paths, referring specifically to fig. 2, the second delayer T2 includes a first output end and a second output end; the first output end of the second delay T2 is connected to each switch of the power plant power generation group electric system, and the second protection outlet signal is used as a complete stop signal to stop the electric system, such as a main-transformer high-voltage side switch, a starting failure, a magnetic-pole-trip switch, a main valve closing and a high-transformer branch switch tripping off; the second output end of the second delay T2 is connected to the station service quick switching device, and the quick switching device is started after receiving a second protection outlet signal.
The fault zero-sequence current disappears after the zero-sequence I section action branch switch is tripped out. According to the characteristics, the circuit structure and connection of the zero sequence overcurrent I section protection logic and the zero sequence overcurrent II section protection logic are improved, and a branch switch position criterion is added for the zero sequence I section, so that the zero sequence I section acts on a jump branch switch and locks the power supply switching for factories; the zero sequence overcurrent II section acts on the complete stop and starts the power supply switching of the plant, achieves the effect that the zero sequence I section returns when the branch switch jumps, and the signal of the locking quick-cutting device disappears, and solves the problem that the quick-cutting cannot be started after the branch zero sequence II section acts. In addition, by adding the judgment condition that the branch switch is not in the split position, when the branch of the low-voltage side of the high-power plant is grounded and the branch switch is tripped after the branch zero sequence I section acts, the zero sequence I section returns without meeting the action condition, and the quick switching outlet of the power plant is locked and returned, so that the quick switching device of the power plant can receive the quick switching starting signal, and the fault processing time is shortened.
In a preferred embodiment of the present utility model, referring to fig. 3, the zero sequence overcurrent I-section protection logic further includes a first not gate U3, and the first not gate U3 is connected between the branch switch and the first input terminal of the first and gate U1. After the no gate is added between the branch switch and the first and gate U1, the first and gate U1 outputs the first protection exit signal through the first delay T1 only when the branch switch is not in the split state and the first zero sequence current detection circuit detects that the fault zero sequence current is greater than the first setting value.
In a power plant, an operator only operates a pressing plate on a protection screen to perform protection, and if the hard pressing plate is not provided, the protection is performed by modifying a fixed value. Thus, in another preferred embodiment of the present utility model, referring to fig. 3, the first and gate U1 further includes a third input terminal, and the second and gate U2 further includes a second input terminal; the third input end of the first AND gate U1 and the second input end of the second AND gate U2 are connected with a branch zero sequence protection hard pressing plate. In this embodiment, a protection hard pressing plate is added for the grounding protection of the low-voltage side branch of the high-voltage plant, and at this time, the action logic of the zero sequence I segment is as follows: the high-factory low-voltage side branch grounding protection hard pressing plate (namely the branch zero-sequence protection hard pressing plate) is put in, the branch switch is not in a split position, the fault zero-sequence current is larger than a first setting value, and then the first delayer T1 outputs a protection signal through the settable delay T1. The action logic of the zero sequence II section is as follows: the high-factory low-voltage side branch grounding protection hard pressing plate (namely the branch zero-sequence protection hard pressing plate) is put in, the fault zero-sequence current is larger than a second setting value, and then the second delayer T2 outputs a protection signal through settable delay T2. On the basis of the embodiment of fig. 2, the embodiment adds a branch zero-sequence protection hard pressing plate switching criterion for the zero-sequence I section and the zero-sequence II section, thereby highlighting the importance of zero-sequence ground protection and facilitating operators to switch protection according to the operation mode of the system.
In another preferred embodiment of the present utility model, referring to fig. 4, the zero sequence over-current II segment protection logic further includes a third delayer T3, and the third delayer T3 is connected between the output terminal of the second and gate U2 and the input terminal of the second delayer T2. Wherein the third delay T3 comprises three output terminals; the first output end of the third delay T3 is connected to a distributed control system, and a second protection outlet signal is sent to a DCS (distributed control system), a fault wave recording system and the like; the second output end of the third delayer T3 is connected with the input end of the second delayer T2, and the first protection output signal is delayed by T3 and then output to the second delayer T2; the third output end of the third delay T3 is connected to the station service power quick switching device, and the quick switching device is reset after receiving the second protection outlet signal output by the third delay T3.
Because the quick power switching device for the plant needs to be manually reset after being protected and locked, an outlet of the quick power switching device for the plant is added for the zero sequence section II, the third delay device T3 is added for the zero sequence section II on the basis of the embodiment of fig. 3, the quick power switching outlet of the zero sequence section I and the quick power switching outlet of the plant are returned after the branch switch is tripped, and the quick power switching of the plant is completely stopped and started after the branch switch is tripped, and the quick power switching device for the plant can automatically reset through the improvement.
In another embodiment of the present utility model, the protection circuit further includes a second not gate, the first and gate U1 further includes a fourth input end, the fourth input end is connected to an output end of the second not gate, and an input end of the second not gate is connected to an output end of the second delay T2, that is, a protection signal output by the zero sequence II segment is not taken as an action condition of the zero sequence I segment, which solves a problem that a defect exists in cooperation between high-factory low-voltage side branch zero sequence overcurrent protection and a plant power supply fast switching device in engineering application, and the plant power supply fast switching device cannot be started correctly when the high-factory low-voltage side branch fails.
It should be noted that, specific examples in this embodiment may refer to examples described in the foregoing embodiments and alternative implementations, and this embodiment is not repeated herein.
It should be understood by those skilled in the art that the technical features of the above-described embodiments may be combined in any manner, and for brevity, all of the possible combinations of the technical features of the above-described embodiments are not described, however, they should be considered as being within the scope of the description provided herein, as long as there is no contradiction between the combinations of the technical features.
The above examples illustrate only a few embodiments of the utility model, which are described in detail and are not to be construed as limiting the scope of the utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of protection of the present utility model is to be determined by the appended claims.
Claims (8)
1. The novel high-factory low-voltage side branch zero-sequence overcurrent relay protection circuit is characterized by comprising zero-sequence overcurrent I-section protection logic and zero-sequence overcurrent II-section protection logic; the zero sequence overcurrent I section protection logic comprises a first AND gate and a first delayer; the zero sequence overcurrent II section protection logic comprises a second AND gate and a second delayer; wherein,,
the first input end and the second input end of the first AND gate are respectively connected with a branch switch and a first zero sequence current detection circuit, and the output end of the first AND gate is connected with the input end of the first delay T1; the first input end of the second AND gate is connected with the second zero sequence current detection circuit, and the output end of the second AND gate is connected with the input end of the second delayer;
when the branch switch is in a closing state and the first zero sequence current detection circuit detects that the fault zero sequence current is greater than a first setting value, the first AND gate outputs a first protection outlet signal through a first delay T1; and when the second zero-sequence current detection circuit detects that the fault zero-sequence current is greater than a second setting value, the second AND gate outputs a second protection outlet signal through a second delay.
2. The protection circuit of claim 1, wherein the zero sequence over-current I-section protection logic further comprises a first not gate connected between the branch switch and a first input of the first and gate; when the branch switch is not in a split state and the first zero sequence current detection circuit detects that the fault zero sequence current is greater than a first setting value, the first AND gate outputs a first protection outlet signal through a first delay.
3. The protection circuit of claim 2, wherein the first and gate further comprises a third input terminal, and the second and gate further comprises a second input terminal; the third input end of the first AND gate and the second input end of the second AND gate are connected with the branch zero sequence protection hard pressing plate.
4. The protection circuit of claim 2, wherein the first delay comprises a first output, a second output, and a third output; the first output end of the first delayer is connected to the distributed control system, the second output end of the first delayer is connected to the station service fast switching device, and the third output end of the first delayer is connected to the branch switch.
5. The protection circuit of claim 2, wherein the second delay comprises a first output and a second output; the first output end of the second delay device is connected to each switch of the power plant power generation group electric system, and the second output end of the second delay device is connected to the power plant power quick switching device.
6. The protection circuit of claim 5, wherein the zero sequence over-current II-stage protection logic further comprises a third delay coupled between the output of the second and gate and the input of the second delay.
7. The protection circuit of claim 6, wherein the third delay comprises three outputs; the first output end of the third delayer is connected to the decentralized control system, the second output end of the third delayer is connected with the input end of the second delayer, and the third output end of the third delayer is connected to the station service quick switching device.
8. The protection circuit of claim 2, further comprising a second not gate, wherein the first and gate further comprises a fourth input coupled to an output of the second not gate, and wherein an input of the second not gate is coupled to an output of the second delay.
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