CN112751319A - Low-power protection control method during unit starting - Google Patents
Low-power protection control method during unit starting Download PDFInfo
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- CN112751319A CN112751319A CN202011602562.5A CN202011602562A CN112751319A CN 112751319 A CN112751319 A CN 112751319A CN 202011602562 A CN202011602562 A CN 202011602562A CN 112751319 A CN112751319 A CN 112751319A
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- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000003111 delayed effect Effects 0.000 claims abstract description 6
- 238000012544 monitoring process Methods 0.000 claims description 2
- 238000010248 power generation Methods 0.000 abstract description 4
- 230000007547 defect Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 8
- 238000011217 control strategy Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
- H02H7/0816—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors concerning the starting sequence, e.g. limiting the number of starts per time unit, monitoring speed during starting
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Abstract
The invention discloses a low-power protection control method during unit starting, and belongs to the field of power generation regulation. A low-power protection control method when a unit is started, when all circuit breakers on a line sending channel are in a disconnected state and the output power of the unit is less than a preset percentage of rated power, protection tripping is carried out, and a boiler and a steam turbine are tripped in a delayed mode; and if the current output power of the unit is greater than or equal to the preset percentage of the rated power, the protection trip is exited. The invention overcomes the defect that when the set is started and the set value of the low-power tripping machine is not reached, a circuit has the working condition of reclosing/tripping, and a single protection device cannot realize reliable shutdown through the existing low-power protection action logic.
Description
Technical Field
The invention belongs to the field of power generation regulation, and particularly relates to a low-power protection control method during unit starting.
Background
The large-scale steam turbine generator unit has large capacity, high steam parameters and large rotor moment of inertia, a circuit breaker on the line side can be tripped due to faults or power grid fluctuation when a power output line of a power plant runs normally, and the power of a generator cannot be output when a power output channel is interrupted (all the power output lines of the power plant are disconnected with a power grid). At the moment, if a series of measures such as closing a main valve, flameout of a boiler, de-excitation of a generator and the like cannot be taken in time, the problems of overspeed of a turbo generator set, over-temperature and over-pressure of a steam thermodynamic system, overvoltage of a generator transformer set and other auxiliary equipment faults and the like can be caused, and the safety operation of the unit equipment is seriously threatened.
At present, the construction and development of power grids in China are rapid, super-huge power grids of regional power grid interconnection, provincial power grid interconnection and national power grid interconnection are built gradually, and the overall stability of the power grids is high. However, in international projects, part of national power grids are still in an operating state with large tidal current fluctuation and high grid vulnerability, and the external delivery conditions of the power plant are extremely unstable. In order to adapt to the working condition that the sending line is easy to trip, a large generator is generally provided with low-power generator tripping protection, also called generator forward power sudden drop protection, and when an external power supply fails (unit output sudden drop), the unit is stopped reliably through the protection.
Referring to FIG. 1, FIG. 1 is a logic diagram of a typical low power trip protection action; in the figure, Δ Uf1Indicating the positive sequence voltage delta, Δ I, of the generatorf1Represents the positive sequence current sudden decrease quantity of the generator side, f represents the frequency of the generator side, delta f represents the frequency sudden increase quantity of the generator side, PGRepresenting the active power of the generator side, delta P representing the sudden drop of the active power of the generator side, delta PsetAnd the active power sudden drop setting value of the generator side is represented. I isfa、Ifb、IfcFor the generator current, Uf1 is the generator side positive sequence voltage and Uf2 is the generator side negative sequence voltage. For low power cuter protection, the power setpoint is set as follows: (1) pre-accident power setting value Pset1: the power of the large-scale generator in normal and stable operation is generally not less than 30-40% of rated power, and therefore the power setting value before an accident is taken to be 0.3-0.4PnAnd the lowest power setting value is not less than the stable operation value of the unit. The stable operation of the unit is the premise of generating protection actions of the unit (starting shutdown protection is put into operation before the stable operation), and other counter units are required to be in failure of a transmission line in the stable operationGroup protection measures. The criterion for the actuation of the device is thus that the pre-accident power measurement is greater than Pset1. (2) Post-accident power setting value Pset2. Large generator when operating suddenly power drops to 2% PnHereinafter, the generator is considered to be operated at low power, and the post-accident power setting value Pset2Should be greater than the power null value. For protection actions, the starting criterion is that the power measured value is less than the setting value P in case of accidentset2. (3) The power variation amount (the amount of sudden drop) is an internal fixed value. Based on the setting, the low-power generator tripping protection can deal with the power sudden-drop situation when the unit operates stably. However, for the working condition that a circuit is reclosed/tripped when the unit is started and the low-power tripping setting value is not reached, a single protection device cannot achieve the purpose of reliable shutdown through the existing low-power protection action logic.
Disclosure of Invention
The invention aims to overcome the defect that when a unit is started and does not reach a low-power cutter setting value, a circuit is subjected to a reclosing/tripping working condition, and a single protection device cannot realize reliable shutdown through the conventional low-power protection action logic, and provides a low-power protection control method during unit starting.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a low-power protection control method when a unit is started is characterized in that the position state quantity of a unit side isolating switch is used as a unit input criterion, and whether the unit is ready to be input is judged according to the position state of the unit side isolating switch.
Furthermore, the position state quantity of the line side disconnecting switch is used as an operation mode criterion, and whether the line in the transformer substation is put into and sent out is judged according to the position state of the line side disconnecting switch.
Furthermore, when all the circuit breakers on the outgoing line channel are in a disconnected state and the output power of the unit is less than the preset percentage of the rated power, starting a protection trip control strategy, and tripping the boiler and the steam turbine in a delayed manner;
and if the current output power of the unit is greater than or equal to the preset percentage of the rated power, the protection trip is exited.
Further, the preset percentage is 40%.
Furthermore, the boiler and the steam engine are delayed for 1s by a computer monitoring system.
Further, the protection trip control strategy starting condition is a logic combination of all switches on the power outgoing channel and the position state of the circuit breaker.
Compared with the prior art, the invention has the following beneficial effects:
according to the low-power protection control method during the starting of the unit, the delayed trip boiler and the steam turbine are started through the protection trip, and the problems that in the starting stage of the unit, when the circuit breaker is disconnected and the output power of the unit is smaller than the preset percentage of the rated power, the electric low-power protection device does not reach the action condition, cannot be started and stopped completely, and the main steam valve is closed are solved.
Drawings
FIG. 1 is a logic diagram of a typical low power trip protection action;
FIG. 2 is an electrical main connection of the power generation engineering of the embodiment;
FIG. 3 is a schematic diagram of the control logic connection during the start-up of the #1 unit according to the embodiment;
FIG. 4 is a schematic diagram of the control logic connections of the #2 unit in the start-up of the embodiment;
FIG. 5 is a schematic diagram of the control box wiring;
fig. 6 is a diagram of the control box trip and reclose lockout exit.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
examples
In a certain power generation project, 2x660MW units are newly built, 2 units are connected into a 500kV power distribution device in a plant through a generator-transformer unit connection wire, the 500kV power distribution device adopts three-half connection wires and is sent out through two lines, and a main connection wire is schematically shown in fig. 2. Due to poor stability of the power grid, a line reclosing/tripping condition may occur in the unit load-up process. In this case, if all the outgoing line breakers are tripped, since the main operating conditions of the electrical protection are generally based on stable operation, and the simple electrical protection is difficult to implement the related protection, it is necessary to add a low-power protection logic in the DCS, and to complete the related protection function when the unit is started in cooperation with the characteristics of the unit and the related control strategy.
According to the electrical main wiring, taking a #1 unit as an example, the following control scheme is given to realize the low-power protection function when the unit is started by comparing the position state of a circuit breaker during the reclosing/tripping period of a transmission line:
1. control logic
1) The isolating switch B1Q10 is in the on-off position, the circuit breaker B1Q2 and the circuit breaker B1Q3 are in the off-position, the circuit breaker B2Q1 and the circuit breaker B2Q3 are in the off-position, the output power of the unit does not exceed 40% of rated power at the moment, the condition is met, and the boiler and the steam turbine are tripped by delaying 1s through DCS;
2) the isolating switch B1Q10 is at the on-off position, the breaker B1Q20 is at the off-position (the series loop), the breaker B2Q1 and the breaker B2Q3 are at the off-position, the output power of the unit does not exceed 40% of the rated power, the condition is met, and the boiler and the steam turbine are tripped by DCS time delay 1 s;
3) the isolating switch B1Q10 is in the on-off position, and the circuit breaker B2Q10 is in the off position (other series-loop), and the output power of the unit does not exceed 40% of the rated power, so that the condition is met, and the boiler and the steam turbine are tripped by DCS in a delayed mode for 1 s.
Corresponding to the position state of the disconnector B1Q10, a schematic connection diagram of the start condition control logic is shown in fig. 3, and the #1 unit-side disconnector B1Q10 is in a closed state, at this time, if the circuit breaker B1Q2, the circuit breaker B1Q3, the circuit breaker B2Q1 and the circuit breaker B2Q3 are all in an open state, or when the line-side disconnector B1Q20, the circuit breaker B2Q1 and the circuit breaker B2Q3 are all in an open state, or when the line-side disconnector B2Q10, the circuit breaker B1Q2 and the circuit breaker B1Q3 are all in an open state, the #1 unit low power protection issues a trip instruction.
Similarly, when the #2 unit is started, the starting condition control logic connection diagram is shown in fig. 4 corresponding to the position state of the isolating switch B2Q20, and the #2 unit side isolating switch B2Q20 is in the closed state, at this time, if the circuit breaker B1Q2, the circuit breaker B1Q3, the circuit breaker B2Q1 and the circuit breaker B2Q3 are all in the open state, or when the line side isolating switch B1Q20, the circuit breaker B2Q1 and the circuit breaker B2Q3 are all in the open state, or when the line side isolating switch B2Q10, the circuit breaker B1Q2 and the circuit breaker B1Q3 are all in the open state, the #2 unit low power protection issues a trip instruction.
4) And when the output power of the unit exceeds 40% of the rated power, exiting the DCS tripping condition corresponding to the logic.
The invention provides a relay lap joint scheme, which comprises the following steps:
for the operated unit with the defect of low power protection when the unit is started, if the related logic of the control system of the control computer is directly modified, the operation of the unit is possibly influenced, therefore, a relay lap joint scheme is provided, the requirement of low power protection is realized by matching the logic of the control box and the control system of the computer, and the modification of the control system is reduced, and the control logic of the scheme is shown in figure 5. The intermediate relay (ZJ) respectively expands the breaker B1Q2, the breaker B1Q3, the breaker B2Q1, the breaker B2Q3, the disconnecting switch B1Q20 and the disconnecting switch B2Q10 to be switched off, and the intermediate relay (ZJ) and the expanded normally-open auxiliary contact are connected with the hard-wired loop of the control box according to the control logic.
In order to reduce external wiring, the scheme is expanded by using an intermediate relay (ZJ) as much as possible, logic lap joint is completed inside a control box, and necessary external outlet and reclosing locking logic are provided, as shown in fig. 6, a tripping outlet of the control box is connected into a tripping loop of a circuit breaker in a unit side circuit breaker convergence cabinet, so that low-power protection reliable action is realized.
It can be seen from the embodiment that, in the starting stage of the unit, if the external network is out of power (all circuit breakers are opened), at this time, the electric low-power protection device does not reach the action condition, the full stop cannot be started, the main throttle is closed, and the low-power protection of the unit needs to be completed through the logic control scheme set forth in the invention.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (6)
1. A low-power protection control method during unit starting is characterized in that the position state quantity of a unit side isolating switch is used as a unit input criterion, and whether a unit is ready to be input is judged according to the position state of the unit side isolating switch.
2. The unit startup low power protection control method according to claim 1, characterized in that the position state quantity of the line side disconnecting switch is used as an operation mode criterion, and whether the line in the substation is put into service or not is judged according to the position state of the line side disconnecting switch.
3. The low power protection control method when the unit is started according to claim 2, wherein when all the circuit breakers on the outgoing line channel are in an off state, and the unit output power is less than a preset percentage of the rated power, the protection trip is entered, and the boiler and the steam turbine are tripped in a delayed manner;
and if the current output power of the unit is greater than or equal to the preset percentage of the rated power, the protection trip is exited.
4. A low power protection control method at set start-up according to claim 3, characterized in that the preset percentage is 40%.
5. A low power protection control method at start-up of a unit according to claim 3 characterized by delaying 1s tripping boiler and steam turbine by computer monitoring system.
6. A low power protection control method at set start-up according to claim 3, characterized by selecting breaker position status to establish control logic.
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| CN202011602562.5A CN112751319B (en) | 2020-12-29 | 2020-12-29 | Low-power protection control method for unit starting |
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| CN202011602562.5A CN112751319B (en) | 2020-12-29 | 2020-12-29 | Low-power protection control method for unit starting |
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|---|---|---|---|---|
| US3156848A (en) * | 1958-10-06 | 1964-11-10 | Merz & Mclellan Services Ltd | Protective arrangements for prime movers coupled to electric generators |
| US4832898A (en) * | 1987-11-25 | 1989-05-23 | Westinghouse Electric Corp. | Variable delay reactor protection system |
| US20160181790A1 (en) * | 2014-12-22 | 2016-06-23 | Schweitzer Engineering Laboratories, Inc. | Generator protection element |
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| CN209896703U (en) * | 2019-04-22 | 2020-01-03 | 协鑫能源工程有限公司 | Anti-reverse power automatic control device and new energy power generation system |
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-
2020
- 2020-12-29 CN CN202011602562.5A patent/CN112751319B/en active Active
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| US3156848A (en) * | 1958-10-06 | 1964-11-10 | Merz & Mclellan Services Ltd | Protective arrangements for prime movers coupled to electric generators |
| US4832898A (en) * | 1987-11-25 | 1989-05-23 | Westinghouse Electric Corp. | Variable delay reactor protection system |
| US20160181790A1 (en) * | 2014-12-22 | 2016-06-23 | Schweitzer Engineering Laboratories, Inc. | Generator protection element |
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| Title |
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| 刘国发等: "《核电厂仪表与控制》", 原子能出版社, pages: 209 - 211 * |
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