Generator forward power split protection logic optimization method

Abstract

The application relates to the technical field of the electric power industry, in particular to a generator positive power split protection logic optimization method, which comprises the following steps: in the starting condition part of the generator positive power split protection logic, df / dt>generator frequency mutation and d sigma>generator voltage phase quantity mutation are added; in the blocking condition part of the generator positive power split protection logic, GCB ON, a generator GCB combined bit signal and a PT disconnection signal are added; the positive power split protection export mode is set as full stop, 6kV incoming line switch tripping and starting of a plant power fast switching device; compared with the prior art, when a unit sheds load, the generator positive power split protection can reliably act; the unit load shedding and short-circuit fault state of a sending-out line can be effectively distinguished, and the generator positive power split protection misoperation is prevented.

Description

Technical Field

[0001] This invention relates to the field of power industry technology, specifically to an optimization method for generator forward power disconnection protection logic. Background Technology

[0002] In power systems, generator protection devices are crucial for ensuring the intelligent and safe operation of generators. Currently, our factory commonly uses the Siemens 7UM6225 generator protection device. When a generator set suddenly experiences load shedding, the forward power disconnection protection of the generator protection device utilizes the characteristics of changes in generator electrical quantities to initiate a complete shutdown. Its protection logic is described in [link to relevant documentation]. Figure 2 When this logic protection is used, if a short-circuit fault occurs on the transmission line during normal operation of the generator, changes in the generator's electrical quantities can cause the generator forward power tripping protection to malfunction. Therefore, this invention proposes an optimized logic method for generator forward power tripping protection. Summary of the Invention

[0003] The purpose of this invention is to provide an optimized logic method for generator forward power disconnection protection to solve the problem of how to effectively distinguish between generator load disconnection and short-circuit fault conditions in the transmission line when the unit is shedding load, thereby preventing maloperation of generator forward power disconnection protection.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a generator forward power disconnection protection logic optimization method, which includes adding df / dt > generator frequency mutation and dσ > generator voltage phasor mutation to the start-up condition part of the generator forward power disconnection protection logic;

[0005] In the blocking condition section of the generator forward power disconnection protection logic, add the GCB ON generator GCB closed signal and PT disconnection signal;

[0006] Set the forward power disconnection protection output mode to fully stop, trip the 6kV incoming line switch, and start the plant power fast-switching device.

[0007] As a preferred technical solution of the present invention, the output terminals of the generator frequency mutation and the generator voltage phasor mutation are both output to the AND gate input terminal of the starting condition section through an OR gate.

[0008] As a preferred technical solution of the present invention, PG>generator active power criterion and UG>85% generator terminal voltage greater than 85% are further provided before the AND gate input terminal of the starting condition section.

[0009] As a preferred technical solution of the present invention, the blocking condition part of the generator forward power disconnection protection logic is further provided with a main steam valve closing signal. The main steam valve closing signal, the GCB ON generator GCB closed signal and the PT disconnection signal are all output to the protection output of the forward power disconnection through an AND gate.

[0010] Compared with the prior art, the beneficial effects of the present invention are:

[0011] 1. In this invention, by adding generator frequency mutation to the protection logic, it is possible to more accurately distinguish whether the generator is experiencing a positive power disconnection condition or whether a fault has occurred in the transmission line at a distance.

[0012] 2. In this invention, by adding generator voltage phasor mutation to the protection logic, it is possible to more accurately distinguish whether the generator is experiencing a positive power disconnection condition or whether a fault has occurred in the transmission line at a distance.

[0013] 3. In this invention, by adding a GCB closing signal to the protection logic, it is possible to effectively prevent the positive power protection device from misjudging the positive power disconnection condition due to the false tripping of GCB.

[0014] 4. In this invention, the PT disconnection signal can effectively prevent the positive power protection device from misjudging the positive power disconnection condition due to a voltage transformer disconnection fault.

[0015] 5. In this invention, the protection output mode of the forward power disconnection protection logic is set to two output modes: full stop, tripping of the 6kV incoming line switch, and starting of the plant auxiliary power fast switching device. In the event that all transmission lines are lost, the power plant can use the forward power protection device to quickly switch the plant auxiliary power and avoid long-term power outages.

[0016] In summary, when the unit sheds load, the forward power disconnection protection of the generator is guaranteed to operate reliably; it can effectively distinguish between the unit shedding load and the short circuit fault state of the transmission line, and prevent the forward power disconnection protection of the generator from malfunctioning.

[0017] Other features and advantages of the present invention will be described in detail in the following specific embodiments.

[0018] Figure 1 This is the generator forward power disconnection protection logic diagram of the present invention;

[0019] Figure 2 This is a logic diagram for the forward power disconnection protection of existing generators. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1-2 In this embodiment, a method for optimizing the generator forward power disconnection protection logic is provided, which includes adding df / dt > generator frequency mutation and dσ > generator voltage phasor mutation to the start-up condition part of the generator forward power disconnection protection logic;

[0022] The outputs of the generator frequency mutation and the generator voltage phasor mutation are both output to the AND gate input of the starting condition section via an OR gate.

[0023] By adding generator frequency mutation to the protection logic, with its setting value set at 1.13Hz / s, it is possible to more accurately distinguish whether the generator is experiencing a positive power disconnection condition or whether a fault has occurred in the transmission line at a distance.

[0024] When the generator experiences a positive power split (i.e., load shedding) condition, the generator side frequency will suddenly increase. Therefore, the value of the criterion df / dt > generator frequency sudden change will be greater than its setting value of 1.13Hz / s. At this time, this criterion is satisfied (the output in the logic diagram is 1).

[0025] When a three-phase short-circuit fault occurs near the transmission line, there is no sudden increase in the generator frequency. Therefore, the value of the criterion that df / dt > generator frequency change will be much lower than its setting value of 1.13Hz / s. At this time, the criterion is not satisfied (the output in the logic diagram is 0).

[0026] By adding generator voltage phasor mutation to the protection logic, and setting its value to 15 degrees (i.e., angle °), it is possible to more accurately distinguish whether the generator is experiencing positive power disconnection (i.e., load shedding) or whether a fault has occurred in the transmission line at a distance.

[0027] When the generator experiences a positive power split (i.e. load shedding) condition, the generator side frequency will suddenly increase. Therefore, the value of the criterion dσ > generator voltage vector sudden change will be greater than its setting value of 15deg. At this time, this criterion is satisfied (the output in the logic diagram is 1).

[0028] When a three-phase short-circuit fault occurs at close range on a transmission line, the generator voltage vector does not change abruptly. Therefore, the value of the criterion dσ > generator voltage vector change abruptly will be much lower than its setting value of 15deg. At this time, this criterion is not satisfied (the output in the logic diagram is 0).

[0029] By adding a GCB closing signal to the protection logic, it is possible to effectively prevent the positive power protection device from misjudging the positive power disconnection condition due to the false tripping of the GCB (generator output circuit breaker).

[0030] The PT disconnection signal can effectively prevent the positive power protection device from misjudging the positive power disconnection condition due to a voltage transformer disconnection fault.

[0031] Setting the protection output mode of the forward power disconnection protection logic to two output modes—full shutdown, tripping the 6kV incoming line switch, and starting the plant auxiliary power fast switching device—enables the power plant to quickly switch the plant auxiliary power supply by using the forward power protection device in the event that all transmission lines are lost, thus avoiding a long-term power outage.

[0032] In the blocking condition section of the generator forward power disconnection protection logic, add the GCB ON generator GCB closed signal and PT disconnection signal;

[0033] Set the forward power disconnection protection output mode to fully stop, trip the 6kV incoming line switch, and start the plant power fast-switching device.

[0034] Before the AND gate input of the starting condition section, there are also PG>generator active power criterion and UG>85% generator terminal voltage greater than 85%.

[0035] The blocking condition section of the generator forward power disconnection protection logic also includes a main steam valve closing signal. This main steam valve closing signal, the GCB ON generator GCB closed signal, and the PT disconnection signal are all output to the forward power disconnection protection output through an AND gate.

[0036] The generator forward power disconnection protection logic also includes low power discrimination. The outputs of the low power discrimination, start-up condition section and lockout condition section are all output to the forward power disconnection protection output through an AND gate.

[0037] The low power discrimination includes the criterion that PG > generator active power and the criterion that I1 < generator positive sequence current.

[0038] Generator forward power disconnection protection uses the rapid decrease in the unit's electrical power to determine the unit's load shedding and directly disconnects the generator unit if certain conditions are met. The electrical power criterion of this protection is also affected by grid short circuits, DC faults, etc., and there is a risk of false tripping.

[0039] To address this, a generator frequency mutation and voltage phasor mutation start-up section was added to the protection logic. This effectively distinguishes between the unit's load shedding and the short-circuit fault state of the transmission line, preventing the generator's positive power disconnection protection from malfunctioning when the transmission line is short-circuited. Furthermore, the protection is subject to GCB position status and PT disconnection blocking.

[0040] In this invention, when the unit sheds load, the forward power disconnection protection of the generator is guaranteed to operate reliably; it can effectively distinguish between the power drop during the unit's load shedding and the state of a short circuit fault in the transmission line, thus solving the problem of protection maloperation when a short circuit fault occurs in the transmission line and achieving correct protection operation when the unit's load shedding power drops.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An optimization method for generator forward power tripping protection logic, characterized in that, Including in the start-up condition section of the generator forward power disconnection protection logic, the following conditions are added: df / dt > generator frequency change and dσ > generator voltage phasor change; the setting value of the generator frequency change is set to 1.13 Hz / s, and the setting value of the generator voltage phasor change is set to 15 deg. In the blocking condition section of the generator forward power disconnection protection logic, a GCB ON generator GCB closed signal and a PT disconnection signal are added. The GCB ON generator GCB closed signal is used to prevent the forward power protection device from misjudging the forward power disconnection condition due to the false tripping of the generator output circuit breaker. The PT disconnection signal is used to prevent the forward power protection device from misjudging the forward power disconnection condition due to the voltage transformer disconnection fault. Set the protection output mode of the forward power disconnection protection logic to full stop, trip the 6kV incoming line switch and start the plant power fast-switching device.

2. The generator forward power disconnection protection logic optimization method according to claim 1, characterized in that, The outputs of the generator frequency mutation and the generator voltage phasor mutation are both output to the AND gate input of the starting condition section via an OR gate.

3. The generator forward power disconnection protection logic optimization method according to claim 2, characterized in that, Before the AND gate input of the starting condition section, there are also PG>generator active power criterion and UG>85% generator terminal voltage greater than 85%.

4. The generator forward power disconnection protection logic optimization method according to claim 1, characterized in that, The blocking condition section of the generator forward power disconnection protection logic also includes a main steam valve closing signal. This main steam valve closing signal, the GCB ON generator GCB closed signal, and the PT disconnection signal are all output to the forward power disconnection protection output through an AND gate.

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