A comprehensive protection method for high voltage power system of power plant

Abstract

The present invention discloses a comprehensive protection method for a high-voltage power supply system of a power plant. The protection of the high-voltage power supply system of a traditional power plant is to achieve the selectivity of protection by increasing the time difference, and at the same time, the power supply switching of the power supply is realized by the power supply switching device. At present, when the zero-sequence II section protection of the power supply branch line is actuated, the power supply device is locked and cannot realize the automatic switching function of the power supply, and the protection and automatic devices are arranged in a scattered manner, the equipment cost is high, and the secondary circuit is complicated. The present invention has the functions of power supply incoming line protection, load side protection, and power supply switching of the power supply, and can realize the rapid action of the phase-to-phase and grounding fault protection of the power supply high-voltage bus, and at the same time realize the differential protection of the power supply single bus, the failure protection of each interval switch, and the intelligent low-voltage load shedding function, which improves the speed of the power supply protection, and at the same time can solve the problem that the power supply automatic switching of the power supply cannot be realized when the zero-sequence II section protection of the branch incoming line is actuated, and a large number of electrical secondary circuits are reduced.

Description

Technical Field

[0001] The invention relates to a comprehensive protection method for a high-voltage power system of a power plant, belongs to the field of power system power generation engineering, and is mainly used for the protection of a high-voltage power system of a power plant and automatic switching of power supply for the plant. Background Art

[0002] At present, the protection and automatic devices of the high-voltage power supply system of power plants mainly include generator-transformer group protection devices, start-up standby transformer protection devices, high-voltage plant equipment comprehensive protection devices, and plant power supply quick-cut devices. Among them, branch overcurrent protection and branch zero-sequence overcurrent protection are configured in the generator-transformer group protection and start-up standby transformer protection, which can be used to quickly cut off the faults of plant high-voltage bus phase-to-phase faults and single-phase grounding faults; the high-voltage plant equipment comprehensive protection device is used to cut off the faults of single-phase grounding faults and phase-to-phase faults of high-voltage plant motors and low-voltage plant transformers; the main function of the plant quick-cut device is to automatically switch to the standby power supply function after the plant incoming power supply loses power due to a fault, so as to prevent the plant power supply from losing power due to the fault. The current problems are mainly that when the high-voltage bus fails between phases, the power incoming line overcurrent protection needs to be coordinated with the plant load protection time in a step-by-step manner, the protection delay time is relatively long, and the phase-to-phase short-circuit current is very large, which can easily cause the internal insulation of the high-voltage plant transformer to fail, expanding the scope of the fault. The neutral point of the high-voltage transformer used in thermal power plants is grounded via a resistor. When a ground fault occurs in the busbar between the low-voltage winding of the high-voltage transformer and the power supply incoming circuit breaker, the zero-sequence overcurrent I protection of the generator-transformer group cannot be quickly returned. Therefore, the high-voltage power supply cannot be switched to the backup power supply through the power supply switching device, resulting in power outage in the entire plant. In addition, the entire high-voltage system is equipped with multiple protection devices, and the wiring is complicated, resulting in high equipment installation and use costs.

[0003] With the technological development of the power system, multiple sets of protection for the plant high-voltage power system and the plant power quick-cutting device can be integrated, the high-voltage plant bus differential protection function can be increased, and the protection action time of the bus fault can be reduced; the plant branch zero-sequence protection principle can be modified, and the zero-sequence power direction element can be added. This can quickly distinguish the protection range of zero-sequence overcurrent protection stage I and stage II, solve the problem of the plant power switching being affected by the simultaneous action of zero-sequence overcurrent protection stage I and stage II to lock the plant power quick-cutting device, reduce secondary circuit equipment and wiring, and improve the reliability of protection and automatic devices. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and provide a comprehensive protection method for the high-voltage power system of a power plant, integrate multiple sets of protection and automatic devices for the power plant high-voltage power system in the power generation enterprise, reduce the repeated investment in protection and automatic devices, reduce the workload of secondary circuit installation and maintenance, and solve the current delay in the action of the plant high-voltage bus phase-to-phase fault protection, and the zero-sequence overcurrent II stage protection, zero-sequence overcurrent protection stage I and stage II simultaneously acting to lock the plant power fast-cut device affecting the plant power switching. The integrated function of protection and plant power switching is realized, the power direction elements of the plant power high-voltage bus differential protection and branch zero-sequence current protection are added, and the plant power switching function is integrated.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problem is: a comprehensive protection method for the high-voltage plant power system of a power plant, which is characterized by adopting a comprehensive protection automatic device to integrate the functions of decentralized working power supply incoming line protection, standby power supply incoming line protection, load interval protection, plant power supply quick cutting and other devices, based on all electrical quantity information of the plant power system, to realize centralized comprehensive protection and automatic power switching functions of the high-voltage plant power supply system, and provide a unified digital interface to the outside.

[0006] Each interval of high-voltage plant power is equipped with an intelligent collection and operation unit, and the comprehensive protection automatic device and the intelligent collection and operation unit are connected in a star network; the intelligent collection and operation unit sends the analog information and switch quantity information of each interval to the comprehensive protection automatic device, and the comprehensive protection automatic device realizes the opening and closing operations of the switches in each interval through the intelligent collection and operation unit; the comprehensive protection automatic device collects all electrical quantity information of the plant power system, and integrates the functions of decentralized working power supply incoming line protection, standby power supply incoming line protection, load interval protection, plant power supply quick cutting and other devices.

[0007] When the load interval protection fault discrimination element is activated, the related quick-acting protection of the working power supply or backup power supply incoming line is automatically locked to avoid over-stepping action. The power incoming line protection and load protection do not need to be coordinated in time, which reduces the protection action time and reduces the damage to the equipment when a fault occurs.

[0008] The action logic of the working or standby power supply incoming line overcurrent and zero-sequence overcurrent protection increases the analog quantity of each load interval and the judgment unit of the protection action; when a fault occurs in the load interval, the working or standby power supply incoming line protection is locked according to the working or standby power supply incoming line switch position; when a fault occurs in the factory bus, the working or standby power supply incoming line protection can act without delay to ensure the speed of the working or standby power supply protection.

[0009] Zero-sequence power direction elements of zero-sequence overcurrent protection are added to the working and standby power switches. The zero-sequence power direction can be used to determine the location of the single-phase grounding fault point and select different protection output tripping logics and factory power switching methods.

[0010] Furthermore, according to the different locations of the fault points, the comprehensive protection automatic device adopts different exit methods; when the fault point is located on the plant bus, the comprehensive protection automatic device trips the working power supply incoming switch and locks the standby power supply incoming switch; when the fault point is located on the high-voltage plant transformer low-voltage branch, the comprehensive protection automatic device trips the working power supply incoming switch, closes the standby power supply incoming switch, and issues a generator tripping command; when the fault point is located on the start-up standby transformer low-voltage branch, the comprehensive protection automatic device trips the standby power supply incoming switch and issues a start-up transformer tripping command.

[0011] Furthermore, the comprehensive protection automatic device sends analog information such as voltage, current, power of each load interval of the factory power and switch information such as switch position, status, protection action, etc. to the DCS system through the digital interface; the DCS system sends the opening and closing commands of the switches in each interval of the factory power to the comprehensive protection automatic device through the digital interface, and the comprehensive protection automatic device completes the switch operation; the generator-transformer group protection starts or locks the factory power fast-cut command and sends it to the comprehensive protection automatic device through the digital interface, and the comprehensive protection automatic device completes the start or lock of the factory power switching.

[0012] Compared with the prior art, the present invention has the following advantages and effects: the present invention has the functions of power supply incoming line protection, load side protection, and power supply switching for the plant, and can realize the rapid action of the plant high-voltage bus phase-to-phase and ground fault protection, and can simultaneously realize the plant power single bus differential protection, each interval switch failure protection, and intelligent low-voltage load shedding function. It can improve the speed of the plant power supply protection, and can solve the problem that the plant power supply cannot be automatically switched when the branch incoming line zero-sequence II section protection is actuated, thereby reducing a large number of electrical secondary circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the system diagram of the comprehensive protection automatic device for the high-voltage power system of a power plant.

[0014] The optical fiber and the local sampling control unit of each high-voltage switch use digital channels to exchange current data and realize protection and control functions.

[0015] Figure 2 It is the structural diagram of the protection control unit of the comprehensive protection automatic device for high-voltage power supply in a power plant.

[0016] The centralized protection of high-voltage loads can be achieved through data transmission, which can reduce the protection action time. There is no need to set the differential time, thus achieving rapid protection action.

[0017] Figure 3 This is the zero-sequence current protection range diagram of the neutral point of the factory high-voltage system grounded by resistance.

[0018] Among them, the zero-sequence overcurrent protection stage I protection is used as the main protection for the single-phase grounding fault of the high-voltage bus, and the zero-sequence overcurrent protection stage II protection is used as the main protection for the single-phase grounding fault of the bus from the high-voltage transformer low-voltage winding to the power supply incoming circuit breaker. The protection ranges at both ends are different.

[0019] Figure 4 It is the factory-used high voltage zero-sequence overcurrent protection logic and protection output diagram.

[0020] The zero-sequence overcurrent protection realizes the selectivity of zero-sequence overcurrent protection stage I and zero-sequence overcurrent protection stage II by adding a zero-sequence power direction element, and the zero-sequence overcurrent protection stage II does not need to increase the time delay. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0022] Example

[0023] In the present embodiment, a comprehensive protection method for a high-voltage power system of a power plant is provided, which adopts a comprehensive protection automatic device, including comprehensive power supply incoming line overcurrent protection, zero-sequence overcurrent protection and standby incoming line overcurrent protection, zero-sequence overcurrent protection functions, adding the plant high-voltage single bus differential protection, each interval switch failure protection, intelligent low-voltage load shedding function, adding the power direction element of the branch zero-sequence overcurrent protection, when the neutral point of the plant high-voltage transformer adopts the operation mode of grounding through a resistor and a branch grounding fault occurs, the protection range of the zero-sequence overcurrent protection section I and section II can be quickly distinguished; the protection function of the comprehensive plant load equipment can reduce the time difference between the incoming line protection and the load protection, and improve the protection speed; the comprehensive plant power switching function can reduce equipment investment and a large number of secondary circuits, and the comprehensive protection automatic device is installed at the main body of the high-voltage plant incoming line circuit breaker.

[0024] In this embodiment, the digital channel is used to exchange current data with the sampling intelligent operation unit installed locally for the high-voltage plant load circuit breaker, and the switch quantity information is also exchanged to realize basic functions, mainly including line selection tripping, local circuit breaker equipment abnormality alarm, current transformer circuit disconnection information, etc. By means of data exchange, the bus differential protection function is set to realize the rapid action of the phase-to-phase fault of the plant high-voltage bus. In addition to the bus differential protection, the plant incoming power overcurrent protection is also configured as the backup protection for bus phase-to-phase faults; the plant incoming branch zero-sequence overcurrent stage I protection is used as the main protection for plant high-voltage bus grounding faults; the plant incoming branch zero-sequence overcurrent stage II protection is used as the main protection for bus grounding faults from the low-voltage side of the high-voltage plant transformer to the branch incoming circuit breaker; when the plant power supply is switched to the standby branch operation, the plant standby incoming power overcurrent protection is used as the backup protection for bus phase faults, the plant standby incoming branch zero-sequence overcurrent stage I protection is used as the main protection for plant high-voltage bus grounding faults, and the plant standby incoming branch zero-sequence overcurrent stage II protection is used as the main protection for bus grounding faults from the low-voltage side of the high-voltage plant transformer to the standby power supply incoming circuit breaker.

[0025] In this embodiment, the branch zero-sequence overcurrent protection uses a zero-sequence power direction element to determine the specific location of the busbar grounding fault and distinguish the protection range of the zero-sequence I section overcurrent protection and the zero-sequence II section overcurrent protection. The zero-sequence power direction element is taken from the zero-sequence current produced by the three-phase current transformer of the incoming circuit breaker and the zero-sequence voltage of the busbar voltage transformer.

[0026] In this embodiment, the above method realizes the centralized protection of load equipment. The protection is divided into low-voltage plant transformer protection and high-voltage plant motor protection. The digital channel is used to exchange current data with the sampling intelligent operation unit installed on-site of the high-voltage plant load circuit breaker, and the protection and control functions are realized.

[0027] In this embodiment, the switching mode can be classified according to the order of switch action or the starting reason. The manual switching function can be realized through DCS remote operation. Since the comprehensive protection automatic device integrates the protection functions of the busbar and the load, the factory power supply switching does not require the external protection circuit to be locked and started, and can realize fast and reliable switching function through its own logical judgment.

[0028] See also Figure 1The protection function of the comprehensive protection automatic device is mainly divided into two parts, which are divided into busbar protection of the high-voltage plant power system and protection of the high-voltage plant load according to the protection object. All protections are concentrated in the comprehensive protection automatic device to realize the protection function through the on-site data collection and transmission. The comprehensive protection automatic device is installed on the main body of the plant power incoming switch cabinet. The current transformer analog circuit, voltage transformer analog circuit, circuit breaker control and signal of the incoming switch are connected to the comprehensive protection automatic device through the secondary circuit. The current analog information of the standby incoming line and high-voltage load interval and the control and fault information of the circuit breaker are transmitted to the comprehensive protection automatic device through on-site data collection. The DCS system sends the opening and closing commands of the plant power interval switches to the comprehensive protection automatic device through the digital interface, and the comprehensive protection automatic device completes the switching operation.

[0029] The main protection for bus phase-to-phase fault configuration is bus differential protection. It realizes rapid action within the protection action area through current sampling information of the incoming line switch interval and other intervals. Its principle is the ratio brake differential protection principle. The differential protection action output jumps the incoming line circuit breaker or the spare incoming line circuit breaker, and at the same time sends out a protection trip signal and starts a fault recording signal. The power incoming line overcurrent protection and the backup power incoming line overcurrent protection serve as backup protection for bus phase-to-phase faults. The main protection criterion is that the incoming line current is greater than the protection action setting value, and the current of other intervals is less than the motor feedback current setting value. The protection action time can be coordinated with the load interval without step difference, and is taken as 0.1s. The protection output is to jump the incoming line circuit breaker or the spare incoming line circuit breaker, and at the same time send out a protection trip signal and start a fault recording signal.

[0030] The main protection for busbar grounding fault is the incoming line zero-sequence current protection or the standby incoming line zero-sequence overcurrent protection. The zero-sequence overcurrent protection is mainly configured with two-terminal zero-sequence current protection. Figure 3 As shown in the figure, the protection range of the zero-sequence overcurrent protection stage I is the high-voltage busbar for the plant, and the protection range of the zero-sequence overcurrent protection stage II is the busbar from the power supply line circuit breaker to the high-voltage plant transformer or high-voltage standby transformer. Its protection logic is as follows Figure 4As shown in the figure, the protection realizes the selectivity of zero-sequence two-stage protection by adding a zero-sequence power direction unit, so the two-stage protection action time is the same. Its main judgment criterion is that the zero-sequence current is greater than the protection setting value, and the zero-sequence power direction unit and the load interval zero-sequence overcurrent protection do not act. In order to prevent the single-phase grounding fault from expanding to the phase-to-phase fault, the protection action time can be reduced to 0.1s. The zero-sequence overcurrent stage I protection action output is to trip the power supply incoming line circuit breaker, and at the same time send out a protection trip signal and start the fault recording signal. The zero-sequence overcurrent stage II protection action output is the unit full stop, and at the same time send out a protection trip signal and start the fault recording signal. The unit full stop signal is connected to the non-electrical quantity protection screen of the generator-transformer group through hard wiring. The non-electrical quantity protection screen of the generator-transformer group adds a non-electrical quantity protection for the fault of the plant power system, and its protection trip matrix is ​​the unit full stop. The standby zero-sequence overcurrent protection stage II action output is the high standby transformer full stop signal, and at the same time send out a protection trip signal and start the fault recording signal. The high standby transformer full stop signal is connected to the high standby transformer non-electrical quantity protection screen through hard wiring. The high standby transformer non-electrical quantity protection panel adds a non-electrical quantity protection for the plant power system failure, and its protection tripping matrix is ​​to trip the high voltage side circuit breaker of the high standby transformer.

[0031] The phase-to-phase protection and grounding protection of the load interval are centralized for protection and tripping control by collecting information and transmitting data on-site through the intelligent sampling operation unit. The protection is mainly divided into motor protection and low-voltage plant transformer protection according to the load type. The motor protection is mainly equipped with quick-break protection, overcurrent protection, zero-sequence overcurrent protection, overload protection, stall protection, and overheating protection. The low-voltage plant transformer protection is mainly equipped with quick-break protection, overcurrent protection, zero-sequence overcurrent protection, low-voltage side zero-sequence overcurrent protection, and overload protection. The protection outlet sends the GOOSE command to the intelligent sampling operation unit through the GOOSE plug-in to realize the protection tripping. All load protection action information is sent to the ECS system through two Ethernets.

[0032] The factory power switching function is realized by judging the position and protection action information of the factory power incoming circuit breaker and the standby incoming circuit breaker, the factory power bus voltage and the incoming voltage analog quantity. The switching method can be classified according to the switch action sequence or the starting reason. According to the starting reason classification, normal manual switching is manually started by the operating personnel, and the opening and closing operations are performed according to the pre-set manual switching method (parallel, simultaneous). Automatic switching in accidents, while the protection action trips the working power switch, the factory power is switched, and the automatic device performs the opening and closing operations according to the pre-set automatic switching method. Automatic switching in abnormal situations, there are two abnormal situations, one is bus voltage loss, the bus voltage is lower than the set voltage for the set delay, the device starts automatically, and switches in an automatic way; the other is the working power switch trips by mistake, the auxiliary contact of the working switch starts the device, and the standby power is closed when the switching conditions are met. Manual switching is connected to the DCS system by hard wiring.

[0033] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0034] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the protection scope of the present invention. Any changes and modifications made by any technician familiar with the technology without departing from the concept and scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A comprehensive protection method for a high-voltage power system of a power plant, characterized in that: The integrated protection automatic device is used to integrate the functions of the decentralized working power supply incoming line protection, standby power supply incoming line protection, load interval protection, and plant power supply quick-cut device. Based on the information of all electrical quantities of the plant power system, the centralized integrated protection and automatic power supply switching functions of the high-voltage plant power supply system are realized, and a unified digital interface is provided to the outside world. Each interval of high-voltage power supply is equipped with an intelligent acquisition operation unit, and the integrated protection automatic device and the intelligent acquisition operation unit are connected by a star network; the intelligent acquisition operation unit sends the analog quantity information and switch quantity information of each interval to the integrated protection automatic device, and the integrated protection automatic device realizes the opening and closing operation of the switches of each interval through the intelligent acquisition operation unit; the integrated protection automatic device collects all the electrical quantity information of the power supply system, and integrates the functions of the decentralized working power supply incoming line protection, standby power supply incoming line protection, load interval protection, and power supply quick-cut device for the power supply; When the load interval protection fault discrimination element is activated, the related quick-acting protection of the working power supply or standby power supply incoming line is automatically locked to avoid overstepping action. The power incoming line protection and the load protection are not coordinated in time, which reduces the protection action time and reduces the damage to the equipment when a fault occurs. The action logic of the overcurrent and zero-sequence overcurrent protection of the working or standby power supply line increases the analog quantity of each load interval and the judgment unit of the protection action; when the fault occurs in the load interval, the working or standby power supply line protection is locked according to the position of the working or standby power supply line switch; when the fault occurs in the factory bus, the working or standby power supply line protection acts without delay, ensuring the quick action of the working or standby power supply protection; Zero-sequence power direction elements of zero-sequence overcurrent protection are added to the working and standby power switches. The zero-sequence power direction is used to determine the location of the single-phase grounding fault point, and different protection output tripping logics and factory power switching methods are selected.

2. The comprehensive protection method for the high-voltage auxiliary power system of a power plant according to claim 1 is characterized in that: Depending on the location of the fault point, the comprehensive protection automatic device adopts different exit methods; when the fault point is located on the plant bus, the comprehensive protection automatic device trips the working power supply incoming switch and locks the standby power supply incoming switch; when the fault point is located on the high-voltage plant transformer low-voltage branch, the comprehensive protection automatic device trips the working power supply incoming switch, closes the standby power supply incoming switch, and issues a generator tripping command; when the fault point is located on the starting standby transformer low-voltage branch, the comprehensive protection automatic device trips the standby power supply incoming switch and issues a starting standby transformer tripping command.

3. The comprehensive protection method for the high-voltage auxiliary power system of a power plant according to claim 1 or 2, characterized in that: The comprehensive protection automatic device sends the analog quantity information and switch quantity information of each load interval of the power supply to the DCS system through the digital interface; the DCS system sends the opening and closing commands of the switches of each interval of the power supply to the comprehensive protection automatic device through the digital interface, and the comprehensive protection automatic device completes the switching operation; The generator-transformer group protection starts or locks the factory power quick-cut command and is sent to the integrated protection automatic device via the digital interface. The integrated protection automatic device completes the start or lock of the factory power switching.

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