A mis-energization protection method and system considering asynchronous switching-on

Abstract

A method and system for mis-energization protection considering asynchronous closing. The method includes: identifying that the generator set is in a system disconnection state; monitoring the state change of the preconditioning characteristic quantity for the generator set to be connected to the grid; after the generator set is in the grid connection and closing state, comparing the operation result of the logic calculation module with the set threshold category to confirm whether the generator set is in an abnormal mis-energization condition; if a mis-energization fault occurs, after meeting the logic discrimination condition, the mis-energization protection acts on the generator set to trip and de-energize the field; if it is a normal grid connection operation of the generator set, the mis-energization protection function module is automatically locked. The present invention considers the mis-closing condition under the asynchronous operation state of the unit; through the setting and discrimination of the working condition and logic, the relay protection of the generator set is more comprehensive when the abnormal mis-energization condition of the generator set occurs. At the same time, the mis-energization protection function is in a locked state during the normal operation of the unit by using the soft method of automatic switching on and off, which improves the usability of the mis-energization protection and facilitates efficient operation and maintenance.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection in power systems, and specifically, relates to a mis-energization protection method and system considering asynchronous closing. Background Art

[0002] When the generator set is in the process of barring gear operation or the rotor is stationary and abnormal energization occurs, after closing, the stator winding is suddenly applied with the three-phase voltage of the system. When the current flows through the stator winding, the rotating magnetic field established will generate differential frequency current in the rotor body, causing the rotor to heat up. In the case of a large slip, the current induced in the rotor body far exceeds the allowable value, and severe heating will damage the rotor. In addition, the sudden acceleration of the rotor may affect key components such as bearing bushes because the oil system, auxiliary equipment, etc. are not fully ready. When the generator set has asynchronous mis-energization (in the extreme case, the phase difference between the grid-connected power supplies is 180°), the huge current flowing through the stator winding after closing will cause serious impacts on the generator, transformer, and the connected system. Under the action of stress, the generator set will vibrate violently, and a series of damage phenomena such as deformation, bending, and insulation cracking of the stator winding will occur. If a large generator set has asynchronous mis-energization and grid connection, it will not only cause power oscillation and damage to the main equipment, but may even cause a large-area collapse accident of the entire power system. Therefore, generally, dedicated mis-energization protection is installed on large generator sets.

[0003] In the prior art, there are various implementation principles for the mis-energization protection of generator sets. The main types applied in engineering are the full impedance characteristic, the offset impedance characteristic, and the low-frequency and low-voltage overcurrent characteristic. For the protection principle using impedance characteristics (including the full impedance characteristic and the offset impedance characteristic), the timing of the impedance criterion input is mostly selected after the generator excitation system is energized, and the working state of the excitation system is judged by introducing the position state of the field switch (excitation breaker). First, since the excitation system is a DC system, the identification of the state of the field switch completely depends on the position signal of the switch auxiliary contact, and the relay protection has no matching means to monitor the actual working state of the excitation system. Second, as a composite action quantity, the impedance calculation needs to simultaneously collect the current and voltage of the generator set, and there are many calculation error introduction links in the process of obtaining the measured impedance, which will cause a part of accuracy loss. For the protection principle using the low-frequency and low-voltage overcurrent characteristic, when the generator set is operating near the rated speed and the excitation system has built up voltage (asynchronous), since the frequency and voltage of the generator set are close to the normal working values, the low-frequency and low-voltage elements cannot meet the logic conditions according to the setting guide values. When the switch is misclosed, only the overcurrent element meets the condition and the protection cannot operate. As the low-frequency and low-voltage elements of the blocking module, if the setting values are greatly increased by correction to barely meet the action conditions, on the one hand, it does not conform to the guiding opinions of the setting guide, and on the other hand, it may cause incorrect operation of the protection under the system disturbance during the normal operation of the generator set, losing the reliability of the protection. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention provides a mis-energization protection method and system considering asynchronous closing, which can be used in various types of power plants or energy power stations to complete the relay protection function during abnormal mis-energization and grid connection of synchronous generating sets, and achieve the purpose of quickly isolating the fault impact of the generating set. This protection method is effective both when the generating set is in the turning gear or the rotor is stationary and there is abnormal mis-energization, and when there is abnormal mis-energization in the state of full voltage, full frequency, and non-synchronous expected grid connection, and also considers the ease of implementation and operation and maintenance in engineering.

[0005] The present invention adopts the following technical solutions.

[0006] On the one hand, the present invention proposes a mis-energization protection method considering asynchronous closing, including:

[0007] Step 1, check and judge the real-time state of the generating set according to the total state of the opening position of the grid connection switch and the current signal on the side of the generating set near the grid connection point; if it is determined that the generating set is in the system disconnection state, the mis-energization protection function module is enabled and ready; otherwise, loop to execute Step 1;

[0008] Step 2, monitor the total state of the opening position before and after the grid connection moment of the generating set, the amplitude of the current signal in the grid connection channel, and the change in the amplitude of the voltage signal of the generating set, and confirm the grid connection moment, and latch the three-phase voltage and measured frequency of the generating set;

[0009] Step 3, after the generating set is in the system grid connection closing state, compare the voltage characteristics of the generating set and the current signal on the side of the generating set near the grid connection point with the corresponding thresholds, where the thresholds are set according to the parameters of different generating sets; when the voltage characteristics of the generating set exceed the corresponding thresholds, synchronously judge whether the current signal exceeds the allowable current that the generating set body can withstand, and if it exceeds, it is determined that the generating set has a mis-energization and grid connection fault; otherwise, it is determined that the generating set has a normal grid connection operation;

[0010] Step 4, when it is determined that the generating set has a mis-energization and grid connection fault, including:

[0011] Step 4.1, before the grid connection switch closes, when the generating set is in a stationary or turning gear or zero-start voltage boosting start state, extract the three-phase voltage and measured frequency of the generating set latched at the grid connection moment for low voltage or low frequency discrimination, and use the comprehensive discrimination result of low voltage or low frequency to enable the protection element in Step 3, so that the mis-energization protection function module acts on the generating set to trip and de-energize the field under the enabling condition, and at the same time start the failure protection of the grid connection switch;

[0012] Step 4.2, before the grid-connected switch is closed, when the generating set is in a non-synchronous grid-connection preparation state where the voltage amplitude is not less than 0.5 times the rated voltage and the operating frequency is not less than 0.96 times the rated frequency, the over-current element is used to judge the amplitude of the current signal on the side of the generating set near the grid connection point. The threshold of the over-current element is taken as 1.2 to 1.5 times the rated current of the generating set; when the amplitude of the current signal on the side of the generating set near the grid connection point exceeds the threshold, the protection element in Step 3 is enabled by using the over-current discrimination result, so that the mis-energization protection function module operates to trip and de-energize the generating set under the enabling condition, and at the same time, the malfunction protection of the grid-connected switch is started; otherwise, it is determined that the mis-energization fault current does not exceed the working allowable capacity of the unit, and the protection does not operate;

[0013] Step 5, when it is determined that the generating set is operating in a normal grid connection, the mis-energization protection function module is automatically locked after a preset enabling delay, and the function is soft-exited.

[0014] Preferably, in Step 1, for the generator-transformer unit wiring mode, when the high-voltage side of the main transformer includes multiple grid-connected switches and grid connection channels, the opening position information of all hot standby grid-connected switches is collected, and the total opening position state is output when the three phases of each group of grid-connected switches are in the opening position; at the same time, the opening state of the grid-connected switch is verified by using the current signals of the grid connection channels corresponding to each group of grid-connected switches;

[0015] When the maximum value of the three-phase current amplitudes of each group of grid-connected switches is less than the no-load current threshold of 0.05I n and the total opening position state is true, it is determined that the total opening state of the grid-connected switch is correct, and I n is the rated current at the grid-connected switch.

[0016] Preferably, in Step 2, when the mis-energization protection function module is enabled and ready, when it is detected in real time that the total opening position state of the grid-connected switch changes, or the maximum value of the current amplitude in the grid connection channel is greater than the no-load current threshold of 0.05I n or the voltage amplitude change of the generating set exceeds 20%, the current grid connection time of the generating set is recorded, and the enabling survival state relay in the mis-energization protection function module is started to start timing.

[0017] While the enabling survival state relay starts timing, the data recording sub-module in the mis-energization protection function is triggered, and the three-phase voltage and measured frequency of the generating set bus in the sampling buffer are migrated to the data backup space for storage and locked.

[0018] Preferably, in Step 3, the voltage characteristics include amplitude and phase angle; the thresholds corresponding to the voltage characteristics include an amplitude threshold and a phase angle threshold, which are respectively taken under the condition of avoiding the maximum voltage difference and angle difference allowed for the synchronous grid connection operation;

[0019] Determine the corresponding threshold value for the current signal on the side of the grid connection point near the generator set. The value is obtained based on the condition that the generator set can be reliably started when there is a mis-energization, and the specific setting result is calculated and determined by the parameters of the system and the unit.

[0020] For the generator-transformer unit wiring mode, when there are multiple grid connection switches and grid connection channels on the high-voltage side of the main transformer, the current signal on the side of the grid connection point near the generator set is the maximum value of the sum of the current phasors of each grid connection channel.

[0021] Preferably, step 4.1 includes:

[0022] Step 4.1.1, extract the latched three-phase voltage of the generator set to obtain the line voltage. When the maximum value of the line voltage amplitude is less than (0.2 - 0.5)U e , keep the low-voltage protection element to meet the action condition, where U e is the rated voltage of the generator set;

[0023] Step 4.1.2, extract the latched measured frequency of the generator set. When the maximum value of the measured frequency is lower than (0.9 - 0.96)f n , keep the low-frequency protection element to meet the action condition, where f n is the rated frequency of the generator set;

[0024] Step 4.1.3, when keeping the low-frequency protection element or the low-voltage protection element to meet the action condition and the voltage and current determination results in step 3 are both satisfied at the same time, the mis-energization protection function module starts the outlet time element to start timing; under the condition that the voltage and current determination results in step 3 are satisfied, the latched three-phase voltage and measured frequency data of the generator set are synchronously maintained until the whole group returns after the mis-energization protection action; for the low-voltage or low-frequency element, set an automatic latching time mode, and the automatic latching time is determined based on the setting value of the protection time element, with a step difference of 0.1s to 0.3s added;

[0025] Step 4.1.4, the mis-energization protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the failure protection of the grid connection switch.

[0026] Preferably, step 4.2 includes:

[0027] Step 4.2.1, extract the latched three-phase voltage and measured frequency of the generator set. According to steps 4.1.1 and 4.1.2, keep both the low-voltage protection element and the low-frequency protection element not to act;

[0028] Step 4.2.2: Input the overcurrent element dedicated for the asynchronous condition to confirm the current intensity. Use the overcurrent element to determine the maximum value of the current signal amplitude on the side of the generator set near the grid connection point. The threshold of the overcurrent element is taken as 1.2 to 1.5 times the rated current of the generator set. When the maximum value of the current signal amplitude on the side of the generator set near the grid connection point is less than or equal to the threshold, it is determined that the misclosing fault current does not exceed the working allowable capacity of the unit, and the misclosing protection switches to the automatic locking sequence.

[0029] When the current signal amplitude on the side of the generator set near the grid connection point exceeds the threshold, use the overcurrent discrimination result to enable the protection element in Step 3, and sequentially execute the subsequent steps.

[0030] Step 4.2.3: When the overcurrent in the asynchronous condition meets the action condition and the voltage and current determination results in Step 3 are simultaneously satisfied, the misclosing protection function module starts the outlet time element to count time.

[0031] Step 4.2.4: The misclosing protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the failure protection of the grid connection switch.

[0032] When the generator set is normally connected to the grid, starting from the current grid connection moment of the generator set, the enabling survival status relay in the misclosing protection function module accumulates time. When the accumulated time reaches the preset enabling delay, the misclosing protection function module is locked, realizing the soft way to exit the function.

[0033] On the other hand, the present invention also proposes a misclosing protection system considering asynchronous closing. The system includes: an enabling module, a grid connection confirmation module, a misclosing grid connection fault judgment module, an action module; and a misclosing protection function module.

[0034] The enabling module is used to check and judge the real-time state of the generator set according to the total opening position state of the grid connection switch and the current signal on the side of the generator set near the grid connection point. If it is determined that the generator set is in the system disconnection state, an enabling ready signal is sent to the misclosing protection function module.

[0035] The grid connection confirmation module is used to monitor the total opening position state before and after the grid connection moment of the generator set, the current signal amplitude of the grid connection channel, and the change in the voltage signal amplitude of the generator set, confirm the grid connection moment, and latch the three-phase voltage and measured frequency of the generator set.

[0036] The mis-energization and grid connection fault judgment module is used to compare the voltage characteristics of the generator set and the current signal on the side of the grid connection point near the generator set with the corresponding thresholds after the generator set is in the system grid connection closing state, where the thresholds are set according to the parameters of different generator sets; when the voltage characteristics of the generator set exceed the corresponding thresholds, it synchronously judges whether the current signal exceeds the allowable current that the generator set itself can withstand. If it exceeds, it is determined that the generator set has a mis-energization and grid connection fault; otherwise, it is determined that the generator set has a normal grid connection operation;

[0037] The action module is used to make the mis-energization protection function module act on the generator set to trip and de-energize the field when it is determined that the generator set has a mis-energization and grid connection fault, and at the same time start the failure protection of the grid connection switch; when it is determined that the generator set has a normal grid connection operation, the mis-energization protection function module is automatically blocked after a preset enable delay to achieve a soft exit of the function;

[0038] The action module includes: a starting state action unit and a grid connection preparation state action unit;

[0039] The starting state action unit is used to extract the three-phase voltage and measured frequency of the generator set latched at the grid connection moment for low voltage or low frequency discrimination when the generator set is in a stationary, barring, or zero-start voltage rise starting state before the grid connection switch closes. The protection element of the mis-energization fault judgment module is enabled by using the comprehensive discrimination result of low voltage or low frequency, so that the mis-energization protection function module acts on the generator set to trip and de-energize the field under the enable condition, and at the same time starts the failure protection of the grid connection switch;

[0040] The grid connection preparation state action unit is used to discriminate the amplitude of the current signal on the side of the grid connection point near the generator set by using an overcurrent element when the generator set is in a non-synchronous grid connection preparation state where the voltage amplitude of the generator set is not less than 0.5 times the rated voltage and the operating frequency is not less than 0.96 times the rated frequency before the grid connection switch closes. The threshold of the overcurrent element is taken as 1.2 to 1.5 times the rated current of the generator set; when the amplitude of the current signal on the side of the grid connection point near the generator set exceeds the threshold, the protection element of the mis-energization fault judgment module is enabled by using the overcurrent discrimination result, so that the mis-energization protection function module acts on the generator set to trip and de-energize the field under the enable condition, and at the same time starts the failure protection of the grid connection switch; otherwise, it is determined that the mis-energization fault current does not exceed the working allowable capacity of the unit and the protection does not operate.

[0041] When it is determined that the generator set has a normal grid connection operation, the mis-energization protection function module is automatically blocked after a preset enable delay to achieve a soft exit of the function.

[0042] The beneficial effects of the present invention are as follows. Compared with the prior art, when the protection method proposed by the present invention identifies whether the generator set is in the ready state of shutdown and disconnection, the total state of the opening position of the grid-connected switch verified by current is adopted, making the total state of the opening position of the grid-connected switch more accurate, and it is also applicable to the main wiring scenario with multiple grid connection points. The accidental power-on protection does not need to introduce the position of the magnetic field switch (excitation switch-off switch); the grid connection transient is identified by multiple signals of current, switch position, and voltage, accurately memorizing the grid connection section and locking the three-phase voltage and measured frequency of the generator set, resulting in high accuracy of the protection analog data calculation and accurate control of the effective interval of the function survival state; based on the simple and reliable conventional voltage characteristic changes and current, it is convenient to confirm the impact of abnormal conditions on the generator set body and reduce unnecessary re-grid connection operations; it is effective in both the case of abnormal accidental power-on during the turning gear of the generator set or when the rotor is stationary and the case of abnormal accidental power-on in the state of full voltage and full frequency non-synchronous grid connection, which not only improves the protection action interval but also increases the protection reliability; the accidental power-on protection function is in a locked state during the normal operation of the unit by using the soft method of automatic switching, improving the usability of the accidental power-on protection and facilitating the simplified operation of the operation and maintenance personnel. Brief Description of the Drawings

[0043] Figure 1 is a flowchart of a method for accidental power-on protection considering non-synchronous closing proposed by the present invention. Detailed Embodiments

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only a part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0045] On the one hand, the present invention proposes a method for accidental power-on protection considering non-synchronous closing, as Figure 1 shown, including:

[0046] Step 1, verify and judge the real-time state of the generator set according to the total state of the opening position of the grid-connected switch and the current signal on the side of the grid connection point close to the generator set; if it is determined that the generator set is in the system disconnection state, the accidental power-on protection function module enables readiness; otherwise, loop to execute Step 1.

[0047] Specifically, in step 1, for the unit wiring mode of the generator-transformer unit, when the high-voltage side of the main transformer includes multiple grid-connected switches and grid-connected channels, the opening position information of all hot standby grid-connected switches is collected, and the total opening position status is output when the three phases of each group of grid-connected switches are in the opening position; meanwhile, the opening status of the grid-connected switches is verified by using the current signals of the grid-connected channels corresponding to each group of grid-connected switches.

[0048] When the maximum value of the three-phase current amplitudes of each group of grid-connected switches is less than the no-current threshold of 0.05I n and the total opening position status is true, it is determined that the total opening status of the grid-connected switches is correct, and I n is the rated current at the grid-connected switch.

[0049] The opening position signal of the grid-connected point switch is verified through the current analog quantity of the affiliated channel. After the obtained information is correct, the mis-energization protection function module is enabled and ready; after the obtained information is abnormal, an alarm is output after a delay. To identify the ready state of the generator set shutdown and disconnection, using the total switch position signal verified by current is more accurate and is also applicable to the cases of the main wiring of multiple grid-connected points.

[0050] In step 2, monitor the total opening position status before and after the grid connection moment of the generator set, the amplitude of the current signal of the grid-connected channel, and the change in the amplitude of the voltage signal of the generator set, and confirm the grid connection moment, and latch the three-phase voltage and measured frequency of the generator set.

[0051] Specifically, in step 2, when the mis-energization protection function module is enabled and ready, it is detected in real time that the total opening position status of the grid-connected switch changes, or the maximum value of the current amplitude of the grid-connected channel is greater than the no-current threshold of 0.05I n or the change in the voltage amplitude of the generator set exceeds 20%, record it as the current grid connection moment of the generator set, and start the enable survival status relay in the mis-energization protection function module to start timing.

[0052] While the enable survival status relay starts timing, trigger the data recording sub-module in the mis-energization protection function, and migrate the three-phase voltage and measured frequency of the generator set bus in the sampling buffer area to the data backup space for storage and locking.

[0053] Real-time monitor the total opening status of the grid-connected switch and the amplitude of the current analog quantity of the corresponding working circuit, capture the time section of the generator set grid connection, migrate the three-phase voltage and unit measured frequency data on the side close to the generator set in the pre-opened sampling buffer area to the data backup space for storage and locking. At the same time, start the timing element of the protection function enable survival status relay. Remember the grid connection section according to the transient change during grid connection, and open up a data area to latch the voltage and measured frequency of the generator set to make the protection data more accurate.

[0054] Step 3, after the generator set is in the system grid-connected closing state, compare the voltage characteristics of the generator set and the current signal on the side of the grid connection point close to the generator set with the corresponding thresholds, where the thresholds are set according to the parameters of different generator sets; when the voltage characteristics of the generator set exceed the corresponding thresholds, synchronously judge whether the current signal exceeds the allowable bearing current of the generator set itself. If it exceeds, it is determined that the generator set has a fault of misclosing the grid during power-on; otherwise, it is determined that the generator set has a normal grid connection operation.

[0055] Specifically, in Step 3, the voltage characteristics include amplitude and phase angle; the thresholds corresponding to the voltage characteristics include amplitude threshold and phase angle threshold, and are respectively taken based on the conditions of avoiding the maximum voltage difference and angle difference allowed for the synchronization grid connection operation;

[0056] The threshold corresponding to the discrimination of the current signal on the side of the grid connection point close to the generator set is taken based on the condition of reliable startup when the generator set miscloses the grid during power-on, and the specific setting result is calculated and determined by the parameters of the system and the unit.

[0057] For the generator-transformer unit wiring mode, when there are multiple grid connection switches and grid connection channels on the high-voltage side of the main transformer, the current signal on the side of the grid connection point close to the generator set is the maximum value of the sum of the current phasors of each grid connection channel.

[0058] In this embodiment, the real-time collected voltage and current analog quantities are subjected to module operations according to the logic, and the output results are compared with the set thresholds for confirmation. The voltage characteristic conditions are respectively subjected to amplitude comparison and phase comparison operations, and the conditions are satisfied when the thresholds are exceeded; the current condition is subjected to amplitude comparison operation, and the conditions are satisfied when the thresholds are exceeded; when the generator-transformer adopts the unit wiring mode and there are multiple grid connection points on the high-voltage side of the main transformer, the amplitude maximum value of the "sum current" of the grid connection point is selected as the amplitude comparison current sample. Based on the simple and reliable voltage characteristic changes and current, the influence of abnormal working conditions on the generator set itself can be conveniently confirmed.

[0059] Step 4, when it is determined that the generator set has a fault of misclosing the grid during power-on, it includes:

[0060] Step 4.1, before the grid connection switch closes, when the generator set is in a stationary or turning gear or zero-start boost startup state, extract the three-phase voltage and measured frequency of the generator set latched at the grid connection moment for low voltage or low frequency discrimination, and use the comprehensive discrimination result of low voltage or low frequency to enable the protection element in Step 3, so that the misclosing protection function module acts on the generator set to trip and de-energize the field under the enabling condition, and at the same time start the malfunction protection of the grid connection switch.

[0061] Specifically, Step 4.1 includes:

[0062] Step 4.1.1, extract the latched three-phase voltage of the generator set to obtain the line voltage, and the maximum value of the line voltage amplitude is less than (0.2 - 0.5)U eWhen, keep the low-voltage protection component to meet the action condition, where U e is the rated voltage of the generator set;

[0063] Step 4.1.2, extract the latched measured frequency of the generator set. When the maximum value of the measured frequency is lower than (0.9 - 0.96)f n keep the low-frequency protection component to meet the action condition, where f n is the rated frequency of the generator set;

[0064] Step 4.1.3, when keeping the low-frequency protection component or the low-voltage protection component to meet the action condition and the voltage and current determination results in Step 3 are both satisfied at the same time, the mis-energization protection function module starts the outlet time element to time; under the condition that the voltage and current determination results in Step 3 are satisfied, the latched three-phase voltage and measured frequency data of the generator set are synchronously maintained until the whole set returns after the mis-energization protection action; for the low-voltage or low-frequency component, set an automatic latching time method. The automatic latching time is determined based on the setting value of the protection time element, with a step difference of 0.1 s to 0.3 s added;

[0065] Step 4.1.4, the mis-energization protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the failure protection of the grid-connected switch.

[0066] Step 4.2, before the grid-connected switch closes, when the generator set is in a non-synchronous grid-connected preparation state with the voltage amplitude not less than 0.5 times the rated voltage and the operating frequency not less than 0.96 times the rated frequency, use the over-current element to discriminate the amplitude of the current signal on the near-generator side of the grid connection point. The threshold of the over-current element is taken as 1.2 to 1.5 times the rated current of the generator set; when the amplitude of the current signal on the near-generator side of the grid connection point exceeds the threshold, use the over-current discrimination result to enable the protection element in Step 3, so that the mis-energization protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the failure protection of the grid-connected switch; otherwise, it is determined that the mis-energization fault current does not exceed the working allowable capacity of the unit, and the protection does not operate;

[0067] Specifically, Step 4.2 includes:

[0068] Step 4.2.1, extract the latched three-phase voltage and measured frequency of the generator set, and according to Step 4.1.1 and Step 4.1.2, keep both the low-voltage protection component and the low-frequency protection component not operating;

[0069] Step 4.2.2: Input the overcurrent element dedicated for the asynchronous condition to confirm the current intensity. Use the overcurrent element to determine the maximum value of the current signal amplitude on the side of the generator set near the grid connection point. The threshold of the overcurrent element is taken as 1.2 to 1.5 times the rated current of the generator set. When the maximum value of the current signal amplitude on the side of the generator set near the grid connection point is less than or equal to the threshold, it is determined that the misclosing fault current does not exceed the working allowable capacity of the unit, and the misclosing protection switches to the automatic locking sequence.

[0070] When the current signal amplitude on the side of the generator set near the grid connection point exceeds the threshold, use the overcurrent discrimination result to enable the protection element in Step 3, and sequentially execute the subsequent steps.

[0071] Step 4.2.3: When the overcurrent in the asynchronous condition meets the action condition and the voltage and current determination results in Step 3 are simultaneously satisfied, the misclosing protection function module starts the outlet time element to start timing.

[0072] Step 4.2.4: The misclosing protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the malfunction protection of the grid connection switch.

[0073] The present invention is effective both when abnormal misclosing occurs during the turning gear of the generator set or when the rotor is stationary and when abnormal misclosing occurs in the state of asynchronous full-voltage and full-frequency non-expected grid connection.

[0074] Step 5: When it is determined that the generator set is operating in a normal grid connection operation, the misclosing protection function module is automatically locked after a preset enabling delay, realizing the soft exit of the function.

[0075] When the generator set is operating in a normal grid connection operation, starting from the current grid connection moment of the generator set, the enabling survival status relay in the misclosing protection function module accumulates time. When the accumulated time reaches the preset enabling delay, the misclosing protection function module is locked, realizing the soft way of exiting the function.

[0076] The soft way of automatic switching on and off realizes that the misclosing protection function is in a locked state during the normal operation of the unit, improves the usability of the misclosing protection, and facilitates the efficient operation and maintenance during the engineering application process.

[0077] On the other hand, the present invention also proposes a misclosing protection system considering asynchronous closing. The system includes: an enabling module, a grid connection confirmation module, a misclosing grid connection fault judgment module, an action module; and a misclosing protection function module.

[0078] The enabling module is used to verify and judge the real-time state of the generator set according to the total state of the opening position of the grid connection switch and the current signal on the side of the generator set near the grid connection point. If it is determined that the generator set is in the system disconnection state, an enabling ready signal is sent to the misclosing protection function module.

[0079] The grid connection confirmation module is used to monitor the total status of the opening position before and after the grid connection moment of the generating unit, the amplitude of the current signal in the grid connection channel, and the change in the amplitude of the voltage signal of the generating unit, confirm the grid connection moment, and latch the three-phase voltage and measured frequency of the generating unit;

[0080] The mis-energization and grid connection fault judgment module is used to compare the voltage characteristics of the generating unit and the current signal on the side of the grid connection point near the generating unit with the corresponding thresholds after the generating unit is in the system grid connection closing state, where the thresholds are set according to the parameters of different generating units; when the voltage characteristics of the generating unit exceed the corresponding thresholds, synchronously judge whether the current signal exceeds the allowable current that the generating unit body can withstand. If it exceeds, it is determined that the generating unit has a mis-energization and grid connection fault; otherwise, it is determined that the generating unit has a normal grid connection operation;

[0081] The action module is used to make the mis-energization protection function module act on the generating unit to trip and de-energize the field when it is determined that the generating unit has a mis-energization and grid connection fault, and at the same time start the failure protection of the grid connection switch; when it is determined that the generating unit has a normal grid connection operation, the mis-energization protection function module is automatically blocked after a preset enable delay to realize the soft exit of the function;

[0082] The action module includes: a start state action unit and a grid connection preparation state action unit;

[0083] The start state action unit is used to extract the three-phase voltage and measured frequency of the generating unit latched at the grid connection moment for low voltage or low frequency discrimination when the generating unit is in a stationary or turning gear or zero-start voltage boost start state before the grid connection switch is closed, and use the comprehensive discrimination result of low voltage or low frequency to realize the opening of the protection element of the mis-energization fault judgment module, so that the mis-energization protection function module acts on the generating unit to trip and de-energize the field when the enable condition is met, and at the same time start the failure protection of the grid connection switch;

[0084] The grid connection preparation state action unit is used to discriminate the amplitude of the current signal on the side of the grid connection point near the generating unit by using the overcurrent element when the generating unit is in a non-synchronous grid connection preparation state where the voltage amplitude of the generating unit is not less than 0.5 times the rated voltage and the operating frequency is not less than 0.96 times the rated frequency before the grid connection switch is closed. The threshold of the overcurrent element is taken as 1.2 to 1.5 times the rated current of the generating unit; when the amplitude of the current signal on the side of the grid connection point near the generating unit exceeds the threshold, use the overcurrent discrimination result to realize the opening of the protection element of the mis-energization fault judgment module, so that the mis-energization protection function module acts on the generating unit to trip and de-energize the field when the enable condition is met, and at the same time start the failure protection of the grid connection switch; otherwise, it is determined that the mis-energization fault current does not exceed the working allowable capacity of the unit and the protection does not act.

[0085] When it is determined that the generating unit has a normal grid connection operation, the mis-energization protection function module is automatically blocked after a preset enable delay to realize the soft exit of the function.

[0086] The identification of the disconnection state of the generator set system is applicable to both the generator set with a single grid connection point and the generator-transformer unit with multiple grid connection points in a high-voltage connection, increasing the application flexibility.

[0087] This disclosure may be a system, a method, and / or a computer program product. The computer program product may include a computer-readable storage medium having thereon computer-readable program instructions for causing a processor to implement various aspects of this disclosure.

[0088] A computer-readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. A computer-readable storage medium may be, for example—but not limited to—an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punch card or raised structures in grooves having instructions stored thereon, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., optical pulses through a fiber optic cable), or electrical signals transmitted through a wire.

[0089] The computer-readable program instructions described herein may be downloaded to respective computing / processing devices from a computer-readable storage medium or may be downloaded to an external computer or an external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing / processing device.

[0090] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine - related instructions, microcode, firmware instructions, state - setting data, or source code or object code written in any combination of one or more programming languages, including object - oriented programming languages such as Smalltalk, C++, etc., and conventional procedural programming languages such as the "C" language or similar programming languages. The computer - readable program instructions may be executed entirely on the user's computer, partially on the user's computer, executed as a stand - alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via an Internet service provider through the Internet). In some embodiments, by using the state information of the computer - readable program instructions to customize an electronic circuit, such as a programmable logic circuit, a field - programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit can execute the computer - readable program instructions to implement various aspects of the present disclosure.

[0091] Aspects of the present disclosure are described herein with reference to the flowchart and / or block diagram of methods, apparatus (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block of the flowchart and / or block diagram, and combinations of blocks in the flowchart and / or block diagram, can be implemented by computer - readable program instructions.

[0092] These computer - readable program instructions can be provided to a processor of a general - purpose computer, a special - purpose computer, or other programmable data - processing apparatus to produce a machine such that the instructions, when executed by the processor of the computer or other programmable data - processing apparatus, result in an apparatus that implements the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer - readable program instructions can also be stored in a computer - readable storage medium, which causes a computer, a programmable data - processing apparatus, and / or other devices to operate in a particular manner, so that the computer - readable medium storing the instructions includes a manufacture, which includes instructions for implementing various aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0093] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device, causing a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process such that the instructions executed on the computer, other programmable data processing apparatus, or other device implement the functions / acts specified in one or more boxes of the flowchart and / or block diagram.

[0094] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a segment of a program, or a portion of an instruction, which contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two consecutive blocks may in fact be executed substantially in parallel, or they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block of the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by a dedicated hardware-based system that performs the specified functions or acts, or by a combination of dedicated hardware and computer instructions.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A mis-energization protection method considering asynchronous switching-on, characterized in that The method includes the following steps: Step 1: Check and judge the real-time state of the generator set according to the total state of the opening position of the grid-connected switch and the current signal on the side of the generator set near the grid connection point. If it is determined that the generator set is in the system disconnection state, the misclosing protection function module enables and is ready; otherwise, loop and execute Step 1; Step 2: Monitor the total state of the opening position before and after the grid connection moment of the generator set, the amplitude of the current signal of the grid connection channel, and the change in the amplitude of the voltage signal of the generator set, and confirm the grid connection moment, and latch the three-phase voltage and measured frequency of the generator set; Step 3: After the generator set is in the system grid connection closing state, compare the voltage characteristics of the generator set and the current signal on the side of the generator set near the grid connection point with the corresponding thresholds, where the thresholds are set according to the parameters of different generator sets. When the voltage characteristics of the generator set exceed the corresponding thresholds, simultaneously judge whether the current signal exceeds the allowable current that the generator set itself can withstand. If it exceeds, it is determined that the generator set has a misclosing grid connection fault; otherwise, it is determined that the generator set has a normal grid connection operation; Step 4: When it is determined that the generator set has a misclosing grid connection fault, it includes: Step 4.1: Before the grid-connected switch closes, when the generator set is in a stationary or turning or zero-start boost start state, extract the three-phase voltage and measured frequency of the generator set latched at the grid connection moment for low voltage or low frequency discrimination, and use the comprehensive discrimination result of low voltage or low frequency to enable the protection element in Step 3, so that the misclosing protection function module operates to disconnect and de-energize the generator set under the enabling condition, and at the same time start the failure protection of the grid-connected switch; Step 4.2: Before the grid-connected switch closes, when the generator set is in a non-synchronous grid connection preparation state with the voltage amplitude not less than 0.5 times the rated voltage and the operating frequency not less than 0.96 times the rated frequency, then use the overcurrent element to discriminate the amplitude of the current signal on the side of the generator set near the grid connection point. The threshold of the overcurrent element is taken as 1.2 to 1.5 times the rated current of the generator set. When the amplitude of the current signal on the side of the generator set near the grid connection point exceeds the threshold, use the overcurrent discrimination result to enable the protection element in Step 3, so that the misclosing protection function module operates to disconnect and de-energize the generator set under the enabling condition, and at the same time start the failure protection of the grid-connected switch; otherwise, it is determined that the misclosing fault current does not exceed the working allowable capacity of the unit, and the protection does not operate; Step 5: When it is determined that the generator set has a normal grid connection operation, the misclosing protection function module automatically locks after a preset enabling delay to realize the soft exit of the function.

2. The misclosing protection method considering non-synchronous closing according to claim 1, characterized in that: In Step 1, for the generator-transformer unit wiring mode, when there are multiple grid-connected switches and grid connection channels on the high voltage side of the main transformer, collect the opening position information of all hot standby grid-connected switches, and output the total state of the opening position when the three phases of each group of grid-connected switches are in the opening position; at the same time, use the current signals of the grid connection channels corresponding to each group of grid-connected switches to check the opening state of the grid-connected switches; When the maximum value of the three-phase current amplitudes of each grid-connected switch is less than the no-current threshold of 0.05I n and the overall breaker position status is true, then it is determined that the overall breaker position status of the grid-connected switch is correct, where I n is the rated current at the grid-connected switch.

3. The misclosing protection method considering non-synchronous closing according to claim 2, characterized in that: In step 2, when the mis-energization protection function module is enabled and ready, if it is detected in real time that the total status of the opening position of the grid-connected switch changes or the maximum value of the current amplitude in the grid-connected channel is greater than the no-current threshold of 0.05I n or the voltage amplitude of the generator set changes by more than 20%, record the current grid connection time of the generator set and start timing of the enable survival status relay in the mis-energization protection function module.

4. The mis-energization protection method considering asynchronous closing according to claim 3, wherein while enabling the survival status relay to start timing, trigger the data recording sub-module in the mis-energization protection function, and transfer the three-phase voltages and measured frequencies of the generator set bus in the sampling buffer to the data backup space for storage and locking.

5. The mis-energization protection method considering asynchronous closing according to claim 1, wherein in step 3, the voltage characteristics include amplitude and phase angle; the thresholds corresponding to the voltage characteristics include an amplitude threshold and a phase angle threshold, which are respectively valued under the condition of avoiding the maximum voltage difference and angle difference allowed for synchronous grid connection operation; the threshold for discriminating the current signal near the generator set side of the grid connection point is valued under the condition of reliable startup during generator set mis-energization, and the specific setting result is calculated and determined from the parameters of the system and the unit.

6. The mis-energization protection method considering asynchronous closing according to claim 5, wherein for the generator-transformer unit wiring mode, when there are multiple grid connection switches and grid connection channels on the high-voltage side of the main transformer, the current signal near the generator set side of the grid connection point is the maximum value of the sum of the current phasors of each grid connection channel.

7. The mis-energization protection method considering asynchronous closing according to claim 1, wherein step 4.1 includes: Step 4.1.1, extract the latched three-phase voltages of the generator set to obtain line voltages, and when the maximum value of the line voltage amplitude is less than (0.2 - 0.5)U e , keep the low-voltage protection element to meet the operating conditions, where U e is the rated voltage of the generator set; Step 4.1.2, extract the latched measured frequency of the generating set. When the maximum value of the measured frequency is lower than (0.9 - 0.96)f n , keep the low-frequency protection element to meet the operating conditions, where f n is the rated frequency of the generating set; step 4.1.3, when keeping the low-frequency protection element or the low-voltage protection element to meet the action condition and the voltage and current determination results in step 3 are both satisfied at the same time, the mis-energization protection function module starts the outlet time element to start timing; under the condition that the voltage and current determination results in step 3 are satisfied, the locked three-phase voltages and measured frequencies of the generator set are synchronously maintained until the whole group returns after the mis-energization protection action; for the low-voltage or low-frequency element, set an automatic locking time mode, and the automatic locking time is determined based on the setting value of the protection time element, with a step difference of 0.1 s to 0.3 s added; step 4.1.4, the mis-energization protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the malfunction protection of the grid connection switch.

8. The mis-energization protection method considering asynchronous closing according to claim 7, wherein step 4.2 includes: step 4.2.1, extract the locked three-phase voltages and measured frequencies of the generator set, and keep the low-voltage protection element and the low-frequency protection element both not operating according to steps 4.1.1 and 4.1.2; step 4.2.2, input the over-current element dedicated to the asynchronous condition to confirm the current intensity, use the over-current element to discriminate the maximum value of the amplitude of the current signal near the generator set side of the grid connection point, and the threshold of the over-current element is taken as 1.2 to 1.5 times the rated current of the generator set; when the maximum value of the amplitude of the current signal near the generator set side of the grid connection point is less than or equal to the threshold, it is determined that the mis-energization fault current does not exceed the working allowable capacity of the unit, and the mis-energization protection switches to the automatic locking sequence; when the amplitude of the current signal near the generator set side of the grid connection point exceeds the threshold, use the over-current discrimination result to open the protection element in step 3 and sequentially execute the subsequent steps; Step 4.2.3: When the overcurrent in the asynchronous operating condition meets the action condition and the voltage and current determination results in Step 3 are both satisfied, the misclosing protection function module starts the outlet time element to count. Step 4.2.4: The misclosing protection function module operates to trip the generator set and extinguish the field under the enabling condition, and at the same time starts the failure protection of the grid connection switch.

9. The misclosing protection method considering asynchronous closing according to claim 3, characterized in that When the generator set is normally connected to the grid, starting from the current grid connection moment of the generator set, the enabling survival state relay in the misclosing protection function module accumulates time. When the accumulated time reaches the preset enabling delay, the misclosing protection function module is blocked, realizing the soft way to exit the function.

10. A mis-energization protection system considering asynchronous closing using the method according to any one of claims 1-9, the system comprising: Enabling module, grid connection confirmation module, misclosing grid connection fault judgment module, action module; The misclosing protection function module, characterized in that The enabling module is used to check and judge the real-time state of the generator set according to the total opening position state of the grid connection switch and the current signal on the side of the generator set near the grid connection point; if it is determined that the generator set is in the system disconnected state, it sends an enabling ready signal to the misclosing protection function module. The grid connection confirmation module is used to monitor the total opening position state before and after the grid connection moment of the generator set, the amplitude of the current signal in the grid connection channel, and the change of the amplitude of the voltage signal of the generator set, and confirm the grid connection moment, and latch the three-phase voltage and measured frequency of the generator set. The misclosing grid connection fault judgment module is used to compare the voltage characteristics of the generator set and the current signal on the side of the generator set near the grid connection point with the corresponding thresholds after the generator set is in the system grid connection closing state, where the thresholds are set according to the parameters of different generator sets; when the voltage characteristics of the generator set exceed the corresponding thresholds, it synchronously judges whether the current signal exceeds the allowable current that the generator set body can withstand. If it exceeds, it is determined that the generator set has a misclosing grid connection fault; otherwise, it is determined that the generator set has a normal grid connection operation. The action module is used to make the misclosing protection function module operate to trip the generator set and extinguish the field under the enabling condition and start the failure protection of the grid connection switch when it is determined that the generator set has a misclosing grid connection fault; when it is determined that the generator set has a normal grid connection operation, the misclosing protection function module is automatically blocked after the preset enabling delay, realizing the soft exit of the function. The action module includes: a starting state action unit and a grid connection preparation state action unit; The starting state action unit is used to extract the three-phase voltage and measured frequency of the generator set latched at the grid connection moment for low voltage or low frequency discrimination when the generator set is in a stationary or turning or zero-start boost starting state before the grid connection switch is closed, and use the comprehensive discrimination result of low voltage or low frequency to realize the protection element that opens the misclosing grid connection fault judgment module, so that the misclosing protection function module operates to trip the generator set and extinguish the field under the enabling condition, and at the same time starts the failure protection of the grid connection switch. Grid connection preparation state action unit. Before the grid connection switch is closed, when the generator set is in an out-of-step grid connection preparation state where the voltage amplitude is not less than 0.5 times the rated voltage and the operating frequency is not less than 0.96 times the rated frequency, the overcurrent element is used to discriminate the amplitude of the current signal on the side of the generator set near the grid connection point. The threshold of the overcurrent element is taken as 1.2 to 1.5 times the rated current of the generator set. When the amplitude of the current signal on the side of the generator set near the grid connection point exceeds the threshold, the overcurrent discrimination result is used to enable the protection element of the misclosing protection fault judgment module, so that the misclosing protection function module operates to trip and de-energize the generator set under the enabling condition, and at the same time starts the failure protection of the grid connection switch; otherwise, it is determined that the misclosing fault current does not exceed the working allowable capacity of the unit, and the protection does not operate. When it is determined that the generator set is operating for normal grid connection, the misclosing protection function module is automatically locked after a preset enabling delay, realizing the soft exit of the function.

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