A method and device for differential protection of main transformer of power generation phase-converting unit

Abstract

The present invention belongs to the technical field of power system relay protection, and specifically relates to a method and device for differential protection of the main transformer of a power generation phase-converter unit. The method comprises the following steps: S1: confirming the power generation, phase modulation, and phase modulation startup operating conditions; S2: during power generation and phase modulation operating conditions, the main transformer differential protection setting adopts the setting in the power generation condition setting zone and the setting in the phase modulation condition setting zone, respectively; during the phase-converter SFC startup, the main transformer differential protection minimum operating current adopts a dynamically adjusted floating setting; S3: determining the main transformer differential protection range; and S4: determining whether the main transformer differential protection is operating. The present invention implements switching of the differential protection setting zone of the main transformer of the power generation phase-converter unit, floating changes in the minimum operating current setting, and automatic switching of the protection range, thereby improving the reliability, sensitivity, speed, and selectivity of the main transformer differential protection and meeting the operational requirements of a power generation unit after retrofitting an old unit with a phase modulation function.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection of power systems, and in particular relates to a differential protection method and device for a main transformer of a power generation phase-shifting unit. Background Art

[0002] With the adjustment of the energy structure and the large-scale development of renewable energy, the survival space of coal-fired power units will continue to shrink. The supply-side reform task is arduous, and a large number of power generation units are facing retirement or vacancy. After the power generation units are retrofitted with phase-shifting functions, they have the dual attributes of generators and phase-shifting units. They can flexibly switch between phase-shifting and power generation modes according to grid demand, fully leveraging the combined efficiency of active power support during high-load periods and reactive power support during low-load periods. This can effectively improve the system's regulation performance and regulation capabilities, achieve coordinated development with new energy, and not only ensure the level of external power absorption, promote the consumption of clean energy, and reduce carbon emissions, but also activate idle equipment of emergency standby generators, save social electricity costs, promote the optimization and upgrading of traditional power generation units, and provide strong support for the clean and low-carbon energy transition.

[0003] After the generator set is renovated and rebuilt with the phase-shifting function, the primary equipment is increased with an SFC (Static Frequency Converter), input circuit, and high-voltage disconnect switch on the high-voltage side of the high-voltage transformer. Since the unit parameters are inconsistent during power generation and phase-shifting conditions, the main transformer protection of the power generation phase-shifting unit is significantly different from the differential protection of the main transformer of a conventional unit. In the prior art, after the generator set is renovated and rebuilt with the phase-shifting function, the unit has both power generation and phase-shifting operation modes. The main transformer differential protection has only one set value. During the phase-shifting ... However, the main transformer differential protection has only one set of fixed values. The minimum operating current is adjusted according to the SFC starting current of the phase regulator. Therefore, the minimum operating current setting needs to be raised, affecting the sensitivity of the main transformer differential protection during normal operation. The phase regulator adopts the locking protection method during the SFC starting period. During the starting period, the main transformer lacks the fast-acting main protection, and the speed of the main transformer differential protection is lost. Moreover, under the operating conditions of the phase regulator, when the high-voltage transformer is out of operation, the influence of the high-voltage side current of the high-voltage transformer is not considered, and the main transformer differential protection range remains unchanged. The high-voltage side current of the high-voltage transformer generated during the test and maintenance of the high-voltage transformer may cause the main transformer differential protection to malfunction, affecting the reliability and selectivity of the main transformer differential protection. Summary of the Invention

[0004] In view of the defects of the prior art, the present invention provides a method and device for differential protection of the main transformer of a power generation phase-converting unit.

[0005] A differential protection method for a main transformer of a power generation phase-converting unit comprises the following steps:

[0006] S1: Set the power generation condition fixed value area and the phase adjustment condition fixed value area, collect the power generation condition signal, phase adjustment condition signal and operation mode handle status signal of the monitoring system, and confirm the power generation and phase adjustment conditions;

[0007] Collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase adjustment starting condition;

[0008] S2: According to the working condition confirmation result, in the power generation condition, the main transformer differential protection setting value adopts the setting value in the power generation condition setting zone;

[0009] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0010] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting;

[0011] S3: Based on the working condition confirmation result, in the power generation condition, the main transformer differential protection range includes the high-voltage side of the main transformer, the generator phase condenser machine end, and the high-voltage side of the high-voltage transformer;

[0012] In phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the high-voltage side of the main transformer and the generator phase regulator end;

[0013] S4: Using the setting value and protection range of the main transformer differential protection, calculate according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated.

[0014] Preferably, the working condition confirmation in step S1 is based on the dual-position verification judgment logic to determine the unique state of the operating condition. The dual-position verification judgment logic is: when the monitoring system power generation condition signal and the operating mode handle power generation state signal are both "1", it is confirmed to be the power generation condition; when the monitoring system phase adjustment condition signal and the operating mode handle phase adjustment state signal are both "1", it is confirmed to be the phase adjustment condition; other states are regarded as error logic, all protections are locked, and an operating condition signal inconsistency alarm signal is given; in the phase adjustment condition, the SFC knife switch closing auxiliary contact signal is "1" and the circuit breaker closing auxiliary contact signal is "0", which is confirmed to be the phase adjustment phase SFC starting condition.

[0015] Preferably, the power generation condition fixed value area in step S1 includes fixed value areas 1, 3, 5, and 7, and the phase adjustment condition fixed value area includes fixed value areas 2, 4, 6, and 8.

[0016] Preferably, in step S2, according to the working condition confirmation result, in the power generation working condition, the main transformer differential protection setting value adopts the power generation working condition setting value zone setting value;

[0017] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0018] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting, including:

[0019] Minimum operating current setting value I of the main transformer differential protection under power generation condition op.0 Stored in the 1, 3, 5, 7 setting areas; the minimum operating current setting value I of the main transformer differential protection under phase modulation condition op.0 Stored in the setting area 2, 4, 6, 8, during the SFC startup of the phase regulator, the minimum operating current setting value I of the main transformer differential protection op.0 Automatically increase floating set value I float .

[0020] Preferably, the main transformer differential protection range in step S3 includes:

[0021] In power generation conditions, the isolating switch on the high-voltage side of the high-voltage transformer is closed. The differential protection range of the main transformer includes the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current High voltage side current of high power transformer

[0022] In phase modulation conditions, the high-voltage side disconnector of the high-voltage transformer is disconnected, and the high-voltage transformer is out of operation. The differential protection range of the main transformer includes the high-voltage side of the main transformer and the generator phase regulator. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current

[0023] Preferably, the step S4 of using the fixed value and protection range of the main transformer differential protection to calculate according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated includes:

[0024] The main transformer differential protection action equation is:

[0025]

[0026] Where, I op is the differential current, I op.0 is the minimum operating current setting value of differential protection, I res is the braking current, I res.0 is the minimum braking current setting value, S is the ratio braking coefficient setting value, and the direction of the current on each side is towards the transformer as the positive direction;

[0027] The main transformer ratio differential protection is calculated according to the above action equation. When the calculation result satisfies the above action equation, it is determined that the main transformer differential protection is in action. When the calculation result does not satisfy the above action equation, it is determined that the main transformer differential protection is in action.

[0028] Preferably, the differential current and braking current in the power generation condition are respectively:

[0029]

[0030] Where: They are the currents at the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer; I op Represents the differential current, I res Indicates braking current;

[0031] The differential current and braking current of the phase modulation working condition are respectively:

[0032]

[0033] Where: They are the current at the high-voltage side of the main transformer and the generator phase regulator terminal; I op Represents the differential current, I res Indicates the braking current.

[0034] A differential protection device for a main transformer of a power generation phase-converting unit, comprising:

[0035] The working condition confirmation module sets the power generation working condition fixed value area and the phase adjustment working condition fixed value area, collects the power generation working condition signal, the phase adjustment working condition signal and the operation mode handle status signal of the monitoring system, and confirms the power generation and phase adjustment working conditions;

[0036] Collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase adjustment starting condition;

[0037] A fixed value determination module, according to the working condition confirmation result, when in power generation condition, the main transformer differential protection fixed value adopts the fixed value of the power generation condition fixed value zone;

[0038] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0039] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting;

[0040] The protection range determination module determines, based on the working condition confirmation result, the power generation working condition, the main transformer differential protection range includes the high-voltage side of the main transformer, the generator phase regulator end, and the high-voltage side of the high-voltage transformer;

[0041] In phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the high-voltage side of the main transformer and the phase-shifting machine end of the generator;

[0042] The discrimination module uses the setting value and protection range of the main transformer differential protection to perform calculations according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated.

[0043] Preferably, the working condition confirmation is based on the dual-position verification judgment logic to determine the only state of the operating condition. The dual-position verification judgment logic is: when the monitoring system power generation condition signal and the operating mode handle power generation state signal are both "1", it is confirmed to be the power generation condition; when the monitoring system phase adjustment condition signal and the operating mode handle phase adjustment state signal are both "1", it is confirmed to be the phase adjustment condition; other states are regarded as error logic, all protections are locked, and an operating condition signal inconsistency alarm signal is given; in the phase adjustment condition, the SFC knife switch closing auxiliary contact signal is "1" and the circuit breaker closing auxiliary contact signal is "0", which is confirmed to be the phase adjustment phase SFC starting condition.

[0044] Preferably, the power generation condition fixed value area includes fixed value areas 1, 3, 5, and 7, and the phase adjustment condition fixed value area includes fixed value areas 2, 4, 6, and 8.

[0045] The positive beneficial effects of the present invention are:

[0046] The present invention proposes a differential protection method and device for the main transformer of a power generation phase-shifting group, which collects power generation condition signals, phase modulation condition signals and operation mode handle status signals of a monitoring system to confirm the power generation and phase modulation conditions, and collects SFC knife switch closing auxiliary contact signals and circuit breaker closing auxiliary contact signals to confirm the phase modulation starting condition; under power generation conditions, the main transformer differential protection setting adopts the power generation condition setting area setting; under phase modulation conditions, the main transformer differential protection setting adopts the phase modulation condition setting area setting; during the phase modulation phase-shifting startup, the main transformer differential protection minimum operating current adopts a dynamically adjusted floating setting; under power generation conditions, the main transformer differential protection range includes the main transformer high-voltage side, the power generation phase-shifting machine end, and the high-voltage side of the high-voltage transformer; under phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the main transformer high-voltage side and the power generation phase-shifting machine end; using the setting value and protection range of the main transformer differential protection, calculation is performed according to the main transformer differential protection action equation, and whether the main transformer differential protection is actuated is determined based on the calculation result. When the phase regulator is in operation, the present invention not only considers the influence of the SFC input current on the differential protection of the main transformer during the process from startup to grid connection, but also considers the influence of the high-voltage transformer being out of operation on the differential protection of the main transformer, thereby realizing the switching of the fixed value zone of the differential protection of the main transformer of the power generation phase regulator unit, the floating change of the minimum operating current fixed value, and the automatic switching of the protection range, thereby improving the reliability, sensitivity, speed and selectivity of the differential protection of the main transformer, and meeting the operating requirements of the generator unit after the old one is modified to add the phase modulation function. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Configuration diagram of main connection and main transformer differential protection for adding phase adjustment function to the generator set by renovating the old one;

[0048] Figure 2 This is the logic diagram of the differential protection method for the main transformer of the power generation phase-converting unit. DETAILED DESCRIPTION

[0049] The present invention is further described below with reference to some specific embodiments.

[0050] Example 1

[0051] See also Figure 1 After the generator set was renovated and the phase-shifting function was added, the primary equipment added SFC (Static Frequency Converter) and input circuit, high-voltage disconnector on the high-voltage side of the high-voltage transformer, and the unit parameters under the power generation condition and the phase-shifting condition were inconsistent. The generator set was renovated and the phase-shifting function main connection and main transformer differential protection configuration were added.

[0052] A differential protection method for the main transformer of a power generation phase-converting unit, see Figure 2 , including the following steps:

[0053] S1: Set the power generation condition fixed value area and the phase adjustment condition fixed value area, collect the power generation condition signal, phase adjustment condition signal and operation mode handle status signal of the monitoring system, confirm the power generation and phase adjustment conditions, and realize automatic switching between the power generation condition fixed value area and the phase adjustment condition fixed value area;

[0054] Collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase adjustment starting condition;

[0055] S2: According to the working condition confirmation result, in the power generation condition, the main transformer differential protection setting value adopts the setting value in the power generation condition setting zone;

[0056] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0057] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting;

[0058] S3: Based on the working condition confirmation result, the power generation condition is established, the high-voltage transformer is put into operation, and the main transformer differential protection range includes the high-voltage side of the main transformer, the generator phase condenser machine end, and the high-voltage side of the high-voltage transformer;

[0059] In phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the high-voltage side of the main transformer and the generator phase regulator end;

[0060] S4: Using the setting value and protection range of the main transformer differential protection, calculate according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated.

[0061] Furthermore, the working condition confirmation in step S1 is based on the dual-position verification judgment logic to determine the unique state of the operating condition. The dual-position verification judgment logic is: when the monitoring system power generation condition signal and the operating mode handle power generation state signal are both "1", it is confirmed to be the power generation condition; when the monitoring system phase adjustment condition signal and the operating mode handle phase adjustment state signal are both "1", it is confirmed to be the phase adjustment condition; other states are regarded as error logic, all protections are locked, and an operating condition signal inconsistency alarm signal is given; in the phase adjustment condition, the SFC knife switch closing auxiliary contact signal is "1" and the circuit breaker closing auxiliary contact signal is "0", which is confirmed to be the phase adjustment phase SFC starting condition.

[0062] Furthermore, the power generation condition fixed value area in step S1 includes fixed value areas 1, 3, 5, and 7, and the phase adjustment condition fixed value area includes fixed value areas 2, 4, 6, and 8.

[0063] Furthermore, in step S2, according to the working condition confirmation result, in the power generation working condition, the main transformer differential protection setting value adopts the power generation working condition setting value zone setting value;

[0064] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0065] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting, including:

[0066] Minimum operating current I of the main transformer differential protection under power generation condition op.0 Stored in the 1, 3, 5, 7 fixed value areas; the minimum operating current I of the main transformer differential protection under phase modulation conditions op.0 Stored in the setting area 2, 4, 6, 8, during the SFC startup of the phase regulator, the minimum operating current setting value I of the main transformer differential protection op.0 Automatically increase floating set value I float .

[0067] Furthermore, the main transformer differential protection range in step S3 includes:

[0068] In power generation conditions, the high-voltage side disconnector of the high-voltage transformer is closed and the high-voltage transformer is put into operation. The differential protection range of the main transformer includes the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current High voltage side current of high power transformer

[0069] In phase modulation conditions, the high-voltage side disconnector of the high-voltage transformer is disconnected, and the high-voltage transformer is out of operation. The differential protection range of the main transformer includes the high-voltage side of the main transformer and the generator phase regulator. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current

[0070] Furthermore, in step S4, the method of using the fixed value and protection range of the main transformer differential protection to calculate according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated includes:

[0071] The main transformer differential protection action equation is:

[0072]

[0073] Where, I op is the differential current, I op.0 is the minimum operating current setting value of the differential protection, where the minimum operating current of the main transformer differential protection in the power generation condition is I op.0 According to DL / T 684-2012, the value of the relay protection setting calculation guide for large generator transformers is (0.3~0.6)I e , I e is the rated current of the secondary of the main transformer; the minimum operating current of the differential protection of the main transformer under phase modulation condition I op.0 According to Q / GDW 11952-2018, the value of relay protection setting calculation guideline for large phase-shifting transformer group is (0.3~0.6)I e , I e The rated current of the secondary of the main transformer; during the SFC startup of the phase regulator, the minimum operating current setting value of the differential protection of the main transformer I op.0 Automatically increase floating set value I float , I float The value is 0.1I e , I e is the secondary rated current of the main transformer;

[0074] I res is the braking current, I res.0 is the minimum braking current setting value, S is the ratio braking coefficient setting value, and the direction of the current on each side is towards the transformer as the positive direction;

[0075] The main transformer ratio differential protection is calculated according to the above action equation. When the calculation result satisfies the above action equation, it is determined that the main transformer differential protection is in action. When the calculation result does not satisfy the above action equation, it is determined that the main transformer differential protection is in action.

[0076] Furthermore, the differential current and braking current in the power generation condition are respectively:

[0077]

[0078] Where: They are the currents at the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer; I op Represents the differential current, I res Indicates braking current;

[0079] The differential current and braking current of the phase modulation working condition are respectively:

[0080]

[0081] Where: They are the current at the high-voltage side of the main transformer and the generator phase regulator terminal; I op Represents the differential current, I res Indicates the braking current.

[0082] Example 2

[0083] A differential protection device for a main transformer of a power generation phase-converting unit, implementing the differential protection method described in Example 1, comprising:

[0084] The working condition confirmation module sets the power generation working condition fixed value area and the phase adjustment working condition fixed value area, collects the power generation working condition signal, the phase adjustment working condition signal and the operation mode handle status signal of the monitoring system, and confirms the power generation and phase adjustment working conditions;

[0085] Collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase adjustment starting condition;

[0086] A fixed value determination module, according to the working condition confirmation result, when in power generation condition, the main transformer differential protection fixed value adopts the fixed value of the power generation condition fixed value zone;

[0087] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0088] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting;

[0089] The protection range determination module determines, based on the working condition confirmation result, the power generation working condition, the main transformer differential protection range includes the high-voltage side of the main transformer, the generator phase regulator end, and the high-voltage side of the high-voltage transformer;

[0090] In phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the high-voltage side of the main transformer and the generator phase regulator end;

[0091] The discrimination module uses the setting value and protection range of the main transformer differential protection to perform calculations according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated.

[0092] Furthermore, the operating condition confirmation is based on a dual-position verification judgment logic to determine the only state of the operating condition. The dual-position verification judgment logic is: when the monitoring system's power generation condition signal and the operating mode handle's power generation condition signal are both "1", it is confirmed to be a power generation condition; when the monitoring system's phase modulation condition signal and the operating mode handle's phase modulation condition signal are both "1", it is confirmed to be a phase modulation condition; other states are regarded as error logic, all protections are locked, and an operating condition signal inconsistency alarm signal is given; in the phase modulation condition, the SFC knife switch closing auxiliary contact signal is "1" and the circuit breaker closing auxiliary contact signal is "0", which is confirmed to be the phase modulation SFC starting condition.

[0093] Furthermore, the device is provided with 8 sets of customized areas, the power generation condition fixed value areas include 1, 3, 5, and 7 fixed value areas, and the phase adjustment condition fixed value areas include 2, 4, 6, and 8 fixed value areas.

[0094] Furthermore, according to the working condition confirmation result, in the power generation working condition, the main transformer differential protection setting value adopts the setting value in the power generation working condition setting zone;

[0095] In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone;

[0096] During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting, including:

[0097] Minimum operating current I of the main transformer differential protection under power generation condition op.0 Stored in the 1, 3, 5, 7 fixed value areas; the minimum operating current I of the main transformer differential protection under phase modulation conditions op.0 Stored in the setting area 2, 4, 6, 8, during the SFC startup of the phase regulator, the minimum operating current setting value I of the main transformer differential protection op.0 Automatically increase floating set value I float .

[0098] Furthermore, the main transformer differential protection range includes:

[0099] In power generation conditions, the high-voltage side disconnector of the high-voltage transformer is closed and the high-voltage transformer is put into operation. The differential protection range of the main transformer includes the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current High voltage side current of high power transformer

[0100] In phase modulation conditions, the high-voltage side disconnector of the high-voltage transformer is disconnected, and the high-voltage transformer is out of operation. The differential protection range of the main transformer includes the high-voltage side of the main transformer and the generator phase regulator. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current

[0101] Furthermore, the method of utilizing the fixed value and protection range of the main transformer differential protection and performing calculation according to the main transformer differential protection action equation to determine whether the main transformer differential protection is actuated includes:

[0102] The main transformer differential protection action equation is:

[0103]

[0104] Where, I op is the differential current, I op.0 is the minimum operating current setting value of the differential protection, where the minimum operating current of the main transformer differential protection in the power generation condition is I op.0 According to DL / T 684-2012, the value of the relay protection setting calculation guide for large generator transformers is (0.3~0.6)I e , I e is the rated current of the secondary of the main transformer; the minimum operating current of the differential protection of the main transformer under phase modulation condition I op.0 According to Q / GDW 11952-2018, the value of relay protection setting calculation guideline for large phase-shifting transformer group is (0.3~0.6)I e , I e The rated current of the secondary of the main transformer; during the SFC startup of the phase regulator, the minimum operating current setting value of the differential protection of the main transformer I op.0 Automatically increase floating set value I float , I f l oat The value is 0.1I e , I e is the secondary rated current of the main transformer;

[0105] I res is the braking current, I res.0 is the minimum braking current setting value, S is the ratio braking coefficient setting value, and the direction of the current on each side is towards the transformer as the positive direction;

[0106] The main transformer ratio differential protection is calculated according to the above action equation. When the calculation result satisfies the above action equation, it is determined that the main transformer differential protection is in action. When the calculation result does not satisfy the above action equation, it is determined that the main transformer differential protection is in action.

[0107] Furthermore, the differential current and braking current in the power generation condition are respectively:

[0108]

[0109] Where: They are the currents at the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer; I op Represents the differential current, I res Indicates braking current;

[0110] The differential current and braking current of the phase modulation working condition are respectively:

[0111]

[0112] Where: They are the current at the high-voltage side of the main transformer and the generator phase regulator terminal; I op Represents the differential current, I res Indicates the braking current.

[0113] The above gives a specific implementation method, but the present invention is not limited to the described implementation method. The basic idea of ​​the present invention is to provide a method for differential protection of the main transformer of the power generation phase modulation unit after the power generation unit is reused and modified to add the phase modulation function, collect the power generation condition signal, phase modulation condition signal and operation mode handle status signal of the monitoring system to confirm the power generation and phase modulation conditions, collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase modulation start condition; under the power generation condition, the main transformer differential protection setting adopts the power generation condition setting area setting, and under the phase modulation condition, the main transformer differential protection setting adopts the phase modulation condition setting area setting. During the SFC startup of the phase shifter, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating fixed value; under the power generation condition, the differential protection range of the main transformer includes the high-voltage side of the main transformer, the generator phase shifter machine end, and the high-voltage side of the high-voltage transformer; under the phase modulation condition, when the high-voltage transformer is out of operation, the differential protection range of the main transformer includes the high-voltage side of the main transformer and the generator phase shifter machine end; using the main differential criterion, fixed value, and protection range of the main transformer differential protection, the action equation of the ratio differential protection is calculated, and the main transformer differential protection is determined to be actuated based on the calculation result. When the phase shifter is in operation, the present invention not only considers the impact of the SFC input current on the main transformer differential protection during the startup to grid connection process, but also considers the impact of the high-voltage transformer out of operation on the main transformer differential protection, realizes the switching of the fixed value area of ​​the differential protection of the main transformer of the generator phase shifter unit, the floating change of the minimum operating current fixed value, and the automatic switching of the protection range, improves the reliability, sensitivity, speed, and selectivity of the main transformer differential protection, and meets the operation requirements of the generator unit after the old unit is modified to add the phase modulation function.

[0114] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Based on the switching of the protection set value zone, the floating change of the minimum operating current set value, and the automatic switching of the protection range, other modifications or equivalent substitutions made to the technical solutions of the present invention by ordinary technicians in this field should be included in the scope of protection of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A differential protection method for the main transformer of a power generation phase-converting unit, characterized in that: The steps include: S1: Set the power generation condition fixed value area and the phase adjustment condition fixed value area, collect the power generation condition signal, phase adjustment condition signal and operation mode handle status signal of the monitoring system, and confirm the power generation and phase adjustment conditions; Collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase adjustment starting condition; S2: According to the working condition confirmation result, in the power generation condition, the main transformer differential protection setting value adopts the setting value in the power generation condition setting zone; In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone; During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting; S3: Based on the working condition confirmation result, in the power generation condition, the main transformer differential protection range includes the high-voltage side of the main transformer, the generator phase condenser machine end, and the high-voltage side of the high-voltage transformer; In phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the high-voltage side of the main transformer and the generator phase regulator end; S4: Using the setting value and protection range of the main transformer differential protection, calculate according to the main transformer differential protection action equation to determine whether the transformer differential protection is actuated; The main transformer differential protection range in step S3 includes: In power generation conditions, the isolating switch on the high-voltage side of the high-voltage transformer is closed. The differential protection range of the main transformer includes the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current High voltage side current of high power transformer In phase modulation conditions, the high-voltage side disconnector of the high-voltage transformer is disconnected, and the high-voltage transformer is out of operation. The differential protection range of the main transformer includes the high-voltage side of the main transformer and the generator phase regulator. The current collected by the differential protection of the main transformer includes the current on the high-voltage side of the main transformer. Generator phase regulator terminal current In step S4, the method of using the fixed value and protection range of the main transformer differential protection to calculate according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated includes: The main transformer differential protection action equation is: Where, I op is the differential current, I op.0 is the minimum operating current setting value of differential protection, I res is the braking current, I res.0 is the minimum braking current setting value, S is the ratio braking coefficient setting value, and the direction of the current on each side is towards the transformer as the positive direction; The main transformer ratio differential protection is calculated according to the above action equation. When the calculation result satisfies the above action equation, the main transformer differential protection is determined to be in action. When the calculation result does not satisfy the above action equation, the main transformer differential protection is determined to be in action. The differential current and braking current in the power generation condition are: Where: They are the currents at the high-voltage side of the main transformer, the generator phase regulator, and the high-voltage side of the high-voltage transformer; I op Represents the differential current, I res Indicates braking current; The differential current and braking current of the phase modulation working condition are respectively: Where: They are the current at the high-voltage side of the main transformer and the generator phase regulator terminal; I op Represents the differential current, I res Indicates the braking current.

2. The differential protection method for the main transformer of a power generation phase condenser group according to claim 1, characterized in that: The working condition confirmation in step S1 is based on the dual-position verification judgment logic to determine the unique state of the operating condition. The dual-position verification judgment logic is: when the monitoring system power generation condition signal and the operating mode handle power generation state signal are both "1", it is confirmed to be the power generation condition; when the monitoring system phase adjustment condition signal and the operating mode handle phase adjustment state signal are both "1", it is confirmed to be the phase adjustment condition; other states are regarded as error logic, all protections are locked, and an operating condition signal inconsistency alarm signal is given; in the phase adjustment condition, the SFC knife switch closing auxiliary contact signal is "1" and the circuit breaker closing auxiliary contact signal is "0", which is confirmed to be the phase adjustment phase SFC starting condition.

3. The differential protection method for the main transformer of a power generation phase condenser group according to claim 2, characterized in that: The power generation condition fixed value area in step S1 includes fixed value areas 1, 3, 5, and 7, and the phase adjustment condition fixed value area includes fixed value areas 2, 4, 6, and 8.

4. The differential protection method for the main transformer of a power generation phase condenser group according to claim 3 is characterized in that: In step S2, according to the working condition confirmation result, in the power generation working condition, the main transformer differential protection setting value adopts the power generation working condition setting value zone setting value; In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone; During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting, including: Minimum operating current setting value I of the main transformer differential protection under power generation condition op.0 Stored in the 1, 3, 5, 7 setting areas; the minimum operating current setting value I of the main transformer differential protection under phase modulation condition op.0 Stored in the setting area 2, 4, 6, 8, during the SFC startup of the phase regulator, the minimum operating current setting value I of the main transformer differential protection op.0 Automatically increase floating set value I float .

5. A differential protection device for a main transformer of a power generation phase condenser unit, based on the differential protection method for a main transformer of a power generation phase condenser unit according to claim 1, characterized in that: include: The working condition confirmation module sets the power generation working condition fixed value area and the phase adjustment working condition fixed value area, collects the power generation working condition signal, the phase adjustment working condition signal and the operation mode handle status signal of the monitoring system, and confirms the power generation and phase adjustment working conditions; Collect the SFC knife switch closing auxiliary contact signal and the circuit breaker closing auxiliary contact signal to confirm the phase adjustment starting condition; A fixed value determination module, according to the working condition confirmation result, when in power generation condition, the main transformer differential protection fixed value adopts the fixed value of the power generation condition fixed value zone; In phase modulation working condition, the main transformer differential protection setting value adopts the setting value in phase modulation working condition setting zone; During the SFC startup of the phase regulator, the minimum operating current of the main transformer differential protection adopts a dynamically adjusted floating setting; The protection range determination module determines, based on the working condition confirmation result, the power generation working condition, the main transformer differential protection range includes the high-voltage side of the main transformer, the generator phase regulator end, and the high-voltage side of the high-voltage transformer; In phase modulation conditions, the high-voltage transformer is out of operation, and the main transformer differential protection range includes the high-voltage side of the main transformer and the phase-shifting machine end of the generator; The discrimination module uses the setting value and protection range of the main transformer differential protection to perform calculations according to the main transformer differential protection action equation to determine whether the main transformer differential protection is activated.

6. The differential protection device for the main transformer of the power generation phase condenser group according to claim 5, characterized in that: The working condition confirmation is based on the dual-position verification judgment logic to determine the unique state of the operating condition. The dual-position verification judgment logic is: when the monitoring system's power generation condition signal and the operating mode handle's power generation condition signal are both "1", it is confirmed to be a power generation condition; when the monitoring system's phase modulation condition signal and the operating mode handle's phase modulation condition signal are both "1", it is confirmed to be a phase modulation condition; other conditions are regarded as error logic, all protections are locked, and an operating condition signal inconsistency alarm signal is given; in the phase modulation condition, the SFC knife switch closing auxiliary contact signal is "1" and the circuit breaker closing auxiliary contact signal is "0", which is confirmed to be the phase modulation phase SFC starting condition.

7. The differential protection device for the main transformer of the power generation phase condenser group according to claim 6, characterized in that: The power generation condition fixed value area includes fixed value areas 1, 3, 5, and 7, and the phase adjustment condition fixed value area includes fixed value areas 2, 4, 6, and 8.

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