Autotransformer wiring group verification method, device, electronic equipment and medium

Abstract

The present invention discloses a method, device, electronic equipment and medium for verifying the connection group of an autotransformer, which relates to the field of power grid control technology. The method includes: analyzing the short-circuit operation of the main transformer and drawing a hexagonal diagram to analyze the CT polarity and the main transformer connection group; adding the short-circuit voltage of the transformer to the medium voltage side to short-circuit the high-voltage side and the low-voltage side, and detecting the three-phase current of the secondary winding of the transformer; disconnecting one of the phase voltages to allow the main transformer to generate zero-sequence current, and inspecting the N line of the secondary winding of the transformer to obtain the main transformer connection group; opening both sides of the short circuit of the transformer to detect the voltage ratio of the transformer; and comparing and verifying the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value. The present invention is not affected by the substation operating environment and can fully check the polarity, ratio and connection group of the current transformer of the autotransformer bushing, while meeting the main transformer protection differential circuit verification. The operation is simple and the installation is convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of transformer substation engineering construction, and in particular to a method, device, electronic equipment and medium for verifying autotransformer connection groups during transformer substation installation and commissioning construction. Background Art

[0002] New or expanded substation construction involves the installation and commissioning of multiple main transformers, with the main transformer differential current circuits and wiring groups being key inspection items. Transformer primary protection is divided into differential protection and gas protection. 500kV autotransformer differential protection includes conventional ratio differential, zero-sequence differential, split-side differential, and phase differential protection, each of which collects current from different locations.

[0003] Traditional inspection methods have limitations and incompleteness. Traditional polarity testing requires batteries of a certain capacity and numerous test leads. Furthermore, during station renovations and expansions, primary transformer bushing conductors are rarely removed after installation due to cross-operation. Otherwise, a crane would be required, forcing personnel to work at height, creating operational risks and increasing labor intensity. Once the primary transformer bushing conductors are connected, strong induction currents can interfere with polarity testing of the main transformer bushing CTs in an operating substation. Testers must perform test wiring at the main transformer bushing terminal block, which poses a high-altitude risk. This results in lengthy measurements and fatigue for testers. Conventional current-raising instruments are bulky, with long insulating rods and heavy current-raising cables. Assembly is time-consuming and labor-intensive, significantly increasing the tester's workload. Using the point polarity method for main transformer bushings requires climbing to the bushing head to make connections, increasing the risk of working at height. Under normal conditions, on-site relay protection personnel are unable to perform a bushing CT ratio check after the main transformer is installed. The common main transformer winding connection method in large grounding systems is the YD11 connection method. In particular, it is a difficult problem to check the triangle connection method of the low-voltage side winding of the 500kV autotransformer after on-site assembly.

[0004] An accident occurred in a substation where a bushing CT of a newly installed #1 main transformer had an open circuit in the secondary circuit of the main body junction box without being checked. As a result, after a period of operation, the open secondary winding generated high voltage, which burned the insulation layer of the bushing CT and caused a serious accident of oil leakage from the main transformer bushing riser. Because the equipment was from different manufacturers, the factory design of the beginning and end of the low-voltage side bushing of the main transformer was inconsistent. During the main transformer expansion project of a substation, the test personnel found through the nameplate that the beginning and end of the low-voltage side bushing were opposite to the design drawing. After verification, the design was redrawn and the triangle connection was changed on site.

[0005] During the 500kV main transformer protection retrofit at a 500kV substation, after startup, the second set of main transformer phase differential protection activated during operation, tripping all three sides of the main transformer. This second set of main transformer protection features phase differential protection, which uses the bushing current on the low-voltage side of the main transformer. When using the head-end current, P1 is required to point to the sky, while when using the tail-end bushing current, P1 is required to point to the transformer itself. The station's low-voltage bushing P1 was always pointed to the sky. Neither the acceptance personnel nor the commissioning personnel paid attention to the polarity requirements of this function. When using the tail-end bushing current, the second set of main transformer protection was wired in the positive-draw configuration as shown in the design diagram, resulting in incorrect polarity for the phase differential current circuit. During operation, due to low load, the protection action value was not reached. After commissioning, as the load increased, the differential current action value was reached, causing the protection to operate.

[0006] The application number in the prior art is CN201910620896, which is named as a method and device for analyzing and recording the closing and opening process of distribution lines. The provided method for analyzing and recording the closing and opening process of distribution lines can quickly and effectively analyze the electrical quantity information required for the closing and opening operations by constructing a loop model, performing consistency verification on the main transformer wiring group, verifying the data before closing the loop, monitoring the closing and opening process, and analyzing and recording the data after closing and opening the loop. It can also perform safety verification before closing and opening the loop, monitor the data during closing and opening the loop, and record the history after closing and opening the loop, thereby reducing the operation of dispatching personnel, providing auxiliary decision-making, and providing historical measured data support for the calculation of closing and opening impact current. It solves the problem of verifying the consistency of the main transformer wiring group during the closing and opening process. It cannot meet the inspection before operation and is not suitable for use in the substation commissioning and construction stage.

[0007] The application number is CN201911368016, and its name is a zero-sequence differential protection verification device and its verification method for an autotransformer. The device uses a central processing unit for detecting the high, medium, and low-voltage side current data, a display unit for displaying the detected high, medium, and low-voltage side current data to the staff in a dynamic curve graph, and an editing unit for editing and inputting corresponding control instructions and importing models. The device verifies and detects the current data at the high-voltage end, medium-voltage end, and low-voltage end of the autotransformer respectively. When protecting and verifying the internal circuit of the autotransformer, verification processing is performed accordingly based on the current data on the high-voltage side, medium-voltage side, and low-voltage side of the autotransformer circuit, thereby improving the accuracy of the verification data. This method improves the accuracy and efficiency of the zero-sequence differential protection verification of the autotransformer, but cannot fully check the external circuit of the autotransformer main transformer protection device, such as the polarity, transformation ratio, and connection group of the bushing current transformer. There are certain limitations and incompleteness.

[0008] Currently available technologies are unable to fully check the polarity and ratio of bushing current transformers, as well as the connection group on the low-voltage side of the autotransformer, thus failing to fully guarantee the reliability and correctness of the circuit. Furthermore, the equipment is bulky and requires multiple people to work together, resulting in low efficiency. A method for verifying the connection group and differential circuit of the autotransformer is needed. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to solve the deficiencies in the prior art and to design a method for verifying the connection groups of autotransformers. This method is not affected by the substation operating environment and can completely check the polarity, transformation ratio and connection group of the autotransformer bushing current transformer, while meeting the requirements of the main transformer protection differential circuit verification.

[0010] The technical solution adopted by the present invention to solve its technical problem is:

[0011] In a first aspect, the present invention provides a method for verifying autotransformer connection groups, comprising:

[0012] Analyze the short-circuit operation of the main transformer and draw a hexagonal diagram to analyze the CT polarity and main transformer wiring group;

[0013] Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer;

[0014] Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group;

[0015] Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer;

[0016] Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

[0017] As a further technical solution of the present invention, the analysis of the short-circuit operation of the main transformer and the drawing of a hexagonal diagram to analyze the CT polarity and the main transformer connection group specifically include:

[0018] When the main transformer is short-circuited, treat it as an inductive element. With the line voltage as a fixed reference, point the primary polarity terminal P1 of the high-resistance line-side bushing CT toward the sky, and the secondary is positively drawn. The secondary current flows out from the terminal S1 with the same name. At this time, the measured angle is that the voltage leads the secondary current of the line-side CT by 90°.

[0019] Add positive sequence to the three-phase AC mains on the medium voltage side and make a theoretical vector diagram of phase A;

[0020] Take U 中A Fixed as the reference voltage phasor, rotating counterclockwise with current to U 中A The angle between 中AThe angle of the leading current; at this time, the inductive transformer U 中A Advance I 中 The angle is 90°, and the secondary current of the high side, common side, and low voltage side a is 中 The angle difference is 180°; I 中 The vector magnitude is I 高 with I 公 Sum of amplitudes, opposite angles, I 高 with I 公 The angles are all 270°; I 低开关 The angle is 240°; I 低绕组a The angle is 270°; I 低绕组x It is the non-polarity end of the primary winding on the low voltage side, and its angle is opposite to the polarity end CT, so I 低绕组x The angle is 90°;

[0021] By carrying out the primary current flow test of the main transformer as described above and measuring the amplitude and phase of the secondary current of the bushings on each side of the main transformer, the polarity and transformation ratio of the bushing current transformer can be determined.

[0022] The short-circuit voltage of the transformer is added to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and the three-phase current of the secondary winding of the transformer is detected; specifically including:

[0023] The short-circuit voltage percentage Vs% given on the transformer nameplate is the percentage of the voltage drop across the impedance when the transformer passes the rated current. For large-capacity transformers, the short-circuit reactance Vx%=Vs%, simulating a short-circuit current generated by a main transformer short circuit.

[0024] Calculation of short-circuit impedance voltage on each side:

[0025] ;

[0026] Among them: V1%, V2%, and V3% are the percentages of the short-circuit voltage on the high, middle, and low sides of the main transformer respectively;

[0027] V 1-2 %,V 2-3 %,V 1-3 % are the percentages of the main transformer high-to-medium, medium-to-low, and high-to-low short-circuit voltages as specified on the manufacturer's nameplate;

[0028] Calculation of equivalent reactance on each side referred to the medium voltage side: (The following are all single-phase calculations)

[0029] ;

[0030] Among them: X1, X2, and X3 are the equivalent reactances of the high, middle, and low sides of the main transformer respectively;

[0031] VN: voltage value of the medium voltage side of the main transformer at this gear, unit: kV;

[0032] S N : Rated capacity of main transformer, unit: KVA;

[0033] Add a three-phase symmetrical 220V AC voltage to the medium voltage side and calculate the current on each side:

[0034] ;

[0035] ;

[0036] I2 is the actual value on the medium voltage side, is the per-unit value on the high-voltage side, The per-unit value on the low-voltage side needs to be converted to the corresponding voltage level side to obtain the actual current generated on each side.

[0037] As a further technical solution of the present invention, the short-circuit voltage of the transformer is added to the medium voltage side to short-circuit the high voltage side and the low voltage side, and the three-phase current of the secondary winding of the transformer is detected; specifically comprising:

[0038] A balanced 380V voltage is added to the medium voltage side of the main transformer, and currents of equal amplitude and positive angle sequence are obtained in the three phases of the secondary winding of each CT.

[0039] As a further technical solution of the present invention, disconnecting one phase voltage to allow the main transformer to generate zero-sequence current, and inspecting the N line of the secondary winding of the transformer to obtain the main transformer connection group; specifically comprising:

[0040] By checking whether the differential current sampling value is zero, even if the collected current value is small, when the polarity is used incorrectly, the current superposition differential current value is obvious; it can be determined that the polarity of the main transformer primary equipment and the polarity of the secondary protection device are incorrectly matched; by measuring the phase difference between the low-voltage bushing CT current and the CT current at the low-voltage side switch, the main transformer connection group can be determined.

[0041] As a further technical solution of the present invention, the method of disconnecting one phase voltage to allow the main transformer to generate zero-sequence current and inspecting the N line of the secondary winding of the transformer further includes:

[0042] Keep one phase voltage disconnected to detect the unbalance of the open delta voltage.

[0043] As a further technical solution of the present invention, the steps of opening both sides of the short-circuited transformer and detecting the voltage transformation ratio of the transformer specifically include:

[0044] Open both sides of the short-circuit transformer, detect the voltage transformation ratio of the transformer, measure the PT secondary voltage on the high voltage side / medium voltage side / low voltage side, and verify the correctness of the open delta connection.

[0045] In a second aspect, the present invention further provides an autotransformer connection group verification device, comprising:

[0046] Theoretical analysis module analyzes the short-circuit operation of the main transformer and draws a hexagonal diagram to analyze the CT polarity and main transformer wiring group;

[0047] The current detection module adds the short-circuit voltage of the transformer to the medium-voltage side, short-circuiting the high-voltage and low-voltage sides, and detecting the three-phase current of the transformer's secondary winding;

[0048] The connection group detection module disconnects one phase voltage to generate zero-sequence current in the main transformer, and then checks the N line of the transformer's secondary winding to obtain the main transformer connection group.

[0049] The voltage ratio detection module opens both sides of the short circuit of the transformer to detect the voltage ratio of the transformer;

[0050] The verification analysis module compares and verifies the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

[0051] In a third aspect, the present invention further provides an electronic device comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program implements the steps of the autotransformer connection group verification method when executed by the processor.

[0052] In a fourth aspect, the present invention further provides a computer-readable storage medium, characterized in that a computer program is stored in the storage medium, and when the computer program is executed by a processor, the following process is implemented:

[0053] Analyze the short-circuit operation of the main transformer and draw a hexagonal diagram to analyze the CT polarity and main transformer wiring group;

[0054] Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer;

[0055] Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group;

[0056] Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer;

[0057] Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention is independent of the substation operating environment and can fully check the polarity, ratio, and connection group of the autotransformer bushing current transformer, while also meeting the requirements for main transformer protection differential circuit verification. It requires simple operation and convenient installation, with test leads capable of withstanding high currents for extended periods. A grounding insulated rod allows for rapid installation of the voltage source on the transformer's drain wire. By utilizing the transformer's short-circuit impedance and applying a 380V AC voltage to generate a short-circuit current in the main transformer, the correctness of the main transformer differential circuit, bushing current transformer polarity, ratio, and connection group can be verified, resolving existing technical issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a flow chart of the autotransformer connection group verification method proposed by the present invention;

[0061] Figure 2 This is the hexagonal diagram proposed by the present invention for analyzing CT polarity and main transformer wiring groups;

[0062] Figure 3 The equivalent circuit diagram proposed by the present invention;

[0063] Figure 4 This is the structure diagram of the autotransformer proposed by the present invention;

[0064] Figure 5 This is a structural diagram of an online verification device for relay protection settings proposed by the present invention. DETAILED DESCRIPTION

[0065] The specific implementation of the present invention is described below with reference to the accompanying drawings and embodiments:

[0066] It should be noted that the structures, colors, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0067] Example 1

[0068] like Figure 1 As shown, the present invention provides a method for verifying the connection group of an autotransformer, comprising:

[0069] Analyze the short-circuit operation of the main transformer and draw a hexagonal diagram to analyze the CT polarity and main transformer wiring group;

[0070] Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer;

[0071] Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group;

[0072] Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer;

[0073] Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

[0074] In the embodiment of the present invention, the short-circuit voltage percentage Vs% given on the transformer nameplate is the percentage of the voltage drop generated on the impedance when the rated current passes through the transformer. For a large-capacity transformer, the resistance of its winding is much smaller than the reactance. It can be approximately considered that the short-circuit reactance Vx%=Vs%, simulating a short-circuit current generated by a main transformer short circuit.

[0075] Applying voltage to the medium voltage side is the most reasonable option based on comparative calculations. Applying voltage to the high voltage side results in a primary current too small to be measured. Applying voltage to the low voltage side results in a current too large, and sometimes a power supply with sufficient capacity is not available on site. Therefore, applying voltage to the medium voltage side short-circuits the high and low voltage sides.

[0076] See also Figure 2 In step 101, the short-circuit operation of the main transformer is analyzed, and a hexagonal diagram is drawn to analyze the CT polarity and the main transformer connection group, specifically including:

[0077] When the main transformer is short-circuited, treat it as an inductive element. With the line voltage as a fixed reference, point the primary polarity terminal P1 of the high-resistance line-side bushing CT toward the sky, and the secondary is positively drawn. The secondary current flows out from the terminal S1 with the same name. At this time, the measured angle is that the voltage leads the secondary current of the line-side CT by 90°.

[0078] Add positive sequence to the three-phase AC mains on the medium voltage side and make a theoretical vector diagram of phase A;

[0079] Take U 中A Fixed as the reference voltage phasor, rotating counterclockwise with current to U 中A The angle between 中A The angle of the leading current; at this time, the inductive transformer U 中A Advance I 中 The angle is 90°, and the secondary current of the high side, common side, and low voltage side a is 中 The angle difference is 180°; I 中 The vector magnitude is I 高 with I 公Sum of amplitudes, opposite angles, I 高 with I 公 The angles are all 270°; I 低开关 The angle is 240°; I 低绕组a The angle is 270°; I 低绕组x It is the non-polarity end of the primary winding on the low voltage side, and its angle is opposite to the polarity end CT, so I 低绕组x The angle is 90°;

[0080] By carrying out the primary current flow test of the main transformer as described above and measuring the amplitude and phase of the secondary current of the bushings on each side of the main transformer, the polarity and transformation ratio of the bushing current transformer can be determined.

[0081] Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer; specifically including:

[0082] The short-circuit voltage percentage Vs% given on the transformer nameplate is the percentage of the voltage drop across the impedance when the transformer passes the rated current. For large-capacity transformers, the short-circuit reactance Vx%=Vs%, simulating a short-circuit current generated by a main transformer short circuit.

[0083] Calculation of short-circuit impedance voltage on each side:

[0084] ;

[0085] Among them: V1%, V2%, and V3% are the percentages of the short-circuit voltage on the high, middle, and low sides of the main transformer respectively;

[0086] V 1-2 %,V 2-3 %,V 1-3 % are the percentages of the main transformer high-to-medium, medium-to-low, and high-to-low short-circuit voltages as specified on the manufacturer's nameplate;

[0087] See also Figure 3 , is the equivalent circuit diagram of the main transformer when the power supply is applied to the medium voltage side. In power system calculations, the equivalent circuit of the transformer often moves the excitation branch forward to the power supply side. As shown in the figure above, when the medium voltage side is pressurized, the excitation branch is moved to the medium voltage side. Calculation of the equivalent reactance on each side of the medium voltage side: (The following are all single-phase calculations)

[0088] ;

[0089] Among them: X1, X2, and X3 are the equivalent reactances of the high, middle, and low sides of the main transformer respectively;

[0090] VN: voltage value of the medium voltage side of the main transformer at this gear, unit: kV;

[0091] S N: Rated capacity of main transformer, unit: KVA;

[0092] Add a three-phase symmetrical 220V AC voltage to the medium voltage side and calculate the current on each side based on the equivalent circuit diagram of the main transformer:

[0093] ;

[0094] ;

[0095] I2 is the actual value on the medium voltage side, is the per-unit value on the high-voltage side, It is the per-unit value on the low-voltage side. The per-unit value needs to be converted to the corresponding voltage level side to obtain the actual current generated on each side.

[0096] In an embodiment of the present invention, the short-circuit voltage of the transformer is added to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and the three-phase current of the secondary winding of the transformer is detected. Specifically, the method includes:

[0097] A balanced 380V voltage is added to the medium voltage side of the main transformer, and currents of equal amplitude and positive angle sequence are obtained in the three phases of the secondary winding of each CT.

[0098] Applying a balanced 380V voltage to the medium-voltage side of the main transformer produces currents of equal amplitude and positive angle sequence across the three phases of each CT's secondary winding. However, due to the balanced power supply, it's impossible to verify the correct alignment of the neutral line in the secondary current loop. Therefore, after performing the three-phase inspection, disconnect one phase to generate zero-sequence current in the main transformer, and then check the neutral line of each CT's secondary winding.

[0099] Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group; specifically, the following steps are involved:

[0100] By checking whether the differential current sampling value is zero, even if the collected current value is small, when the polarity is used incorrectly, the current superposition differential current value is obvious; it can be determined that the polarity of the main transformer primary equipment and the polarity of the secondary protection device are incorrectly matched; by measuring the phase difference between the low-voltage bushing CT current and the CT current at the low-voltage side switch, the main transformer connection group can be determined.

[0101] Since the voltage is balanced at 380V, the open delta voltage is 0V, so it is impossible to check whether the cable core connection from the PT terminal box to the indoor voltage interface panel is correct. Therefore, after checking the zero-sequence current of the main transformer, keep one phase voltage disconnected and continue to check the unbalance of the open delta voltage.

[0102] That is, disconnect one phase voltage to allow the main transformer to generate zero-sequence current and check the N line of the transformer's secondary winding; it also includes:

[0103] Keep one phase voltage disconnected to detect the unbalance of the open delta voltage.

[0104] In order to better inspect the main transformer and its three-side voltage circuits, after checking the current circuit, the two sides of the transformer that were originally short-circuited can be opened. At this time, due to the voltage transformation ratio of the transformer, the PT secondary voltages on the high, medium and low sides can be measured to check the correctness of the open delta connection.

[0105] Example 2

[0106] Figure 4 This is a schematic diagram of the 500kV Meilin transformer #1 autotransformer and its three-side connections. Voltage is applied to the rear end of switch 2001 on the medium-voltage side, and the busbar switch is open. On the high-voltage side, earthing switches 503117 and 503227 are closed, as are switches 5031 and 5032, and switches 50312 and 50321. On the low-voltage side, switch 301 and switch 3016 are closed, and the low-voltage side IM busbar earthing switch 3117 is closed. The neutral point of the autotransformer is grounded. The primary P1 terminal of each switch CT and the main transformer bushing CT is marked with an * in the diagram. The secondary winding tap current of all CTs is drawn from the same-name terminal S1 to the secondary load equipment (protection, measurement, and metering).

[0107] Draw a hexagonal diagram to analyze the CT polarity and main transformer wiring group: When the main transformer is short-circuited, it can be approximately regarded as an inductive element. This is like the line running with a high-voltage reactor at no load. If the line voltage is fixed as a reference, the primary polarity terminal P1 of the high-voltage reactor line-side bushing CT points to the sky, the secondary is positively drawn, and the secondary current flows out from the terminal S1 with the same name. At this time, the measured angle is that the voltage leads the secondary current of the line-side CT by 90°.

[0108] The specific operation method is as follows:

[0109] The short-circuit current of the main transformer is accurately calculated using the short-circuit impedance provided on the nameplate of the main transformer manufacturer. The correctness of the main transformer differential circuit and wiring group is checked by adding AC 380V voltage on the medium voltage side to generate a short-circuit current in the main transformer.

[0110] The switches, knife switches and earth switches in the substation switchyard are used to perform switching operations to simulate a short circuit in the main transformer. The main purpose is to allow primary current to flow through the main transformer bushing CT and the switches CT on the three sides of the main transformer, thereby generating current in the secondary winding.

[0111] Using the A-phase voltage of the added AC 380V power supply as a reference, measure the magnitude and angle of the secondary current of each winding.

[0112] Draw a hexagonal diagram in advance for analysis and compare it with the test results to determine whether the CT ratio and polarity are correct and whether the main transformer wiring group is correct.

[0113] When the high and low sides of the main transformer are open, the transformation ratio of the PTs on the three sides of the main transformer and the correctness of the secondary voltage circuit can be checked at the same time by adding 380V voltage to the medium voltage side.

[0114] The parameters of the autotransformer installed in this 500kV Meilin substation are as follows:

[0115] Model: ODFS-334000 / 550

[0116] Manufacturer: Xi'an XD Transformer Co., Ltd.

[0117] Rated voltage:

[0118] high pressure: kV

[0119] Medium pressure: kV

[0120] Low voltage: 36.75kV

[0121] Single-phase rated capacity (when cooling method is ONAF):

[0122] High voltage: 334000 kVA

[0123] Medium voltage: 334,000 kVA

[0124] Low voltage: 80000 kVA

[0125] Wiring group: Yna0d11

[0126] Nameplate short-circuit impedance voltage: (three-phase average value)

[0127]

[0128] Theoretical calculation of primary current of main transformer

[0129] Calculation of short-circuit impedance voltage on each side:

[0130]

[0131] Referred to the medium voltage side (V N =230kV) calculation of equivalent reactance on each side: (the following are single-phase calculations)

[0132]

[0133] Add a three-phase symmetrical 220V AC voltage to the medium voltage side and calculate the current on each side: (ignore the transformer excitation current)

[0134]

[0135] Due to magnetic induction, the actual current on the high side and low side is calculated as:

[0136]

[0137] Since the low-pressure side is connected in a triangle, the internal

[0138]

[0139] According to Kirchhoff's current law KCL, the current flowing through the common winding is:

[0140]

[0141] The entire process from wiring the test to completing the measurement and data collection took only 3.5 hours. The actual measured current on the medium-voltage side was consistent with the theoretical calculation (theoretical calculation on the medium-voltage side: 44.04A).

[0142] The measured data table is as follows:

[0143] Taking UA = 220V as a reference, the transformer primary coil behaves like an inductive load. Due to the need for excitation current on the medium-voltage side, as well as losses in the equipment, particularly circulating current heat loss from the delta connection on the low-voltage side, the primary current may deviate slightly from the actual value. Angle analysis can confirm the correct polarity of the main transformer's CT.

[0144] CT measurement data table on each side of the main transformer

[0145]

[0146] Since the deviation between the theoretical angle diagram on each side of the main transformer and the actual measured angle is between 5° and 10°, which is within a reasonable range, the main transformer body is successfully tested once for the differential current circuit of the main transformer and the circuit is ensured to be correct.

[0147] Through inspection, it was found that the nameplate of the autotransformer was wrong. The transformation ratio of the common bushing CT in the nameplate was 1500 / 5, but the actual current flow inspection found that the CT transformation ratio should be 1500 / 1, and it was verified by the manufacturer that it should be 1500 / 1.

[0148] Example 3

[0149] See also Figure 5 The present invention also provides an autotransformer connection group verification device, comprising:

[0150] Theoretical analysis module 201 analyzes the short-circuit operation of the main transformer and draws a hexagonal diagram to analyze the CT polarity and main transformer wiring group;

[0151] The current detection module 202 adds the short-circuit voltage of the transformer to the medium-voltage side, short-circuiting the high-voltage side and the low-voltage side, and detecting the three-phase current of the secondary winding of the transformer;

[0152] The connection group detection module 203 disconnects one phase voltage to allow the main transformer to generate zero-sequence current, and checks the N line of the secondary winding of the transformer to obtain the main transformer connection group;

[0153] The voltage transformation ratio detection module 204 opens both sides of the short circuit of the transformer to detect the voltage transformation ratio of the transformer;

[0154] The verification and analysis module 205 compares and verifies the three-phase current / main transformer connection group and voltage transformation ratio with the transformer calibration value.

[0155] The various variations and specific examples of the autotransformer connection group verification method in the aforementioned embodiment are also applicable to the autotransformer connection group verification device in the present embodiment. Based on the aforementioned detailed description of the autotransformer connection group verification method, those skilled in the art will clearly understand the autotransformer connection group verification device in the present embodiment. Therefore, for the sake of brevity, a detailed description thereof will not be given here.

[0156] Example 4

[0157] The present invention also provides an electronic device. At the hardware level, the electronic device includes a processor and optionally an internal bus, a network interface, and a memory. The memory may include internal memory, such as high-speed random-access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device. Of course, the electronic device may also include hardware required for other services.

[0158] The processor, network interface, and memory can be interconnected via an internal bus, which can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus. The bus can be divided into an address bus, a data bus, a control bus, and the like.

[0159] The memory is used to store programs. Specifically, the program may include program code, which includes computer operating instructions. The memory may include internal memory and non-volatile memory, and provides instructions and data to the processor.

[0160] The processor reads the corresponding computer program from the non-volatile memory into the internal memory and then runs it, forming a protective pressure plate monitoring device at the logical level. The processor executes the program stored in the memory and is specifically used to perform the following operations:

[0161] Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer;

[0162] Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group;

[0163] Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer;

[0164] Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

[0165] The method performed by the autotransformer connection group verification device disclosed in the third embodiment can be applied to a processor or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the method can be completed by hardware integrated logic circuits in the processor or by software instructions. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The methods, steps, and logic block diagrams disclosed in one or more embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in conjunction with one or more embodiments of the present application can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module can be located in a storage medium well-known in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the memory, and the processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above method.

[0166] Of course, in addition to software implementation, the electronic device of this application does not exclude other implementation methods, such as logic devices or a combination of software and hardware, etc. That is to say, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0167] Example 5

[0168] The embodiment of the present application also provides a computer-readable storage medium, which stores one or more programs, wherein the one or more programs include instructions, which, when executed by a portable electronic device including multiple application programs, can enable the portable electronic device to execute Figure 1 The method of the embodiment shown is specifically used to perform the following operations:

[0169] Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer;

[0170] Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group;

[0171] Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer;

[0172] Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

[0173] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. The method for verifying the connection group of an autotransformer is characterized by: include: Analyze the short-circuit operation of the main transformer and draw a hexagonal diagram to analyze the CT polarity and main transformer wiring group; Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer; Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group; Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer; Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value; The analysis of the short-circuit operation of the main transformer and the drawing of a hexagonal diagram to analyze the CT polarity and main transformer wiring group specifically include: When the main transformer is short-circuited, treat it as an inductive element. With the line voltage as a fixed reference, point the primary polarity terminal P1 of the high-resistance line-side bushing CT toward the sky, and the secondary is positively drawn. The secondary current flows out from the terminal S1 with the same name. At this time, the measured angle is that the voltage leads the secondary current of the line-side CT by 90°. Add positive sequence to the three-phase AC mains on the medium voltage side and make a theoretical vector diagram of phase A; Take U 中A Fixed as the reference voltage phasor, rotating counterclockwise with current to U 中A The angle between 中A The angle of the leading current; at this time, the inductive transformer U 中A Advance I 中 The angle is 90°, and the secondary current of the high side, common side, and low voltage side a is 中 The angle difference is 180°; I 中 The vector magnitude is I 高 with I 公 Sum of amplitudes, opposite angles, I 高 with I 公 The angles are all 270°; I 低开关 The angle is 240°; I 低绕组a The angle is 270°; I 低绕组x It is the non-polarity end of the primary winding on the low voltage side, and its angle is opposite to the polarity end CT, so I 低绕组x The angle is 90°; By carrying out the primary current flow test of the main transformer and measuring the amplitude and phase of the secondary current of the bushings on each side of the main transformer, the polarity and transformation ratio of the bushing current transformer can be determined.

2. The method for verifying autotransformer connection groups according to claim 1, characterized in that: The short-circuit voltage of the transformer is added to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and the three-phase current of the secondary winding of the transformer is detected; specifically Include: Specifically include: The short-circuit voltage percentage Vs% given on the transformer nameplate is the percentage of the voltage drop across the impedance when the transformer passes the rated current. For large-capacity transformers, the short-circuit reactance Vx%=Vs%, simulating a short-circuit current generated by a main transformer short circuit. Calculation of short-circuit impedance voltage on each side: ； Among them: V1%, V2%, and V3% are the percentages of the short-circuit voltage on the high, middle, and low sides of the main transformer respectively; V 1-2 %,V 2-3 %,V 1-3 % are the percentages of the main transformer high-to-medium, medium-to-low, and high-to-low short-circuit voltages as specified on the manufacturer's nameplate; Calculation of equivalent reactance on each side converted to the medium voltage side: The following are all single-phase calculations; ； Among them: X1, X2, and X3 are the equivalent reactances of the high, middle, and low sides of the main transformer respectively; VN: voltage value of the medium voltage side of the main transformer at this gear, unit: kV; S N : Rated capacity of main transformer, unit: KVA; Add a three-phase symmetrical 220V AC voltage to the medium voltage side and calculate the current on each side: ； ； I2 is the actual value on the medium voltage side, is the per-unit value on the high-voltage side, It is the per-unit value on the low-voltage side. The per-unit value needs to be converted to the corresponding voltage level side to obtain the actual current generated on each side.

3. The method for verifying autotransformer connection groups according to claim 1, characterized in that: The short-circuit voltage of the transformer is added to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and the three-phase current of the secondary winding of the transformer is detected, which specifically includes: A balanced 380V voltage is applied to the medium voltage side of the main transformer, and three-phase currents with equal amplitude and positive angle sequence are obtained through three-phase detection of the secondary windings of each CT.

4. The method for verifying autotransformer connection groups according to claim 1, characterized in that: The method of disconnecting one phase voltage to generate zero-sequence current in the main transformer and inspecting the N line of the secondary winding of the transformer to obtain the main transformer connection group specifically includes: By checking whether the differential current sampling value is zero, even if the collected current value is small, when the polarity is used incorrectly, the current superposition differential current value is obvious; it can be determined that the polarity of the main transformer primary equipment and the polarity of the secondary protection device are incorrectly matched; by measuring the phase difference between the low-voltage bushing CT current and the CT current at the low-voltage side switch, the main transformer connection group can be determined.

5. The method for verifying autotransformer connection groups according to claim 4, characterized in that: The method of disconnecting one phase voltage to allow the main transformer to generate zero-sequence current and inspecting the N line of the secondary winding of the transformer also includes: Keep one phase voltage disconnected to detect the unbalance of the open delta voltage.

6. The method for verifying autotransformer connection groups according to claim 1, characterized in that: The step of opening both sides of the short-circuit transformer and detecting the voltage transformation ratio of the transformer specifically includes: Open both sides of the short-circuit transformer, detect the voltage transformation ratio of the transformer, measure the PT secondary voltage on the high voltage side / medium voltage side / low voltage side, and verify the correctness of the open delta connection.

7. Autotransformer connection group verification device, characterized in that: The method for verifying the connection group of an autotransformer according to any one of claims 1 to 6 comprises: Theoretical analysis module analyzes the short-circuit operation of the main transformer and draws a hexagonal diagram to analyze the CT polarity and main transformer wiring group; The current detection module adds the short-circuit voltage of the transformer to the medium-voltage side, short-circuiting the high-voltage and low-voltage sides, and detecting the three-phase current of the transformer's secondary winding; The connection group detection module disconnects one phase voltage to generate zero-sequence current in the main transformer, and then checks the N line of the transformer's secondary winding to obtain the main transformer connection group. The voltage ratio detection module opens both sides of the short circuit of the transformer to detect the voltage ratio of the transformer; The verification analysis module compares and verifies the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value.

8. An electronic device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the method for verifying the connection group of an autotransformer according to any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that The storage medium stores a computer program, which, when executed by the processor, implements the following process: Analyze the short-circuit operation of the main transformer and draw a hexagonal diagram to analyze the CT polarity and main transformer wiring group; Add the short-circuit voltage of the transformer to the medium-voltage side to short-circuit the high-voltage side and the low-voltage side, and detect the three-phase current of the secondary winding of the transformer; Disconnect one phase voltage to allow the main transformer to generate zero-sequence current, and check the N line of the transformer's secondary winding to obtain the main transformer connection group; Open both sides of the short-circuit transformer and check the voltage transformation ratio of the transformer; Compare and verify the three-phase current / main transformer connection group and voltage ratio with the transformer calibration value; The analysis of the short-circuit operation of the main transformer and the drawing of a hexagonal diagram to analyze the CT polarity and main transformer wiring group specifically include: When the main transformer is short-circuited, treat it as an inductive element. With the line voltage as a fixed reference, point the primary polarity terminal P1 of the high-resistance line-side bushing CT toward the sky, and the secondary is positively drawn. The secondary current flows out from the terminal S1 with the same name. At this time, the measured angle is that the voltage leads the secondary current of the line-side CT by 90°. Add positive sequence to the three-phase AC mains on the medium voltage side and make a theoretical vector diagram of phase A; Take U 中A Fixed as the reference voltage phasor, rotating counterclockwise with current to U 中A The angle between 中A The angle of the leading current; at this time, the inductive transformer U 中A Advance I 中 The angle is 90°, and the secondary current of the high side, common side, and low voltage side a is 中 The angle difference is 180°; I 中 The vector magnitude is I 高 with I 公 Sum of amplitudes, opposite angles, I 高 with I 公 The angles are all 270°; I 低开关 The angle is 240°; I 低绕组a The angle is 270°; I 低绕组x It is the non-polarity end of the primary winding on the low voltage side, and its angle is opposite to the polarity end CT, so I 低绕组x The angle is 90°; By carrying out the primary current flow test of the main transformer and measuring the amplitude and phase of the secondary current of the bushings on each side of the main transformer, the polarity and transformation ratio of the bushing current transformer can be determined.

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