A method and device for detecting open phase of a power supply of an injection transformer

Abstract

The application provides a kind of injection transformer power phase failure detection method, comprising: selecting a transformer from multiple transformers as injection transformer;Using injection signal device, the current output by the injection signal device continuously injects interharmonic current signal to the neutral point of injection transformer through injection CT;Collecting the current waveform data of the neutral point of each transformer, and carrying out digital filtering or fast Fourier transform on the collected neutral point current waveform data of each transformer to obtain the interharmonic current value of the neutral point of each transformer;According to the interharmonic voltage of the output end of the injection signal device and the interharmonic current of the neutral point of each transformer, the zero sequence impedance value measured at the neutral point of each transformer is obtained;Judge whether phase failure occurs and determine the phase failure position, and give the information of phase failure and its position.The application avoids the signal attenuation and interference problem caused by long-distance transmission of the weak current analog signal of the neutral point of each transformer, and improves the reliability of phase failure detection.

Description

Technical Field

[0001] This invention relates to the field of transformer power supply phase loss detection technology, and in particular to an injection-type transformer power supply phase loss detection method and apparatus. Background Technology

[0002] The existing injection-type transformer power supply phase loss detection method works by injecting a voltage signal with a preset amplitude and frequency into the transformer neutral point. This preset voltage signal generates a current signal related to the injected voltage in the zero-sequence network composed of the transformer and the power grid. By detecting the preset frequency current at the transformer neutral point, a zero-sequence impedance value measured at the transformer neutral point can be obtained. The presence of a phase loss in the transformer's power supply circuit is then detected based on whether the zero-sequence impedance measurement significantly increases (greater than a set value). However, this existing method has the following problems:

[0003] First, when a circuit carries three or more transformers, it is very likely that a phase loss will not be detected. This is because when a phase loss occurs, a closed loop of zero-sequence current is still formed between the high-voltage side of the injection-type transformer with its neutral point directly grounded and the high-voltage side of the other non-injection-type transformers with their neutral points also directly grounded. Therefore, when a phase loss occurs, the change in zero-sequence impedance detected at the neutral point of the injection-type transformer is very small, making it very likely that the phase loss will not be detected.

[0004] Secondly, because the zero-sequence impedance of the line and system power supply is connected in series, then in parallel with the zero-sequence impedance of the non-injection transformer, and then in series with the zero-sequence impedance of the injection transformer, when the zero-sequence impedance of the injection transformer is much larger than that of the non-injection transformer, the change (increase) in the zero-sequence impedance value measured at the neutral point of the injection transformer after a phase loss will be very small, resulting in the inability to detect the phase loss state of the line. Even if a line only carries two transformers, it is very likely that the phase loss of the line will not be detected.

[0005] Third, since multiple transformers supplied by the same circuit are often hundreds of meters or even further apart in space, and the analog current signal measured from the current transformer (hereinafter referred to as CT) at the neutral point of each non-injection transformer is very weak, there are problems of current signal attenuation and susceptibility to interference during long-distance transmission, which reduces the reliability of this method in detecting phase loss.

[0006] Fourth, this existing method is only used to detect whether there is a phase failure in the system, but it cannot locate the point of phase failure. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for detecting phase loss in power supply of an injection transformer, which solves the problems of existing methods for detecting phase loss in power supply of an injection transformer in systems with two or more transformers on a single line, such as the possibility of not being able to detect the phase loss and the inability to locate which circuit the phase loss point is in.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for detecting phase loss in an injection transformer power supply includes the following steps:

[0010] Step 1: Select one transformer from multiple transformers as the injection transformer;

[0011] Step 2: Using an injection signal device, the output current is continuously injected into the neutral point of the injection transformer through an injection CT (current transformer).

[0012] Step 3: Collect the current waveform data of the neutral point of each transformer, and perform digital filtering or fast Fourier transform on the collected neutral point current waveform data to obtain the interharmonic current value of the neutral point of each transformer.

[0013] Step 4: Based on the interharmonic voltage at the output of the injection signal device and the interharmonic current at the neutral point of each transformer, obtain the zero-sequence impedance value measured at the neutral point of each transformer.

[0014] Step 5: Based on the measured values ​​of each zero-sequence impedance Z 0j Measurements when phase is not interrupted Determine whether a phase failure has occurred and determine the location of the phase failure, and provide information on the phase failure and its location;

[0015] Step 6: Determine if the "phase loss delay T seconds have elapsed" condition is met. If it is, output a phase loss alarm and record the zero-sequence impedance, voltage, and current data, then return to Step 3 to start the next detection cycle. If it is not met, clear the phase loss delay timer and then directly return to Step 3 to start the next detection cycle. The purpose of setting the phase loss delay is to avoid the inrush current of the transformer when it is closed under no-load and the symmetrical or asymmetrical short-circuit ground faults in the system from affecting the device's detection results.

[0016] In step 1, by comparing the zero-sequence impedance of each transformer on the high-voltage side, the transformer with the smallest zero-sequence impedance is selected as the injection transformer.

[0017] In step 4, the calculation formula is as follows:

[0018] Z 0j =U o / I 0j (j = 1, 2, 3...n),

[0019] In the formula: Z 0j The zero-sequence impedance values ​​measured at the neutral point of each transformer;

[0020] U o The output voltage of the injected signal device;

[0021] I 0j This refers to the interharmonic current at the neutral point of each transformer.

[0022] In step 5, if the following conditions are met... If a phase is broken in the incoming circuit between the busbar of this side switch station and the busbar of the opposite substation, the value of k1 is 1.1 to 1.4, the value of k2 is 0.5 to 0.9, and 2 ≤ m ≤ n.

[0023] In step 5, if the following conditions are met... Then it is determined that there is a phase break in the circuit between the injection transformer and the busbar of the local switch station. The value of k3 is in the range of 3 to 30, and 2≤m≤n.

[0024] In step 5, if the following conditions are met... Then it is determined that there is a phase break in the circuit between the non-injection transformer numbered m and the busbar of the switch station on this side. The value range of k3 is 3 to 30, and the value range of k4 is 1.2 to 1.5.

[0025] In addition, the present invention also provides an injection-type transformer power supply phase loss detection device, including a host, a slave, an injection CT, and a measuring CT. The output terminal of the host is connected to the secondary coil of the injection CT. The iron core of the injection CT is sleeved on the grounding conductor of the transformer neutral point. The current input terminal of the host is connected to the secondary coil of the measuring CT at the neutral point of the transformer. The current input terminal of the slave is connected to the secondary coil of the measuring CT at the neutral point of its respective transformer.

[0026] Furthermore, the master unit is located in the injection transformer area, and the slave units are located in each non-injection transformer area, with one slave unit corresponding to one non-injection transformer.

[0027] Furthermore, the host includes:

[0028] The data acquisition and calculation unit is used to convert the analog signal of the transformer neutral point current into a digital signal and calculate the corresponding zero-sequence impedance data.

[0029] The communication unit is used to communicate with the slave device.

[0030] The logic discrimination unit is used to use the received zero-sequence impedance data for phase loss discrimination, and to provide alarm prompts for phase loss, output phase loss location information, and store fault data.

[0031] Furthermore, the slave device includes:

[0032] The data acquisition and calculation unit performs the corresponding zero-sequence impedance data calculation according to the instructions issued by the host.

[0033] The communication unit is used to communicate with the host, and the slave device transmits the calculated impedance data information to the host.

[0034] Compared with the prior art, the injection transformer power supply phase loss detection method and device provided by the present invention have the following beneficial effects:

[0035] This invention proposes for the first time a method for determining an injection transformer. By using this method to identify a transformer as an injection transformer, the sensitivity of line phase failure detection can be improved.

[0036] This invention proposes for the first time a configuration scheme that uses a master and slave device to detect together and exchange data via communication, which avoids the signal attenuation and interference problems caused by long-distance transmission of weak current analog signals at the neutral point of each transformer, and improves the reliability of phase loss detection.

[0037] This invention can locate the phase failure position by partitioning based on whether different criteria are met. It can accurately identify whether the phase failure position is in the incoming line circuit, the injection transformer circuit, or the non-injection transformer circuit, which can effectively shorten the time for maintenance personnel to troubleshoot and restore system operation.

[0038] The phase failure detection device described in this invention can adapt to changes in system operation mode and avoid false alarms of phase failure in the transformer circuit when a non-injection transformer is out of service. Attached Figure Description

[0039] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the technical description will be briefly introduced below.

[0040] Figure 1 This is a schematic diagram of the wiring for phase loss detection of the injection transformer power supply provided by the present invention;

[0041] Figure 2 The flowchart of the injection transformer power supply phase loss detection method provided by the present invention;

[0042] Figure 3 The logic block diagram of the injection transformer power supply phase loss detection method provided by the present invention is shown. Detailed Implementation

[0043] The following detailed description provides further details on specific implementation methods.

[0044] like Figures 1 to 3As shown, this valve provides an injection-type transformer power supply phase loss detection method. In a system with two or more transformers connected to a single circuit and directly grounded neutral points, a specific frequency interharmonic current signal is injected into the neutral point of the transformer with the lower zero-sequence impedance. By collecting and extracting the interharmonic current flowing through the neutral point of each transformer, the zero-sequence impedance value corresponding to the interharmonic current at each transformer's neutral point is calculated. A set of logic criteria is designed to detect phase loss at any location in the transformer power supply circuit and to locate the region to which the phase loss location belongs. Specifically, the method includes the following steps:

[0045] Step 1: Select a transformer with low zero-sequence impedance as the injection transformer. When the zero-sequence impedances on the high-voltage side of each transformer differ significantly, the transformer with the lowest zero-sequence impedance should be selected as the injection transformer. When the zero-sequence impedances on the high-voltage side of each transformer differ very little, any transformer can be selected as the injection transformer.

[0046] Step 2: Using an injection signal device, the current output by the injection signal device is continuously injected into the neutral point of the injection transformer through the injection CT to produce an interharmonic current signal of a specific frequency (e.g., 75Hz).

[0047] Step 3: Collect the current waveform data of the neutral point of each transformer, and perform digital filtering or fast Fourier transform on the collected neutral point current waveform data to obtain the interharmonic current value of the neutral point of each transformer.

[0048] Step 4: Based on the interharmonic voltage at the output of the injected signal device and the interharmonic current at the neutral point of each transformer, the zero-sequence impedance value measured at the neutral point of each transformer can be obtained. The calculation formula is as follows:

[0049] Z 0j =U o / I 0j (j=1,2,3……n) (1)

[0050] In the formula: Z 0j —Zero-sequence impedance values ​​measured at the neutral point of each transformer, in Ω;

[0051] U o — Output voltage of the injected signal device, in V;

[0052] I 0j —Interharmonic current at the neutral point of each transformer, A.

[0053] Step 5: Measure the zero-sequence impedance values ​​Z as described above. 0j Measurements when phase is not interrupted The system uses comparison and logical judgment to determine whether a phase failure has occurred and whether the failure occurs in any transformer circuit within the plant or in an external incoming circuit, including transmission lines. It provides information on the phase failure and its location. Assuming the injection-type transformer is numbered 1, and the other non-injection-type transformers are numbered 2, 3, ..., n sequentially, the determination method is as follows:

[0054] Step 5.1: If condition (2) is met, then it is determined that there is a phase failure in the incoming circuit (including transmission lines) between the busbar of this side switch station and the busbar of the opposite substation:

[0055]

[0056] In the formula: k1 = 1.1~1.4, k2 = 0.5~0.9, 2≤m≤n. The values ​​of k1 and k2 are related to factors such as the impedance of the system power supply, the line length, the number of transformers, and the zero-sequence impedance of each transformer. With other factors remaining constant, the more transformers there are, the smaller the value of k1 and the larger the value of k2, and vice versa.

[0057] Step 5.2: If condition (3) is met, then it is determined that there is a phase break in the circuit between the injection transformer and the busbar of this side switch station:

[0058]

[0059] In formula (3): k3=3~30, 2≤m≤n.

[0060] Step 5.3: If condition (4) is met, then it is determined that there is a phase break in the circuit between the non-injection transformer numbered m and the busbar of this side switch station:

[0061]

[0062] In equation (4): k3 takes the same value as in equation (3), and k4 = 1.2 to 1.5.

[0063] Step 6: If any of the criteria in steps 5.1 to 5.3 is met, output a phase loss signal after a delay of T seconds and save the zero-sequence impedance values, injected signal voltage values, injected signal current values, and other data for this phase loss. Then, execute step 3 to start the next detection cycle. Otherwise, clear the phase loss delay timer and then execute step 3 to start the next detection cycle.

[0064] Furthermore, this invention also provides an injection-type transformer power supply phase loss detection device, which has the function of implementing the injection-type transformer power supply phase loss detection method as described above. This function is implemented by hardware executing corresponding software. The device includes a host, a slave, an injection CT, and a measuring CT (high-precision current transformer or Rogowski coil).

[0065] The main unit is located in the injection transformer area. The output terminal of the main unit is connected to the secondary coil of the injection CT, and the core of the injection CT is wrapped around the grounding conductor of the transformer neutral point. The current input terminal of the main unit is connected to the secondary coil of the measuring CT at the neutral point of this transformer.

[0066] The slave devices are located in each non-injection transformer area, with one slave device corresponding to one non-injection transformer. The current input terminal of the slave device is connected to the secondary coil of the measuring CT at the neutral point of its respective transformer.

[0067] The host machine has a data acquisition and calculation unit, a communication unit, and a logic discrimination unit, while the slave machine has a data acquisition and calculation unit and a communication unit.

[0068] The data acquisition and calculation unit is used to convert the analog signal of the transformer neutral point current into a digital signal and calculate the corresponding zero-sequence impedance data. Each calculation is initiated by the master unit, and the slave unit must complete the corresponding zero-sequence impedance data calculation according to the instructions issued by the master unit.

[0069] The master and slave communicate through a communication unit, with the slave transmitting the calculated impedance data to the master.

[0070] The host uses the received zero-sequence impedance data through the logic discrimination unit for phase loss discrimination, and performs operations such as alarm prompts, outputting phase loss location information, and storing fault data.

[0071] The host will transmit the phase failure and its location information to each slave unit via communication. Both the host and slave units can output multiple dry contact phase failure signals, which can be used for remote alarm and disconnection of transformers affected by the phase failure.

[0072] In addition, the device also has the function of adapting to changes in system operation mode. When a non-injection transformer is out of service, the zero-sequence impedance comparison result of the transformer in the above formula (4) can be automatically or manually forced to 0 in order to avoid false alarms of phase failure in the transformer circuit.

[0073] For example, the technical solution of the present invention will be further described below using the 220kV auxiliary power system of a nuclear power plant as an example.

[0074] like Figure 1As shown, the normal operating mode is one circuit with three auxiliary transformers running under no-load conditions. Auxiliary transformers AT1 and AT2 both use a Yn / △11-△11 connection, with rated capacities of 70 / 35-35MVA and 63 / 31.5-31.5MVA respectively, and a voltage transformation ratio of 220±8×1.25% / 6.3kV. AT3 uses a Yn / Yn0-△11 connection (△ is the balancing winding), with a rated capacity of 34 / 34-11.3MVA and a voltage transformation ratio of 230±8×1.25% / 6.9kV. The zero-sequence impedances of auxiliary transformers AT1 to AT3 are 73.9Ω, 86.8Ω, and 198.0Ω respectively, the line zero-sequence impedance is 7.2Ω, and the system reactance (opposite busbar) is 8.3Ω in the large mode and 21.4Ω in the small mode.

[0075] In this embodiment, a method for detecting phase loss in an injection transformer power supply specifically includes the following steps:

[0076] Step 1: Select a transformer with low zero-sequence impedance as the injection transformer. When the zero-sequence impedances on the high-voltage side of each transformer differ significantly, the transformer with the lowest zero-sequence impedance should be selected as the injection transformer. When the zero-sequence impedances on the high-voltage side of each transformer differ very little, any transformer can be selected as the injection transformer.

[0077] In this embodiment, the zero-sequence impedances on the high-voltage side of the three transformers differ greatly. AT3 has the largest zero-sequence impedance, while AT1 has the smallest zero-sequence impedance. The ratio between the two is 2.68. Therefore, AT1, the transformer with the smallest zero-sequence impedance, is selected as the injection transformer, while the other two transformers, AT2 and AT3, are non-injection transformers.

[0078] Step 2: Using an injection signal device, the output current is continuously injected into the neutral point of the injection transformer through an injection CT to produce an interharmonic current signal of a specific frequency.

[0079] In this embodiment, a 75Hz interharmonic current signal is injected into the neutral point of the injection transformer AT1.

[0080] Step 3: Collect the current waveform data of the neutral point of each transformer, and perform a fast Fourier transform on the collected neutral point current waveform data to obtain the interharmonic current value of the neutral point of each transformer.

[0081] This embodiment uses the Fast Fourier Transform (FFT) method to extract interharmonic current signals from the neutral point current of each transformer.

[0082] Step 4: Calculate the zero-sequence impedance value corresponding to the interharmonic current at the neutral point of each transformer based on the interharmonic voltage at the output of the injected signal device and the interharmonic current value at the neutral point of each transformer.

[0083] Z0j =U o / I 0j (j=1,2,3……n) (1)

[0084] In the formula: Z 0j —Calculated zero-sequence impedance corresponding to the harmonic current between the neutral points of each transformer, in Ω;

[0085] U o — Output voltage of the injected signal device, in V;

[0086] I 0j —Interharmonic current at the neutral point of each transformer, A.

[0087] In this embodiment, n = 3.

[0088] Step 5: Measure the zero-sequence impedance values ​​Z as described above. 0j Measurements when phase is not interrupted Comparison and logical judgment are used to determine whether a phase failure has occurred and whether the phase failure is in which transformer circuit within the plant or in an external incoming circuit, including transmission lines, and information on the phase failure and its location is provided.

[0089] Step 5.1: If the condition of equation (2) is met, it is determined that there is a phase break in the incoming circuit (including transmission line) between the switch station bus and the opposite substation bus.

[0090]

[0091] In the formula: k1 = 1.1~1.4, k2 = 0.5~0.9, 2≤m≤n. The values ​​of k1 and k2 are related to factors such as the impedance of the system power supply, the line length, the number of transformers, and the zero-sequence impedance of each transformer. With other factors remaining constant, the more transformers there are, the smaller the value of k1 and the larger the value of k2, and vice versa.

[0092] In this embodiment, m = n = 3, k1 = 1.15, and k2 = 0.75.

[0093] Step 5.2: If the condition of equation (3) is met, it is determined that there is a phase break in the circuit between the injection transformer and the switch station bus.

[0094]

[0095] In formula (3): k3=3~30, 2≤m≤n.

[0096] In this embodiment, m = n = 3, and k3 = 20.

[0097] Step (5.3): If the condition of equation (4) is met, it is determined that there is a phase break in the circuit between the non-injection transformer numbered m and the switch station bus.

[0098]

[0099] In equation (4): k3 takes the same value as in equation (3), and k4 = 1.2 to 1.5.

[0100] In this embodiment, n=3, k3=20, and k4=1.5.

[0101] Step 6: If any of the criteria in steps 5.1 to 5.3 is met, the phase loss delay timer accumulates the count. After the accumulated time reaches T seconds, it outputs a phase loss signal and saves the zero-sequence impedance values, injected signal voltage values, injected signal current values, and other data for this phase loss. Then, it executes step 3 to start the next detection cycle. Otherwise, the phase loss delay timer is cleared, and then step 3 is executed directly to start the next detection cycle. The phase loss delay time T is adjustable within the range of 0 to 30 seconds. The specific setting is based on reliably avoiding the continuous impact of transformer no-load closing on the device's detection results and the backup protection action time for system short-circuit grounding faults.

[0102] In this embodiment, the improved flow chart for the injection transformer power supply phase loss detection is as follows: Figure 2 As shown, the phase loss detection logic block diagram is as follows: Figure 3 As shown.

[0103] Combined with appendix Figure 1 The injection-type transformer power supply phase loss detection device of the present invention mainly includes the following components: host 1, slave 2, ..., slave n, injection CT, measurement CT1, ..., measurement CTn.

[0104] Main unit 1 is located in the injection transformer AT1 area;

[0105] The output terminal of host 1 is connected to the secondary coil of the injection CT, and the iron core of the injection CT is wrapped on the neutral point grounding conductor of transformer AT1; host 1 continuously injects interharmonic current signals into the system through the injection CT.

[0106] The current input terminal of host 1 is connected to the secondary coil of measuring CT1 at the neutral point of transformer AT1. Measuring CT1 is used to measure the interharmonic current I flowing through the neutral point of the injection transformer. 01 .

[0107] Slave 2 to slave n are arranged in the area of ​​each non-injection transformer AT2 to ATn, with one slave corresponding to one non-injection transformer;

[0108] The current input terminals of slave devices 2 through n are connected to the secondary coils of measuring CT2 through CTn at the neutral point of their respective transformers. Measuring CT2 through CTn are used to measure the interharmonic current I flowing through the neutral point of their respective transformers. 02 ~I 0j .

[0109] The host 1 has a data acquisition and calculation unit, a communication unit, and a logic discrimination unit, while slave 2 to slave n have data acquisition and calculation units and communication units.

[0110] Data acquisition and calculation unit. A high-performance 24-bit AD chip with a conversion accuracy of ±0.1% converts the acquired analog current signal into a binary digital signal, which is then output to the data calculation CPU board to complete the data processing and calculate the corresponding zero-sequence impedance data. The data calculation CPU board consists of a digital signal processing chip (DSP) and peripheral power supply circuits, opto-isolation circuits, etc.

[0111] The logic discrimination unit consists of a 32-bit STM32 microcontroller, peripheral power supply circuitry, LCD screen circuitry, etc., and is used to implement functions such as criterion comparison, phase loss alarm, phase loss information output, and fault data storage.

[0112] Communication Unit. The master unit 1 and slave units 2 to n communicate via CAN. The slave units and the master unit are connected to a common CAN network. The CAN ID number of each slave unit is set by a DIP switch, so that the CAN ID number of each slave unit is different.

[0113] Each calculation is initiated by master 1, and slave devices 2 through n must complete the corresponding zero-sequence impedance data calculation according to the instructions issued by the master. Slave devices 2 through n then transmit the calculated impedance data information to the master.

[0114] The host 1 uses the received zero-sequence impedance data for phase failure detection through the logic discrimination unit, and performs operations such as alarm prompts, outputting phase failure location information, and storing fault data. The host 1 transmits the phase failure and its location information to slave 2 to slave n via communication. The host 1 and slave 2 to slave n can all output multiple dry contact phase failure signals through their respective relay boards, which can be used for remote alarm and disconnection of transformers affected by phase failure.

[0115] In addition, to adapt to changes in system operation, this embodiment includes n-1 toggle switches on the device panel. During normal operation, all toggle switches are in the ON position. When a non-injection transformer is decommissioned, the corresponding numbered toggle switch is switched to the OFF position. When the device detects that a toggle switch is in the OFF position, it automatically... Figure 3 The input signal of the AND gate for the phase loss detection of the non-injection transformer circuit is forced to 0 to avoid false alarms of phase loss in the transformer circuit.

[0116] This invention can be used for phase failure detection in a neutral point directly grounded system with two or more transformers on a single line, and can perform zoned location of the phase failure—locating whether the phase failure is in the incoming circuit between the busbar of this side switch station and the busbar of the opposite substation or in the power supply circuit between a transformer and the busbar of this side switch station.

[0117] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting phase loss in an injection-type transformer power supply, characterized in that, Includes the following steps: Step 1: Select one transformer from multiple transformers as the injection transformer; Step 2: Using an injection signal device, the output current is continuously injected into the neutral point of the injection transformer through an injection CT to inject interharmonic current signals. Step 3: Collect the current waveform data of the neutral point of each transformer, and perform digital filtering or fast Fourier transform on the collected neutral point current waveform data to obtain the interharmonic current value of the neutral point of each transformer. Step 4: Based on the interharmonic voltage at the output of the injection signal device and the interharmonic current at the neutral point of each transformer, obtain the zero-sequence impedance value measured at the neutral point of each transformer. Step 5: Based on the measured values ​​of each zero-sequence impedance Measurements when phase is not interrupted Determine whether a phase failure has occurred and determine the location of the phase failure, and provide information on the phase failure and its location; if the conditions are met... & &…& If the condition is met, it is determined that there is a phase break in the incoming circuit between the busbar of this side switch station and the busbar of the opposite substation. The value of k1 ranges from 1.1 to 1.4, the value of k2 ranges from 0.5 to 0.9, and 2 ≤ m ≤ n; if the condition is met... & &…& If the circuit between the injection transformer and the busbar of this switch station is determined to have a phase break, the value of k3 is in the range of 3~30, and 2≤m≤n; if the following conditions are met... & If the circuit between the non-injection transformer numbered m and the busbar of the switch station on this side is determined to have a phase break, the value range of k3 is 3~30, and the value range of k4 is 1.2~1.5; Step 6: Determine whether the phase loss delay time T seconds is met. If it is met, output a phase loss alarm and record the zero-sequence impedance, voltage, and current data, then return to step 3 to start the next detection cycle; if it is not met, directly return to step 3 to start the next detection cycle.

2. The method for detecting phase loss in an injection transformer power supply according to claim 1, characterized in that, In step 1, by comparing the zero-sequence impedance of each transformer on the high-voltage side, the transformer with the smallest zero-sequence impedance is selected as the injection transformer.

3. The method for detecting phase loss in an injection transformer power supply according to claim 1, characterized in that, In step 4, the calculation formula is as follows: ,j=1,2,3…n, In the formula: The zero-sequence impedance values ​​measured at the neutral point of each transformer; The output voltage of the injected signal device; This refers to the interharmonic current at the neutral point of each transformer.

4. A phase loss detection device for injection-type transformer power supply, characterized in that, Based on the method of any one of claims 1 to 3, the device includes a host, a slave, an injection CT, and a measuring CT. The output terminal of the host is connected to the secondary coil of the injection CT. The iron core of the injection CT is sleeved on the grounding conductor of the transformer neutral point. The current input terminal of the host is connected to the secondary coil of the measuring CT at the neutral point of the transformer. The current input terminal of the slave is connected to the secondary coil of the measuring CT at the neutral point of its respective transformer.

5. The injection-type transformer power supply phase loss detection device according to claim 4, characterized in that, The master unit is located in the injection transformer area, and the slave units are located in each non-injection transformer area, with one slave unit corresponding to one non-injection transformer.

6. The injection-type transformer power supply phase loss detection device according to claim 4, characterized in that the main unit... include: The data acquisition and calculation unit is used to convert the analog signal of the transformer neutral point current into a digital signal and calculate the corresponding zero-sequence impedance data. The communication unit is used to communicate with the slave device. The logic discrimination unit is used to use the received zero-sequence impedance data for phase loss discrimination, and to provide alarm prompts for phase loss, output phase loss location information, and store fault data.

7. The injection-type transformer power supply phase loss detection device according to claim 4, characterized in that, Slave devices include: The data acquisition and calculation unit performs the corresponding zero-sequence impedance data calculation according to the instructions issued by the host. The communication unit is used to communicate with the host, and the slave device transmits the calculated impedance data information to the host.

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