SFC isolation transformer control device, system and method

Abstract

The invention relates to the technical field of SFC isolation transformers, in particular to an SFC isolation transformer control device, system and method.The SFC isolation transformer control device comprises a protection DSP board, and the input end of the protection DSP board is indirectly connected with the output end of a CT / VT and / or directly connected with the output end of a first ECVT; the input end of the starting DSP board is indirectly connected with the output end of the CT / VT and / or directly connected with the output end of the second ECVT, and the protection DSP board and the starting DSP board are connected through a parallel bus; the main control chip is connected with the starting DSP through a data feedback link; the starting relay is connected with the starting DSP board; and the outlet relay is connected with the protection DSP board, and a contact of the starting relay is connected in series in a positive power supply loop of the outlet relay. The device supports analog quantity input of CT / VT and digital quantity input of ECVT at the same time, does not need to additionally configure a signal conversion module, and adapts to different scenes of a traditional transformer substation and a digital transformer substation.

Description

Technical Field

[0001] This invention relates to the field of SFC isolation transformer technology, and in particular to an SFC isolation transformer control device, system and method. Background Technology

[0002] SFC (Static Variable Frequency Drive) isolation transformers are key equipment in power systems adapted to static frequency converters. They are primarily used to achieve electrical isolation between the frequency converter and the power grid and loads, while also stabilizing voltage and suppressing harmonics. They are widely used in pumped storage power stations, large-scale industrial speed control systems, and other scenarios. Because SFC isolation transformers operate under high voltage, high current, and strong electromagnetic interference environments for extended periods, real-time monitoring of their operating status and fault protection are crucial for power grid safety. However, existing SFC isolation transformer control devices still suffer from several technical bottlenecks, making it difficult to meet the requirements for high reliability and high real-time protection.

[0003] First, most existing control devices adopt a "single DSP (Digital Signal Processor) architecture," meaning that the same DSP simultaneously performs both "fault initiation criterion detection" and "protection logic operation" functions. Since fault signals from SFC isolation transformers (such as short-circuit current and non-full-phase current) require millisecond-level responses, while protection operations (such as differential protection and non-electrical logic judgment) require complex data processing, the single DSP architecture is prone to "operational delays," leading to delayed fault response. For example, when a short-circuit fault occurs in the transformer, the single DSP must complete the current protection operation before detecting the initiation criterion, potentially missing the optimal tripping time and increasing the risk of equipment burnout.

[0004] Secondly, the relay control of existing devices lacks a "hardware-level interlocking mechanism." Most devices only have a single output relay, whose operation is directly controlled by DSP software instructions. If the DSP malfunctions due to electromagnetic interference, malfunctions by issuing incorrect instructions, or if there are logical vulnerabilities in the software, it can easily lead to malfunctions of the output relay (tripping when there is no fault). As a critical piece of equipment in the power grid, the SFC isolation transformer's malfunction can directly cause the frequency converter to stop operating and the load to lose power, resulting in huge economic losses. Existing designs cannot eliminate such risks at the hardware level.

[0005] Furthermore, the "electrical isolation" design between external signals and internal core circuits is insufficient. Non-electrical signals (such as high oil temperature, cold control power failure) of the SFC isolation transformer originate from the transformer body itself, and its transmission circuit is prone to carrying interference signals such as surge voltage and ground potential difference. Existing devices often directly connect non-electrical signals to the DSP without taking effective isolation measures. Interference signals can easily enter the internal circuit, causing the DSP to misjudge the fault state. For example, surge voltage may cause the DSP to misidentify the "high oil temperature" signal, triggering unnecessary delayed tripping. Summary of the Invention

[0006] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0007] To address the shortcomings of existing technologies, one objective of this invention is to provide an SFC isolation transformer control device, comprising a protection DSP board, whose input terminal is indirectly connected to the output terminal of the CT / VT and / or directly connected to the output terminal of a first ECVT; a starting DSP board, whose input terminal is indirectly connected to the output terminal of the CT / VT and / or directly connected to the output terminal of a second ECVT, wherein the protection DSP board and the starting DSP board are connected via a parallel bus; a main control chip, which is connected to the starting DSP board via a data feedback link; a starting relay, which is connected to the starting DSP board; and an output relay, which is connected to the protection DSP board, wherein the contacts of the starting relay are connected in series in the positive power supply circuit of the output relay.

[0008] As a preferred embodiment of the SFC isolation transformer control device of the present invention, it further includes: a first AD converter, the input terminal of which is connected to the output terminal of the CT / VT and the output terminal of which is connected to the input terminal of the protection DSP board; and a second AD converter, the input terminal of which is connected to the output terminal of the CT / VT and the output terminal of which is connected to the input terminal of the start-up DSP board.

[0009] As a preferred embodiment of the SFC isolation transformer control device of the present invention, it further includes: an optocoupler, the input of which is connected to the non-electrical quantity status signal of the transformer or reactor, and the output of which is simultaneously connected to the digital input pins of the protection DSP board and the start-up DSP board; and pull-up resistors are provided on the paths through which the optocoupler is connected to the protection DSP board and the start-up DSP board respectively.

[0010] In a preferred embodiment of the SFC isolation transformer control device of the present invention, the coil of the starting relay is connected to the positive terminal of the DC operating power supply, and the contacts of the starting relay are connected in series with the positive power supply circuit of the output relay; the positive terminal of the coil of the output relay is connected to the contacts of the starting relay, and the negative terminal of the coil of the output relay is connected to the negative terminal of the DC operating power supply.

[0011] Another objective of this invention is to provide an SFC isolation transformer control system, comprising: a data acquisition module that receives non-electrical quantity status signals from the transformer or reactor and acquires AC electrical quantity signals from a current transformer; a processing module that performs real-time protection calculations and output logic judgments based on the non-electrical quantity status signals and the AC electrical quantity signals; and a digital output module that generates a trip command based on the calculation results of the processing module and / or the non-electrical quantity status signals, wherein the trip command is output if the calculation results satisfy the protection action logic and / or if the non-electrical quantity status signals satisfy the direct output conditions.

[0012] As a preferred embodiment of the SFC isolation transformer control system of the present invention, it further includes a human-machine interaction module, which includes a display unit connected to the processing module and an instruction input unit; wherein the display unit is used to display the equipment operating status and protection information and indicate the equipment operating status, and the instruction input unit is used for users to input operation instructions and configure the equipment.

[0013] Another objective of this invention is to provide an SFC isolation transformer control method, comprising: receiving at least one non-electrical quantity status signal and multiple AC electrical quantity signals; performing real-time calculations on the received multiple AC electrical quantity signals and determining whether the calculation results meet preset electrical quantity protection start criteria; dividing the non-electrical quantity status signal into two paths, one of which is used for logical judgment, and the other is sent to the re-operation output contact; if the calculation results meet the protection action logic and / or if the non-electrical quantity status signal meets the direct output condition, then outputting a trip command.

[0014] As a preferred embodiment of the SFC isolation transformer control method of the present invention, it further includes non-full-phase protection logic, wherein the full-phase protection logic is configured to: monitor the three-phase position inconsistency state of the circuit breaker, and use the calculated zero-sequence current or negative-sequence current value as a blocking condition, and use it for two-stage delayed tripping.

[0015] As a preferred embodiment of the SFC isolation transformer control method of the present invention, it further includes circuit breaker failure start logic, wherein the circuit breaker failure start logic is configured to start after receiving an external protection action contact signal, and use phase current, zero-sequence current, negative-sequence current, circuit breaker three-phase inconsistent contact or closing position contact as blocking or starting conditions.

[0016] As a preferred embodiment of the SFC isolation transformer control method of the present invention, it further includes non-electrical quantity delay protection logic, wherein the non-electrical quantity delay protection logic is configured to: start an adjustable delay timer for a preset specific non-electrical quantity state signal, and output a trip command after the timer expires.

[0017] The beneficial effects of this invention are as follows: This invention supports both analog input of CT / VT and digital input of ECVT through a device, without the need for additional signal conversion modules, and is suitable for different scenarios of traditional substations and digital substations; wherein, the CT / VT signal is converted by an independent AD converter to avoid signal interference and meet the high-precision protection requirements of SFC isolation transformer. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is the core wiring diagram of the SFC isolation transformer control device of the present invention.

[0020] Figure 2 This is a wiring diagram of the components of the SFC isolation transformer control device of the present invention.

[0021] Figure 3 Wiring diagram of the SFC isolation transformer control system of this invention. Detailed Implementation

[0022] To make the objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0025] Example 1

[0026] Reference Figure 1This embodiment is the first embodiment of the invention. This embodiment discloses an SFC isolation transformer control device. The core structure includes a protection DSP board 101, a CT / VT 102, a first ECVT 103, a starting DSP board 104, a second ECVT 105, a main control chip 106, a starting relay 107, and an output relay 108. The connection relationship and function of each technical feature are as follows.

[0027] The protection DSP board 101, as the core of the device's protection logic operation, has two signal input methods: one is to indirectly connect to the output of the CT / VT102 to receive the analog AC power signals (such as three-phase current and voltage) collected by the CT / VT102 from the SFC isolation transformer; this signal needs to be converted from analog to digital before being input. The other is to directly connect to the output of the first ECVT103 to receive the digital signals (such as digitized current and voltage) collected by the first ECVT103, without additional conversion. The core function of the protection DSP board 101 is to perform complex protection operations, such as differential protection and non-electrical delay protection logic judgments, and output the drive signal of the output relay 108 based on the calculation results.

[0028] The starting DSP board 104 serves as the core of the device's rapid fault start-up mechanism. Its input terminals form a symmetrical design with those of the protection DSP board 101. Firstly, it is indirectly connected to the output of the CT / VT 102 to receive the same AC analog signal from the CT / VT 102. Secondly, it can be directly connected to the output of the second ECVT 105 to receive its digital signal. The core function of the starting DSP board 104 is to detect fault start-up criteria, such as sudden current exceeding limits or zero-sequence current exceeding limits. Once the criteria are met, it immediately outputs a start-up relay drive signal. The protection DSP board 101 and the starting DSP board 104 are connected via a parallel bus. The parallel bus uses a high-speed Localbus, with a 32-bit width, a 100MHz clock frequency, and a data transmission delay of <1μs, ensuring that both boards share fault signals and criterion results in real time.

[0029] The main control chip 106 uses a 32-bit ARM microprocessor and is bidirectionally connected to the starter DSP board 104 via a data feedback link CAN bus. The core function of the main control chip 106 is to receive fault start status and self-test information such as DSP temperature and program running status uploaded by the starter DSP board 104; and to send setpoint modification instructions such as adjusting the sudden change current threshold and soft pressure plate enabling / disabling instructions to the starter DSP board 104 to realize remote configuration of start-up criteria.

[0030] The starting relay 107 is an electromagnetic DC relay (such as model HH52P). Its coil control terminal is connected to the digital output pin of the starting DSP board 104 to receive the drive signal from the starting DSP board 104. The core function of the starting relay 107 is to control the positive power supply path of the output relay. Its contacts are normally open and only close when the starting DSP board 104 outputs a drive signal.

[0031] The output relay 108 is an electromagnetic DC relay (such as model HH53P). Its coil control terminal is connected to the digital output pin of the protection DSP board 101 to receive the drive signal from the protection DSP board 101. Simultaneously, the normally open contact of the starting relay 107 is connected in series in the positive power supply circuit of the output relay 108. That is, the positive terminal of the output relay 108 coil must pass through the contact of the starting relay 107 to be connected to the DC operating power supply, while the negative terminal of the coil is directly connected to the negative terminal of the DC operating power supply. The core function of the output relay 108 is to perform a tripping action. Its normally open contact is connected to the external tripping circuit of the SFC isolation transformer (such as the circuit breaker tripping coil), and the external tripping is triggered when the contact closes.

[0032] This embodiment uses dual-DSP parallel control and hardware interlocking design to ensure that when the SFC isolation transformer fails, the device can respond quickly and avoid false tripping, thus meeting the requirements for high reliability protection.

[0033] Example 2

[0034] Reference Figure 1 and Figure 2 This is the second embodiment of the invention, based on embodiment 1. It further includes a first AD converter 109, a second AD converter 1010, an optocoupler 1011, and a pull-up resistor 1012.

[0035] Specifically, both the first AD converter 109 and the second AD converter 1010 employ a 16-bit high-precision AD chip (such as model ADS8364). Their connections and functions are as follows: The input terminal of the first AD converter 109 is connected to the output terminal of the CT / VT102 via a shielded twisted-pair cable, receiving analog AC electrical signals such as 0-5A current and 0-100V voltage output from the CT / VT102. Its output terminal is connected to the analog input pin of the protection DSP board 101 via an SPI bus, transmitting the converted digital signal to the protection DSP board 101. The sampling frequency of the first AD converter 109 is set to 278Hz to match the protection operation requirements of the protection DSP board 101, ensuring the time accuracy of the acquired signal. The input of the second AD converter 1010 is also connected to the output of the CT / VT102. The second AD converter 1010 and the first AD converter 109 are connected in parallel and acquire the same analog signal. The output is connected to the analog input pin of the starter DSP board 104 via the SPI bus. The sampling frequency is set to 500Hz, which is higher than that of the first AD converter 109, to meet the requirements of the starter DSP board 104 for rapid fault detection. By setting independent first AD converter 109 and second AD converter 1010, the sampling circuits of the protection DSP board 101 and the starter DSP board 104 are completely isolated, avoiding sampling interference caused by sharing AD converters, such as protection operations occupying AD resources and affecting start-up criterion detection. At the same time, different sampling frequencies are set according to the functional requirements of the two, which improves the real-time performance of fault start-up detection while ensuring the accuracy of protection operations, and the sampling error is controlled within ±0.1%.

[0036] Preferably, the optocoupler 1011 uses a high-speed optocoupler chip (such as model 6N137). Its input terminal is connected to the non-electrical signal source of the SFC isolation transformer body through a shielded cable to receive non-electrical status signals such as high oil temperature signal, cold control power failure signal, and body heavy gas signal. A 1kΩ current-limiting resistor is connected in series at the input terminal to prevent the light-emitting diode from burning out due to overcurrent. The output terminal has an open collector structure and is connected to the digital input pins of the protection DSP board 101 and the start-up DSP board 104. The core function of the optocoupler 1011 is to achieve electrical isolation between external non-electrical signals and internal DSP circuits, blocking the input of external interference signals such as surges and ground potential differences.

[0037] Preferably, the pull-up resistor 1012 is a 10kΩ surface mount resistor. Each connection path between the optocoupler 1011 and the DSP is connected in series with a pull-up resistor 1012, and the other end of the pull-up resistor 1012 is connected to the DSP's 3.3V power supply. Since the output terminal of the optocoupler 1011 has an open collector structure, the output level is unstable when there is no signal. The pull-up resistor 1012 can pull the level to a high level of 3.3V when there is no signal. Only when a non-electrical quantity signal is valid (i.e., the optocoupler is conducting) will the output level become low, ensuring that the protection DSP board 101 and the starting DSP board 104 can accurately identify the signal status. The isolation effect of the optocoupler 1011 reduces the false judgment rate of non-electrical quantity signals by 90% in the strong electromagnetic environment of the substation. The level stabilization effect of the pull-up resistor 1012 avoids false non-electrical quantity signals caused by signal fluctuations, further improving the reliability of the non-electrical quantity protection logic and ensuring that critical non-electrical quantity faults such as cold control power failure and high oil temperature can be accurately detected.

[0038] Furthermore, the positive terminal of the starting relay 107 coil is connected to the positive terminal of the DC operating power supply (DC220V+) through a 2A fuse, and the negative terminal of the coil is connected to the digital output pin of the starting DSP board 104. When the starting DSP board 104 outputs a high level, the coil forms a loop of DC220V+ → fuse → coil → output pin of the starting DSP board 104 → ground. The coil is energized and its normally open contact closes. When the output is low, the coil is de-energized and the contact opens. The positive terminal of the coil of the output relay 108 is connected to the positive terminal (DC220V+) of the DC operating power supply through the normally open contact of the starting relay 107, and the negative terminal of the coil is directly connected to the negative terminal (DC220V-) of the DC operating power supply. The coil control terminal is connected to the digital output pin of the protection DSP board 101. Only when the contact of the starting relay 107 is closed (providing positive power) and the protection DSP board 101 outputs a high level (driving the coil), the coil forms a complete circuit of DC220V+ → starting relay 107 contact → output relay 108 coil → DC220V-, and the coil is energized and closes, triggering an external trip. If any condition is not met, there is no current in the coil and it cannot operate. By connecting the start relay 107 contacts in series with the positive power supply circuit of the output relay 108, a double hardware interlock is formed. Even if the protection DSP board 101 erroneously sends a drive signal due to a fault, if the start relay 107 does not operate (no fault), the output relay 108 will still not be energized, thus avoiding false tripping caused by a single DSP fault. At the same time, a fuse is connected in series with the coil circuit to prevent the coil from short-circuiting and burning out the DC operating power supply, thereby improving the power supply safety of the device.

[0039] Example 3

[0040] Reference Figures 1-3This embodiment discloses an SFC isolation transformer control system, the core of which includes a data acquisition module 200, a processing module 300, a digital output module 400, and a human-machine interaction module 500.

[0041] The acquisition module 200 serves as the core of the system's signal input, acquiring AC electrical signals from the SFC isolation transformer, such as three-phase current, three-phase voltage, zero-sequence current, and negative-sequence current. The analog voltage and current signals are converted into digital quantities by the first AD converter 109 and the second AD converter 1010, while the ECVT signal is directly received as a digital quantity. The module also acquires non-electrical status signals from sensors on the SFC isolation transformer itself, such as oil temperature sensor, gas relay, and cooling system status sensor, including high oil temperature, heavy gas discharge, and cooling system power failure. These signals are isolated by optocoupler 1011 before being transmitted to subsequent modules. The signal sampling period of the acquisition module 200 is set to 2ms to ensure real-time signal transmission.

[0042] The processing module 300, as the core of the system's computation, consists of the protection DSP board 101, the start-up DSP board 104, and the main control chip 106 as described in Embodiment 1. The start-up DSP board 104 performs fault start-up criterion calculations on the electrical signals received from the acquisition module 200, such as sudden change current = current - average current of the previous 3 cycles. If the sudden change current > 0.04In (In is the CT rated current), the start-up criterion is satisfied. The protection DSP board 101 performs protection logic operations on the electrical signals, such as differential protection and non-full-phase protection, and performs logic judgments on non-electrical signals, such as whether cold-controlled power failure meets the delayed tripping condition. The main control chip 106 receives the computation results from the processing module 300 and generates status feedback information such as fault type and action time.

[0043] The digital output module 400, serving as the system's execution core, comprises the starting relay 107, the output relay 108, and the external trip circuit interface as described in Example 1. It receives the calculation results from the processing module 300. If the starting DSP board 104 determines that the starting criteria are met, it outputs a signal to control the starting relay 107 to operate. If the protection DSP board 101 determines that the protection operation logic is met (e.g., differential current > set value) or that the non-electrical signal meets the direct output condition (e.g., mains gas), it outputs a signal to control the output relay 108 to operate. A trip command is generated. After the contacts of the output relay 108 close, the trip command is transmitted to the circuit breaker of the SFC isolation transformer through the external trip circuit interface, achieving fault isolation.

[0044] Preferably, this embodiment adds a human-machine interaction module 500, including a display unit 501 and an instruction input unit 502, as follows: The display unit 501 adopts an LCD touch screen and an LED screen, and is connected to the main control chip 106 of the processing module 300 via an RS-232 bus. Its core functions include: displaying the operating status of the equipment, displaying parameters such as the three-phase current, voltage, oil temperature, and cooling system status of the SFC isolation transformer in real time, with a parameter refresh cycle of 1 second; displaying protection information, displaying protection action reports such as action time, fault type, action element, self-test information such as DSP fault, AD sampling abnormality, setting information such as the current setting zone number and each protection setting, and supporting pagination to view 64 historical action reports.

[0045] The instruction input unit 502 includes virtual buttons on a touchscreen and physical buttons such as confirm, cancel, and up / down selection keys. It is connected to the main control chip 106 via a bus. Its core functions include: user input of operation instructions, such as signal reset (reset trip relay and alarm indicator), manual waveform recording (record current current and voltage waveforms), and print control (print setting sheet or action report); and configuration of equipment parameters, such as modifying protection settings (requires 4-digit password verification), switching setting zones (zones 1 to 10 are selectable), and enabling / disabling soft control panels (such as non-full-phase protection soft control panel and failure start soft control panel).

[0046] Example 4

[0047] Reference Figures 1-3 This embodiment discloses a control method for an SFC isolation transformer. The core steps of the SFC isolation transformer control method are as follows:

[0048] Step 1: Receive signals: The acquisition module 200 receives at least one non-electrical status signal, such as high oil temperature, cold control power failure, and multiple AC electrical signals, such as three-phase current Ia / Ib / Ic, zero-sequence current I0, and negative-sequence current I2. The non-electrical signals are isolated by the optocoupler 1011 and then transmitted to the processing module 300. The AC electrical signals are converted by AD or directly received and then transmitted to the processing module 300.

[0049] Step 2: Real-time calculation of electrical signals and start-up criterion judgment: The start-up DSP board 104 of the processing module 300 performs real-time calculations on multiple AC electrical signals. The calculations include: sudden change current (ΔI = I current - I average of the previous 3 cycles), zero-sequence current (I0 = (Ia + Ib + Ic) / 3), negative-sequence current (I2 = (Ia + a) / 3) / 3, and negative-sequence current (I2 = (Ia + a) / 3). 2 Ib+aTc) / 3, where a is a complex number operator); Based on the calculation result, determine whether the preset power protection start criterion is met (such as ΔI>0.04In, I0>0.04In, I2>0.04In). If it is met, mark the start criterion as valid.

[0050] Step 3: Non-electrical quantity signal splitting processing: The non-electrical quantity status signal is split into two transmission paths: one path is sent to the protection DSP board 101 for logic judgment, such as whether the cold control power failure needs to be combined with high oil temperature lockout; the other path is directly sent to the re-operation output contact. The re-operation output contact is independent of the DSP's hardware contact. If the non-electrical quantity signal is a direct output type, such as the main body heavy gas, the re-operation output contact directly triggers the alarm signal, such as the central signal relay action.

[0051] Step 4: Trip command output: Processing module 300 makes a comprehensive judgment: If the power calculation result meets the protection action logic such as differential current > set value, or the non-power status signal meets the direct output condition such as main body heavy gas, then the starting relay 107 and the output relay 108 are controlled by the switch output module 400 to output a trip command to the external circuit breaker to achieve fault isolation.

[0052] This method uses a combination of electrical and non-electrical quantity processing and start-up / protection dual judgment to cover both electrical faults (short circuit, non-full phase) and non-electrical faults (gas, high oil temperature) of the SFC isolation transformer. It also ensures that the trip command is only output when the fault actually exists, avoiding false tripping. At the same time, the re-output design of non-electrical quantity signals ensures that even if the DSP fails, critical non-electrical quantity faults can still trigger alarms, improving system redundancy.

[0053] The incomplete phase protection logic, as a sub-logic of the control method, is configured as follows for incomplete phase operation faults of the SFC isolation transformer circuit breaker, such as one or two phases being disconnected: Status monitoring: The three-phase position contact signals of the circuit breaker (phase A closed / open, phase B closed / open, phase C closed / open) are collected by the acquisition module 200. If any one phase contact signal is open and the other two phases are closed, it is determined that the three-phase positions of the circuit breaker are inconsistent. Blocking condition setting: The zero-sequence current I0 or negative-sequence current I2 of the SFC isolation transformer is calculated and used as the blocking condition for incomplete phase protection. If I0 < the incomplete phase zero-sequence current setting (adjustable from 0.04 to 150A) or I2 < the incomplete phase negative-sequence current setting (adjustable from 0.04 to 150A), the incomplete phase protection is blocked to prevent maloperation due to minor disturbances; if I0 or I2 meets the setting, the protection is unlocked. Two-stage delayed tripping: Two delay stages are set: 1st time limit (adjustable from 0 to 360 seconds), the 1st time limit timer starts immediately after unlocking, and outputs the first-stage tripping command (tripping the non-faulty phase of the circuit breaker) after the timer ends; 2nd time limit (adjustable from 0 to 360 seconds), if the three-phase positions are still inconsistent after the 1st time limit tripping, the 2nd time limit timer starts, and outputs the second-stage tripping command (tripping the three phases of the circuit breaker) after the timer ends.

[0054] The circuit breaker failure start logic, as a sub-logic of the control method, is specifically configured for circuit breaker failure to trip faults (circuit breaker does not trip after protection action). Start conditions: After receiving an external protection action contact signal, such as an SFC system protection action signal, the circuit breaker failure start logic is started. The external protection action contact signal is transmitted to the processing module 300 through the acquisition module 200 as the trigger signal for failure start. Lockout / Start Condition Settings: The following parameters determine whether failure start is allowed: Current Conditions: Phase current > failure phase current setting (adjustable from 0.04 to 150A), zero-sequence current > failure zero-sequence current setting (adjustable from 0.04 to 150A), negative-sequence current > failure negative-sequence current setting (adjustable from 0.04 to 150A). Start is allowed if any current condition is met. Contact Conditions: Circuit breaker three-phase inconsistent contact signal (start is allowed if closed), circuit breaker closed position contact signal (start is allowed if closed). Start is allowed if any contact condition is met. If none of the above conditions are met, the failure start logic is locked. Start Output: If the start conditions are met, a failure start command is output to the upper-level protection device, such as bus protection, which trips other circuit breakers related to the faulty circuit breaker to isolate the failure fault. The circuit breaker failure start logic is triggered by an external signal and interlocked by multiple conditions to ensure that it only starts when the circuit breaker actually fails, avoiding false starts caused by signal interference. At the same time, the start command is uploaded to the upper-level protection to form a hierarchical protection system and prevent the failure fault from spreading to the entire power grid.

[0055] The non-electrical quantity delay protection logic, as a sub-logic of the control method, is configured as follows for non-electrical quantity faults requiring delay judgment, such as cold control power failure and high oil temperature: Signal Filtering: From the collected non-electrical quantity status signals, preset delay protection signals, such as cold control power failure signals and high oil temperature signals, are filtered out. These signals must avoid false tripping caused by instantaneous fluctuations. Delay Timer Start: When the delay protection signal is valid, such as the cold control power failure signal closing, an adjustable delay timer is started. The timer setpoint is set according to the field requirements (adjustable from 0 to 12000 seconds). For example, the fixed delay for cold control power failure is set to 1200 seconds (20 minutes), and the protection delay is set to 3600 seconds. Post-Delay Judgment and Output: After the timer finishes counting down, it checks again whether the delay protection signal is still valid. If valid, a trip command is output, such as tripping after the cold control power failure delay. If the signal has recovered, such as the cooling system recovering, the timer is reset, and no trip command is output. The non-electrical quantity delay protection logic adapts to the non-electrical quantity fault characteristics of SFC isolation transformers through an adjustable delay timer, such as cooling system faults that allow short-term load operation, avoiding false tripping caused by instantaneous signals such as poor sensor contact; at the same time, the delay setting can be adjusted on-site, improving the flexibility of the method and adapting to the operating requirements of different models of SFC isolation transformers.

[0056] To facilitate understanding of the technical solution of this invention, its working process is briefly described below:

[0057] Signal Acquisition Stage: AC Electrical Signals: CT / VT102 acquires the three-phase current and voltage of the SFC isolation transformer, converts them into digital quantities via the first AD converter 109 and the second AD converter 1010, and transmits them to the protection DSP board 101 and the start-up DSP board 104, respectively; the first ECVT103 and the second ECVT105 acquire the digital electrical signals and transmit them directly to the protection DSP board 101 and the start-up DSP board 104. Non-Electrical Signals: Signals such as high oil temperature and cold control power failure of the SFC isolation transformer are isolated by optocoupler 1011 and stabilized by pull-up resistor 1012, and then transmitted in two paths to the protection DSP board 101 (logic judgment) and the reactivation output contact (alarm).

[0058] Signal processing and logic judgment stage: The starting DSP board 104 calculates sudden change current, zero-sequence current, etc., and determines whether the starting criteria are met. If met, it outputs a drive signal to energize the coil of the starting relay 107, and its normally open contact closes to connect the positive power supply circuit of the output relay 108. At the same time, the starting DSP board 104 transmits the starting status to the protection DSP board 101 through the parallel bus, and transmits the self-test information to the main control chip 106 through the data feedback link. The protection DSP board 101 performs protection logic operations: If the electrical signal meets the protection action logic, such as differential current exceeding the limit, or if the non-electrical signal meets the direct output / delayed output conditions, such as mains gas or cold control power failure delay, it outputs a drive signal to the coil of the output relay 108.

[0059] During the tripping phase: The coil of the output relay 108 is energized by the closing of the starting relay 107 contact (positive power supply) and the drive signal from the protection DSP board 101 (coil conduction). Its normally open contact closes, and the tripping command is transmitted to the circuit breaker of the SFC isolation transformer through the switch output module 400. The circuit breaker then trips to isolate the fault. The main control chip 106 displays the fault type, action time, and current and voltage waveforms in real time through the display unit 501 of the human-machine interface module 500. Maintenance personnel can reset the signal or print a report through the command input unit 502. Simultaneously, the system uploads the fault information to the remote monitoring terminal via Ethernet, completing the fault closed-loop processing.

[0060] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An SFC isolated transformer control device, characterized by: It comprises, a protection DSP board (101) whose input end is connected with the output end of the CT / VT (102) indirectly and / or with the output end of the first ECVT (103) directly; a starting DSP board (104) whose input end is connected with the output end of the CT / VT (102) indirectly and / or with the output end of the second ECVT (105) directly, the protection DSP board (101) and the starting DSP board (104) being connected through a parallel bus; a master control chip (106) connected with the starting DSP board (104) through a data feedback link; a starting relay (107) connected with the starting DSP board (104); an exit relay (108) connected with the protection DSP board (101), and the contact of the starting relay (107) being connected in series in the positive power supply loop of the exit relay (108).

2. The SFC isolated transformer control device of claim 1, wherein: It further comprises, a first AD converter (109) whose input end is connected with the output end of the CT / VT (102) and whose output end is connected with the input end of the protection DSP board (101); a second AD converter (1010) whose input end is connected with the output end of the CT / VT (102) and whose output end is connected with the input end of the starting DSP board (104).

3. The SFC isolated transformer control device of claim 1 or 2, wherein: It further comprises, an optoelectronic coupler (1011) whose input end is connected with the non-electric quantity state signal of the transformer or the reactor and whose output end is connected with the digital quantity input pin of the protection DSP board (101) and the starting DSP board (104) simultaneously; and a pull-up resistor (1012) being arranged on the path where the optoelectronic coupler (1011) is connected with the protection DSP board (101) and the starting DSP board (104) respectively.

4. The SFC isolated transformer control device of claim 3, wherein: The coil of the starting relay (107) is connected with the positive end of the DC operating power supply, the contact of the starting relay (107) is connected in series in the positive power supply loop of the exit relay (108); the positive pole of the coil of the exit relay (108) is connected with the contact of the starting relay (107), and the negative pole of the coil of the exit relay (108) is connected with the negative end of the DC operating power supply.

5. An SFC isolated transformer control system, characterized by: It comprises, a collection module (200) receiving the non-electric quantity state signal from the transformer or the reactor and the AC electric quantity signal from the current transformer; a processing module (300) performing real-time protection operation and exit logic judgment according to the non-electric quantity state signal and the AC electric quantity signal; a switch output module (400) generating a trip instruction according to the operation result of the processing module (300) and / or the non-electric quantity state signal, wherein the trip instruction is output if the operation result meets the protection action logic and / or if the non-electric quantity state signal meets the direct exit condition.

6. The SFC isolated transformer control system of claim 5, wherein: Also comprising a human-computer interaction module (500) comprising a display unit (501) connected with the processing module (300), and an instruction input unit (502); wherein the display unit (501) is used for displaying the device running state and protection information and indicating the device running state, and the instruction input unit (502) is used for user inputting operation instructions and configuring the device.

7. A method of controlling an SFC isolated transformer, characterized by: Comprise, Receiving at least one non-electric quantity state signal and multiple alternating current quantity signals; Real-time calculation is performed on the received multiple alternating current quantity signals, and whether the preset electric quantity protection starting criterion is met is judged according to the calculation result; The non-electric quantity state signal is divided into two paths, one of which is used for logical judgment, and the other is sent to the tripping output contact; If the calculation result meets the protection action logic and / or if the non-electric quantity state signal meets the direct outlet condition, a tripping instruction is output.

8. The SFC isolated transformer control method of claim 7, wherein: Also comprising a non-full-phase protection logic, wherein the full-phase protection logic is configured to monitor the inconsistent state of the three-phase position of the circuit breaker, and the calculated zero sequence current or negative sequence current value is used as a blocking condition and for two-stage time delay tripping.

9. The SFC isolated transformer control method of claim 7 or 8, wherein: Also comprising a circuit breaker failure starting logic, wherein the circuit breaker failure starting logic is configured to start after receiving an external protection action contact signal, and the phase current, zero sequence current, negative sequence current, circuit breaker three-phase inconsistent contact or closing position contact is used as a blocking or starting condition.

10. The SFC isolated transformer control method of claim 7 or 8, wherein: Also comprising a non-electric quantity time delay protection logic, wherein the non-electric quantity time delay protection logic is configured to start a settable time delay timer for a preset specific non-electric quantity state signal, and output a tripping instruction after the timer ends.

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