CN110071481B - Digital gas protection device and method for power transformer - Google Patents
Digital gas protection device and method for power transformer Download PDFInfo
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- CN110071481B CN110071481B CN201910375867.8A CN201910375867A CN110071481B CN 110071481 B CN110071481 B CN 110071481B CN 201910375867 A CN201910375867 A CN 201910375867A CN 110071481 B CN110071481 B CN 110071481B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/40—Structural association with built-in electric component, e.g. fuse
- H01F27/402—Association of measuring or protective means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
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Abstract
A digital gas protection device and method for a power transformer comprise a transient oil flow characteristic measurement module, a switching value input module, a signal conditioning and acquisition module, a digital core module, an external communication interface module, a man-machine conversation module and a switching value output module; the transient oil flow characteristic measurement module is connected with the signal conditioning and acquisition module, and the signal conditioning and acquisition module, the switching value input module, the external communication interface module, the man-machine conversation module and the switching value output module are all connected with the digital core module. The method and the device can acquire the transient oil flow digital information in the oil conservator connecting pipe in real time, calculate to obtain the oil flow action quantity representing the oil flow surging strength, construct a protection principle and criterion by utilizing the obvious difference of the action quantity under different running conditions of the transformer, realize reliable, quick and sensitive discrimination and removal of the internal fault of the transformer oil tank, and are not influenced by the excitation surging flow.
Description
Technical Field
The invention belongs to the field of power systems, and relates to a digital gas protection device and method for a power transformer, which are used for reliably, quickly and sensitively discriminating internal faults of an oil tank of an oil-immersed power transformer.
Background
As a key electric power main device, a transformer plays a very important role in an electric power system, and the stable operation of the transformer is an important prerequisite for ensuring the reliable transmission, flexible distribution and safe use of electric energy of the whole electric power system. When the transformer has an internal fault, if the relay protection device fails or cannot act in time, the transformer body may be damaged due to internal fault pressure impact, and even explosion and fire accidents are caused; on the other hand, once the protection device malfunctions under a non-internal fault condition, economic loss due to power outage is inevitable. Especially for the high-voltage level and large-capacity junction transformer, because the junction transformer has high manufacturing cost, complex structure and a large amount of loads, the safe and stable operation of the power system is seriously influenced no matter the protection is failed or is mistakenly operated. Therefore, it is very important to research and search transformer protection with high reliability, fast operation speed and high sensitivity.
The transformer internal fault process is accompanied by three main features: increased phase current, increased differential current, and the generation of fault gases. For the three remarkable features, relay protection workers design over-current protection, differential protection, non-electric quantity protection and the like. The non-electric quantity characteristics such as oil flow, temperature and pressure in the transformer change along with the fault gas in the fault gas generation process, and the fault electric energy is converted into energy in other forms such as internal energy, kinetic energy and potential energy. For weak faults in the transformer, due to the fact that fault power is small, the weak faults are difficult to sensitively discriminate only by means of electric quantity protection. However, due to the accumulation of fault energy for a period of time, the inside of the transformer oil tank has obvious non-electric characteristic changes such as oil flow surge, temperature rise, pressure increase and the like. Therefore, constructing transformer protection with non-electrical characteristics tends to have higher sensitivity than electrical protection. Further, as an important component in an electric power system, a power transformer is an expensive device in which a plurality of components such as a winding, an iron core, insulation, an oil tank, a switch, and a cooler are integrated. The failure mode is often expressed as overheating failure of each component: such as overheating between iron core silicon steel sheets, burning of windings, melting or burning of tap changer contacts; or a mechanical failure: loose iron core structure, mechanical deformation or collapse of winding, cracking of transformer oil tank, oil leakage and the like. When a non-electric network fault is faced, the electric quantity protection is difficult to reliably discriminate, and the non-electric quantity protection based on characteristics such as flow velocity, temperature, pressure and the like can more comprehensively and directly reflect the fault state of the transformer.
Therefore, as early as 1921, german transformer experts Max Buchholz invented a gas relay, and the gas relay was installed on a connecting pipe between a main oil tank and an oil conservator of a transformer, and the gas relay is mainly suitable for a large oil-immersed transformer with the oil conservator and no gas space at the top of the oil tank, so as to protect various internal faults outside an electrical quantity protection sensitive area and make up for the defects of electrical quantity protection. The gas protection device based on the generation of the fault gas inside the transformer widens the existing thought of relay protection research, and is widely applied to oil-immersed power transformers by virtue of the advantage of sensitivity. The regulations "relay protection and automation design specifications for electric power equipment" specify: the oil immersed transformer with the capacity of 0.4MVA and above in the workshop, the oil immersed transformer with the capacity of 0.8MVA and above and the oil-filled voltage regulating switch of the loaded voltage regulating transformer are provided with gas protection, and when a fault in a shell generates slight gas or the oil level drops, the oil immersed transformer and the oil-filled voltage regulating switch instantaneously act on signals; when a large amount of gas is generated, it should act to open the circuit breakers on each side of the transformer.
At present, the widely used Buchholz relay still continues to use the basic principle and mechanical structure of the Buchholz relay hundreds of years ago, but with the high-speed development of the power system for decades, the existing mechanical Buchholz protection is more and more difficult to meet the higher requirement of the high-capacity and high-voltage-level power transformer on the protection performance. The recent frequent transformer explosion, fire accident or false tripping accident caused by external short circuit fault shows that the traditional mechanical gas protection mainly has the problems of principle defect, threshold value obtained by experience, low mechanical structure action performance and the like, and the protection performance of the traditional mechanical gas protection is more and more difficult to meet the higher requirements of the current high-capacity and high-voltage level power transformer. Traditional mechanical type gas protection utilizes mechanical structure response gas production such as floater, spring, baffle and flows with oil stream and rush, mainly exists two aspects problem: firstly, the spring mechanism can only reflect the flow rate of oil flow, a trip signal is sent once the flow rate of the oil flow exceeds a preset threshold, and the characteristic information of oil flow surging change is not measured and analyzed, so that the protection reliability is low; secondly, the mechanical structure is soaked in the insulating oil for a long time, and oil sludge generated by falling of oxides and degradation of the insulating oil is attached to mechanical components such as a relay baffle, a floater or a spring, so that the accuracy and the sensitivity of the action of the mechanical structure are seriously influenced. Therefore, there is a need to develop a digital gas protection device that improves the mechanical gas protection based on experience and feeling to a new stage of quantitative analysis, high-reliability determination, and digital implementation.
Disclosure of Invention
The invention aims to provide a digital gas protection device and method for a power transformer, which can reliably, quickly and sensitively discriminate internal faults of an oil tank of the oil-immersed power transformer.
In order to achieve the purpose, the invention adopts the following technical scheme:
a digital gas protection device for a power transformer comprises: the device comprises a transient oil flow characteristic measurement module, a switching value input module, a signal conditioning and acquisition module and a digital core module; the device comprises a digital core module, a transient oil flow characteristic measurement module, a signal conditioning and acquisition module, a switching value input module and a signal conditioning and acquisition module, wherein the transient oil flow characteristic measurement module is connected with the signal conditioning and acquisition module;
the transient oil flow characteristic measurement module is used for measuring transient oil flow change characteristics inside the transformer oil conservator connecting pipe at a high speed in real time and outputting a corresponding analog voltage/current signal; the transient oil flow characteristic measurement module consists of an outer bundle type high-frequency ultrasonic flowmeter, a flowmeter transmitter and a communication cable;
the signal conditioning and acquisition module is used for receiving the analog voltage/current signal output by the transient oil flow characteristic measurement module, converting the analog voltage/current signal into a standard digital signal which can be identified by the digital core module, and outputting the standard digital signal;
the switching value input module is used for acquiring relevant switching value signals needing to be known, outputting the relevant switching value signals as high level 1 or low level 0, and using the high level 1 or the low level 0 as input digital values of the digital core module;
and the digital core module is used for executing protection operation after receiving the input digital quantity and the standard digital signal, finishing a digital signal processing task and further realizing a relay protection function.
The invention is further improved in that the external-binding type high-frequency ultrasonic flowmeter is arranged on the transformer conservator connecting pipe, the external-binding type high-frequency ultrasonic flowmeter is connected with the flowmeter transmitter, and the flowmeter transmitter is connected with the communication cable.
The invention has the further improvement that the measuring frequency of the external-binding type high-frequency ultrasonic flowmeter is more than 100Hz, the measuring error is less than 1%, the working temperature is-30-80 ℃, and the flow speed range is-20 m/s.
The invention has the further improvement that the signal conditioning and collecting module consists of a wiring terminal, a signal conditioning circuit, a low-pass filter, a signal sampling circuit and an analog-digital A/D conversion circuit; the wiring terminal is connected with the signal conditioning circuit, the signal conditioning circuit is connected with the low-pass filter, the low-pass filter is connected with the signal sampling circuit, the signal sampling circuit is connected with the analog-to-digital A/D conversion circuit, and the analog-to-digital A/D conversion circuit is connected with the digital core module; the wiring terminal is also connected with a communication cable.
The invention has the further improvement that the digital core module consists of a bus, a central processing unit, a timer/counter, a random access memory, a read-only memory and a control circuit; the bus comprises a data bus, an address bus and a control bus, and realizes data exchange and operation control; the central processing unit realizes digital signal processing by utilizing a single chip microprocessor, a general microprocessor or a digital signal processor; the timer/counter is used for providing a timing sampling trigger signal, forming interruption and protecting delayed action timing; the random access memory is used for temporarily storing temporary data, including data information input by the signal conditioning and acquisition module and intermediate results in the calculation processing process; the read-only memory is used for storing data; the control circuit realizes the connection and coordination work of the whole digital circuit through a complex programmable logic device or a field programmable gate array.
The invention has the further improvement that the invention also comprises an external communication interface module, a man-machine conversation module and a switching value output module which are connected with the digital core module;
the external communication interface module is used for providing an information channel with a computer communication network and a remote communication network;
the man-machine conversation module is used for establishing information relation between the digital protection device and a user;
and the switching value output module is used for controlling the on or off of the trip circuit through the output 0 or 1 state.
The invention is further improved in that the man-machine conversation module comprises a compact keyboard, a display screen, an indicator light, a button, a printer interface and a debugging communication interface; the switching value output module consists of a photoelectric isolation device and an outlet relay, and the photoelectric isolation device is connected with the outlet relay.
A protection method based on the digital gas protection device of the power transformer comprises the following steps:
firstly, a transient oil flow characteristic measurement module measures transient oil flow change characteristics in a transformer oil conservator connecting pipe in real time and outputs a corresponding analog voltage/current signal; the signal conditioning and acquisition module receives the analog voltage/current signal output by the transient oil flow characteristic measurement module, converts the analog voltage/current signal into a standard digital signal which can be identified by the digital core module, and outputs the standard digital signal; after the digital core module receives the input digital quantity and the standard digital signal, temporarily locking the protection function, waiting for the data of one to two cycles stored in the sampling data buffer area, and then opening the protection function;
② comparing the oil flow velocity v at the current time tms(t) and a starting threshold vstDetermining whether the digital gas protection is started or not by judging whether the formula (1) is established or not, setting a starting mark if the formula (1) is established, and entering the step (c);
vms(t)-vst≥0 (1)
calculating the oil flow motion v at the current time t by using the formula (2)op(t) comparing the oil flow operating quantity vop(t) and a protection threshold value vthThe amplitude value relationship between the two components, namely whether the formula (3) is established or not is judged to discriminate the internal fault of the transformer oil tank; if the formula (3) is established, a tripping signal is sent out, the whole set of protection is reset, and manual reset is waited;
in the formula (2), T is the length of a data window, and f is the signal sampling frequency of an acquisition module;
vop(t)/kre≥vth (3)
in the formula (3), kreTo protect the reliability factor; v. ofthIs a digital gas protection threshold value.
A further development of the invention is that in formula (1) the start threshold v isstIs 0.2 to 0.4 m/s.
A further development of the invention is that in formula (3), the protection reliability factor kreIs 1.2.
Compared with the prior art, the invention has the following beneficial effects:
the invention realizes digital real-time measurement of oil flow in the oil conservator connecting pipe by using the external-clamping high-frequency ultrasonic flowmeter on the premise of not damaging the existing structural integrity of the transformer. Compared with the traditional mechanical gas relay in which the spring structure is soaked in insulating oil for a long time, the ultrasonic flowmeter is not directly contacted with the insulating oil, so that on one hand, the loss of flow velocity and kinetic energy cannot be caused by an indirect measurement mode; on the other hand, the oil sludge generated by the falling of the oxide and the degradation of the insulating oil can not be attached to the measuring device, so that the device has higher flow rate measuring precision, induction sensitivity, long-term operation reliability and stability. The invention overcomes the problems that in the prior art, although tens of thousands of oil-immersed transformers are successfully protected by the traditional mechanical non-electric quantity protection in the using process of nearly one hundred years, the higher requirements of the current high-capacity and high-voltage-level power transformers are more and more difficult to meet due to the problems of difficult theoretical modeling, principle defects, threshold value acquisition by experience, insufficient mechanical structure action performance and the like. Meanwhile, system power failure and transformer explosion accidents caused by protection failure and misoperation accidents occur, so that the safe and reliable operation of a power system is seriously influenced, and the safety of transformer substation operators and the lives and properties of people around the transformer substation is seriously threatened.
According to the invention, the oil flow inside the oil conservator connecting pipe is measured in real time by the high-frequency ultrasonic flowmeter on the premise of not damaging the existing structural integrity of the transformer. The protection device is independent of a power network, the measurement of oil flow characteristics and signal transmission are less interfered, and harmonic waves are not injected into a power system; the data acquisition element and the oil flow operation analysis element can completely meet the requirements of rapidly and real-timely processing multi-channel and high-frequency data.
Furthermore, the flow meter with the measuring frequency of more than 100Hz, the measuring error of less than 1 percent, the working temperature of minus 30-80 ℃ and the flow rate range of minus 20-20 m/s is adopted for measurement, the external-bundling high-frequency ultrasonic flow meter can realize the real-time measurement of the flow rate of the oil flow on the premise of not damaging the structural integrity of the transformer conservator connecting pipe, and meanwhile, the high-frequency ultrasonic flow meter in both precision and use range can meet the requirements of the power transformer body on high-temperature and strong electromagnetic environment.
The invention designs a digital gas protection device comprising a transient oil flow characteristic quantity measuring module, a switching value input module, a signal conditioning and acquisition module and a digital core module, controls a hardware system according to a protection principle and functional requirements, has the functions of monitoring, fault processing, man-machine conversation, communication, self-checking, accident recording and analysis reporting and debugging of the protection device, and realizes quick, sensitive and reliable discrimination of internal faults of a transformer oil tank by utilizing transient change information of oil flow in an oil conservator connecting pipe and flow rate difference under different operating conditions without being influenced by excitation surge flow. The invention has simple principle and easy realization of the device, improves the mechanical gas protection formed by experience and feeling to the new stage of quantitative analysis, high reliability judgment and digital realization on the premise of not damaging the existing structural integrity of the transformer, thereby being suitable for the requirements of the current and future high-capacity and high-voltage level power transformers on the four properties of the gas protection. The invention overcomes the problems that the traditional gas relay can only sense the flow velocity through a mechanical spring device and can only output switching value information, and the single flow velocity amplitude cannot correctly distinguish the faults inside and outside the transformer area, thereby causing protection misoperation or failure operation.
Drawings
FIG. 1 is a schematic diagram of the system architecture of the present invention.
FIG. 2 is a flow chart of the present invention.
Fig. 3 shows the field test verification result of the digital gas protection device of the power transformer.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
The high-frequency ultrasonic flowmeter of the external bundle type is also called an external clamp type high-frequency ultrasonic flowmeter in the invention.
Referring to fig. 1, a digital gas protection device for a power transformer includes: the device comprises a transient oil flow characteristic measurement module, a switching value input module, a signal conditioning and acquisition module, a digital core module, an external communication interface module, a man-machine conversation module and a switching value output module. The system comprises a transient oil flow characteristic measurement module, a signal conditioning and acquisition module, a switching value input module, an external communication interface module, a man-machine conversation module and a switching value output module, wherein the transient oil flow characteristic measurement module is connected with the signal conditioning and acquisition module;
the transient oil flow characteristic measurement module is used for measuring transient oil flow change characteristics inside the transformer oil conservator connecting pipe at a high speed in real time and outputting a corresponding analog voltage/current signal;
the transient oil flow characteristic measurement module is composed of an outer-bundling high-frequency ultrasonic flowmeter, a flowmeter transmitter and a communication cable, wherein the outer-bundling high-frequency ultrasonic flowmeter is installed on the transformer oil conservator connecting pipe and is connected with the flowmeter transmitter, and the flowmeter transmitter is connected with the communication cable. The transient oil flow change characteristics in the transformer conservator connecting pipe are measured in real time at high speed by using the external-binding type high-frequency ultrasonic flowmeter, and analog voltage/current signals corresponding to the transient oil flow change characteristics are output by using a flowmeter transmitter and a communication cable. In order to ensure the reliability, the quick action performance and the sensitivity of the protection device, the measurement frequency of the high-frequency ultrasonic flowmeter needs to be higher than 100Hz, the measurement error needs to be less than 1 percent, the working temperature needs to reach minus 30 to 80 ℃, and the flow speed range needs to reach minus 20 to 20 m/s.
The switching value input module collects relevant switching value signals needing to be known, outputs the relevant switching value signals to be high level '1' or low level '0' through the photoelectric isolation device, and uses the high level '1' or the low level '0' as input digital values of the digital core module.
The signal conditioning and collecting module consists of a wiring terminal, a signal conditioning circuit, a low-pass filter, a signal sampling circuit and an analog-to-digital (A/D) conversion circuit. The wiring terminal is connected with the signal conditioning circuit, the signal conditioning circuit is connected with the low-pass filter, the low-pass filter is connected with the signal sampling circuit, the signal sampling circuit is connected with an analog-to-digital (A/D) conversion circuit, and the A/D conversion circuit is connected with the digital core module; the wiring terminal is also connected with a communication cable. The signal conditioning and acquisition module is used for receiving the analog voltage/current signal output by the transient oil flow characteristic measurement module, converting the analog voltage/current signal into a standard digital signal which can be identified by the digital core module, and outputting the standard digital signal.
The digital core module is composed of a bus, a Central Processing Unit (CPU), a timer/counter, a Random Access Memory (RAM), a read-only memory (ROM) and a control circuit. The bus comprises a data bus, an address bus and a control bus, and realizes data exchange, operation control and the like. The Central Processing Unit (CPU) is a command center of the digital core module, and can rapidly realize digital signal processing in real time by utilizing devices such as a single chip microprocessor, a general microprocessor, a Digital Signal Processor (DSP) and the like. The timer/counter is used for providing functions of timing sampling trigger signals, forming interrupts, protecting accurate timing of delayed actions and the like. The Random Access Memory (RAM) is used for temporarily storing a large amount of temporary data needing to be quickly exchanged, including data information input by the signal conditioning and acquisition module, intermediate results in the calculation processing process and the like. A Read Only Memory (ROM) for storing data; the control circuit can realize the effective connection and coordination work of the whole digital circuit through a Complex Programmable Logic Device (CPLD) or a Field Programmable Gate Array (FPGA) and the like.
The digital core module is used for receiving the input digital quantity and the standard digital signal and then executing protection operation to complete a digital signal processing task, commanding the normal operation of the connected modules, realizing data exchange and operation control and further realizing a relay protection function.
The external communication interface module consists of a computer network communication interface and a special communication interface with a protection function, is used for providing an information channel with a computer communication network and a remote communication network, and realizes the functions of information interaction, data sharing, remote operation, remote maintenance and the like.
The man-machine conversation module comprises a compact keyboard, a display screen, an indicator light, a printer interface, a debugging communication interface and the like. The digital protection device is used for establishing information connection between the digital protection device and a user so as to facilitate manual operation and debugging of the protection device by an operator, information feedback and the like.
The switching value output module consists of a photoelectric isolation device and an outlet relay, and the 'on' or 'off' of a trip circuit is controlled and executed through the output '0' or '1' state, so that the reliable action of protection is realized.
Referring to fig. 2, based on the protection method of the protection device, the monitoring device is controlled according to the protection principle and the function requirement, and various operations such as data acquisition, external communication, digital operation, logic judgment, and action instruction execution are sequentially completed, and the specific steps are as follows:
firstly, after a power supply is switched on (power-on for short) or hardware is reset (reset for short), the protection device executes system initialization to enable the device to be in a normal working state.
Secondly, performing comprehensive self-checking after power-on, detecting the correctness and integrity of the working state of the device, sending an alarm signal and locking the whole device if the device is found to be defective, and waiting for technical personnel to remove the fault and manually reset.
If the data acquisition initialization is carried out through self-checking, and the timing sampling interruption is started to carry out address allocation on the buffer area for circularly storing the sampling data, a dynamic address pointer for marking the current latest data is set, then an interruption timer for controlling the circular sampling is assigned and started according to the sampling period, and the sampling interruption is opened;
the transient oil flow characteristic measuring module measures the transient oil flow change characteristics in the transformer oil conservator connecting pipe at high speed in real time and outputs corresponding analog voltage/current signals; the signal conditioning and acquisition module receives the analog voltage/current signal output by the transient oil flow characteristic measurement module, converts the analog voltage/current signal into a standard digital signal which can be identified by the digital core module, and outputs the standard digital signal; after the digital core module receives the input digital quantity and the standard digital signal, the protection function is locked temporarily, enough data (data of one to two cycles) are stored in the sampling data buffer area, and then the protection function is opened;
initializing the whole group, carrying out operation self-checking, detecting the device in an operation state, sending an alarm signal and locking the whole device if the device is found to be defective, and waiting for the technical staff to remove the fault and manually reset.
If no fault occurs, executing communication task processing and preparing data for information sending and receiving.
And seventhly, executing man-machine conversation processing, performing tasks such as scanning a keyboard, controlling buttons, displaying data on a display screen and the like, interpreting and classifying various operation commands, and delivering corresponding task processing according to task types.
And determining whether the protection device is in a working operation mode. If the operation mode is not the working operation mode, debugging task processing is carried out, and the step (v) is returned after the debugging task is finished; and if the operation mode is in the working operation mode, entering the step ninthly.
Ninthly, judging whether the starting mark is set, if so, indicating that the protection device has detected possible accident disturbance, and entering the step
(ii) a Otherwise proceed to step r.
R comparing current t time oil flow velocity vms(t) and a starting threshold vstDetermining whether the digital gas protection is started or not by judging whether the formula (1) is established or not, and returning to the fifth step if the formula (1) is not established; if the formula (1) is established, setting the starting flag, and entering the step
。
vms(t)-vst≥0 (1)
In the formula (1), the starting threshold vstCan be selected within the flow velocity range of 0.2-0.4 m/s according to the pipe diameter size of the conservator connecting pipe.
In the formula (2), T is a data window length. f is the signal sampling frequency of the acquisition module.
vop(t)/kre≥vth (3)
In the formula (3), kreTo protect the reliability factor, 1.2 is usually taken. v. ofthThe numerical gas protection threshold value can be selected according to the pipe diameter size of the oil conservator connecting pipe and by referring to the national or industrial standard of heavy gas protection of the mechanical gas relay.
The device comprises a transient oil flow characteristic quantity measuring module, a switching value input module, a signal conditioning and collecting module, a digital core module, an external communication interface module, a man-machine conversation module and a switching value output module. And controlling the protection device according to the protection principle and the function requirement, and realizing the functions of system monitoring, fault processing, man-machine conversation, communication, self-checking, accident recording and analysis reporting and debugging of the protection device.
According to the invention, the oil flow in the oil conservator connecting pipe is measured in real time by the external-clamping type high-frequency ultrasonic flowmeter on the premise of not damaging the existing structural integrity of the transformer. The external-clamping type high-frequency ultrasonic flowmeter is independent of a power network, the measurement of oil flow characteristics and signal transmission are less interfered, and harmonic waves are not injected into a power system; the data acquisition element and the oil flow operation analysis element can completely meet the requirements of rapidly and real-timely processing multi-channel and high-frequency data. Furthermore, the invention adopts the external-bundling high-frequency ultrasonic flowmeter with the measuring frequency of more than 100Hz, the measuring error of less than 1 percent, the working temperature of-30 to 80 ℃ and the flow rate range of-20 to 20m/s, and the external-bundling high-frequency ultrasonic flowmeter can meet the requirements of high-temperature, greasy dirt and strong electromagnetic environment in the power transformer no matter from the precision or the use range.
The invention discriminates the internal fault of the transformer oil tank by utilizing the transient change characteristic of oil flow in the oil conservator connecting pipe and the flow rate difference under different operating conditions, improves the mechanical gas protection formed by experience and feeling in the past to a new stage of quantitative analysis, high reliability judgment and digital realization, thereby being suitable for the requirements of the current and future high-capacity and high-voltage grade power transformers on the four properties of gas protection, and having no relevant research, report and product at home and abroad.
The SFSZ8-40000/110 three-phase three-winding transformer is used as a test platform for field test to illustrate the effect of the invention, and the main geometric structure and the nameplate parameters of the transformer are shown in Table 1. As shown in FIG. 3, when the transformer is in normal operation (t < 0ms), the oil flow inside the transformer conservator connecting pipe does not change significantly, and the instantaneous flow rate v measured by the device at the momentmsLess than starting threshold vstThe protection device is not started. When the transformer bursts the internal arc at the time when t is 0ms, the internal arc is not generatedAnd the fault gas is generated due to the injection of fault energy, so that the insulating oil inside the oil conservator connecting pipe flows directionally. When t is 64.27ms, the oil flow action quantity v obtained by the measurement and calculation of the device of the inventionopGreater than a protection preset action threshold value vthAt the moment, the protection device judges that the inside of the transformer has a fault and sends a tripping signal to cut off the fault transformer. The field test result shows that: the device can capture the sudden change characteristics of the oil flow in the oil conservator connecting pipe of the oil immersed power transformer in a very short time, obtains the oil flow action quantity capable of representing the surge intensity of the oil flow in the transformer through calculation, correctly discriminates the arc fault in the transformer according to comparison with the preset protection criterion, and reliably, sensitively and quickly removes the fault.
TABLE 1 SFSZ8-40000/110 Transformer principal geometry and nameplate parameters
While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. The utility model provides a digital gas protection device of power transformer which characterized in that includes: the device comprises a transient oil flow characteristic measurement module, a switching value input module, a signal conditioning and acquisition module and a digital core module; the device comprises a digital core module, a transient oil flow characteristic measurement module, a signal conditioning and acquisition module, a switching value input module and a signal conditioning and acquisition module, wherein the transient oil flow characteristic measurement module is connected with the signal conditioning and acquisition module;
the transient oil flow characteristic measurement module is used for measuring transient oil flow change characteristics inside the transformer oil conservator connecting pipe at a high speed in real time and outputting a corresponding analog voltage/current signal; the transient oil flow characteristic measurement module consists of an outer bundle type high-frequency ultrasonic flowmeter, a flowmeter transmitter and a communication cable;
the signal conditioning and acquisition module is used for receiving the analog voltage/current signal output by the transient oil flow characteristic measurement module, converting the analog voltage/current signal into a standard digital signal which can be identified by the digital core module, and outputting the standard digital signal;
the switching value input module is used for acquiring relevant switching value signals needing to be known, outputting the relevant switching value signals as high level 1 or low level 0, and using the high level 1 or the low level 0 as input digital values of the digital core module;
the digital core module is used for executing protection operation after receiving the input digital quantity and the standard digital signal, finishing a digital signal processing task and further realizing a relay protection function;
the external-binding type high-frequency ultrasonic flowmeter is arranged on the transformer conservator connecting pipe and is connected with the flowmeter transmitter, and the flowmeter transmitter is connected with the communication cable;
the system also comprises an external communication interface module, a man-machine conversation module and a switching value output module which are connected with the digital core module;
the external communication interface module is used for providing an information channel with a computer communication network and a remote communication network;
the man-machine conversation module is used for establishing information relation between the digital protection device and a user;
the switching value output module is used for controlling the on or off of the trip circuit through the output 0 or 1 state;
the protection device executes the following protection method, including the steps of:
firstly, a transient oil flow characteristic measurement module measures transient oil flow change characteristics in a transformer oil conservator connecting pipe in real time and outputs a corresponding analog voltage/current signal; the signal conditioning and acquisition module receives the analog voltage/current signal output by the transient oil flow characteristic measurement module, converts the analog voltage/current signal into a standard digital signal which can be identified by the digital core module, and outputs the standard digital signal; after the digital core module receives the input digital quantity and the standard digital signal, temporarily locking the protection function, waiting for the data of one to two cycles stored in the sampling data buffer area, and then opening the protection function;
② comparing the oil flow velocity v at the current time tms(t) and a starting threshold vstDetermining whether the digital gas protection is started or not by judging whether the formula (1) is established or not, setting a starting mark if the formula (1) is established, and entering the step (c);
vms(t)-vst≥0 (1)
calculating the oil flow motion v at the current time t by using the formula (2)op(t) comparing the oil flow operating quantity vop(t) and a protection threshold value vthThe amplitude value relationship between the two components, namely whether the formula (3) is established or not is judged to discriminate the internal fault of the transformer oil tank; if the formula (3) is established, a tripping signal is sent out, the whole set of protection is reset, and manual reset is waited;
in the formula (2), T is the length of a data window, and f is the signal sampling frequency of an acquisition module;
vop(t)/kre≥vth (3)
in the formula (3), kreTo protect the reliability factor; v. ofthIs a digital gas protection threshold value.
2. The digital gas protection device for the power transformer as claimed in claim 1, wherein the measurement frequency of the outer bundle type high frequency ultrasonic flowmeter is more than 100Hz, the measurement error is less than 1%, the working temperature is-30 to 80 ℃, and the flow speed range is-20 to 20 m/s.
3. The digital gas protection device of the power transformer as claimed in claim 1, wherein the signal conditioning and collecting module is composed of a wiring terminal, a signal conditioning circuit, a low pass filter, a signal sampling circuit and an analog-to-digital A/D conversion circuit; the wiring terminal is connected with the signal conditioning circuit, the signal conditioning circuit is connected with the low-pass filter, the low-pass filter is connected with the signal sampling circuit, the signal sampling circuit is connected with the analog-to-digital A/D conversion circuit, and the analog-to-digital A/D conversion circuit is connected with the digital core module; the wiring terminal is also connected with a communication cable.
4. The digital gas protection device of the power transformer of claim 1, wherein the digital core module is composed of a bus, a central processing unit, a timer/counter, a random access memory, a read only memory and a control circuit; the bus comprises a data bus, an address bus and a control bus, and realizes data exchange and operation control; the central processing unit realizes digital signal processing by utilizing a single chip microprocessor, a general microprocessor or a digital signal processor; the timer/counter is used for providing a timing sampling trigger signal, forming interruption and protecting delayed action timing; the random access memory is used for temporarily storing temporary data, including data information input by the signal conditioning and acquisition module and intermediate results in the calculation processing process; the read-only memory is used for storing data; the control circuit realizes the connection and coordination work of the whole digital circuit through a complex programmable logic device or a field programmable gate array.
5. The digital gas protection device for the power transformer as claimed in claim 4, wherein the man-machine conversation module comprises a compact keyboard, a display screen, an indicator light, a button, a printer interface and a debugging communication interface; the switching value output module consists of a photoelectric isolation device and an outlet relay, and the photoelectric isolation device is connected with the outlet relay.
6. A digital gas protection device for power transformer as claimed in claim 1, wherein in formula (1), the start threshold v is setstIs 0.2 to 0.4 m/s.
7. The digital gas protection device for power transformer of claim 1, wherein in formula (3), the protection reliability coefficient k isreIs 1.2.
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| CN110086257B (en) * | 2019-05-07 | 2020-10-27 | 西安交通大学 | Digital gas protection and oil flow surge monitoring integrated device and method for transformer |
| CN112928741B (en) * | 2021-02-08 | 2022-12-02 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Heavy gas protection locking method for tapping switch based on oil pressure fluctuation of converter transformer |
| CN113078615B (en) * | 2021-02-25 | 2022-11-22 | 国电南瑞科技股份有限公司 | Active protection method and device for large power transformer |
| CN114661014B (en) * | 2022-04-27 | 2023-07-25 | 西安热工研究院有限公司 | Switching value control method and system |
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