CN102780212B - Single-phase grounding traveling-wave protection device for distribution line - Google Patents
Single-phase grounding traveling-wave protection device for distribution line Download PDFInfo
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Abstract
The invention provides a single-phase grounding traveling-wave protection device for a distribution line, which comprises at least one convertor inserted on a circuit substrate, a protector, a monitor and an outlet relay, wherein the convertor is used for traveling-wave signal input and power frequency signal input, and a zero-mode current traveling-wave signal, a zero-mode voltage traveling-wave signal, a power frequency current signal and a power frequency voltage signal can be obtained; the protector comprises a traveling-wave module and a power frequency module; the traveling-wave module can obtain a zero-mode current traveling wave and a zero-mode voltage traveling wave under the line frequency range of 0-100KHz; meanwhile, according to the polarity of the zero-mode current traveling wave and the zero-mode voltage traveling wave, a protection criterion is formed; the power frequency module can be used for obtaining three-phase current and zero-sequence voltage for protecting a traveling-wave module from erroneous judgement; meanwhile, the device is locked when interphase faults are caused; and the outlet relay can give a tripping signal or an alarm signal according to the requirement. According to the technical scheme disclosed by the invention, when a neutral point non-effective grounding system of the distribution line is subjected to single-phase grounding faults, the faults can be quickly and accurately detected, and reliable protection action can be performed.
Description
Technical Field
The invention relates to the protection and control technology of an electric power system, in particular to a single-phase grounding traveling wave protection device for a distribution line.
Background
After a single-phase grounding fault occurs on a distribution line of a neutral point non-effective grounding system, a circuit can be formed only through a ground capacitor, and the fault current is very small. Overcurrent protection, distance protection and the like based on traditional power frequency electric quantity cannot reliably act under the fault condition. The single-phase grounding traveling wave protection does not reflect the steady-state process of the fault, and after the single-phase grounding fault occurs, the polarity relation of the voltage traveling wave and the current traveling wave is reliably established in any neutral point grounding system, so that the single-phase grounding traveling wave protection can be an effective means for solving the problem. The implementation of the protection device also becomes a key to solving this problem.
The development of the traveling wave protection device is always concerned by scholars at home and abroad. As early as the 70's of the last century, the first traveling wave direction protection device (RALDA type traveling wave protection) was successfully developed abroad. In China, two sets of RALDA type protections are introduced from Sweden in the early 80 s and are respectively installed on Jinliao lines and Pingwu lines. In practice, the sampling rate of the RALDA type protection is only 10KHz, which cannot effectively acquire the traveling wave signal, and at the same time, a mathematical means for effectively processing the signal is lacked, and finally the RALDA type protection ends up failing. The development of the traveling wave protection device then falls into a valley. Because the traveling wave protection needs to acquire the high-frequency traveling wave after the fault, the protection device needs to have a high-speed data acquisition function; meanwhile, a hardware circuit should have strong anti-interference performance. In addition, in the case of a high sampling rate, the amount of data is large, and therefore, the apparatus is also required to have a strong digital signal processing function. With the development of modern technology, the comprehensive utilization of a high-speed Digital Signal Processor (DSP) and a Complex Programmable Logic Device (CPLD) is generally considered as an effective means for realizing the acquisition and processing of traveling wave signals on hardware.
In addition, in order to solve the problem of low traveling wave protection reliability, the device needs to have a power frequency signal acquisition and processing function, so that when the traveling wave protection module is started by mistake, locking is performed through power frequency voltage, and meanwhile, a single-phase earth fault and a two-phase earth fault are distinguished through power frequency current.
Therefore, there is a need for a single-phase grounding traveling wave protection device suitable for distribution lines, which can simultaneously acquire and process traveling wave signals and power frequency signals, and simultaneously reliably operate when a single-phase grounding fault occurs in a line, and reliably lock when other types of faults or other line faults occur in the same bus. Therefore, the defect that the traditional protection device is insensitive or ineffective due to the fact that the single-phase earth fault phenomenon of a neutral point non-effective earth system is not obvious is overcome, and the sensitivity and the reliability of single-phase earth fault detection are improved.
Disclosure of Invention
The invention provides a single-phase grounding protection device for a distribution line, which is based on the problems and can simultaneously acquire and process traveling wave signals and power frequency signals, accurately and quickly detect faults when a single-phase grounding fault occurs in a neutral point non-effective grounding system, and make responsive protection actions.
In view of the above, the present invention provides a single-phase grounding traveling wave protection device for a distribution line, comprising at least one converter, a protector, a monitor and an outlet relay inserted on a circuit substrate; the converter converts the current signal and the voltage signal from the loop to be tested into a secondary side current signal and a secondary side voltage signal; the converter comprises traveling wave signal input and power frequency signal input, and can obtain a zero-mode current traveling wave signal, a zero-mode voltage traveling wave signal, a power frequency current signal and a power frequency voltage signal; the protector receives the secondary side current and the secondary side voltage signals obtained by conversion from the converter, processes the signals, executes a protection algorithm, further judges whether the circuit to be tested has a single-phase earth fault, and outputs the result to the monitor and the outlet relay if the circuit to be tested has the fault; the monitor is connected to the protector, displays and stores fault information transmitted by the protector, displays and transmits a fixed value set by a user to the protector, and detects the running state of the protector; the outlet relay is connected to the protector, receives the judgment result of the traveling wave protector, and determines whether to send a tripping command or an alarm command according to the judgment result.
In the above scheme, preferably, the protector includes a traveling wave module and a power frequency module; the traveling wave module is used for acquiring and processing traveling wave signals, and the power frequency module is used for acquiring and processing power frequency signals.
In the above scheme, preferably, the traveling wave module includes a traveling wave data acquisition loop, a traveling wave start loop, and a traveling wave signal processing loop; the traveling wave data acquisition loop can acquire zero-mode current waves with the frequency range of 0-100 kHz and zero-mode voltage traveling waves with the frequency range of 0-100 kHz in the loop to be detected in real time at the sampling rate of 200 KHz; the traveling wave data acquisition loop comprises a second-order active low-pass filtering module, a multi-path conversion switch module, an A/D conversion module and a double-port RAM module; the second-order active low-pass filtering module is used for filtering a secondary side current signal and a secondary side voltage signal, wherein the passband range of the second-order active low-pass filtering module is 0-100 KHz, and the secondary side current signal and the secondary side voltage signal comprise a zero-mode current traveling wave signal and a zero-mode voltage traveling wave signal; the multi-channel conversion switch module is connected to the second-order active low-pass filtering module and is used for sequentially outputting the zero-mode current traveling wave signal and the zero-mode voltage traveling wave signal to the A/D conversion module; the A/D conversion module is connected to the multi-channel conversion switch module, carries out A/D conversion on the traveling wave analog signal, the A/D conversion rate of each channel of signal is 200KHz, obtains a zero-mode current wave signal and a digital signal of a zero-mode voltage traveling wave signal after A/D conversion, and transmits the conversion result to the double-port RAM module; the double-port RAM module is provided with two groups of data buses and two groups of address buses and is used for storing digital signal conversion results of the zero-mode electric prevailing wave signal and the zero-mode voltage traveling wave signal from the A/D conversion module and reading the digital signal conversion results of the zero-mode electric prevailing wave signal and the zero-mode voltage traveling wave signal by the traveling wave signal processing circuit; the traveling wave starting loop comprises a second-order active band-pass filtering module and a voltage comparison module; the passband range of the second-order active band-pass filtering module is 500 Hz-3 KHz, and the component of 500 Hz-3 KHz in the zero-mode electric current wave signal can be obtained as a signal for starting judgment; the voltage comparison module is connected to the second-order active low-pass filtering module, receives the signal for starting judgment from the second-order active low-pass filtering module, determines whether the amplitude of the signal for starting judgment is higher than a first preset amplitude, and sends a starting signal to the traveling wave signal processing loop when the amplitude of the signal for starting judgment is higher than the first preset amplitude; the traveling wave signal processing loop comprises a data acquisition module, a wavelet transformation module, a fault judgment module and a power frequency communication module; the data acquisition module receives a starting signal from the voltage comparison module and reads digital signals of a zero-mode current wave signal and a zero-mode voltage traveling wave signal from the dual-port RAM; the wavelet transformation module is used for performing wavelet transformation on the zero-mode prevailing wave digital signal and the zero-mode voltage traveling wave digital signal acquired by the data acquisition module to obtain a modulus maximum value and the polarity of the modulus maximum value of the wavelet transformation, and obtaining the wave head polarity of the zero-mode prevailing wave and the zero-mode voltage traveling wave according to the polarity of the modulus maximum value; and the fault starting judging module compares the wave head polarities of the zero-mode current traveling wave and the zero-mode voltage traveling wave acquired by the wavelet transformation module, if the polarities are the same, the protection device is reset, and if the polarities are opposite, the power frequency communication module is started. And if the power frequency communication module receives the starting signal of the fault starting judging module, the power frequency communication module communicates with the power frequency module to start the power frequency module.
In the above scheme, preferably, the wavelet transform decomposes the zero mode epidemic digital signal in the following form:
wherein i (n) is the zero mode epidemic wave digital signal,for the wavelet approximation coefficients of said zero-mode epidemic wave digital signal i (n),wavelet transform coefficients of the zero-mode wavelet digital signal i (n).
After the binary wavelet transform, decomposing the zero-mode voltage traveling wave digital signal into the following forms:
wherein u (n) is the voltage traveling wave digital signal,is the wavelet approximation coefficient of the zero-mode voltage traveling wave digital signal u (n),and the wavelet transformation coefficient is the wavelet transformation coefficient of the zero-mode voltage traveling wave digital signal u (n).
The binary wavelet transform adopts a derivative function of a cubic center B-spline function as a wavelet function, and wavelet coefficient sequences (hk) are arrangedk∈z，﹛gk﹜k∈zComprises the following steps:
﹛hk﹜k∈z=（0.125，0.375，0.375，0.125）（k=-1，0，1，2），﹛gk﹜k∈z=（-2，2）（k=0，1）。
in the above scheme, preferably, the wavelet transform modulo maximum is defined as: for any given positive number epsilon>0, when | n-n is satisfied0|<When epsilon, for arbitrary n ≠ n0Is provided withIt is true that the first and second sensors,the positive and negative of the wavelet transform modulus maximum value of the zero-mode current traveling wave are the polarity of the wavelet transform modulus maximum value of the zero-mode current traveling wave; for any given positive number ε > 0, when | n-n is satisfied0|<When epsilon, for arbitrary n ≠ n0Is provided withIt is true that the first and second sensors,the positive and negative of the wavelet transformation modulus maximum value of the zero-mode voltage traveling wave are the polarity of the wavelet transformation modulus maximum value of the zero-mode voltage traveling wave.
In the above scheme, preferably, the power frequency module includes a power frequency data acquisition loop and a power frequency signal processing loop; the power frequency data acquisition loop comprises a second-order active low-pass filtering module, a multi-way change-over switch module and an A/D (analog/digital) conversion module; the second-order active low-pass filtering module is used for filtering a secondary side voltage signal, wherein the cut-off frequency of the second-order active low-pass filtering module is 1.2KHz, and the secondary side voltage signal comprises a three-phase current signal and a zero-sequence voltage signal; the multi-channel conversion switch module is connected to the second-order active low-pass filtering module and is used for sequentially transmitting the three-phase current signals and the zero-sequence voltage signals to the A/D conversion module; the A/D conversion module is connected to the multi-way conversion switch module, carries out A/D conversion on the three-phase current signals and the zero-sequence voltage signals to obtain three-phase current digital signals and zero-sequence voltage digital signals, the A/D conversion rate of each path is 2.4KHz, and the conversion result is transmitted to the power frequency signal processing circuit; the power frequency signal processing loop comprises a Fourier transform module, a zero sequence voltage judging module, a phase current judging module and a signal issuing module; the Fourier transform module performs Fourier transform on the three-phase current digital signal and the zero-sequence voltage digital signal to acquire a three-phase current amplitude and a zero-sequence voltage amplitude; the zero-sequence voltage judging module compares the zero-sequence voltage amplitude with a first preset amplitude, and if the zero-sequence voltage amplitude is larger than the first preset amplitude, the phase current judging module is started, otherwise, the protection device is reset; the phase current judging module compares the three-phase current amplitude with a second preset amplitude, if the three-phase current amplitudes are smaller than the second preset amplitude, a signal issuing module is started, and if not, the protection device is reset; the signal issuing module can give a tripping signal or an alarm signal according to the setting of a user and transmits the signal to the outlet relay.
Drawings
Figure 1 shows a block diagram of a single-phase grounded traveling wave protection device of a distribution line according to an embodiment of the invention;
FIG. 2 is a block diagram showing a hardware configuration of a protection module according to an embodiment of the present invention;
FIG. 3 illustrates a protection module software flow diagram according to an embodiment of the present invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments disclosed below.
Figure 1 shows a block diagram of a single-phase grounded traveling wave protection device of a distribution line according to an embodiment of the invention.
As shown in fig. 1, the single-phase grounded traveling wave protection apparatus for a distribution line according to the present invention includes at least one converter, a protector, a monitor, and an outlet relay inserted on a circuit substrate; the converter converts the current signal and the voltage signal from the loop to be tested into a secondary side current signal and a secondary side voltage signal; the converter comprises traveling wave signal input and power frequency signal input, and can obtain a zero-mode current traveling wave signal, a zero-mode voltage traveling wave signal, a power frequency current signal and a power frequency voltage signal; the protector receives the secondary side current and the secondary side voltage signals obtained by conversion from the converter, processes the signals, executes a protection algorithm, further judges whether the circuit to be tested has a single-phase earth fault, and outputs the result to the monitor and the outlet relay if the circuit to be tested has the fault; the monitor is connected to the protector, displays and stores fault information transmitted by the protector, displays and transmits a fixed value set by a user to the protector, and detects the running state of the protector; the outlet relay is connected to the protector, receives the judgment result of the traveling wave protector, and determines whether to send a tripping command or an alarm command according to the judgment result.
In the above scheme, preferably, the protector includes a traveling wave module and a power frequency module; the traveling wave module is used for acquiring and processing traveling wave signals, and the power frequency module is used for acquiring and processing power frequency signals.
In the above scheme, preferably, the traveling wave module includes a traveling wave data acquisition loop, a traveling wave start loop, and a traveling wave signal processing loop; the traveling wave data acquisition loop can acquire zero-mode current waves with the frequency range of 0-100 kHz and zero-mode voltage traveling waves with the frequency range of 0-100 kHz in the loop to be detected in real time at the sampling rate of 200 KHz; the traveling wave data acquisition loop comprises a second-order active low-pass filtering module, a multi-path conversion switch module, an A/D conversion module and a double-port RAM module; the second-order active low-pass filtering module is used for filtering a secondary side current signal and a secondary side voltage signal, wherein the passband range of the second-order active low-pass filtering module is 0-100 KHz, and the secondary side current signal and the secondary side voltage signal comprise a zero-mode current traveling wave signal and a zero-mode voltage traveling wave signal; the multi-channel conversion switch module is connected to the second-order active low-pass filtering module and is used for sequentially outputting the zero-mode current traveling wave signal and the zero-mode voltage traveling wave signal to the A/D conversion module; the A/D conversion module is connected to the multi-channel conversion switch module, carries out A/D conversion on the traveling wave analog signal, the A/D conversion rate of each channel of signal is 200KHz, obtains a zero-mode current wave signal and a digital signal of a zero-mode voltage traveling wave signal after A/D conversion, and transmits the conversion result to the double-port RAM module; the double-port RAM module is provided with two groups of data buses and two groups of address buses and is used for storing digital signal conversion results of the zero-mode electric prevailing wave signal and the zero-mode voltage traveling wave signal from the A/D conversion module and reading the digital signal conversion results of the zero-mode electric prevailing wave signal and the zero-mode voltage traveling wave signal by the traveling wave signal processing circuit; the traveling wave starting loop comprises a second-order active band-pass filtering module and a voltage comparison module; the passband range of the second-order active band-pass filtering module is 500 Hz-3 KHz, and the component of 500 Hz-3 KHz in the zero-mode electric current wave signal can be obtained as a signal for starting judgment; the voltage comparison module is connected to the second-order active low-pass filtering module, receives the signal for starting judgment from the second-order active low-pass filtering module, determines whether the amplitude of the signal for starting judgment is higher than a first preset amplitude, and sends a starting signal to the traveling wave signal processing loop when the amplitude of the signal for starting judgment is higher than the first preset amplitude; the traveling wave signal processing loop comprises a data acquisition module, a wavelet transformation module, a fault judgment module and a power frequency communication module; the data acquisition module receives a starting signal from the voltage comparison module and reads digital signals of a zero-mode current wave signal and a zero-mode voltage traveling wave signal from the dual-port RAM; the wavelet transformation module is used for performing wavelet transformation on the zero-mode prevailing wave digital signal and the zero-mode voltage traveling wave digital signal acquired by the data acquisition module to obtain a modulus maximum value and the polarity of the modulus maximum value of the wavelet transformation, and obtaining the wave head polarity of the zero-mode prevailing wave and the zero-mode voltage traveling wave according to the polarity of the modulus maximum value; and the fault starting judging module compares the wave head polarities of the zero-mode current traveling wave and the zero-mode voltage traveling wave acquired by the wavelet transformation module, if the polarities are the same, the protection device is reset, and if the polarities are opposite, the power frequency communication module is started. And if the power frequency communication module receives the starting signal of the fault starting judging module, the power frequency communication module communicates with the power frequency module to start the power frequency module.
In the above scheme, preferably, the power frequency module includes a power frequency data acquisition loop and a power frequency signal processing loop; the power frequency data acquisition loop comprises a second-order active low-pass filtering module, a multi-way change-over switch module and an A/D (analog/digital) conversion module; the second-order active low-pass filtering module has a passband of 0-1.2 KHz, and is used for filtering the secondary side voltage signals, wherein the secondary side voltage signals comprise three-phase current signals and zero-sequence voltage signals; the multi-channel conversion switch module is connected to the second-order active low-pass filtering module and is used for sequentially transmitting the three-phase current signals and the zero-sequence voltage signals to the A/D conversion module; the A/D conversion module is connected to the multi-way conversion switch module, carries out A/D conversion on the three-phase current signals and the zero-sequence voltage signals to obtain three-phase current digital signals and zero-sequence voltage digital signals, the A/D conversion rate of each path is 2.4KHz, and the conversion result is transmitted to the power frequency signal processing circuit; the power frequency signal processing loop comprises a Fourier transform module, a zero sequence voltage judging module, a phase current judging module and a signal issuing module; the Fourier transform module performs Fourier transform on the three-phase current digital signal and the zero-sequence voltage digital signal to acquire a three-phase current amplitude and a zero-sequence voltage amplitude; the zero-sequence voltage judging module compares the zero-sequence voltage amplitude with a first preset amplitude, and if the zero-sequence voltage amplitude is larger than the first preset amplitude, the phase current judging module is started, otherwise, the protection device is reset; the phase current judging module compares the three-phase current amplitude with a second preset amplitude, if the three-phase current amplitudes are smaller than the second preset amplitude, a signal issuing module is started, and if not, the protection device is reset; the signal issuing module can give a tripping signal or an alarm signal according to the setting of a user and transmits the signal to the outlet relay.
FIG. 2 is a block diagram showing a hardware configuration of a protection module according to an embodiment of the present invention;
as shown in fig. 2, after entering the protector, the zero-mode electric prevailing wave signal and the zero-mode voltage traveling wave signal first enter a second-order active low-pass filtering module, the cutoff frequency of which is 100kHz, and the main function is to filter out high-frequency interference and prevent frequency aliasing. The multi-channel conversion switch MAX4639 can realize an alternative high-speed switch of a zero-mode electric popular wave signal and a zero-mode voltage traveling wave signal, two analog signals are sequentially output to the A/D conversion module, 1 AD9240 high-speed analog/digital conversion switch is adopted in the A/D conversion module to realize high-speed analog/digital conversion of the analog signals, and the data sampling rate of each analog signal reaches 200 KHz. The dual-port RAM IDT7028 is used for storing the 2-channel digital signals after a/D conversion, and has a storage space of 128 Kbyte.
In addition, the zero-mode electric epidemic wave signals also enter the second-order active band-pass filtering module after passing through the second-order active low-pass filtering module, the band-pass frequency of the second-order active band-pass filtering module is 500 Hz-3 kHz, and signals of 500 Hz-3 kHz in current fault traveling waves are extracted and serve as starting signals of traveling wave protection hardware. After the current fault traveling wave passes through the second-order active band-pass filtering module, a signal enters a level comparison loop formed by an operational amplifier, when the signal level of 500 Hz-3 kHz in the current fault traveling wave passing through the band-pass filter exceeds a preset hardware starting level, the hardware traveling wave starting loop sends a starting signal to a complex programmable logic device EMP7128S, the complex programmable logic device EMP7128S triggers the high-speed digital signal processor TMS320C6713 to be interrupted, and the traveling wave criterion is executed.
The complex programmable logic device EMP7128S is a core control part of the traveling wave data acquisition loop, and is used for realizing coordination control of the multi-way conversion switch module, the a/D conversion module and the dual-port RAM module and decoding of address/data signals, further realizing conversion of analog signals into digital signals and storage of the digital signals in the dual-port RAM IDT7028 module, and simultaneously triggering the high-speed digital signal processor TMS320C6713 to start execution of traveling wave criteria after the traveling wave protection hardware is started by the complex programmable logic device EMP 7128S.
The traveling wave judgment is completed by taking the DSP TMS320C6713 as a core, the traveling wave judgment is a high-speed digital signal processing chip, 32 bits of a data bus can be used for carrying out floating point operation, the precision is high, 8 operation units are arranged in the chip, 16 hundred million instructions can be executed per second, and the requirements of ultra-high-speed traveling wave protection on the data processing speed and precision can be met simultaneously. And when the traveling wave criterion of the fault processing program in the DSP TMS320C6713 is met, the DSP sends the traveling wave criterion to the processor MCF5282 through an interrupt signal to process the power frequency criterion.
After a three-phase current analog signal enters the protector, the three-phase current analog signal firstly enters a second-order active low-pass filtering module, the cut-off frequency of the second-order active low-pass filtering module is 1.2KHz, the main function is to filter high-frequency interference, and meanwhile, the frequency aliasing is prevented. The A/D conversion module adopts 1 MAX 125A/D conversion chip, the chip is internally provided with a high-speed analog switch, the high-speed A/D conversion of multiple analog signals can be realized, and the data sampling rate of each analog signal is 2.4 KHz. The sampled data is stored in the internal RAM of MCF 5282. And when the MCF5282 receives the DSP interrupt signal, the power frequency criterion is started to be executed. When the power frequency criterion is met, the MCF5282 controls the output module to give out outlet information and operates the outlet relay to act.
FIG. 3 illustrates a protection module software flow diagram according to an embodiment of the present invention.
As shown in fig. 3, after receiving the traveling wave start signal:
directly acquiring the zero-mode current traveling wave of the loop to be detected, performing binary wavelet transform on the acquired zero-mode current traveling wave, and decomposing the zero-mode current traveling wave into the following forms after the binary wavelet transform:
wherein,is the wavelet approximation coefficient of the current traveling wave,is the wavelet transform coefficient of the zero-mode current traveling wave. And calculating the modulus maximum of the wavelet transform of the current traveling wave according to the wavelet transform coefficient, wherein the modulus maximum is defined as: for any given positive number ε > 0, when | n-n is satisfied0|<When epsilon, for arbitrary n ≠ n0Is provided withIt is true that the first and second sensors,the wavelet transform modulus maximum value is a zero-modulus electric popular wave; the polarity of the zero-mode current traveling wave is represented by the positive and negative of the zero-mode current traveling wave wavelet transform modulus maximum;
directly acquiring the zero-mode voltage traveling wave of the loop to be detected, performing binary wavelet transformation on the acquired zero-mode voltage traveling wave, and decomposing the zero-mode voltage traveling wave into the following forms after the binary wavelet transformation:
wherein,is the wavelet approximation coefficient of the traveling wave of the zero mode voltage,is the wavelet transform coefficient of the zero-mode voltage traveling wave. And calculating the modulus maximum of the zero-mode voltage traveling wave wavelet transform according to the wavelet transform coefficient, wherein the modulus maximum is defined as: for any given positive number ε > 0, when | n-n is satisfied0|<When epsilon, for arbitrary n ≠ n0Is provided withIt is true that the first and second sensors,the traveling wave wavelet transformation modulus maximum value is zero-mode voltage; and the polarity of the voltage traveling wave is represented by the positive and negative of the zero-mode voltage traveling wave wavelet transform mode maximum value.
In the above scheme, the dyadic wavelet transform uses the derivative function of cubic center B-spline function as wavelet function, wavelet coefficient sequence (h)k﹜k∈z，﹛gk﹜k∈zComprises the following steps:
﹛hk﹜k∈z=（0.125，0.375，0.375，0.125）（k=-1，0，1，2），﹛gk﹜k∈z=（-2，2）（k=0，1）。
comparing the positive and negative of the zero-mode voltage traveling wave and the zero-mode voltage traveling wave wavelet transform mode maximum value, and starting a protection power frequency module under the condition that the polarities of the two are opposite; otherwise, the protection is reset.
Meanwhile, three-phase current and zero-sequence voltage power frequency signals are directly obtained. Under the condition of protecting the starting of the power frequency module, the three-phase current and the zero sequence voltage amplitude are obtained by utilizing Fourier transform. Comparing the zero sequence voltage amplitude with the first preset amplitude, and if the zero sequence voltage amplitude is greater than a setting value, protecting to execute the next criterion; otherwise, the protection is reset. And then comparing the three-phase current amplitude with a second preset amplitude, if the three-phase current amplitudes are all smaller than the second preset amplitude, judging that the single-phase earth fault occurs, starting a signal output module, and if not, resetting the protection device.
The technical scheme of the invention is explained in detail by combining the drawings, and the invention provides the single-phase grounding traveling wave protection device for the distribution line, which can accurately and quickly detect the fault and make reliable action when the single-phase grounding fault occurs in the neutral point non-effective grounding system of the distribution line.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A single-phase grounding traveling wave protection device for a distribution line is characterized by comprising at least one converter, a protector, a monitor and an outlet relay which are arranged on a circuit substrate;
the converter converts the current signal and the voltage signal from the loop to be tested into a secondary side current signal and a secondary side voltage signal;
the protector receives the secondary side current signal and the secondary side voltage signal, then wave head polarities of a zero-mode current traveling wave and a zero-mode voltage traveling wave and power frequency current and power frequency voltage amplitudes are obtained according to the secondary side current signal and the secondary side voltage signal, finally whether a single-phase ground fault occurs in a protected line is judged according to the wave head polarities and the amplitudes, and if the single-phase ground fault occurs, a tripping signal is transmitted to the outlet relay; if the single-phase grounding fault does not occur, resetting the single-phase grounding protection device of the distribution line;
the outlet relay is connected to the protector, and if the tripping signal is received, a tripping command or an alarm command is sent.
The protector comprises a traveling wave module and a power frequency module; wherein,
the power frequency module is used for processing the power frequency signal;
the power frequency module comprises a power frequency data acquisition loop and a power frequency signal processing loop, wherein,
the power frequency data acquisition circuit filters, transmits and A/D converts the power frequency current signal and the power frequency voltage signal; the power frequency current signal comprises a three-phase current signal, and the power frequency voltage signal comprises a zero-sequence voltage signal;
and after the power frequency module is protected and started, the power frequency signal processing circuit performs Fourier transformation on the three-phase current signal and the zero-sequence voltage signal to obtain a zero-sequence voltage signal amplitude and a three-phase current signal amplitude, and judges the zero-sequence voltage signal amplitude and the three-phase current signal amplitude, if the zero-sequence voltage signal amplitude is greater than a first preset amplitude and the three-phase current signal amplitude is smaller than a second preset amplitude, a trip signal or an alarm signal is given out and transmitted to the outlet relay, and if not, the single-phase grounding protection device of the distribution line is reset.
2. The distribution line single-phase grounding traveling-wave protection device of claim 1, wherein the converter converts the current signal and the voltage signal input on the loop to be tested to obtain the secondary-side current signal and the secondary-side voltage signal,
the secondary side current signal comprises: a zero-mode current ripple signal and a power frequency current signal; the secondary side voltage signal comprises: zero mode voltage traveling wave signal, power frequency voltage signal.
3. The distribution line single-phase grounding traveling-wave protection device according to claim 1, further comprising:
and the monitor is connected to the protector, displays and stores the fault information transmitted by the protector, receives and displays the operation information of a user, transmits the operation information to the protector, and monitors the running state of the protector.
4. The distribution line single-phase grounding traveling-wave protection device according to claim 1, wherein the traveling-wave module comprises a traveling-wave data acquisition loop, a traveling-wave start loop and a traveling-wave signal processing loop; wherein,
the traveling wave data acquisition circuit acquires a zero-mode current wave signal with the frequency range of 0-100 kHz and a zero-mode voltage traveling wave signal with the frequency range of 0-100 kHz in the converter in real time; filtering, transmitting and A/D converting the zero-mode electric traveling wave signal and the zero-mode voltage traveling wave signal;
the starting loop extracts a signal for starting judgment from an output signal of the traveling wave data acquisition loop according to a preset frequency band, and judges whether to send a starting signal according to a first preset amplitude;
the traveling wave signal processing circuit receives the starting signal and performs wavelet transformation on the zero-mode current traveling wave signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave signal with the frequency range of 0-100 kHz output by the traveling wave data acquisition circuit to obtain the wave head polarities of the zero-mode current traveling wave and the zero-mode voltage traveling wave, then judges whether the wave head polarities of the zero-mode current traveling wave and the zero-mode voltage traveling wave are the same, and if the wave head polarities are the same, the single-phase grounding protection device of the power distribution line is reset; if not, the power frequency module is started.
5. The distribution line single-phase grounding traveling-wave protection device according to claim 4, wherein the traveling-wave data acquisition loop specifically comprises: the device comprises a second-order active low-pass filtering module, a multi-path conversion switch module, an A/D conversion module and a double-port RAM module; wherein,
the passband range of the second-order active low-pass filtering module is 0-100 kHz, and the zero-mode electric popular wave signal and the zero-mode voltage traveling wave signal are filtered to obtain the zero-mode electric popular wave signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave signal with the frequency range of 0-100 kHz;
the multi-channel conversion switch module is connected to the second-order active low-pass filtering module and is used for sequentially transmitting the zero-mode electric popular wave signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave signal with the frequency range of 0-100 kHz to the A/D conversion module;
the A/D conversion module is connected to the multi-channel conversion switch module, and is used for carrying out A/D conversion on the zero-mode current wave signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave signal with the frequency range of 0-100 kHz to obtain the zero-mode current wave digital signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave digital signal with the frequency range of 0-100 kHz, and then transmitting the conversion result to the dual-port RAM module;
the double-port RAM module is provided with two groups of data buses and two groups of address buses and is used for storing the conversion result from the A/D conversion module and reading the conversion result by the traveling wave signal processing circuit.
6. The distribution line single-phase grounding traveling-wave protection device according to claim 5, wherein the traveling-wave start-up loop specifically comprises: a second-order active band-pass filter module and a voltage comparison module, wherein,
the second-order active band-pass filtering module is connected to the second-order active low-pass filtering module and is used for extracting a component of 500 Hz-3 kHz from a zero-mode electric popular wave signal with a frequency range of 0-100 kHz output by the second-order active low-pass filtering module to serve as the signal for starting judgment;
the voltage comparison module receives the signal for starting judgment from the second-order active band-pass filter module, judges whether the amplitude of the signal for starting judgment is higher than the first preset amplitude, and sends a starting signal to the traveling wave signal processing loop when the amplitude of the signal for starting judgment is higher than the first preset amplitude.
7. The distribution line single-phase grounding traveling-wave protection device according to claim 6, wherein the traveling-wave signal processing circuit specifically comprises: a data acquisition module, a wavelet transformation module, a fault start judging module and a power frequency communication module, wherein,
the data acquisition module receives the starting signal from the traveling wave starting circuit, and reads the zero-mode current wave digital signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave digital signal with the frequency range of 0-100 kHz from the traveling wave data acquisition circuit;
the wavelet transformation module is used for performing wavelet transformation on the zero-mode current wave digital signal with the frequency range of 0-100 kHz and the zero-mode voltage traveling wave digital signal with the frequency range of 0-100 kHz to respectively obtain a first modulus maximum value and a first modulus maximum value of the zero-mode current traveling wave and a second modulus maximum value of the zero-mode voltage traveling wave, and then obtaining a first wave head polarity of the zero-mode current traveling wave and a second wave head polarity of the zero-mode voltage traveling wave according to the polarity of the first modulus maximum value and the polarity of the second modulus maximum value;
the fault starting judging module compares the first wave head polarity with the second wave head polarity, and if the first wave head polarity is the same as the second wave head polarity, the single-phase grounding protection device of the distribution line is reset; if the first wave head polarity is opposite to the second wave head polarity, the power frequency communication module is started;
and if the power frequency communication module receives the starting signal of the fault starting judging module, the power frequency communication module communicates with the power frequency module to inform the power frequency module of starting protection.
8. The single-phase grounding traveling-wave protection device for the distribution line according to claim 1, wherein the power frequency data acquisition loop specifically comprises: a second-order active low-pass filter module, a multi-path conversion switch module and an A/D conversion module, wherein,
the second-order active low-pass filtering module filters the three-phase current signals and the zero-sequence voltage signals;
the multi-way conversion switch module is connected to the second-order active low-pass filtering module and is used for sequentially transmitting the three-phase current signals and the zero-sequence voltage signals to the A/D conversion module;
the A/D conversion module is connected to the multi-way conversion switch module, carries out A/D conversion on the three-phase current signals and the zero-sequence voltage signals to obtain three-phase current digital signals and zero-sequence voltage digital signals, and then transmits conversion results to the power frequency signal processing circuit.
9. The single-phase grounded traveling-wave protection device for the distribution line of claim 8, wherein the power frequency signal processing circuit specifically comprises: a Fourier transform module, a zero sequence voltage judging module, a phase current judging module and a signal development module, wherein,
the Fourier transform module performs Fourier transform on the three-phase current digital signal and the zero-sequence voltage digital signal to obtain a three-phase current amplitude and a zero-sequence voltage amplitude;
the zero-sequence voltage judging module compares the zero-sequence voltage amplitude with the first preset amplitude, if the zero-sequence voltage amplitude is larger than the first preset amplitude, the sequence phase current judging module is started, and if not, the single-phase grounding protection device of the distribution line is reset;
the phase current judging module compares the three-phase current amplitude with the second preset amplitude, if the three-phase current amplitudes are all smaller than the second preset amplitude, a signal opening module is started, and if not, the distribution line single-phase grounding protection device is reset;
the signal issuing module can give a tripping signal or an alarm signal according to the setting of a user and transmits the signal to the outlet relay.
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