CN102932294A - Power frequency communication system applied to oil field power grid - Google Patents

Abstract

The invention provides a power frequency communication system applied to an oil field power grid. A main station device of the power frequency communication system comprises a downlink drive unit and an uplink demodulation unit, wherein the downlink drive unit is used for generating a voltage distortion signal at a voltage zero passage moment through a transformer arranged in a power substation for loading modulation information and sending the voltage distortion signal; and the uplink demodulation unit is used for obtaining the current zero passage moment according to the current distortion signal and demodulating a current modulation signal at a current zero passage time domain according to the current zero passage moment. A power frequency communication terminal comprises a downlink demodulation unit and a central processing unit, wherein the downlink demodulation unit is used for judging whether the voltage distortion signal of loading the modulation information, generated by at the voltage zero passage moment, exists in the power grid, and sending a demodulation command to the central processing unit if the voltage distortion signal of loading the modulation information exists in the power grid; and the central processing unit is used for demodulating the voltage distortion signal according to the demodulation command sent by a synchronization detection unit so as to obtain position information of the voltage zero passage moment, and modulating the voltage distortion signal through an uplink coding control drive circuit so as to obtain a current distortion signal of the current zero passage moment in a preset range, and sending the current distortion signal. The invention can realize synchronization detection in the oil field power grid with stronger harmonic interference.

Description

A kind of power frequency communication system that is applied to oilfield electric net

Technical field

The present invention relates to a kind of power frequency communication system that is applied to oilfield electric net, belong to field production management, power system network structure, motor, communication and signal processing technology field.

Background technology

Have humorous wave interference to a certain degree in the existing oilfield electric net, voltage distortion signal and electrical network that the frequency communication terminal is difficult to distinguish from electric substation disturb, and therefore can't realize synchronous detection.Oil-well motor belongs to periodically variable working condition load, the strong interference that can produce during operation, traditional time domain detection mode is difficult to distinguish modulation signal and interference noise, because electrical network disturbs strong, there is error in the voltage over zero that obtains by positive and negative comparison circuit, can affect data demodulates, traditional frequency communication mode is difficult to guarantee communication performance at oilfield electric net.Present Synchronous Detection has only proposed principle and the laboratory simulations research of frequency communication, is applicable to the good place of power grid quality, and actual oilfield electric net is owing to existing humorous wave interference and electrical network phase shift can't accurately judge the position of zero crossing.

Summary of the invention

The objective of the invention is can realize the synchronously power frequency communication system of detection in order to provide a kind of in the stronger oilfield electric net of humorous wave interference, this power frequency communication system comprises master station device and frequency communication terminal, and described master station device comprises:

The downlink drive unit is used for constantly producing voltage distortion signal loading modulation intelligence by the transformer that is arranged on electric substation at voltage zero-cross, and described voltage distortion signal is sent;

The uplink demodulation unit is used for according to described current distortion signal acquisition current over-zero constantly, and is engraved in the current over-zero time domain during according to described current over-zero current modulated is carried out demodulation.

Described frequency communication terminal comprises:

Descending demodulating unit is used for judging whether electrical network appears at the voltage distortion signal that voltage zero-cross is worth the load-modulate information of generation constantly, and judged result is yes, then sends the order of demodulation to CPU;

CPU, be used for the order according to the demodulation of synchronous detection unit transmission, described voltage distortion signal is carried out demodulation, thereby obtain voltage zero-cross positional information constantly, thereby and modulate the current distortion signal that the current over-zero that obtains preset range is worth constantly by up coding-control drive circuit, and described current distortion signal is sent.

The present invention has following beneficial effect: realized the oil well remote monitoring by power frequency communication system, reduced the oil recovery worker and patrol the well number of times, improved the operating efficiency of field produces pipe well, will provide technical guarantee for optimizing production crew's post setting; Frequency communication technology can realize that the electric weight of synchronization in the supply line calculates, and will be the dynamic optimization operation of power distribution network, and realizing saving energy and reduce the cost provides technical support, has potential economic benefit; Can strengthen the management of outlying village village well by frequency communication technology, reduce the probability that oil recovery workman body security incident occurs, for a kind of new model is explored in the rod-pumped well management.

Description of drawings

Fig. 1 is the structural representation of the power frequency communication system that is applied to oilfield electric net that provides of the specific embodiment of the present invention;

Fig. 2 is the electrical block diagram of the downlink drive unit that provides of the specific embodiment of the present invention;

Fig. 3 is the downstream signal coding structure schematic diagram that the specific embodiment of the present invention provides;

Fig. 4 is the electrical block diagram of the CPU that provides of the specific embodiment of the present invention;

Fig. 5 is the electrical block diagram of the up modulation circuit that provides of the specific embodiment of the present invention;

Fig. 6 is the short-circuit structure schematic diagram of the uplink demodulation unit that provides of the specific embodiment of the present invention.

Embodiment

The specific embodiment of the present invention provides a kind of power frequency communication system that is applied to oilfield electric net, corresponding master station device comprises downlink drive unit and uplink demodulation unit, the downlink drive unit is used for constantly producing voltage distortion signal loading modulation intelligence by the transformer that is arranged on electric substation at voltage zero-cross, and described voltage distortion signal is sent; The uplink demodulation unit is used for according to described current distortion signal acquisition current over-zero constantly, and is engraved in the current over-zero time domain during according to described current over-zero current modulated is carried out demodulation.Corresponding frequency communication terminal comprises descending demodulating unit and CPU, descending demodulating unit, be used for judging whether electrical network appears at the voltage distortion signal that voltage zero-cross is worth the load-modulate information of generation constantly, and judged result is yes, then send the order of demodulation to CPU; CPU is used for the order according to the demodulation of synchronous detection unit transmission, described voltage distortion signal is carried out demodulation, thereby obtain voltage zero-cross positional information constantly, thereby and modulate the current distortion signal that the current over-zero that obtains preset range is worth constantly by up coding-control drive circuit, and described current distortion signal is sent.。

For this technical scheme of clearer explanation, describe below in conjunction with Figure of description, as shown in Figure 1, corresponding master station device comprises:

Downlink drive unit 11 is used for constantly producing voltage distortion signal loading modulation intelligence by the transformer that is arranged on electric substation at voltage zero-cross, and described voltage distortion signal is sent;

Uplink demodulation unit 12 is used for according to described current distortion signal acquisition current over-zero constantly, and is engraved in the current over-zero time domain during according to described current over-zero current modulated is carried out demodulation.

Corresponding frequency communication terminal comprises:

Descending demodulating unit 21 is used for judging whether electrical network appears at the voltage distortion signal that voltage zero-cross is worth the load-modulate information of generation constantly, and judged result is yes, then sends the order of demodulation to CPU;

CPU 22, be used for the order according to the demodulation of synchronous detection unit transmission, described voltage distortion signal is carried out demodulation, thereby obtain voltage zero-cross positional information constantly, thereby and modulate the current distortion signal that the current over-zero that obtains preset range is worth constantly by up coding-control drive circuit, and described current distortion signal is sent.

Concrete, descending voltage side signal transmission is to being to oil well from oil field electric substation, one represents command information, realize the expression of information with near the faint distortion of the voltage voltage over zero, downlink drive unit 11 produces the voltage distortion signal by the house transformer of electric substation constantly at voltage zero-cross; Downlink drive unit 11 is made of microprocessor, controllable silicon, reactance, protective circuit etc., and as shown in Figure 2, wherein the microprocessor of downlink drive unit 11 is selected Atmega8.Used low pressure side is installed in downlink drive unit 11, downlink drive unit 11 in the present embodiment can adapt to the various connected modes of place oilfield electric net, when place oilfield electric net connected mode is consistent with the 10KV circuit, adopt phase-ground modulation system, downlink drive unit 11 can be modulated mutually in any one in mutually of A, the B of place oilfield electric net low pressure output, C, when there are variable star angle in place oilfield electric net connected mode and 10KV circuit, downlink drive unit 11 adopts alternate modulation system, can modulate mutually at AB, AC, BC.

Because it is little that the electrical network in the electric substation disturbs, voltage zero-cross is sought constantly by positive and negative comparison circuit in downlink drive unit 11, the output of the low pressure of place oilfield electric net forms square wave behind PT and signal conditioning circuit, positive and negative comparison circuit, microprocessor in the downlink drive unit 11 just can judge that by square wave voltage zero-cross constantly, microprocessor gathers voltage signal by built-in A/D converter, calculate the caused voltage distortion amplitude size of modulated current by the time-domain difference computing, then self adaptation is modulated between front 25 ° to 32 ° of voltage zero-cross.When the voltage distortion amplitude surpasses certain thresholding, can stop to carry out current-modulation by the zero passage detection subelement in the downlink drive unit 11 and report to the police and shut down, so both guaranteed the modulation electric strength of flow, realized again the automatic protection to circuits for triggering.

The amplitude of voltage distortion signal is relevant with the capacity that main transformer and modulation become, also relevant with the modulation angle, at Oil Field, the main transformer capacity of electric substation is different, and the selection of modulation varying capacity is subject to the restriction of engineering-environment, when main transformer with when definite, change by the modulation angle can adapt to site environment, and the modulation angle is larger, voltage distortion signal longer with the duration, just more favourable to descending demodulation, but the power of required modulation transformer is just larger.Microprocessor is by the instruction of RS485 interface reception from industrial computer, when needs send descending frequency communication information, for security consideration, prevent mistake and drive, microprocessor forms logical signal by 8 I/O interfaces by decoding circuit and drives controllable silicon through circuits for triggering.Controlling used transformation low-voltage output modulates.The present embodiment selects inductance as driving element, and in identical voltage distortion amplitude situation, the shared time domain of voltage distortion signal that produces is wider than resistance type of drive, and is favourable to descending demodulation.

In order to comprise device security; in downlink drive unit 11, also be provided with the protective circuit subelement; the protective circuit subelement is comprised of air switch and fast acting fuse; when the device short circuit occurring; when modulated current strengthened suddenly, the protective circuit subelement can cut off rapidly and drive the loop, can not damage device; after fault is got rid of, can conveniently recover.

In the downlink drive process, the coded system that microprocessor is fit to oilfield electric net drives downlink command formation control coding, bits per inch according to this in continuous 2 power frequency periods voltage modulation signal place period position represent, such as Fig. 3 institute not.

The reception of downstream signal is finished by the frequency communication terminal, at first will detect synchronously by descending demodulating unit 21, the start cycle that judges whether voltage modulation signal to occur and reach synchronously data message, then just can carry out data demodulates.The descending receiving terminal of traditional power frequency communication system carries out demodulation by the time domain mode, at first voltage zero-cross is judged by positive and negative comparison circuit constantly, and the demodulation of downstream signal realizes in time-related impact power-frequency voltage according to distorted signal, judge whether to occur the voltage distortion signal by the change threshold that the voltage zero-cross time is set and realize synchronous detection, by the positive and negative data demodulates that realizes of front and back power frequency period zero passage moment difference.

Because the strong interference that produces during the oil-well motor operation, the accurate judgement of descending demodulation mode voltage zero-cross time of traditional frequency communication still detects synchronously, data demodulates is all very difficult.In order to realize synchronous detection, described frequency communication terminal is at first carried out calculus of differences with the voltage signal of adjacent periods and is removed most fundamental frequency and other harmonic wave, and differential signal s (t) can be expressed as:

s(t)＝v(t)+n(t) (1)

V wherein (t) is modulation signal, and n (t) is differentiated electric network noise, and the electrical network that produces during owing to the oil-well motor operation disturbs strong, judges whether to occur the voltage distortion signal from time domain very difficult.

The voltage distortion signal spectrum at 150HZ between the 600HZ, differential signal is carried out spectrum analysis, come modulate signal and electric network noise can improve synchronous detected status by the thresholding that the frequency domain energy parameter is set, but the interference of oil-well motor is very strong, when because field condition restriction, during the voltage distortion insufficient amplitude, also can't distinguish the voltage distortion modulation from the frequency domain energy parameter and disturb with electrical network.

In the present embodiment, can select voltage differential signal is carried out related operation with the reference signal that arranges in advance first by the related operation subelement, after reducing electrical network and disturbing, carry out again spectrum analysis and distinguish the voltage distortion modulation and disturb with electrical network and can effectively improve the quality of synchronous detection.

Because the capacity that main transformer and modulation become, driving element parameter, modulation angle determine, the reference signal v of Corticofugal Modulation of Somatosensory (t) can know in advance, and the cross-correlation between reference signal v (t) and the differential signal s (t) is output as:

Cross-correlation output R (τ) is expressed as: $R\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)v(t+\mathrm{\τ})h(t+\mathrm{\τ})\mathrm{dt}---\left(2\right)$

Wherein, s (t) is voltage differential signal, and τ is the cross-correlation time delay, and h (t) is rectangular window function, and in order to reduce the interference of unwanted signal, h (t) is limited in computing cross-correlation near the shared time domain of modulation signal.

$R\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}v\left(t\right)v(t+\mathrm{\τ})h(t+\mathrm{\τ})\mathrm{dt}+\underset{-\∞}{\overset{+\∞}{\∫}}n\left(t\right)v(t+\mathrm{\τ})h(t+\mathrm{\τ})\mathrm{dt}---\left(3\right)$

Both comprised the cross-correlation composition between modulation signal and the electric network noise in the cross-correlation output, and also comprised the auto-correlation composition of modulation signal, and be independent of each other between electric network noise and the modulation signal, noise is subject to the inhibition of certain degree.

R (τ) changes with τ, the present embodiment with the corresponding τ of absolute value of R (τ) as detecting time domain τ ₀

Therefore to detecting the cross-correlation output R (τ of time domain ₀) carry out spectrum analysis and realize that synchronous detection can reduce the requirement to the voltage distortion rate, improve the performance that detects synchronously.The voltage distortion signal spectrum at 200HZ between the 600HZ, R (τ ₀) the main frequency composition at 400HZ between the 800HZ, when the modulation angle is 30 °, there is the time of about 3ms in the voltage distortion signal, consider angular range and the oscillation effect of Corticofugal Modulation of Somatosensory, the present embodiment was chosen in the time of the 4ms the voltage zero-cross near, calculated R (τ by the short distance Fourier transform ₀) just can realize synchronous detection at 400HZ to the spectrum distribution situation between the 800HZ.

Fourier transform belongs to linear transformation, each frequency can be calculated separately the effective value of its this frequency according to the short distance Fourier transform, and the present embodiment passes through to calculate 400HZ, 500HZ, and 600HZ, the effective value sum of these 4 radio-frequency components of 700HZ reflects R (τ ₀) in the spectrum distribution situation.

For certain frequency component ω _i, its effective value is:

Wherein,

With

Be respectively ω _iReal part and the imaginary part of Fourier transform.

Like this, R (τ ₀) frequency spectrum parameter be expressed as: $W=\underset{i=1}{\overset{4}{\mathrm{\Σ}}}X\left({\mathrm{\ω}}_i\right)---\left(5\right)$

When not sending voltage modulation signal, the continuous calculating parameter W of described frequency communication terminal, its mean value is W ₀, when receiving signal, continuous 4 times frequency spectrum parameter W obviously surpasses W ₀The time, can judge descending voltage modulation signal to have occurred, finished synchronous detection.

When data demodulates, owing to representing by voltage modulation signal place period position in continuous 2 power frequency periods, the positive and negative data message that depends on of modulation signal direction is realized data demodulates by the similarity degree of poor sub-signal and positive and negative modulation signal in the differential signal.

In the voltage zero-cross context of detection, the present embodiment is sought voltage zero-cross constantly by Fourier transform,

Voltage signal can be expressed as:

Wherein, X ₀Be DC component; ω ₁Be the fundamental frequency angular frequency; X _k,

Being amplitude and the phase place of k order harmonic components, is first-harmonic according to the composition of national standard 95%, constantly unstable by the zero passage that positive and negative comparison circuit obtains because the humorous wave interference of oilfield electric net is strong, zero passage also might occur repeatedly repeating.

The local function of the present embodiment adopts standard 50HZ function, and its real part and imaginary part are respectively:

$X_r=\cos \left(n\frac{2\mathrm{\π}}{N}\right)---\left(7\right)$

$X_i=\sin \left(n\frac{2\mathrm{\π}}{N}\right)---\left(8\right)$

Voltage sampling signal x (n) is by the harmonious wave component of first-harmonic, is first-harmonic according to the composition of national standard 95%, supposes the first-harmonic part X among the x (n) _JBe expressed as:

Wherein,

Be the initial phase of voltage fundamental, this numerical value has reflected the phase difference of voltage fundamental and local function, as long as calculate

, just can access voltage zero-cross constantly.

Utilize real part and the imaginary part of standard 50HZ function that input signal is carried out respectively holocyclic integral operation,

${\mathrm{\ψ}}_i=\underset{0}{\overset{T}{\∫}}{X}_j*X_r\mathrm{dt}\≈\underset{0}{\overset{T}{\∫}}{U}_m\cos (n\frac{2\mathrm{\π}}{N}+\∂)*\cos \left(n\frac{2\mathrm{\π}}{N}\right)\mathrm{dt}=U_m\cos \∂---\left(9\right)$

${\mathrm{\ψ}}_r=\underset{0}{\overset{T}{\∫}}{X}_J*X_i\mathrm{dt}=\underset{0}{\overset{T}{\∫}}{U}_m\cos (n\frac{2\mathrm{\π}}{N}+\∂)*\sin \left(n\frac{2\mathrm{\π}}{N}\right)\mathrm{dt}=U_m\sin \∂---\left(10\right)$

So can access: $\∂=\mathrm{arctg}\left(\frac{{\mathrm{\ψ}}_r}{{\mathrm{\ψ}}_i}\right)---\left(11\right)$

X (n) overwhelming majority is the first-harmonic composition, and the harmonic wave part is calculated because frequency and 50HZ differ greatly

Initial phase that can the reflecting voltage first-harmonic, thus the positional information of voltage zero-cross obtained.

When the oilfield electric net frequency fluctuation, the present embodiment can also adopt digital phase-locked loop to calculate work frequency, to guarantee voltage zero-cross accurate judgement constantly.

The circuit structure of corresponding CPU 22 as shown in Figure 4, the up frequency communication drive circuit that mainly comprise the processing module that has take dsp processor as core, 16 A/D converters, voltage current transformer, signal conditioning circuit, is consisted of by controllable silicon and resistance etc.

The function of frequency communication terminal is that the demodulation of descending voltage distorted signal, communication protocol are processed, the ascending current modulation, and these functions all are to finish take the DSP calculation process as core; DSP gathers, processes voltage signal by 16 A/D and realizes the downlink data demodulation, its synchronously detection and data demodulation method are as previously mentioned, owing to need not just can realize detecting synchronously by decision threshold, even the row modulation is given birth in the used sell of one's property, distorted signal is faint and in the environment that the oilfield electric net noise is strong, the present embodiment also can guarantee communication performance, after data demodulates is finished, the processing of communication protocol is fairly simple, needs to adapt to the communication characteristics of oil field remote monitoring.

When needs sent data to electric substation, DSP carried out the modulation of current distortion signal according to up coding-control drive circuit, thereby can realize two-way communication; The transmission of upward signal is to rely on front 30 ° of the voltage over zero of distribution transformer secondary phase to trigger controlled silicon conducting, makes near the distortion of the generation of voltage over zero Weak current carry signal.

In the frequency communication upward signal process of transmitting, DSP determines that according to upstream data and modulating-coding needs carry out the power frequency period of distortion current, during modulation, DSP obtains front 30 ° of moment of voltage over zero by collection, analytical voltage signal, DSP drives controlled silicon conducting by circuits for triggering, makes near the distortion of the generation of voltage over zero Weak current carry signal.

Optionally, for the danger that prevents that the controllable silicon false triggering from bringing, can generate subelement by current distortion and drive controlled silicon conducting by circuits for triggering, the current distortion signal that the voltage zero-cross of generation preset range is worth constantly, and decipher to control silicon controlled by three IO mouths by logical circuit and trigger, so just greatly reduce the danger that interference signal, single chip microcomputer halt etc. make the controllable silicon false triggering, improved the reliability of equipment.

Optionally, because telecommunication terminal quantity is large, the present embodiment is driven described silicon controlled circuits for triggering by resistance by the driven element unit; Because controllable silicon in serial connection resistance directly has been connected on the 220V power supply, and resistance is very little, in order to ensure system safety, has added the passive protection circuit in the series loop of controllable silicon and resistance.When the fortuitous events such as controllable silicon punctures, false triggering, the passive protection circuit can cut off circuit rapidly, guarantees the device securities such as oil field distribution transformer, motor like this.The circuit structure of up modulation circuit as shown in Figure 5, DSP wherein can select MB91F467D, 16 A/D can select AD7656.

The circuit structure of corresponding uplink demodulation unit 12 as shown in Figure 6, by formations such as the voltage and current instrument transformer (PT, CT) of industrial computer, 16 A/D capture cards, 10KV circuit, Signal Matching modulate circuits, voltage, the current sensing signal of PT, CT output carry out digitlization through signal conditioning circuit and A/D card, industrial computer judges that by voltage signal voltage zero-cross constantly, then carries out Digital Signal Processing at the right current sampling signal of voltage zero-cross time domain and realizes uplink demodulation.

2 PT, CT in the uplink demodulation unit 12 obtain voltage, current signal from 1 PT, CT of the 10KV of electric substation or 6KV circuit.Owing to being that industrial computer control downlink drive unit 11 sends descending frequency communication information to the frequency communication terminal, so formulate in advance communication protocol, industrial computer can be learnt the zero-time of up power frequency information, in the detection of upward signal, do not have synchronization detection process, directly carry out data demodulates, its demodulation method is to be realized by the frequency communication terminal, modulation principle and Corticofugal Modulation of Somatosensory are basically identical, also are to modulate front 30 ° of voltage zero-cross; The up coding that its coding adopts traditional frequency communication mode to use is separated timing because the uplink demodulation device of electric substation can know the initial power frequency period of coding, just can carry out demodulation by difference and cross-correlation mode.After data demodulates is finished, industrial computer will be stored, manage from the information of each frequency communication terminal.

The technical scheme that adopts this embodiment to provide has realized the oil well remote monitoring by power frequency communication system, reduces the oil recovery worker and patrols the well number of times, improves the operating efficiency of field produces pipe well, will provide technical guarantee for optimizing production crew's post setting; Frequency communication technology can realize that the electric weight of synchronization in the supply line calculates, and will be the dynamic optimization operation of power distribution network, and realizing saving energy and reduce the cost provides technical support, has potential economic benefit; Can strengthen the management of outlying village village well by frequency communication technology, reduce the probability that oil recovery workman body security incident occurs, for a kind of new model is explored in the rod-pumped well management.

The above; only for the better embodiment of the present invention, but protection scope of the present invention is not limited to this, anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claims.

Claims (8)

1. a master station device that is applied to the power frequency communication system of oilfield electric net is characterized in that, comprising:

The downlink drive unit is used for constantly producing voltage distortion signal loading modulation intelligence by the transformer that is arranged on electric substation at voltage zero-cross, and described voltage distortion signal is sent;

The uplink demodulation unit is used for according to described current distortion signal acquisition current over-zero constantly, and is engraved in the current over-zero time domain during according to described current over-zero current modulated is carried out demodulation.

2. the master station device that is applied to the power frequency communication system of oilfield electric net according to claim 1 is characterized in that, described downlink drive comprises in the unit:

The zero passage detection subelement for detection of the distortion amplitude of described voltage distortion signal, if when described distortion amplitude surpasses threshold value, sends the order that stops to produce described voltage distortion signal, and shuts down to descending driver element.

3. the master station device that is applied to the power frequency communication system of oilfield electric net according to claim 1 is characterized in that, described downlink drive comprises in the unit:

The protective circuit subelement is used for when the equipment of master station device is short-circuited, and cuts off current supply circuit by air switch and fast acting fuse.

4. a frequency communication terminal that is applied to the power frequency communication system of oilfield electric net is characterized in that, comprising:

Descending demodulating unit is used for judging whether electrical network appears at the voltage distortion signal that voltage zero-cross is worth the load-modulate information of generation constantly, and judged result is yes, then sends the order of demodulation to CPU;

CPU, be used for the order according to the demodulation of synchronous detection unit transmission, described voltage distortion signal is carried out demodulation, thereby obtain voltage zero-cross positional information constantly, thereby and modulate the current distortion signal that the current over-zero that obtains preset range is worth constantly by up coding-control drive circuit, and described current distortion signal is sent.

5. the frequency communication terminal that is applied to the power frequency communication system of oilfield electric net according to claim 4 is characterized in that, comprises in descending demodulating unit:

The related operation subelement is used for voltage differential signal and the reference signal that sets in advance are carried out related operation, carries out spectrum analysis again, disturb to distinguish voltage distortion signal and electrical network, adopt and dynamically judge zero passage mode constantly, realize under the high reject signal background information that demodulation loads.

6. the frequency communication terminal that is applied to the power frequency communication system of oilfield electric net according to claim 4 is characterized in that, comprises in CPU:

Current distortion generates subelement, is used for driving controlled silicon conducting by circuits for triggering, and the current distortion signal that the voltage zero-cross of generation preset range is worth constantly, and decipher to control silicon controlled by three IO mouths by logical circuit and trigger.

7. the frequency communication terminal that is applied to the power frequency communication system of oilfield electric net according to claim 6 is characterized in that, comprises in CPU:

The driven element unit is used for by resistance described silicon controlled circuits for triggering being driven.

8. power frequency communication system that is applied to oilfield electric net, it is characterized in that, comprise master control set and frequency communication terminal, described master control set is provided with the described master station device that is applied to the power frequency communication system of oilfield electric net of claims 1 to 3 any one, and described frequency communication terminal is provided with the described frequency communication terminal that is applied to the power frequency communication system of oilfield electric net of claim 4 to 7 any one.

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