CN1492234A - Multiphase digital synchronously sampling photoelectric current mutual inductor - Google Patents

Abstract

The synchronously sampling multiphase digital photoelectric current mutual inductor consists of several high voltage side circuits, several transmitting fibers and one low voltage side circuit. The basic characteristics of the digital photoelectric current mutual inductor include the control of several phase circuit sampling in the high voltage side by the clock from the low voltage side, the hardware implementation of the simultaneous sampling of the three phase, A, B and C, current, the simultaneous sampling based on the united clock GPS and software quasi-synchronous sampling tracking power network frequency, and the simple combination of photoelectric current/voltage measurement. The present invention can raise the measurement precision of current in power system and optimize the interface performance of secondary output to accommodate the development of digital, microcomputerized and intelligent electric power measurement and protection.

Description

The multiphase digital photo-electric current transformer of synchronized sampling

(1) technical field

The invention belongs to the power system measuring field, particularly a kind of digitized electronic current measuring equipment of photoelectricity combination.

(2) technical background

In electric system, conventional CT is used to measure the history in existing more than 100 year of electric current.It provides input signal for metering, relay protection, control and the supervision of electric system, has very important significance.Increasing along with the power capacity of electric system transmission, electric pressure is more and more higher, conventional CT unsurmountable problem occurs because of its sensor mechanism: (1) insulation technology requires complicated, volume is big and weigh the cost height; (2) saturated transient response speed and the precision that has limited CT under the transformer iron core malfunction; (3) owing to the influence of iron core magnetic saturation and magnetic hysteresis loop, the transient state output current of CT seriously distorts, and has increased the complicacy of protective relaying device for overcoming this distortion.

When electric system was broken down, the aperiodic component of a transient current can cause that conventional CT is saturated, and current waveform distorts.The degree of distortion is difference with the difference of CT degree of saturation.Therefore, real time discriminating CT degree of saturation is very difficult exactly.The secondary current wave form distortion is differentiated the quick, accurate of fault directly influencing, thereby influenced rapidity, sensitivity, selectivity and the reliability of relay protection, and is particularly bigger to the differential protection influence, even malfunction can occur.At present; is lower based on the differential protection performance factor of conventional CT with respect to the protection of other types; China Electric Power Research Institute and The National Electric Power Communication Center have done statistical study to national relay protected operation situation in 1998; wherein differential protection incorrect operation rate is higher; its reason is many-sided; but have a bit and generally acknowledged that by everybody promptly the differential protection incorrect operation is relevant with the saturation characteristic of conventional CT.Overcome the above-mentioned shortcoming of current transformer, the new transformer of development of practical is very necessary.The second interface dilatation inconvenience of conventional CT simultaneously, digital photoelectric current measurement adopt digitized second interface technology to make following secondary device now to insert existing using by Modularly.

The photo-electric current transformer OECT that is developing has higher accuracy both at home and abroad.From the document of delivering at present, photo-electric current transformer OECTH is made up of high side circuitry, Transmission Fibers and low side circuitry, high-end data sampling all is that three-phase is controlled separately, the controlling of sampling sequential of each phase is produced by the single-chip microcomputer on the every phase sampler plate of hot side, such structured data bit error rate height.Because three-phase is controlled separately, three phase samplers are asynchronous, and low potential side can not reproduce the waveform of high-pressure side three-phase current.When measuring the electric system three phase power, need the three-phase synchronized sampling, otherwise, three-phase electric weight sampling instant difference, measured power error is big, even wrong result occurs.In addition, if the current sample three-phase of electric power system fault record ripple, high-tension line fault location system is asynchronous, the result of mistake can appear.

(3) summary of the invention

The objective of the invention is to overcome the problem of the deficiencies in the prior art and existence, and the multiphase digital photo-electric current transformer of a kind of synchronized sampling that proposes, the waveform of on high-tension side polyphase current is restored undistortedly (comprise that the phase place between frequency, phase place and the three-phase current is identical, the linear ratio of current value (comprising effective value and amplitude)), no saturated, the measurement frequency is wide, the precision height.

Technical scheme of the present invention is: a kind of multiphase digital photo-electric current transformer of synchronized sampling, it is by a plurality of high-pressure sides circuit, a plurality of Transmission Fibers and a lower-voltage circuit are formed, and high-pressure side circuit---data acquisition board (2) has current sampling element (2.1), digital light electric weight slowdown monitoring circuit (2.3), power-supply circuit (2.2); Lower-voltage circuit (1) has digital light electric weight observing and controlling system (1.2), receives and output (1.1) device (DOIU); It is characterized in that: each phase Transmission Fibers (4) is divided into from the measuring optical fiber (4.2) of high-pressure side circuit to lower-voltage circuit transmission measurement amount, with the control optical fiber (4.1) of lower-voltage circuit to high-pressure side circuit transmission sampling control signal, each controls the serial a/d sampling control signal input end that optical fiber (4.1) one ends connect digital optical quantum slowdown monitoring circuit (2.3) mutually, and the other end of respectively controlling optical fiber (4.1) mutually is connected to the sampling control signal output terminal of lower-voltage circuit jointly.

Aforesaid current transformer is characterized in that lower-voltage circuit is connected to GPS.

The present invention removes the CPU in the circuit of the every high-pressure side of prior art, utilize the same cpu controller of lower-voltage circuit every on high-tension side serial AD C (MAX187) to be carried out controlling of sampling by optical fiber, realize each phase serial AD C image data and high-speed synchronous transmitting serial data simultaneously, thereby realization is sent to low-pressure side by optical fiber after analog current signal is converted to digital signal, and be sent to PC by DAC (MAX531) output with by digital interface, for Computer Analysis and processing.

The software module formation comprises the control timing generator program, and serial data is read in, discriminating program, external trigger, synchronized sampling control program, and autodiagnosis, supervisory programme reach the program with the PC communication.

The present invention has the following advantages and good effect:

1. realized that from hardware each phase current samples simultaneously, carried out interpolation, each phase ADC has been carried out a plurality of passages expansions, then can understand high-end running state information in real time without software;

2. ADC work is controlled by low side, can be revised sampling instant by outside time service clock (as GPS), is implemented in sampling simultaneously under the unified clock command;

3. each phase ADC can realize following the tracks of mains frequency and carries out equal interval sampling under low side control, and (as frequency analysis) is essential sometimes for the occasion that requires to carry out power quality analysis for this;

4. the controllability of high-side current sampling makes finally can simply the mixed photoelectric current/voltage be measured and combines, and the realization current/voltage is measured simultaneously.

The present invention adopts synchronous sampling technique, forms the simple and practical new transformer of a generation.The Rogowski power pack does not have iron core, bandwidth, and distortion is few, saturation problem can not occur.The photoelectric current transducer can accurately measure transient current one time under the electric power system fault situation, comprises the aperiodic component in the secondary current that can filter.Therefore the outstanding advantage that should numeral photoelectricity current measurement be applied to relay protection is: no saturated, no current wave form distortion, the measurement frequency is wide, precision is high.These characteristics are very favourable for rapidity, selectivity and the reliability of relay protection.The power pack volume is little simultaneously, cost is low.

Studies show that the digital light electric weight examining system based on the Rogowski coil has good performance, as stable, precision is high, the linearity is good etc., digital photoelectricity current measurement system has adapted to the requirement of electric system electrical secondary system total digitalization.

(4) description of drawings

Fig. 1 is the single-phase theory diagram of digital photoelectric formula current transformer of the embodiment of the invention.

Fig. 2 is Fig. 1 mesohigh side data collection plate theory diagram.

Fig. 3 is Fig. 1 mesolow lateral circuit theory diagram.

Fig. 4 is a simulation output interface theory diagram among Fig. 3.

(5) embodiment

Below in conjunction with drawings and Examples principle of work of the present invention is described further.

High-pressure side data acquisition board (2) is installed in transmission line of electricity (3) side, current sensing (2.1) on the data acquisition board (2) is transformed to the output of small voltage signal with the big current signal on the current (3), be sent to ADC (2.3.4) through signal conditioning circuit (2.3.1), every ADC transmits at control optical fiber (4.1) under the control timing come up simulating signal sample simultaneously (control timing is produced by the waveform logic unit (1.2.2) of lower-voltage circuit (1)), convert to after the digital signal luminous by driving circuit (2.3.5) driven for emitting lights diode (LED) (2.3.6), the light signal of LED output is sent to lower-voltage circuit by optical fiber (4.2), this light signal of the controller of lower-voltage circuit (1.5) demodulation obtains the digital quantization value of primary current in the current, carry out the no-load voltage ratio conversion and revise realization analog quantity output (1.4) and digital quantity storage (1.3), functions such as PC waveform display analysis.Adopting to install on the circuit assists quick-magnetic saturated current transformer (2.2.1) to provide working power by the mode of rectification circuit (2.2.2) energy supply for high-end collection plate.

When require A, B, when the C three-phase is worked together, lower-voltage circuit is controlled each phase ADC respectively by 3 optical fiber, samples simultaneously because of control timing equally promptly realizes three-phase ADC, certainly system also can expand to more than 3 phase currents and sample simultaneously.

Realize the control method of the synchronized sampling of three-phase:

This photo-electric current transformer adopts a kind of simple and practical control method to realize the synchronized sampling of three-phase.Control timing is produced by the control panel of lower-voltage circuit, and a control panel is controlled the sampling of three-phase current simultaneously.Regularly overflow interruption by the automatic heavy cartridges pattern of T2 timer of single-chip microcomputer 80C320 (as 1.5 modules of Fig. 4) on the control panel and produce control timing CSAD, control timing CSAD produces three identical sequential SRCLK1, SRCLK2, SRCLK3 by logic gate 74LS14 (as the 1.2.2.4 module of Fig. 4).Wherein SRCLK1 is used for controlling the synchronized sampling of three-phase.Enable signal ENVA, the ENVB of SRCLK1 sequential and three phase samplers, ENVC are by the work of programmable logic chip GAL16V8A (as the 1.2.2 module of Fig. 4) control noble potential sampling plate.When the three-phase enable signal is effective, the 1.2.2 module of programmable logic chip GAL16V8A such as Fig. 4) three identical steering logic sequential CSADA, CSADB, CSADC of output control the three-phase synchronized sampling respectively.This control method not only can realize single-phase sampling but also can realize the synchronous sample of three-phase that utilization flexibly.After steering logic sequential CSADA, CSADB, CSADC pass to the high-pressure side sampling plate by optical fiber, sampling plate (as 1.2.2.1,1.2.2.2, the 1.2.2.3 module of Fig. 4) is gone up and is adopted two monostalbe triggers, realizes the extraction of serial A D chip chip selection signal/CS and employing serial data shift clock SCLK.What hand down by measuring optical fiber (4.2) from the high-pressure side is serial data, needs also conversion of string, and sequential SRCLK2 is used for realizing the shift clock of going here and there and changing.Shift clock shift clock identical with SRCLK1 and the serial AD chip is synchronous, can become parallel data to the serial samples data-switching and the mistake of data can not occur.SRCLK3 is used for for the sequential of simulation output board D/A chip.

This control structure can realize the synchronized sampling of three-phase simply.And the conversion of sampling, data, analog quantity reduction output can realize synchronously, because the high-pressure side sampling plate does not need to produce the single-chip microcomputer of control timing, improved sample rate, simplified the structure of sampling plate, reduced the power consumption of sampling plate, dwindle the volume of high-pressure side sampling plate and sensing head part, simple and practical, the T2 timer refitting that can change electronegative potential 80C320 easily is worth the length that changes the T2 timing, thereby change the width of control timing pulse, change on high-tension side sample frequency.

1, high-pressure side data acquisition board explanation:

High-pressure side data acquisition board (2) is made of (2.3.9) primary current sensing head (2.1), sqignal conditioning device (2.3.1), multi-way switch (2.3.2), time sequence control logic (2.3.3), ADC translation circuit (2.3.4), power circuit (2.2) and the transmitting-receiving of a pair of optical fiber.

Current sensing head is small voltage output with the current transformation of a lead, through the prime signal conditioning circuit, is transformed to the simulating signal that meets the ADC conversion and is input to multi-way switch; Semaphores such as temperature, supply voltage, reference voltage are also through the parallel multi-way switch that is input to of corresponding signal conditioning circuit; Multi-way switch periodically switches under the control of sequential logic; The optical fiber transmitting-receiving receives the optical data stream that control optical fiber (4.1) transmits up from low-pressure side to (2.3.9), be converted into the electronics bit stream, and be transformed to and TTL through signal transformation circuit, the level logic of CMOS interfaces, this control signal of time sequence control logic demodulation generates the clock signal of control multi-way switch circulation switching and the clock signal of ADC sampling and serial-shift output, the serial data stream that ADC exports under the effect of the synchronous clock that demodulation obtains is through the driving circuit of fiber optic transmitter LED, form the luminous electronics bit stream of driving LED, the optical data stream of LED output is transferred on the photodetector of low-pressure side by measuring optical fiber (4.2), finishes a signals sampling job.The data acquisition board basic parameter:

● 4 tunnel single-ended inputs;

● input channel number optional 1,2 or 4 tunnel;

● 12 bit data resolution;

● the high sampling rate 75kHz of ADC, the sample frequency low side is controlled;

● A/D switching time is less than 8.5 μ s;

● serial transmission maximum rate 4MHz, general 1.5-2.0MHz.The basic function of data acquisition board:

1. two current signal input channels;

Can with Rogowski coil or CT interface;

3. temperature and supply voltage monitoring can be used for the temperature correction of test result;

4. have forward path and ADC serviceability diagnostic function;

5. adapt to sample frequency adjusting (0～50kHz) in a big way.2, lower-voltage circuit explanation:

Lower-voltage circuit (1) is made of 3 pairs of fiber optic interface circuits (1.1.1,1.2.1), waveform logic circuit (1.2.2), serial-parallel conversion circuit (1.1.2), single chip circuit (1.5), data interface circuit (1.3) and analog output circuit (1.4).

The principle of work of hardware circuit is such.Waveform logic circuit (1.2.2) generates the signal of clock signal, string and the conversion of controlling high-pressure side ADC sampling and the signal of DAC output; The clock signal of control high-pressure side ADC sampling is input on the driving circuit (1.2.1) of three road optical transmitter LED, and LED is converted into optical data stream and is coupled into 3 tunnel control optical fiber (4.1) and is sent to the high-pressure side, realizes the controlling of sampling to high-pressure side ADC; The high-pressure side forms the electronics bit stream by the optical data stream of the performance ADC transformation result that measuring optical fiber (4.2) transmits under the effect of photoelectric detector PIN (1.1.1), output in serial-parallel conversion circuit (1.1.2) and the serial D AC output circuit (1.4.1), and serial-parallel conversion circuit (1.1.2) is under the effect of synchronous shift clock, converting this serial data to 12 bit parallel data reads for singlechip controller (1.5), another road then is input in the DAC output module (1.4.1), 6 road DAC chips are reduced into stair-stepping simulating signal output with digital signal under the control signal effect that the waveform logic circuit provides, by the recovery of back level smoothing filter realization to the high-pressure side simulating signal; And singlechip controller is read into parallel data in the internal memory, again it is dumped in the dual port RAM of digital interface after doing necessary detection, processing, the opposite side interface of this dual port RAM can with other user's plates or PC interfaces, realize PC or other user's plates sharing to the data that collect;

The realization of software is such.Scm software mainly contains control timing and generates, and serial data is read in, differentiated, external trigger, the control of accurate synchronized sampling and and several functions of PC communication.

Control timing is generated by the interrupt service routine that overflows of the timer T2 of controller 80C320.T2 is the 16 bit timings/counter with multiple function, but it is set under 16 automatic heavy cartridges and the external trigger heavy cartridges counting working method, the spill-over of each counting will respond T2 when going out and interrupt, and finish the ADC controlling of sampling in interrupt service routine, the controlling of sampling of property performance period.

Serial data is read in by control string and conversion chip and is realized, string and conversion chip will high-endly convert parallel data to by the serial data stream under the optical fiber transmission and latch in parallel output terminal under the effect of synchronous shift clock, chip microcontroller being read in and adjusting parallel data, and deposit in successively in the dual port RAM, read for PC.

With the PC communication program, being read into sampled point in the single-chip microcomputer is derived successively to be deposited in the dual port RAM and is gone, and the dual port RAM of 4K byte is divided into two parts, and the upper half address is: 000H-77FH, the bottom half address is: 781H-FEOH.When half district is filled with, send out interrupt request and be filled with flag information, read for PC with putting to PC.Other communication informations are stored in the FE2H-FFFH unit.

When not having outer triggering signal, the cycle of operation control sampling work that configures in the T2 follow procedure of controller; When outer triggering signal, will carry out heavy cartridges to the count value of T2 at the trigger pulse negative edge, make the T2 count value by force synchronously once by pulse edge, so promptly realized externally sampling simultaneously under the trigger action---external trigger is sampled simultaneously.When this trigger pip was gps signal, the sampling of each phase ADC can be sampled under the commander of gps clock simultaneously, and the three-phase synchronously sampled data is stamped corresponding markers.

We introduce software frequency measurement algorithm, by low side the sample frequency of ADC are revised in real time, realize the basic synchronization of sample frequency and signal frequency, finish the accurate synchronized sampling with frequency-tracking performance.The control of high-end ADC sample frequency is realized by controller, the ADC control program then is to be finished by the interrupt service routine that overflows of T2 counter in the controller, and T2 works under 16 automatic heavy cartridges modes, so can realize that counter overflows the occurrence frequency of interruption as long as the automatic heavy cartridges value of T2 counter controlled, also being the frequency that control timing generates, also is the sample frequency of high-end ADC simultaneously.

Controller parameter and basic function have: basic parameter has:

1.3 at the plate optical fiber interface, optical fiber interface basic frequency 1.5MHz, highest frequency 10MHz;

2.4kBytes the dual port RAM extended memory;

3. 8 isa bus expansion interfaces that have interruption, inquiry and programmable functions;

4. high-performance 80C320 controller, basic frequency 24MHz;

5.6 road photoelectricity is isolated 12 DAC outputs of serial;

Basic function has:

1. can pass through isa bus or serial ports and PC communication function;

2. ADC sampling function resets;

3. block or enable the DAC output function;

4. multichannel synchronous data collection function simultaneously;

5. sampled data monitoring, processing capacity.

Simulation output board basic parameter has:

1. high speed optoelectronic isolation, DC/DC isolate;

2.6 road 12 bit serial DAC output channels;

3.4.096V reference voltage source;

4. bipolarity, gain, the adjustable output of zero drift;

5. outstanding integrated second-order low-pass filter;

Claims (2)

1, the multiphase digital photo-electric current transformer of synchronized sampling, it is by a plurality of high-pressure sides circuit, a plurality of Transmission Fibers and a lower-voltage circuit are formed, and high-pressure side circuit---data acquisition board (2) has current sampling element (2.1), digital light electric weight slowdown monitoring circuit (2.3), power-supply circuit (2.2); Lower-voltage circuit (1) has digital light electric weight observing and controlling system (1.2), receives and output (1.1) device (DOIU); It is characterized in that: each phase Transmission Fibers (4) is divided into measuring optical fiber (4.2) and control optical fiber (4.1), each controls the serial a/d sampling control signal input end that optical fiber (4.1) one ends connect digital optical quantum slowdown monitoring circuit (2.3) mutually, and the other end is connected to the sampling control signal output terminal of lower-voltage circuit jointly.

2, aforesaid current transformer is characterized in that lower-voltage circuit is connected to GPS.

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