Foreword

An advanced electric force line monitor system is usually made up of power monitoring, load balancing, protection and meter function, this framework can make the electricity get effective transmission, users fully utilize the electric power resource, guarantee the high-efficient operation of the electric wire netting. With the effective transmission of the electricity, the advanced electric force line monitoring system can predict the electric demand, measure and report the trouble condition, can also record, dynamic equilibrium support by saving energies, monitor and control Electric quality of transmission, assistance protection device.

In order to realize these systematic supervisory functions, need to use ADC the A/D converter Monitor much phase voltages and electric current. In addition, in order to meet various canonial harsh requirements, measure and optimize the power factor and loss, these converters can sample three passways and a phase passway synchronously at the same time . Considered that it is more difficult to move ahead simultaneously to the single converter, the manufacturer integrated in single capsulation multi-channelly to sample ADC at the same time. If the scheme of high integration density, can choose to customize ASIC and sample the converter at the same time.

Performance test- Local standards and international canonial requirements

Different international standards are not the same to the regulation of electric energy survey accuracy, this brings certain difficulty for development of the monitor system of electric force line, the products designed are very difficult to be generally approved. The measurement characteristic of quantity of supplying power must meet local standards or international canonial regulations. EU European Community Standard the intersection of EN and 50160, the intersection of IEC and 62053 and IEC 61850 provide rigorous lower limit, require to the intersection of multiple channel and precision of ADC that modern PSS use. In addition, it is stricter and stricter that the monitor system of electric force line transmissive to the electricity monitors the requirement for the precision in real time, and need complete fault detection, protection and dynamic load balancing function. For example the intersection of EU and standard the intersection of IEC and 62053 0.2 generally regard as a kind of global public standard Require the meter precision to reach 0.2% of the nominal current and voltage. For the power factor of precision measure, it is even better that degree should be up to 0.1% in phase matching.

International standard and local standard not merely provide requirement for short precision the most, still provide the modern electric force line monitoring and measuring system to the requirement for the sampling rate. Require that carries on the harmonic analysis of more rigorous high order to the AC supply, measure the trouble condition fast, for example, instantaneous voltage burr and trouble of falling of voltage. Therefore, this kind of application needs in the dynamic range up to 90dB, with 16ksps even more high sampling rate, carry on high precision to a plurality of passways, measure at the same time.

At present, a lot of countries of the whole world have already adopted EU standard, so, preferably consults these measurement criterias, regard it as index that the system must meet. Have summed up the requirement of EN 50160 in Table 1. As to the harmonic voltage, EN 50160 requirement can measure 25 subharmonics of 50Hz/60Hz mains voltage, it is not linear load to some, for example: Perceptual electrical machinery and switching power supply driver, demand to measure 127 subharmonics of 50Hz/60Hz mains voltage. In addition, it should be particularly noted that: Still propose recording the transient incident of the electric system in IEC 61850,etc. some new developing standards, it is even higher to exchange the number of times of periodic sample and reach each one for 256 times.

Typical electric wire netting monitoring system

The distribution form of the global three-phase electric wire netting is adopted so-called ” the Y type is connected ” ,” Y type ” Represent three-way voltage of 120 degrees of phase place deflection 1/3 of one week between each other . The 4th stripline, a phase, it is not the balanced load to usually supply. If every phase load in three phases keeps equality, keep balanced systematically, there is not electric current that flow into a phase. The typical electric wire netting monitors the framework and is shown as in Fig. 1, every looks power the voltage and electric current Can pass the voltage transformer of the electric current CT And the voltage transformer measurement of voltage electric distribution system is called the electro-motive force voltage transformer, PT . One intact system should include four to circuit corresponding to one each time in the three phases, zero corresponds to one pair .

According to the show of Fig. 1, ADC measures the voltage, electric current of the looks and a phase at the same time, to sampling and after the data of digital conversion are carried on digital handling, can receive active power, reactive power, apparent power, power factor isoparameter, and the all right electric force line of dynamic regulation is supported, revise the power factor, thus raise the efficiency of supplying power. Carry on FFT Fu set up the leaf to vary fast to sampled data Operation, can measure frequency and harmonic distortion, confirm information such as system loss, noise effect.

Fig. 1. Typical electric wire netting monitoring system, adopt and sample ADC at the same time.

Requirement for the electric monitoring system

Electric monitoring aid must can with up to 256 60Hz x or higher than 15,360sps to be per second to sample counting Sampling rate measure transient current and voltage,standard requirement in order to meeting. According to the accuracy requirement, the dynamic range of ADC used needs to reach 90dB in the system.

The dynamic range of voltage measurement ADC can be according to peak voltage and nominal voltage monitored, calculate according to the metric accuracy requirement of the power. For example, if the designing requirement measures 1.5kV 1500V Provisional overvoltage lower than trouble terms ,The nominal value of the mains voltage is 220V, the precision index demands to be up to 0.2%, the total dynamic range of the voltage measurement subsystem is at least:

20log 1500 220 *2000 =83dB

Note: All suppose while calculating that designs accuracy requirement as 0.05%, is superior to the standard whose precision is 0.2% to require. Margin of this design can guarantee to meet the standard requirement systematically finally.

The electric current measures the specification that will influence ADC too, if the electric monitoring system designing requirement reaches the representative value it is 100A: 10A 10A nominal value, 100A maximum value And 0.2 kinds 0.2% The norm requires, the total dynamic range that the electric current measures the subsystem is:

20log 100 10 *2000 =86dB

Can find out and design the demand for high-performance ADC from the above-mentioned case at present clearly, as to the dynamic range of 86dB, need sampling rate as 16 ADCs of 16ksps even higher sampling rate. In order to guarantee electric current and voltage of precision measure three-phase and a phase Model Y system, ADC can sample up to eight passways the voltage of No. four, electric current of No. four at the same time . In addition, also need to revise the phase excursions of the incoming electric current of the voltage transformer, voltage or delay time ,This is for measuring and revising the power factor, it is very important to raise the system of efficiency of supplying power effectively. ADC chooses

While monitoring system selection accurate ADC for the electric wire netting, the designer must understand sampling rate and standard are required. As to designing at present, they must also consider other factors, for example: Effective input impedance ZIN , signal phase control, small dimension are capsulated etc.. After understanding these demands, the designer turns attention to high-performance ADC supported the multiple channel to sampled at the same time, used in controlling or multiple channel SCADA supervisory control and data collecting system of electric force line . Several kinds of ADC schemes can meet the harsh requirement that electric wire netting monitors, the overwhelming majority in the scheme of these goal is that 6 passways, 16 sample ADC at the same time, sampling rate reachable 250ksps.

Some companies offer six passway, low power consumption, 250ksps SAR successive approximation register Type ADC. In integrate eight No. high precision, low power consumption, 16, 250ksps SAR ADC while being on-chip while being single * MAX11046 that Maxim offer. MAX11046 can reach the signal to noise ratio higher than 90dB.

Effective input impedance ZIN

ZIN is confirmed by input capacitance and sampling frequency:

ZIN =1/CIN * FSAMPLE

In the type, FSAMPLE is the sampling frequency, CIN =15pF.

If ADC has higher ZIN, for instance: MAX11046, can be connected to the voltage and electric current and measured the voltage transformer directly. This kind of connection saves the external accurate instrument amplifier or dashpot, thus reduce system cost, area and system power consumption of circuit board effectively. Fig. 2 shows and employs the case to provide because of MAX11046EV assess The single-phase monitor system on the board, is connected to the electric force line and monitored the voltage transformer. Can be found out from the structure chart: The voltage transformer of electric force line and sampling at the same time, connection between the multiple channel data converters are very simple, can save cost and space effectively. As to the intersection of three-phase and power supply system, can duplicate every one-phase and zero phase to get three phases circuit this.

Phase control of signal

Will produce certain phase difference or delay time when and high-pressure signal passing voltage transformer changes to the lower voltage in wink ,It causes more severe problem in electric management or electric wire netting is controlled and employed that this delays time. In order to solve these problems, the designer needs to pass the control phase of the software on the rear end, or through ADC retrimming number on the forward end, dispel the deflections of voltage and electric current signal, obtain actual, rigorous power factor measurement in order to dispose in Y type. Three-phase electric phase difference deviate from, show, have power consumption, the intersection of precision measure and power factor of reaching by 120, can revise, make the electric wire netting keep high-efficient to operate it.

In the traditional scheme, it was digital form that utilized sampling at the same time, the multiple channel, 16 ADCs to adopt while solving the phase control problem of signals, carry on subsequent processing to ADC output data. MAX11046 of Maxim adopts this way promptly, uses this kind of ADC, need to take up the expenses conditioning signal phase place of greater software.

Some ADC schemes put out newly at present can regulate the input phase place of each passway independently, the adjustable delays time for 0 to 333 s, it is 1.33 s to regulate step length. The design save above-mentioned the intersection of software and expenses, 24 of MAX11040, 4 passway, – ADC adopt this scheme promptly, adopt cascade to sample 32 passways at most while carrying on high precision after disposing. It can be in the external voltage transformer of internal compensation or phase difference that the input filter produces that what each passway possesses is adjustable to sample the phase place function. /SYNC can utilize the distal clock source to periodically reach the conversion sequence of eight devices to input synchronously.

Foreword

An advanced electric force line monitor system is usually made up of power monitoring, load balancing, protection and meter function, this framework can make the electricity get effective transmission, users fully utilize the electric power resource, guarantee the high-efficient operation of the electric wire netting. With the effective transmission of the electricity, the advanced electric force line monitoring system can predict the electric demand, measure and report the trouble condition, can also record, dynamic equilibrium support by saving energies, monitor and control Electric quality of transmission, assistance protection device.

In order to realize these systematic supervisory functions, need to use ADC the A/D converter Monitor much phase voltages and electric current. In addition, in order to meet various canonial harsh requirements, measure and optimize the power factor and loss, these converters can sample three passways and a phase passway synchronously at the same time . Considered that it is more difficult to move ahead simultaneously to the single converter, the manufacturer integrated in single capsulation multi-channelly to sample ADC at the same time. If the scheme of high integration density, can choose to customize ASIC and sample the converter at the same time.

Performance test- Local standards and international canonial requirements

Different international standards are not the same to the regulation of electric energy survey accuracy, this brings certain difficulty for development of the monitor system of electric force line, the products designed are very difficult to be generally approved. The measurement characteristic of quantity of supplying power must meet local standards or international canonial regulations. EU European Community Standard the intersection of EN and 50160, the intersection of IEC and 62053 and IEC 61850 provide rigorous lower limit, require to the intersection of multiple channel and precision of ADC that modern PSS use. In addition, it is stricter and stricter that the monitor system of electric force line transmissive to the electricity monitors the requirement for the precision in real time, and need complete fault detection, protection and dynamic load balancing function. For example the intersection of EU and standard the intersection of IEC and 62053 0.2 generally regard as a kind of global public standard Require the meter precision to reach 0.2% of the nominal current and voltage. For the power factor of precision measure, it is even better that degree should be up to 0.1% in phase matching.

International standard and local standard not merely provide requirement for short precision the most, still provide the modern electric force line monitoring and measuring system to the requirement for the sampling rate. Require that carries on the harmonic analysis of more rigorous high order to the AC supply, measure the trouble condition fast, for example, instantaneous voltage burr and trouble of falling of voltage. Therefore, this kind of application needs in the dynamic range up to 90dB, with 16ksps even more high sampling rate, carry on high precision to a plurality of passways, measure at the same time.

At present, a lot of countries of the whole world have already adopted EU standard, so, preferably consults these measurement criterias, regard it as index that the system must meet. Have summed up the requirement of EN 50160 in Table 1. As to the harmonic voltage, EN 50160 requirement can measure 25 subharmonics of 50Hz/60Hz mains voltage, it is not linear load to some, for example: Perceptual electrical machinery and switching power supply driver, demand to measure 127 subharmonics of 50Hz/60Hz mains voltage. In addition, it should be particularly noted that: Still propose recording the transient incident of the electric system in IEC 61850,etc. some new developing standards, it is even higher to exchange the number of times of periodic sample and reach each one for 256 times.

Typical electric wire netting monitoring system

The distribution form of the global three-phase electric wire netting is adopted so-called ” the Y type is connected ” ,” Y type ” Represent three-way voltage of 120 degrees of phase place deflection 1/3 of one week between each other . The 4th stripline, a phase, it is not the balanced load to usually supply. If every phase load in three phases keeps equality, keep balanced systematically, there is not electric current that flow into a phase. The typical electric wire netting monitors the framework and is shown as in Fig. 1, every looks power the voltage and electric current Can pass the voltage transformer of the electric current CT And the voltage transformer measurement of voltage electric distribution system is called the electro-motive force voltage transformer, PT . One intact system should include four to circuit corresponding to one each time in the three phases, zero corresponds to one pair .

According to the show of Fig. 1, ADC measures the voltage, electric current of three phases and a phase at the same time, to sampling and after the data of digital conversion are carried on digital handling, can receive active power, reactive power, apparent power, power factor isoparameter, and the all right electric force line of dynamic regulation is supported, revise the power factor, thus raise the efficiency of supplying power. Carry on FFT Fu set up the leaf to vary fast to sampled data Operation, can measure frequency and harmonic distortion, confirm information such as system loss, noise effect.

Fig. 1. Typical electric wire netting monitoring system, adopt and sample ADC at the same time.

Requirement for the electric monitoring system

Electric monitoring aid must can with up to 256 60Hz x or higher than 15,360sps to be per second to sample counting Sampling rate measure requirement transient current and voltage is getting more standard in order to meeting. According to the accuracy requirement, the dynamic range of ADC used needs to reach 90dB in the system.

The dynamic range of voltage measurement ADC can be according to peak voltage and nominal voltage monitored, calculate according to the metric accuracy requirement of the power. For example, if the designing requirement measures 1.5kV 1500V Provisional overvoltage lower than trouble terms ,The nominal value of the mains voltage is 220V, the precision index demands to be up to 0.2%, the total dynamic range of the voltage measurement subsystem is at least:

20log 1500 220 *2000 =83dB

Note: All suppose while calculating that designs accuracy requirement as 0.05%, is superior to the standard whose precision is 0.2% to require. Margin of this design can guarantee to meet the standard requirement systematically finally.

The electric current measures the specification that will influence ADC too, if the electric monitoring system designing requirement reaches the representative value it is 100A: 10A 10A nominal value, 100A maximum value And 0.2 kinds 0.2% The norm requires, the total dynamic range that the electric current measures the subsystem is:

20log 100 10 *2000 =86dB

Can find out and design the demand for high-performance ADC from the above-mentioned case at present clearly, as to the dynamic range of 86dB, need sampling rate as 16 ADCs of 16ksps even higher sampling rate. In order to guarantee electric current and voltage of precision measure three-phase and a phase Model Y system, ADC can sample up to eight passways the voltage of No. four, electric current of No. four at the same time . In addition, also need to revise the phase excursions of the incoming electric current of the voltage transformer, voltage or delay time ,This is for measuring and revising the power factor, it is very important to raise the system of efficiency of supplying power effectively. ADC chooses

While monitoring system selection accurate ADC for the electric wire netting, the designer must understand sampling rate and standard are required. As to designing at present, they must also consider other factors, for example: Effective input impedance ZIN , signal phase control, small dimension are capsulated etc.. After understanding these demands, the designer turns attention to high-performance ADC supported the multiple channel to sampled at the same time, used in controlling or multiple channel SCADA supervisory control and data collecting system of electric force line . Several kinds of ADC schemes can meet the harsh requirement that electric wire netting monitors, the overwhelming majority in the scheme of these goal is that 6 passways, 16 sample ADC at the same time, sampling rate reachable 250ksps.

Some companies offer six passway, low power consumption, 250ksps SAR successive approximation register Type ADC. In integrate eight No. high precision, low power consumption, 16, 250ksps SAR ADC while being on-chip while being single * MAX11046 that Maxim offer. MAX11046 can reach the signal to noise ratio higher than 90dB.

Effective input impedance ZIN

ZIN is confirmed by input capacitance and sampling frequency:

ZIN =1/CIN * FSAMPLE

In the type, FSAMPLE is the sampling frequency, CIN =15pF.

If ADC has higher ZIN, for instance: MAX11046, can be connected to the voltage and electric current and measured the voltage transformer directly. This kind of connection saves the external accurate instrument amplifier or dashpot, thus reduce system cost, area and system power consumption of circuit board effectively. Fig. 2 shows and employs the case to provide because of MAX11046EV assess The looks monitor system on the board, is connected to the electric force line and monitored the voltage transformer. Can be found out from the structure chart: The voltage transformer of electric force line and sampling at the same time, connection between the multiple channel data converters are very simple, can save cost and space effectively. As to the intersection of three-phase and power supply system, can duplicate every one-phase and zero phase to get three phases circuit this.

Phase control of signal

Will produce certain phase difference or delay time when and high-pressure signal passing voltage transformer changes to the lower voltage in wink ,It causes more severe problem in electric management or electric wire netting is controlled and employed that this delays time. In order to solve these problems, the designer needs to pass the control phase of the software on the rear end, or in the conditioning signal through ADC again of forward end, dispel the deflections of voltage and electric current signal, obtain actual, rigorous power factor measurement in order to dispose in Y type. Three-phase electric phase difference deviate from, show, have power consumption, the intersection of precision measure and power factor of reaching by 120, can revise, make the electric wire netting keep high-efficient to operate it.

In the traditional scheme, it was digital form that utilized sampling at the same time, the multiple channel, 16 ADCs to adopt while solving the phase control problem of signals, carry on subsequent processing to ADC output data. MAX11046 of Maxim adopts this way promptly, uses this kind of ADC, need to take up the expenses conditioning signal phase place of greater software.

Some ADC schemes put out newly at present can regulate the input phase place of each passway independently, the adjustable delays time for 0 to 333 s, it is 1.33 s to regulate step length. The design save above-mentioned the intersection of software and expenses, 24 of MAX11040, 4 passway, – ADC adopt this scheme promptly, adopt cascade to sample 32 passways at most while carrying on high precision after disposing. It can be in the external voltage transformer of internal compensation or phase difference that the input filter produces that what each passway possesses is adjustable to sample the phase place function. /SYNC can utilize the distal clock source to periodically reach the conversion sequence of eight devices to input synchronously.

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Fig. 2. MAX11046 wait for multiple channel sample ADC can simplify advanced the intersection of electric wire netting and design of monitoring system effectively at the same time

Small dimension is capsulated

Need to consider the physical size question in a lot of electric wire netting is monitored and employed, because the system usually needs to monitor the multi-channel heterogeneous power, especially in the electric distribution center. As to different schemes, the circuit board taken up in each passway of ADC is different too in area, for example: MAX11040 15.9mm2 in each area that passway take up, size have only other the intersection of manufacturer and half of scheme. ADC more high packaging density allows to hold the multiple channel on PCB board, contributes to reducing the size, power consumption and cost of the whole measuring system.

Overvoltage protection

Optimizing system design must also prevent the system from failing under the circumstances that overvoltage or other electric force lines are interfered with, other devices of MAX11040 and this series have integrated and pressed and protected the function similar to ESD to protect ,Protective circuit use the intersection of 6V and clamping diode and internal logical circuit, logical circuit measure, it beens to be can the location of fault location press. Other ADC suppliers have adopted one’s own protecting a framework, but the majority needs to use the external diode.

While using ADC, short circuit and open circuit trouble which measures the electric wire netting are this kind of protection system most important function. Measure through the data observing ADC. It is a complicated question to make and touch off relay protection under some conditions, depend on the monitoring system manufacturer to a great extent. Even so, a kind of generally more acknowledged views are: The trigger relay is protected as result not touched off terribly under the trouble condition.

Conclusion

Have framework more basic while lasting power transmission people growth against demands electric or ” The intellectual electric wire netting ” Investment increase rapidly,through being integrated monitor power, load balancing, protection and meter function, construct the advanced electric force line monitoring system, the utility and users Can monitor, transmit, use and control the electric wire netting more effectively.

Difficulty of development that canonial diversity and all sorts of requirements not put forward with enterprises have increased the monitoring system of the electric wire netting on one hand, on the other hand even need these apparatuses to be approved by the more generally one. Some comparatively rigorous standards, for example: EN 50160, IEC 62053 and IEC 61850, stipulate higher energy measures the precision, provides rigorous lower limit to require; These standards still require the sampling rate to meet monitoring, fault detection and isostatic requirement of dynamic load of real-time power transmission. ADC that the standard used for modern multiple channel monitoring system has made the strict, sharp principle. Test the factor while being other, comprising: Effective input impedance ZIN , signal phase control and small dimension are capsulated etc., will influence the choice of ADC. At present, high performance, sampling ADC to usually direct against three-phase electric and a phase at the same time Monitoring and measuring system optimize, be lasted schemes first-selected that high density designed these device, can also reduce the cost of the integrated system while offering high performance index, make the area of the circuit board minimum.