CN105891605A - Distribution transformer grounding resistor, current online measurement equipment and method thereof - Google Patents
Distribution transformer grounding resistor, current online measurement equipment and method thereof Download PDFInfo
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- CN105891605A CN105891605A CN201410614170.9A CN201410614170A CN105891605A CN 105891605 A CN105891605 A CN 105891605A CN 201410614170 A CN201410614170 A CN 201410614170A CN 105891605 A CN105891605 A CN 105891605A
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Abstract
The invention relates to a distribution transformer grounding resistor, current online measurement equipment and a method thereof. The equipment comprises a sampling circuit, a low pass filter, a switch capacitance filter, a PGA circuit, a DSP and an excitation circuit. The sampling circuit, the low pass filter, the switch capacitance filter, the PGA circuit, the DSP and the excitation circuit are sequentially connected. The equipment also comprises a communication interface module or a display interface module. The communication interface module or the display interface module is connected to the DSP. Hardware maximization of the equipment adopts a digital signal processing technology so that a disadvantage of hardware filtering is overcome. The method is a measurement and calculating method which uses a signal processing system formed by the switch capacitance filter, the programmable amplifier (PGA) and the DSP to realize carrying out digital filtering on a sampling signal and calculates an effective value based on a sine wave.
Description
Technical field
The present invention relates to a kind of measurement equipment and measuring method, more specifically distribution become
Depressor (platform district transformer) earth resistance, the in-situ measurement equipment of electric current and method.
Background technology
A kind of can monitoring grounding linear contact lay is the best in real time equipment, can send out in time
Existing distribution transformer earthing resistance is abnormal, informs the hidden danger that user exists, processes rapidly
Equipment fault, trouble-saving generation.
Some products are not on-line real time monitoring on the market, even real-time online
The most generally there is bigger measured deviation in the equipment of monitoring, temperature influence is relatively big, surveys
Weight range is less, measures the problems such as inaccurate.
The I of Long Yuan for product, can on-line real time monitoring earth resistance, the change of current value,
But this product, is designed as the appearance of ring-shaped cylinder, and not only inner circle is less, and does not has
External interface, needs to take bottom apart, safeguards communication module.Further, circuit
Realize complexity, general through what amplification, what hardware filtering, then, have
Valid value rectification circuit or peak holding circuit, input Chip Microcomputer A/D sampling, calculate
Valid value, uses hardware circuit in a large number, it is achieved complicated, and easily by temperature interference, shadow
Ring certainty of measurement.
Summary of the invention
The present invention is directed in problem above and/or other problem of the prior art extremely
A few problem, it is provided that a kind of distribution transformer earthing resistance, electric current on-line measurement set
Standby and method.
The invention provides a kind of employing SCF and integrated PGA combination should
Signal processing method, application DSP measures equipment and the side of calculating to signal
Method.
The present invention is including, but not limited to following scheme.
A kind of distribution transformer earthing resistance, electric current in-situ measurement equipment, wherein, institute
The equipment of stating includes sample circuit, low pass filter, SCF, PGA electricity
Road, DSP, exciting circuit,
Described sample circuit, described low pass filter, described SCF,
Described PGA circuit, described DSP and described exciting circuit are sequentially connected with.
Preferably, described equipment also includes communication interface modules or display interface module,
Described communication interface modules or described display interface module are connected with described DSP.
Preferably, described sample circuit for induced signal is sampled, described in take
Sample circuit includes sampling precision resistance, protection device and voltage follower；
Described low pass filter, for being filtered HF noise signal, does not affects
The measurement signal of 50HZ；
Described SCF is high q-factor circuit, has tunable center frequency；
Described PGA circuit selects the PGA chip of Low Drift Temperature, and carries out two-stage amplification；
Described DSP is used for realizing signal transacting and main control function；
Described exciting circuit use low-pass filter circuit, can realize regulable center frequency,
The sinewave output of big electric current.
Preferably, described communication interface modules or described display interface module use module
Change external design, it is possible to insert carrier communication module or GPRS communication module or small wireless
One in module or display apparatus module.
Preferably, described DSP directly samples sine wave, again carries out digital filtering,
Calculate virtual value rather than virtual value of directly sampling.
Preferably, described sample circuit completes the sampling to induced signal, after sampling,
After passive filtering, enter voltage follower, send the first voltage to described low pass
Wave filter.
Preferably, described low pass filter is 2 rank low pass filters, by frequency is
2.5KHZ, described low pass filter exports the second voltage to described switch-capacitor filtering
Device.
Preferably, described SCF includes that 2 single-chip integration clocks are adjustable
Filter block, is used for forming 14 rank bandpass filter.
Preferably, described PGA circuit output signal is adopted to described DSP, described DSP
N number of input data in sample a period of time, record is in RAM, to the N in RAM
Individual sampled value carries out digital filtering, and filtered data carry out convolution algorithm, calculates
Draw the virtual value of its sine wave, and then calculate corresponding resistance or current value size.
Preferably, described DSP controls described exciting circuit, sends swashing of various frequency
Encourage signal.
A kind of distribution transformer earthing resistance, electric current On-line Measuring Method, wherein, institute
The method of stating comprises the steps:
Initialize；
Judgement is measuring resistance or surveys electric current；
Sampling；
Make sampled data through SCF；
Make described data through PGA circuit；
Data carry out DSP sampling digital filtering process；And
Virtual value is calculated by DSP.
Preferably, in the case of measuring resistance, open exciting circuit, then take
Sample；
In the case of surveying electric current, it is sampled in the case of closing exciting circuit.
The equipment of the preferably practical present invention of the described method of the present invention realizes.
The present invention propose a kind of based on DSP observing and controlling can real-time online, accurately survey
Amount distribution transformer earthing line resistance, the design of electric current, accomplished accurately, reliably
Measure distribution transformer earthing resistance, electric current, solve indeterminable problem.
And, it is achieved through low pass circuit after grab sampling, pass through switch-capacitor filtering
Device, inputs PGA, then directly inputs DSP and carry out numerical calculation.
In shape, for distribution transformer earthing resistance, electric current in-situ measurement equipment
This outdoor hanging apparatus, devises external, pluggable shell, is a pole
Innovative breakthrough.
The product using this programme has certainty of measurement height, measures wide ranges, anti-power frequency
Interference performance is strong, anti-loading noise immune is strong, insensitive to temperature change, can be automatic
Select the features such as multi-frequency measurement, external communication module.
Accompanying drawing explanation
Fig. 1 be the distribution transformer earthing resistance according to an embodiment of the invention,
The measuring circuit block diagram of electric current in-situ measurement equipment.
Fig. 2 shows a concrete example of the sample circuit measuring signal.
Fig. 3 shows a concrete example of low pass filter.
Fig. 4 shows that of the SCF of tunable center frequency specifically shows
Example.
Fig. 5 shows an example of the typical frequencies response diagram of SCF.
Fig. 6 shows a concrete example of PGA circuit.
Fig. 7 shows the bottom view of the shelling machine of the equipment according to the present invention.
Fig. 8 shows the measurement procedure of the equipment according to the present invention.
Detailed description of the invention
Principle and the illustrative embodiments of the present invention are described with reference to the accompanying drawings.
Fig. 1 be the distribution transformer earthing resistance according to an embodiment of the invention,
The measuring circuit block diagram of electric current in-situ measurement equipment.Noting, the distribution in the present invention becomes
Depressor can advantageously be platform district transformer, and in-situ measurement equipment sometimes referred to as exists
Line is measured equipment, on-line measurement terminal, is measured equipment, measuring terminals, they essence
Upper identical.
In FIG, the circuit in dotted line be the present invention hardware design core content it
One.The equipment of the present invention is by sample circuit 1, low pass filter 2, switch-capacitor filtering
Device 3, PGA circuit 4, DSP 5, exciting circuit 6 and general module 7 form.
Sample circuit 1, low pass filter 2, SCF 3, PGA circuit 4,
DSP 5, exciting circuit 6 are sequentially connected with, and general module 7 is connected with DSP 5.
One of this equipment feature: measurement resistance, current sampling are united two into one, only uses
One road sample circuit, filter circuit can realize measuring.
The two of this equipment feature: application switch capacitive filter, integrated PGA electricity simultaneously
Road and DSP.
The three of this equipment feature: this equipment can measure by multiple centre frequencies, main
Want Applied Digital filtering technique.
Below modules in circuit block diagram is illustrated:
1) sample circuit 1, it completes the sampling to induced signal, it preferably includes take
Sample precision resistance, protection device and voltage follower.
2) HF noise signal is filtered by low pass filter 2, does not affect 50HZ's
Measure signal.
3) SCF 3, it is high q-factor circuit, and temperature influence is minimum,
There is tunable center frequency.In one example, SCF uses Ling Li
The LTC1067 that you are special.
4) PGA circuit 4, this circuit selected the PGA chip that Low Drift Temperature is integrated, and
Carry out two-stage amplification.Measurement scope can reach 0.01-1200 ohm.An example
In, this PGA circuit 4 uses the PGA280 of TI.
5) DSP 5 microcontroller is as one of core devices, its realize signal transacting and
Main control function, it is preferred to use the high-performance microcontroller with DSP core of TI company
TMS320F28035。
6) exciting circuit 6, it uses low-pass filter circuit, and can realize centre frequency can
Sinusoidal wave output that adjust, big electric current.
7) general module 7, it can be communication interface modules or display interface module.
Use the design of modularization external.Load communication module or display module can be inserted, described
Communication module includes but not limited to wave communication module or GPRS communication module or small wireless
Module, described display module for example, liquid crystal display device module, system can be automatically
Identify the kind of the module of grafting.In the structure shown here, interface is unified, selects different mould
Block need not carry out any amendment to hardware.
In equipment, resistance, current sampling, filtering, measuring circuit share a circuit,
Make full use of circuit characteristic, provide cost savings.
In equipment, application switch capacitive filter, integrated PGA circuit and DSP numeral
Signal processing technology improves circuit anti-interference performance, resisting temperature sensitive property, noise
Low, certainty of measurement is high.
In equipment, circuit can realize multicenter frequency and measure, and circuit is simple, can
Lean on, make measurement frequency be prevented effectively from interference.
In equipment, the design of general module makes easy to maintenance, simple to operate.
Preferably, DSP directly samples sine wave, again carries out digital filtering, carries out
Calculate virtual value rather than virtual value of directly sampling, thus be avoided that true rms circuit band
The temperature come is floated, interference, improves accuracy.
Apply the design of this circuit block diagram, there is high anti-interfering performance, high temperature resistance
Degree sensitive property.The equipment of the present invention is tested by the initial stage, measures scope, measurement
Precision has reached requirement, have passed through high/low temperature test, and certainty of measurement is produced with similar other
Condition ratio increases substantially.The overall plan of the present invention has creativeness.To production
There is certain positive effect.
Below a concrete example of the present invention is made an explanation, but, the present invention is not
It is limited to following concrete example and explanation.
In fig. 2 it is shown that measure a concrete example of the sample circuit of signal.Take
Sample circuit 1 completes the sampling to induced signal.After sampling, enter after passive filtering
The voltage follower being made up of OPA2180ID.Output voltage 1 (voltage 1) is given low
Bandpass filter 2.
In fig. 3 it is shown that low pass filter concrete example.Low pass filter
2 pairs of HF noise signals are filtered.This wave filter is 2 rank low pass filters,
It is 2.5KHZ by frequency.The signal that frequency is i.e. only more than 2.5KHZ has more apparent
Attenuation, high-frequency signal is filtered, the signal to 40HZ to 1.6KHZ
Substantially there is no attenuation.Low pass filter 3 inputs Voltage 1, exports Voltage 2
(voltage 2) is to SCF 3.
Fig. 4 shows of the SCF (circuit) of tunable center frequency
Concrete example.
SCF 3,160khz is that it controls clock, exports Voltage 3
(voltage 3).In one example, this SCF 3 uses Ling Lier spy's
LTC1067, the filter Q of design is high, and temperature influence is minimum.Make full use of
There are 2 adjustable filter block of single-chip integration clock in LTC1067, are used for forming 14
Rank bandpass filter.Devise Butterworth bandpass filter, its representative center frequency
Rate is set to 1.6kHz, and-three dB bandwidth is not more than 50Hz, by controlling the clock of CLK,
Its centre frequency can be changed.Its typical frequency response curve is as shown in Figure 5.
This bandpass filter bandwidth only has 50HZ, Q value up to 45.2516, general 4
Rank active filter continuous time can not accomplish the highest Q value, the narrowest
Bandwidth.Interference noise can be further filtered out by the design of this wave filter, increases and measures
Precision.And it is possible to change this bandpass filter by changing input clock frequency
Centre frequency so that increase measuring center frequency become relatively easy.If with one
As General operational amplifier composition band lead to, it is impossible to realize multicenter frequency measurement.
Fig. 6 is a concrete example of PGA circuit 4, and it preferably selects the collection of zero temp shift
Become circuit PGA280, and carry out two-stage amplification.Reach measurement scope 0.01-1200
Ohm.
This circuit has a zero temp shift characteristic, and have 1/8,1/2,1,2,4,8,
32,64,128 totally 8 grades of gains available.This modular circuit, completes analog circuit
With the isolation of digital circuit, signal is amplified further, through by 10K resistance and 10p
After the passive low pass of electric capacity composition, the ADC sampling pipe of output ADC0 to DSP
Pin.Have excellence performance: low shutoff voltage: 3 μ V (G=128)；Close to 0
Gain drift: 0.5ppm/ DEG C；Excellent is linear: 1.5ppm；Excellent common mode
Rejection ratio CMRR: 140dB；High input impedance；Low-down noise；Differential signal
Output, and inputting and output isolation, save analog signal and data signal every
From device.Circuit is very simple, excellent performance.
PGA outputs signal to DSP digital processing unit, DSP complete input ADC0
The sampling of signal, N number of data of sampling a period of time T, record is in RAM.Right
N number of sampled value in RAM carries out digital filtering.And by filtered data, carry out
Convolution algorithm, calculates the virtual value of its sine wave, and then calculates corresponding electricity
Resistance or current value size.
DSP also controls communication or display module communicates or shows；Control excitation electricity
Road 6, sends the pumping signal of various frequency.
Exciting circuit 7 can use low-pass filter circuit, can realize just exporting big electric current
String ripple.
Communication interface modules have employed the design of modularization external.Earth resistance, electric current
The bottom view of the shelling machine figure of in-situ measurement equipment is as shown in Figure 7.
Equipment designs and includes following feature: 1) integrated design, wearing of earth connection to be measured
String holes 70 is oval；2) slotted eye 70 both sides be respectively electric power incoming line hole and
RS485 line or GPRS antenna wire inlet/outlet hole；3) lower right corner be generic communications modules or
Display module slot, and it is designed with transparent plastic cover；4) slot can insert carrier communication
Module or GPRS communication module or small wireless module, or liquid crystal display device module, interface
Unified, select disparate modules hardware need not be carried out any amendment.
Noting, each size in Fig. 7 is only schematically, is not used in the restriction present invention.
Fig. 8 shows the measurement procedure of the equipment according to the present invention.
First, in step sl, equipment initialization is carried out.Then, enter step S2,
Judgement is measuring resistance or surveys electric current.In the case of measuring resistance, enter step S3,
Open exciting circuit, then, enter step S4, be sampled.In the feelings surveying electric current
Under condition, it is directly entered step S4 from step S2, is sampled.In step s 5, number
According to through SCF, in step s 6, data through PGA circuit,
In step S7, data are carried out DSP sampling digital filtering and processes, in step s 8,
Virtual value is calculated by DSP.
The innovation of the present invention includes uniting two into one measurement resistance, current sampling,
Zhi Yong mono-road sample circuit, filter circuit can realize measuring.During measurement of Grounding Resistance,
Opening exciting circuit, export 1.6KHZ sinusoidal signal, sensor circuit can be coupled to
The electric current of 1.6KHZ, sampling, it can be calculated after filtering.When measuring electricity
During stream signal, closing exciting circuit, sensor circuit will only sense city's telecommunications of 50HZ
Number, sample equally, control SCF through DSP, form 50HZ center
The band of frequency is logical to be filtered, and input DSP calculates its 50HZ current value.
The innovation of the present invention also includes this earth resistance, electric current in-situ measurement equipment
After sampling, the filtering of SCF that signal is carried out, integrated PGA amplify and
Digital filtering processes, and the storage overcoming discrete device amplifier and hardware filter lacks more
Point, such as: Hz noise, load disturbance, temperature impact etc..
The innovation of the present invention also includes this earth resistance, electric current in-situ measurement equipment
Have employed external communication module, the exterior design of hot swappable generic communications modules.
Support external pluggable single-phase carrier communication module, GPRS communication module, small wireless
Any one in module, liquid crystal display device module etc., has the tune of external simultaneously
Examination RS485 interface, visual running indicator show.
The preferred embodiment of the present invention is illustrated above with reference to accompanying drawing, but, it should
Understanding, described above is only exemplary.Those skilled in the art can not take off
On the premise of the spirit and scope of the present invention, to the present invention, various modification can be adapted and becomes
Type.Protection scope of the present invention is limited by the accompanying claims.
Claims (13)
1. distribution transformer earthing resistance, an electric current in-situ measurement equipment, its feature
Be, described equipment include sample circuit, low pass filter, SCF,
PGA circuit, DSP, exciting circuit,
Described sample circuit, described low pass filter, described SCF,
Described PGA circuit, described DSP and described exciting circuit are sequentially connected with.
Equipment the most according to claim 1, it is characterised in that
Described equipment also includes communication interface modules or display interface module, described communication
Interface module or described display interface module are connected with described DSP.
Equipment the most according to claim 2, it is characterised in that
Described sample circuit is used for being sampled induced signal, described sample circuit bag
Include sampling precision resistance, protection device and voltage follower；
Described low pass filter, for being filtered HF noise signal, does not affects
The measurement signal of 50HZ；
Described SCF is high q-factor circuit, has tunable center frequency；
Described PGA circuit selects the PGA chip of Low Drift Temperature, and carries out two-stage amplification；
Described DSP is used for realizing signal transacting and main control function；
Described exciting circuit use low-pass filter circuit, can realize regulable center frequency,
The sinewave output of big electric current.
Equipment the most according to claim 3, it is characterised in that
Described communication interface modules or described display interface module use modularization external
Design, it is possible to insert carrier communication module or GPRS communication module or small wireless module or aobvious
Show the one in device module.
Equipment the most according to claim 4, it is characterised in that
Described DSP directly samples sine wave, again carries out digital filtering, calculates effectively
Value rather than virtual value of directly sampling.
6. according to the equipment according to any one of claim 1-5, it is characterised in that
Described sample circuit completes the sampling to induced signal, after sampling, through passive
Enter voltage follower after filtering, send the first voltage to described low pass filter.
Equipment the most according to claim 6, it is characterised in that
Described low pass filter is 2 rank low pass filters, is 2.5KHZ by frequency,
Described low pass filter exports the second voltage to described SCF.
Equipment the most according to claim 7, it is characterised in that
Described SCF includes 2 adjustable wave filters of single-chip integration clock
Block, is used for forming 14 rank bandpass filter.
Equipment the most according to claim 8, it is characterised in that
When described PGA circuit output signal is to described DSP, described DSP sampling one section
Interior N number of input data, record is in RAM, to the N number of sampled value in RAM
Carry out digital filtering, filtered data are carried out convolution algorithm, just calculate it
The virtual value of string ripple, and then calculate corresponding resistance or current value size.
Equipment the most according to claim 9, it is characterised in that
Described DSP controls described exciting circuit, sends the pumping signal of various frequency.
11. 1 kinds of distribution transformer earthing resistance, electric current On-line Measuring Method, it is special
Levying and be, described method comprises the steps:
Initialize；
Judgement is measuring resistance or surveys electric current；
Sampling；
Make sampled data through SCF；
Make described data through PGA circuit；
Data carry out DSP sampling digital filtering process；And
Virtual value is calculated by DSP.
12. methods according to claim 11, it is characterised in that
In the case of measuring resistance, open exciting circuit, be then sampled；
In the case of surveying electric current, it is sampled in the case of closing exciting circuit.
13. according to the method described in claim 11 or 12, it is characterised in that
Described method uses the equipment described in any one in claim 1 to 10 to realize.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410614170.9A CN105891605A (en) | 2014-11-04 | 2014-11-04 | Distribution transformer grounding resistor, current online measurement equipment and method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410614170.9A CN105891605A (en) | 2014-11-04 | 2014-11-04 | Distribution transformer grounding resistor, current online measurement equipment and method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN105891605A true CN105891605A (en) | 2016-08-24 |
Family
ID=56697921
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410614170.9A Pending CN105891605A (en) | 2014-11-04 | 2014-11-04 | Distribution transformer grounding resistor, current online measurement equipment and method thereof |
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| Country | Link |
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| CN (1) | CN105891605A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108037344A (en) * | 2018-01-26 | 2018-05-15 | 河南云拓智能科技有限公司 | Multicircuit relay intelligent switch based on AC current collecting |
| CN108169566A (en) * | 2017-12-29 | 2018-06-15 | 江苏海湾电气科技有限公司 | Online testing impedance circuit and method |
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