CN108152784A - A kind of circuit and method that external CT states are detected for mutual inductor access electric energy meter - Google Patents
A kind of circuit and method that external CT states are detected for mutual inductor access electric energy meter Download PDFInfo
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- CN108152784A CN108152784A CN201711476656.0A CN201711476656A CN108152784A CN 108152784 A CN108152784 A CN 108152784A CN 201711476656 A CN201711476656 A CN 201711476656A CN 108152784 A CN108152784 A CN 108152784A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/04—Testing or calibrating of apparatus covered by the other groups of this subclass of instruments for measuring time integral of power or current
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Abstract
The present invention provides a kind of circuit that external CT states are detected for mutual inductor access electric energy meter, the circuit includes external mutual inductor, built-in double loop mutual inductor, self-maintained circuit and CPU sample circuits, the output terminal of the external CT is connected with the input terminal of built-in double loop CT, one signal output end of built-in double loop mutual inductor is connected with the sampled signal input of CPU sample circuits, another signal end cooperation self-maintained circuit is connected to CPU sample circuits, obtains the state of current external mutual inductor.The present invention can accurately detect the state of external CT using low cost CT electric energy meters, metering sampled signal can pass through low-pass filter, oscillator signal will not have an impact metering, CT states are checked compared to artificial, the present invention's is versatile, promptness is strong, and overcomes the problem of difference of mutual inductor is with mutual inductor aging, and a large amount of uses can very easily be put by substantially increasing reliability.
Description
Technical field
The present invention relates to a kind of CT electricity of Function detection external CT (i.e. mutual inductor) state of difference algorithm and artificial memory
Energy table, accuracy of detection is high, at low cost, suitable for the mutual inductor access electric energy meter occasion with external CT.
Background technology
CT electric energy meters are first city's electric signal of high current to be converted into low current signal, then with inside ammeter with external CT
Mutual inductor detects transformed low current signal.CT is the tie between electrical secondary system and primary system, work in alternating current circuit
Principle is essentially identical with transformer, and CT is close to short-circuit condition to CT under normal circumstances.The size of CT secondary currents is by primary electricity
Stream determines that the magnetic potential that secondary current generates is the magnetic potential for balancing primary current.If second open circuit, impedance is infinitely great, secondary
Electric current is equal to zero, and magnetic potential is also equal to zero, the magnetic potential that balance primary current cannot be gone to generate, then primary current is by whole works
For excitatory, make the serious saturation of iron core.Magnetic saturation increases iron loss, and CT fevers, the insulation of CT coils can also be burnt due to overheat
It is bad.Remanent magnetism can be also generated on iron core, increases transformer error.The most serious is due to magnetic saturation, the sine wave of alternating flux
Become trapezoidal wave, in magnetic flux vertiginous moment, very high voltage will be induced on secondary coil, peak value is up to thousands of
Volt, so high voltage are acted on secondary coil and secondary circuit, and to personal and equipment, all there is serious threats.So
CT is not allow secondary side open running at any time.If CT secondary circuit short-circuits can cause secondary side current to become smaller, lead
Measurement error negative bias is caused, is caused damages to electric company.Therefore CT open circuits can be detected in CT tables to have been very urgent with short circuit.
The mode of traditional detection CT states mainly has：
1st, the electric current of continuous a period of time ammeter sampling is 0 always.
2nd, the state of staff's periodic detection CT terminal bases.
The several method mentioned above, although it can be found that CT open faults, also have very big simultaneously
Limitation：
1st, it is 0 that CT open-circuit currents, which are, but electric current for 0 not necessarily CT open a way.And CT short circuits cannot judge.
2nd, staff's periodic detection needs to spend very big manpower, can't accomplish to detect in real time.
It follows that there are no can accurate, timely, automatically detection CT secondary circuit states work(in electric energy meter at present
Energy.For this purpose, we be badly in need of seek it is a kind of can judge in time CT secondary sides whether occur open circuit, short circuit new method.
Invention content
The purpose of the present invention is being directed to, there is presently no accurate, timely, automatic detection CT secondary circuit states can ask
Topic proposes a kind of circuit and method that external CT states are detected for mutual inductor access electric energy meter, can be accurate, timely, low
The detection CT states of cost.
The present invention provides a kind of circuit that external CT states are detected for mutual inductor access electric energy meter, which includes outer
Mutual inductor, built-in double loop mutual inductor, self-maintained circuit and CPU sample circuits are put, the external mutual inductor, that is, CT's is defeated
Outlet is connected with the input terminal of built-in double loop mutual inductor, a signal output end and the CPU sampling electricity of built-in double loop mutual inductor
The sampled signal input on road is connected, and another signal end cooperation self-maintained circuit is connected to CPU sample circuits, and the CPU is adopted
The frequency of the aforementioned self-maintained circuit of sample circuit sampling obtains the state of current external mutual inductor.
Further, in external mutual inductor, the input of user's electric current as its primary side, ab ends as external mutual inductor two
Secondary side interface, primary side of the cd ends as double loop mutual inductor built in ammeter, ac, bd are the external mutual inductor secondary side of connection and electricity
The conducting wire of mutual inductor primary side inside table.
Further, self-maintained circuit includes resistance R15, R14, capacitance C53, C54 and by Schmidt trigger structure
Into phase inverter U6A, U6F, wherein the frequency sampling signal end of one end of the resistance R15 and built-in double loop mutual inductor connects
It connects, the other end is connect with the input terminal of phase inverter U6F, U6A and one end of capacitance C53；The other end ground connection of capacitance C53, electricity
One end of resistance R14 is connect with the frequency sampling signal end of built-in double loop mutual inductor, the output terminal of the other end and phase inverter U6F and
One end of capacitance C54, the other end ground connection of capacitance C54, the output of the output terminal of the phase inverter U6A as self-maintained circuit
It is connect with the sampling pin of CPU sample circuits.
A kind of method that external CT states are detected for mutual inductor access electric energy meter, using for mutual inductor access type electricity
Energy table detects the circuit of external CT states, and this method includes the following steps：The frequency of CPU sampling circuit samples self-maintained circuits
Rate detects the frequency of current external mutual inductor sample with reference to difference algorithm, obtains the state of external mutual inductor.
Further, the difference algorithm includes the following steps：First, an array is established, includes multiple elements,
The array disengaging mode is first in first out, acquires a current frequency and is placed in the array each second, the array abandons
Most advanced next data first remove an element of difference maximum in the array, to remaining element when calculating effective frequency
It is averaged；Then, frequency departure, frequency departure=(average frequency-basic frequency)/basic frequency × 100%, according to accidentally are calculated
The range of difference obtains the state of current external mutual inductor.
Further, error range judges that the specific method of the state of external mutual inductor is：
When error range is within ± 5%, external mutual inductor state is normal；
When error range is more than 10%, external mutual inductor state is open circuit；
When error range is less than -15%, external mutual inductor state is short circuit；
During other error ranges, external mutual inductor state is normal.
Further, the sample frequency is within ± the 5% of basic frequency, then it is assumed that the error is due to mutual inductor aging
It is caused, by sample frequency update to basic frequency, complete artificial memory's function.
Beneficial effects of the present invention：
Detection mutual inductor makees inductance inside present invention ammeter, coordinates the LRC oscillating circuits of self-excitation, is then sampled with CPU
The frequency of oscillating circuit can effectively detect the frequency of present sample with reference to difference algorithm, reuse artificial memory's function
Error problem caused by effectively solving mutual inductor aging；It can be accurate further according to the ratio of efficiently sampling frequency and basic frequency
Really, detection CT states in time, inexpensive.
The present invention can accurately detect the state of external CT using low cost CT electric energy meters, and the frequency generated approaches
200KHz, the frequency for measuring sampling are 60Hz, and metering sampled signal can pass through low-pass filter, therefore the oscillator signal of the present invention
Metering will not be had an impact, check CT states compared to artificial, of the invention is versatile, and promptness is strong, and overcomes
The problem of difference of mutual inductor is with mutual inductor aging, a large amount of uses can very easily be put by substantially increasing reliability.
Other features and advantages of the present invention will be described in detail in subsequent specific embodiment part.
Description of the drawings
Exemplary embodiment of the invention is described in more detail in conjunction with the accompanying drawings, it is of the invention above-mentioned and its
Its purpose, feature and advantage will be apparent, wherein, in exemplary embodiment of the invention, identical reference label
Typically represent same parts.
Fig. 1 is the mutual inductor interstar connection figure of the present invention；
Fig. 2 is the self-maintained circuit of the present invention；
Fig. 3 is the design frame chart of the present invention；
Fig. 4 is the frequency differential algorithm of the present invention and artificial memory's functional flow diagram.
Specific embodiment
The preferred embodiment of the present invention is more fully described below with reference to accompanying drawings.Although the present invention is shown in attached drawing
Preferred embodiment, however, it is to be appreciated that may be realized in various forms the present invention without the embodiment party that should be illustrated here
Formula is limited.
The present invention provides a kind of circuit that external CT states are detected for mutual inductor access electric energy meter, which includes outer
Mutual inductor, built-in double loop mutual inductor, self-maintained circuit and CPU sample circuits are put, wherein internal mutual inductor is defeated for dual signal
The mutual inductor gone out, as metering sampling, another way is used as external CT states are detected for output all the way.With detection mutual inductance inside ammeter
Device makees inductance, coordinates the LRC oscillating circuits of self-excitation, then with the frequency of CPU sample oscillations circuits, can have with reference to difference algorithm
The frequency for detecting present sample of effect, reuses artificial memory's function and effectively solves error problem caused by mutual inductor aging.
Further according to the ratio of efficiently sampling frequency and basic frequency can accurately, in time, low cost detection CT states.
It is exactly the external CT in Fig. 1 that the present invention, which needs the CT detected,.User's electric current is the equal of the primary side of external CT, outside
Secondary side interfaces of the ab as external mutual inductor of mutual inductor, primary sides of the cd as mutual inductor inside ammeter are put, ac, bd are to connect
The conducting wire of external mutual inductor secondary side and mutual inductor primary side inside ammeter is connect, is connected on off-balancesheet, therefore user is easy for
It can open a way to ac, bd or ab ends carry out short circuit.
The oscillating circuit of the present invention is exactly the self-maintained circuit of Fig. 2, in CTA1, CTA2 difference connection figure 1 in Fig. 2
G, h ends.If external CT connections are intact, the inductance value of the mutual inductor of detection CT is certain inside ammeter, and the frequency of CPU samplings is shaken
Swinging the period is：4.68 microsecond.When ac or bd opens a way, cycle of oscillation is 5.56 microseconds, when user's short circuit ab or cd short circuit
When, frequency of oscillation is 2.76 microseconds.The high frequency rising edge that CPU opens a period of time interrupts, obtain in this period into interruption
Number is then converted into frequency, and the shape of current external mutual inductor is precisely judged further according to difference algorithm and artificial memory's function
State.
The difference algorithm of the present invention is shown in Fig. 4 with the function of artificial memory's frequency.Since mutual inductor is variant, each ammeter
There is the basic frequency (external mutual inductor connects normal frequency) of oneself, therefore need to acquire currently practical frequency after installing ammeter
For rate as basic frequency, when normal operation, may there is interference, may collected frequency it is inaccurate, therefore using difference algorithm,
Difference algorithm is exactly to open an array, and by taking three elements as an example, the mode of array disengaging is first in first out, calculates effective frequency
When be all to remove maximum one of difference, be then averaged to remaining, thus can effectively avoid interfering.
But aging is used due to external mutual inductor, causes the variation of inductance value, at this moment basic frequency can also change,
At this time also with the basic frequency of most original compared with the frequency sampled will necessarily false alarm, make accuracy of detection low.Therefore it needs
Artificial memory's function is quoted, frequency is calculated after a certain number of effective frequencies are collected, when sample frequency and basic frequency are missed
When difference is smaller, it is possible to update elementary error.Thus can effectively solve the problems, such as false alarm, the detection essence of raising
Degree.
Error=(average frequency-basic frequency)/basic frequency * 100%.It just can know that according to the range of error current outer
Put the state of CT.
When error thinks that CT states are normal at this time within ± 5%, may occur due to the aging of mutual inductor, basic frequency
Variation, therefore original basic frequency is not met with practical basic frequency, needs update basic frequency,
When error range is more than 10%, it is believed that mutual inductor is opened a way.
When error range is less than -15%, it is believed that mutual inductor short circuit.
When error is not at above-mentioned three kinds, it is normal to be also considered as current CT states, but does not allow to update basic frequency.
The state of external mutual inductor can accurately be detected according to the result of 4 kinds of above-mentioned frequencies, and overcome mutually
The difference of sensor, the problems caused by with mutual inductor aging.
The present invention can accurately detect the state of external CT using low cost CT electric energy meters, and the frequency generated approaches
200KHz, the frequency for measuring sampling are 60Hz, and metering sampled signal can pass through low-pass filter, therefore the oscillator signal of the present invention
Metering will not be had an impact, check CT states compared to artificial, of the invention is versatile, and promptness is strong, and overcomes
The problem of difference of mutual inductor is with mutual inductor aging, a large amount of uses can very easily be put by substantially increasing reliability.
Various embodiments of the present invention are described above, above description is exemplary, and non-exclusive, and
It is not limited to disclosed each embodiment.In the case of without departing from the scope and spirit of illustrated each embodiment, for this skill
Many modifications and changes will be apparent from for the those of ordinary skill in art field.
Claims (7)
1. a kind of circuit that external CT states are detected for mutual inductor access electric energy meter, which is characterized in that the circuit includes outer
Mutual inductor, built-in double loop mutual inductor, self-maintained circuit and CPU sample circuits are put, the external mutual inductor, that is, CT's is defeated
Outlet is connected with the input terminal of built-in double loop mutual inductor, a signal output end and the CPU sampling electricity of built-in double loop mutual inductor
The sampled signal input on road is connected, and another signal end cooperation self-maintained circuit is connected to CPU sample circuits, and the CPU is adopted
The frequency of the aforementioned self-maintained circuit of sample circuit sampling obtains the state of current external mutual inductor.
2. the circuit according to claim 1 that external CT states are detected for mutual inductor access electric energy meter, feature exist
In：In external mutual inductor, the input of user's electric current is as its primary side, secondary side interface of the ab ends as external mutual inductor, cd ends
As the primary side of double loop mutual inductor built in ammeter, ac, bd are mutual inductors inside the external mutual inductor secondary side of connection and ammeter
The conducting wire of primary side.
3. the circuit according to claim 1 that external CT states are detected for mutual inductor access electric energy meter, feature exist
In：Self-maintained circuit includes resistance R15, R14, capacitance C53, C54 and the phase inverter U6A being made of Schmidt trigger,
U6F, wherein one end of the resistance R15 is connect with the frequency sampling signal end of built-in double loop mutual inductor, the other end and reverse phase
One end connection of the input terminal and capacitance C53 of device U6F, U6A；Capacitance C53 the other end ground connection, one end of resistance R14 with it is interior
The frequency sampling signal end connection of double loop mutual inductor, the other end and the output terminal of phase inverter U6F and one end of capacitance C54 are put,
The other end ground connection of capacitance C54, the output terminal of the phase inverter U6A is as the output of self-maintained circuit and CPU sample circuits
Sampling pin connection.
4. a kind of method that external CT states are detected for mutual inductor access electric energy meter, using described in one of claim 1-3
The circuit that external CT states are detected for mutual inductor access electric energy meter, which is characterized in that this method includes the following steps：
The frequency of CPU sampling circuit samples self-maintained circuits detects the frequency of current external mutual inductor sample with reference to difference algorithm,
Obtain the state of external mutual inductor.
5. the method according to claim 4 that external CT states are detected for mutual inductor access electric energy meter, feature exist
Include the following steps in the difference algorithm：First, an array is established, includes multiple elements, the array disengaging side
Formula is first in first out, acquires a current frequency and is placed in the array each second, and the array abandons most advanced next data,
First remove an element of difference maximum in the array when calculating effective frequency, remaining element is averaged；Then, it calculates
Frequency departure, frequency departure=(average frequency-basic frequency)/basic frequency × 100% obtain current according to the range of error
The state of external mutual inductor.
6. the method according to claim 5 that external CT states are detected for mutual inductor access electric energy meter, feature exist
In：Error range judges that the specific method of the state of external mutual inductor is：
When error range is within ± 5%, external mutual inductor state is normal；
When error range is more than 10%, external mutual inductor state is open circuit；
When error range is less than -15%, external mutual inductor state is short circuit；
During other error ranges, external mutual inductor state is normal.
7. the method according to claim 5 that external CT states are detected for mutual inductor access electric energy meter, feature exist
In：The sample frequency is within ± the 5% of basic frequency, then it is assumed that the error will be sampled caused by mutual inductor aging
In frequency update to basic frequency, artificial memory's function is completed.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711476656.0A CN108152784A (en) | 2017-12-29 | 2017-12-29 | A kind of circuit and method that external CT states are detected for mutual inductor access electric energy meter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201711476656.0A CN108152784A (en) | 2017-12-29 | 2017-12-29 | A kind of circuit and method that external CT states are detected for mutual inductor access electric energy meter |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108845286A (en) * | 2018-09-03 | 2018-11-20 | 海盐星创电子有限公司 | Calibration equipment while a kind of two current loops of single-phase electric energy meter |
| CN109100603A (en) * | 2018-09-30 | 2018-12-28 | 中国电力科学研究院有限公司 | The detection device and method of secondary loop of mutual inductor short circuit |
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| CN108845286A (en) * | 2018-09-03 | 2018-11-20 | 海盐星创电子有限公司 | Calibration equipment while a kind of two current loops of single-phase electric energy meter |
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Application publication date: 20180612 |