The content of the invention
In view of above-mentioned existing situation and deficiency, the present invention is intended to provide a kind of be used for tested CT secondary side circuits outside ammeter
The detection means and detection method of state, to realize that different type is tested CT secondary side circuits open circuit, short circuit, part outside ammeter
Short-circuit and normal the real-time of four kinds of states, high accuracy, high accuracy detection.
The present invention is achieved through the following technical solutions:
A kind of detection means for tested CT secondary side circuit states outside ammeter, including test CT, impedance matching circuit, drive
Dynamic circuit, protection circuit, isolation filter circuit and MCU;Test CT primary sides in parallel with impedance matching circuit;MCU passes through driving
Circuit is connected with testing the input of CT secondary sides, and the output end of test CT secondary sides passes through protection circuit and isolation filter circuit
It is connected with MCU.MCU is used for the generation of swept-frequency signal, passes the collection analysis of signal back, and live self study and logical with ammeter
Letter;Impedance matching circuit is electric capacity and resistance parallel with one another;Drive circuit is used for the frequency sweep square wave excitation signal for producing MCU
Isolation amplification, and be coupled to after test CT inputs input on tested CT secondary side circuits;Protection circuit is used to prevent high pressure
Damage detection module;Isolation filter circuit is used to filter out the signal useless to testing result, and by load signal and tested CT bis-
Secondary side loop isolation.
A kind of detection method for tested CT secondary side circuit states outside ammeter, specific steps include:
Before step 1, in-site installation, demarcated in advance in the MCU of detection means and store each high frequency letter in high frequency swept-frequency signal
The theoretical decision threshold U open circuits i of corresponding open-circuit condition is U1i ± X% and short-circuit condition theory judgement during number as pumping signal
Threshold value U short circuits i is that U4i ± Y%, U1i and U4i are respectively the square amplitude of the corresponding output signal of open-circuit condition and short-circuit condition pair
The square amplitude of the output signal answered, i is the sequence number set of all high-frequency signals in swept-frequency signal, i={ 1,2,3 ..., n }, X and Y
For regulated variable.
When step 2, in-site installation, staff confirms that tested CT secondary side circuits state is normal condition, by tested CT
Secondary side and ammeter measure CT, the primary side of testing CT is composed in series tested CT secondary side circuits, meanwhile, by MCU and ammeter
Metering module is connected.
Step 3, MCU send high frequency swept-frequency signal, and tested CT secondary side circuits are coupled to from test CT through overdrive circuit,
Meanwhile, signal is coupled to receive from test CT, MCU is passed back by protection circuit and isolation filter circuit, MCU receives all frequency sweeps and swashed
Encourage the signal that signal is passed back, pass signal back for different excitation signal i corresponding output signals in normal condition, signal it is square
Amplitude is set to U2i, according to the stability for passing signal back and passes signal side amplitude U2i and the phase demarcated in advance in step 1 back
The corresponding relation of U1i and U4i under high frequency swept-frequency signal is answered, MCU judges to be adapted to the high frequency swept-frequency signal of the tested CT, and selects
The signal is used as detection pumping signal.
Step 4, the live self-learning function of MCU startups write down the corresponding live normal condition of the pumping signal and pass letter back automatically
Number square amplitude, and be set as that U2j, j are any sequence number in set i, the theoretical decision threshold U of generation normal condition is normal
For U2j ± Z%, Z is regulated variable.
The lower limit of the theoretical decision threshold U partial short circuits of step 5, MCU setting sections short-circuit condition is the theory of normal condition
The normal upper limit U2j+Z% of decision threshold U, the upper limit of setting section short-circuit condition theory decision threshold U partial short circuits is step 1
In corresponding high frequency swept-frequency signal the theoretical decision threshold U short circuits j of short-circuit condition lower limit U4j-Y%, for any high frequency pumping letter
Relation between number each theoretical decision threshold is:U short circuits>U partial short circuits>U is normal>U opens a way.
Step 6, artificially changed when tested CT secondary sides state, during the high frequency swept-frequency signal j that MCU transmitting selections are completed,
The square amplitude of signal of passing back received changes, and MCU passes the square amplitude of signal back and obtained above each according to reception
Relation between theoretical decision threshold judges the connection status of tested CT secondary side circuits, i.e.
When the square amplitude for passing signal back falls in the theoretical decision threshold of open-circuit condition, it is judged as open circuit;
When the square amplitude for passing signal back falls in the theoretical decision threshold of short-circuit condition, it is judged as short circuit;
When the square amplitude for passing signal back falls in partial short circuit regime theory decision threshold, it is judged as partial short circuit;
When the square amplitude for passing signal back falls in the theoretical decision threshold of normal condition, it is judged as normal.
In the step 3, MCU judges that the high frequency swept-frequency signal process for being adapted to the tested CT includes:First, selected excitation letter
Number to ensure that what MCU received passes signal stabilization back;Secondly, when U2i is located at U1i and U4i centre, i.e.,(U2i-U1i)-
(U4i-U2i)->When 0, it is detection pumping signal to select the high frequency swept-frequency signal.
In the step 3, MCU judges that the process for being adapted to the tested CT high frequency swept-frequency signals also includes:When there is several groups U2i
When U1i and U4i centre, selection make Δ Ui=(U4i-U2i)Maximum high frequency swept-frequency signal.
Detection means and detection method of the present invention for tested CT secondary side circuit states outside ammeter, by just
Under normal connection status, demarcated using MCU and send multiple high frequency swept-frequency signals, obtain tested CT secondary sides in corresponding high frequency frequency sweep
Theoretical decision threshold under signal under the theoretical decision threshold and each state of the square amplitude of normal condition output signal, as tested CT
During secondary side state change, according to the relation between the square amplitude received and each theoretical decision threshold, complete outside ammeter
Different type is tested CT secondary side circuits open circuit, short circuit, partial short circuit and normal the real-time of four kinds of states, high accuracy, Gao Zhun
Exactness is detected, improves anti-electricity-theft level, the problem of different type CT is detected can not be applicable by solving existing signal injection method, be carried
The high applicability of detection process, reliability is high, cost is low, easy to detect, is adapted to produce in enormous quantities and uses.
Embodiment
Below in conjunction with the accompanying drawings to the detection means of the present invention for tested CT secondary side circuit states outside ammeter
It is described in further detail:
As shown in Fig. 2 the detection means of the present invention for tested CT secondary side circuit states outside ammeter, including test
CT, impedance matching circuit, drive circuit, protection circuit, isolation filter circuit and MCU.Wherein, test CT primary sides and impedance
With circuit in parallel, MCU is connected by drive circuit with testing the input of CT secondary sides, and the output end of test CT secondary sides passes through
Protection circuit and isolation filter circuit are connected with MCU.During specific works, CT secondary side and ammeter metering CT, test CT is tested
Primary side be composed in series tested CT secondary side circuits, MCU is connected with ammeter metering module.
MCU is used for the generation of swept-frequency signal, passes the collection analysis of signal back, and live self study and is communicated with ammeter,
MCU is needed to select a certain high-frequency signal first in high frequency swept-frequency signal for different tested CT, it is normal as the tested CT
The detection signal of state, when tested CT normal conditions are changed, MCU according to the high-frequency signal pass back the square amplitude of signal with
Relation between each regime theory decision threshold, it is in open circuit, short circuit, partial short circuit, just to judge tested CT secondary side circuits
It is any in normal state, so as to complete tested CT detection.
The frequency sweep square wave excitation signal isolation that drive circuit is used to produce MCU is amplified, and is inputted from test CT inputs
After be coupled on tested CT secondary side circuits.Impedance matching circuit is electric capacity and resistance parallel with one another, with test CT, tested CT
Etc. collectively constituting RLC parallel circuits.As shown in figure 3, drive circuit is made up of two amplifiers and resistance R1, R2, first fortune
Composition follower is put, plays a part of signal isolation, second amplifier and resistance R1, R2 composition amplifier, plays signal and put
Big effect.
Protection circuit is mainly made up of devices such as piezo-resistance, amplitude limits, for avoiding issuable high pressure from damaging inspection
The occurrence of surveying module.As shown in figure 4, protection circuit by resistance R, two diodes VD1 and VD2, two source of stable pressure E1 and
E2 and piezo-resistance RV composition, Ui is input, and Uo is the series connection of output end, wherein VD1 and E1, and VD2 and E2 connect,
And the opposite polarity connected, then both are in parallel, then are connected with resistance R, and this part is double limiting circuit, the amplitude of limitation
For E1+VD1 and-(E2+VD2), piezo-resistance RV is parallel in circuit, when the voltage being added on piezo-resistance RV exceedes its threshold
During value, flow through its electric current and increase sharply, equivalent to the infinitesimal resistance of resistance, so as to play a part of overvoltage protection.
Isolation filter circuit is used to filter out the signal useless to testing result, and load signal and tested CT secondary sides are returned
Road isolates, and prevents load from being interfered to loop state, influences judged result.As shown in figure 5, isolation filter circuit is by two fortune
Put, resistance R1, R2, R3, Ra, Rb and electric capacity C1, C2 are constituted.Wherein first amplifier constitutes follower, circuit input resistance
Anti- height, output impedance is low, plays buffer action, and load signal is isolated with self-maintained circuit, prevents load to self-oscillation
Circuit produces influence;Second amplifier and resistance R1, R2, R3, Ra, Rb and electric capacity C1, C2 composition bandwidth-limited circuit, are used for
Filter out to detecting useless low frequency and high-frequency interferencing signal.
In said structure, swept-frequency signal is sent using MCU, is selected according to the tested CT of difference in swept-frequency signal suitably
Frequency is as pumping signal, and the theoretical decision threshold of the live self-learning function generation normal condition using MCU, as tested CT
After state change, by the ratio for passing the square amplitude of signal and theoretical decision threshold under each state back for selecting frequency excitation signal
Compared with realizing different type outside ammeter and be tested CT secondary side circuits open circuit, short circuit, partial short circuit and normal four kinds of state realities
When, the detection of high accuracy, high accuracy, solve existing injection method can not be applicable different type be tested CT the problem of.
Below to the specific inspection of the present invention for the detection means of tested CT secondary side circuit states outside ammeter
Survey process is described in further detail:
Detection method of the present invention for tested CT secondary side circuit states outside ammeter, specific steps include:
Before step 1, in-site installation, demarcated in advance in the MCU of detection means and store each high frequency letter in high frequency swept-frequency signal
The theoretical decision threshold U open circuits i of corresponding open-circuit condition is U1i ± X% and short-circuit condition theory judgement during number as pumping signal
Threshold value U short circuits i is that U4i ± Y%, U1i and U4i are respectively the square amplitude of the corresponding output signal of open-circuit condition and short-circuit condition pair
The square amplitude of the output signal answered, i is the sequence number set of all high-frequency signals in swept-frequency signal, i={ 1,2,3 ..., n }, X and
Y is regulated variable.
When MCU enters row energization one by one by the high frequency swept-frequency signal of demarcation to tested CT, it can readily obtain in open circuit
The theoretical decision threshold of open-circuit condition corresponding with the high frequency swept-frequency signal under short-circuit condition and the theoretical decision threshold of short-circuit condition, be
Later stage judges that tested CT secondary sides square amplitude of signal under the high frequency swept-frequency signal is delimitated.
Under open circuit or short-circuit condition, tested CT theoretical decision threshold will not change with the change of its structure or model
Become, therefore CT theoretical judgement is tested under when being directed to each high-frequency signal as pumping signal of deposit, its open circuit or short-circuit condition
Threshold value is consistent.
When step 2, in-site installation, staff confirms that tested CT secondary side circuits state is normal condition, by tested CT
Secondary side and ammeter measure CT, the primary side of testing CT is composed in series tested CT secondary side circuits, meanwhile, by MCU and ammeter
Metering module is connected.
For convenience of detection process, this method is that, in the external test CT of ammeter, test CT primary sides measure CT once with ammeter
Side is concatenated, and test CT primary sides are concatenated with tested CT secondary sides outside ammeter, and tested CT secondary sides are measured with ammeter outside ammeter
CT primary sides are concatenated.Inside detection means, test CT primary sides are in parallel with impedance matching circuit, MCU by drive circuit and
The input connection of CT secondary sides is tested, the output end of test CT secondary sides passes through protection circuit and isolation filter circuit and MCU
Connection.
Step 3, MCU send high frequency swept-frequency signal, and tested CT secondary side circuits are coupled to from test CT through overdrive circuit,
Meanwhile, signal is coupled to receive from test CT, MCU is passed back by protection circuit and isolation filter circuit, MCU receives all frequency sweeps and swashed
Encourage the signal that signal is passed back, pass signal back for different excitation signal i corresponding output signals in normal condition, signal it is square
Amplitude is set to U2i, according to the stability for passing signal back and passes signal side amplitude U2i and the phase demarcated in advance in step 1 back
The corresponding relation of U1i and U4i under high frequency swept-frequency signal is answered, MCU judges to be adapted to the high frequency swept-frequency signal of the tested CT, and selects
The signal is used as detection pumping signal.
Specific deterministic process includes:First, selected pumping signal will ensure the stability for passing signal back that MCU is received;
Secondly, selected pumping signal can guarantee that square amplitude U2i of the output signal of different tested CT secondary side circuit normal conditions
In the middle of the square amplitude U4i of output signal of output signal side amplitude U1i and the short-circuit condition of open-circuit condition, i.e.,(U2i-
U1i)-(U4i-U2i)->0;Finally, when having several groups of pumping signals while meeting above-mentioned condition, selection make Δ Ui=(U4i-U2i)
Maximum pumping signal, makes the square amplitude difference maximum of the signal between different conditions, and the different connection status after change are more held
Easily distinguish.
Step 4, the live self-learning function of MCU startups write down the corresponding live normal condition of the pumping signal and pass letter back automatically
Number square amplitude, and be set as that U2j, j are the either element in set i, the theoretical decision threshold U of generation normal condition is normal
For U2j ± Z%, Z is regulated variable.
The lower limit of the theoretical decision threshold U partial short circuits of step 5, MCU setting sections short-circuit condition is the theory of normal condition
The normal upper limit U2j+Z% of decision threshold U, the upper limit of setting section short-circuit condition theory decision threshold U partial short circuits is step 1
In corresponding high frequency swept-frequency signal the theoretical decision threshold U short circuits j of short-circuit condition lower limit U4j-Y%, for any high frequency pumping letter
Relation between number each theoretical decision threshold is:U short circuits>U partial short circuits>U is normal>U opens a way.
So far, under the normal connection status of tested CT secondary sides, the theoretical decision threshold of each state is set, and is stored in
In MCU.
Step 6, it is changed when tested CT secondary side states, during the high frequency swept-frequency signal j that MCU transmitting selections are completed, receives
To the square amplitude of signal of passing back change, MCU passes the square amplitude of signal and each theory obtained above back according to reception
Relation between decision threshold judges the connection status of tested CT secondary side circuits, i.e.
When the square amplitude for passing signal back falls in the theoretical decision threshold of open-circuit condition, it is judged as open circuit;
When the square amplitude for passing signal back falls in the theoretical decision threshold of short-circuit condition, it is judged as short circuit;
When the square amplitude for passing signal back falls in partial short circuit regime theory decision threshold, it is judged as partial short circuit;
When the square amplitude for passing signal back falls in the theoretical decision threshold of normal condition, it is judged as normal.
The theoretical foundation of the deterministic process of above-mentioned steps 6 is described as follows:
As shown in fig. 6, the circuit of whole detection means can be regarded as by testing CT primary side equivalent inductance Lcs, CT bis- is tested
Secondary side equivalent inductance Lbc measures CT primary side equivalent inductance Ljl sum Lbc+Ljl, and impedance matching circuit parallel connection with ammeter
The RLC parallel circuits that collectively constitute of R, C, the equivalent admittance of circuit is:
Wherein w is the frequency of Injection Signal, and j is vector,
The equivalent input impedance of circuit is:
When frequency is fixed, ammeter metering CT primary side equivalent inductances Ljl, impedance matching circuit shunt capacitance C, test CT are once
Side equivalent inductance Lcs is constant, and input impedance Zin is determined by Lbc, and tested CT secondary side circuits state change can cause Lbc change
Change, when tested CT secondary sides are opened a way, Lbc approach infinities,
When short-circuit, Lbc is 0,
When normal,
The input impedance value of partial short circuit is located at normal between short circuit, tested CT secondary side circuits state difference, input impedance
Difference, MCU receive pass back signal square amplitude it is also different, MCU is according to the square amplitude and each state of passing signal back of reception
Relation between lower theoretical decision threshold judges tested CT secondary side circuit connection status.
When changing tested CT, Lbc changes, if using same frequency, normal value changes, and opens a way constant with short circuit value,
Normal value is not located at open circuit with that in the middle of short circuit value, if Lbc changes very big, can cause normal value close to quiescent value or short circuit
Value, causes that normal condition is not easily distinguishable with open-circuit condition or normal condition is not easily distinguishable with short-circuit condition, so replacing is tested
During CT, need to select suitable pumping signal according to the above method in high frequency swept-frequency signal again, and need again live self study,
Obtain the theoretical decision threshold of new normal condition and the theoretical decision threshold of partial short circuit state, open circuit and the reason of short-circuit condition
It is not change with tested CT change by decision threshold, so as to realize different type CT secondary side circuit states well
Detection.