CN203811737U - Direct-current electric-leakage monitoring and warning device - Google Patents

Direct-current electric-leakage monitoring and warning device Download PDF

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Publication number
CN203811737U
CN203811737U CN201420150469.9U CN201420150469U CN203811737U CN 203811737 U CN203811737 U CN 203811737U CN 201420150469 U CN201420150469 U CN 201420150469U CN 203811737 U CN203811737 U CN 203811737U
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warning
amplifier
microprocessor
mutual inductor
connects
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盛方正
张钻
邱明义
沈光敏
唐正利
王文成
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State Grid Shanghai Electric Power Co Ltd
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State Grid Shanghai Electric Power Co Ltd
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Abstract

The utility model discloses a direct-current electric-leakage monitoring and warning device. The direct-current electric-leakage monitoring and warning device comprises a mutual inductor, a filter circuit, a rectifying circuit and a microprocessor which are connected in order; also comprises a voltage excitation source which is connected with the mutual inductor and the filter circuit and provides square wave voltage excitation to the mutual inductor; and a power supply module providing electric energy to the whole circuit. The microprocessor is further connected with an alarm indication unit, after the mutual inductor detects an electric-leakage current signal, the current signal is processed by the filter circuit and the rectifying circuit, the current signal is converted into a signal which can be recognized by the microprocessor, after the microprocessor carries out operation, the result is output to the alarm indication unit, and the alarm indication unit makes corresponding actions in dependence on corresponding instructions. The direct-current electric-leakage monitoring and warning device is high in monitoring precision and flexible in installation place, and maloperations are avoided, the direct-current electric-leakage monitoring and warning device can be used just after replacing a direct current terminal, and does not need to be grounded for drawing tests, manpower is saved, and the direct-current electric-leakage monitoring and warning device is convenient to replace, the direct-current electric-leakage monitoring and warning device can be maintained with no need for power outage (plug-in manner), and grounded direct currents existing in the system can be warned and recorded.

Description

Direct current leakage current detect warning device
Technical field
The utility model relates to electronics and electromagnetic technology field, is specifically related to direct current leakage current detect warning device.
Background technology
For a long time, the detection of DC earthing is all a difficult problem for relay protection work.At present, the accuracy and efficiency that the introduction of pc detecting instrument detects DC system grounding promotes greatly, but current all kinds of pick-up units, although can detect total insulation of whole system, but all there is certain defect, and due to the restriction of centralized installation, for the earth point in branch road, still cannot effectively detect, still need artificial cooperation to search earth point.
In generating plant and transformer station, direct supply is emergency power supply and the control signal power supply of electric equipments, most important to guaranteeing the normal operation of electrical equipment.Because straight-flow system is the supply network of huge a, multiple-limb, once break down, influence surface is very wide.The existence of direct current Abnormal Grounding problem is the major hidden danger of transformer station direct current system.
The detection method that the DC earthing pick-up unit moving in China's straight-flow system is at present used mainly contains three kinds:
The one, by adjusting, balance bridge threshold value is carried out ground connection detection, there is the shortcomings such as location is inaccurate, error is large, insensitive in bridge balance method, need artificial cooperation, use open line method to search earth point, because needs cut off direct supply, can cause power-off loop can not split at short notice and close and carry out a deciliter operation, jeopardize the normal operation of system, and for multipoint earthing, the method cannot find rapidly earth point;
The 2nd, by inject AC signal in straight-flow system, enter to detect, AC signal injection method is when capacitance current is greater than pick-up unit to the setting valve of insulation resistance leakage current, to cause mistaking signal, affect the correct judgement of device, and in straight-flow system, inject AC signal, can form certain threat to the safe operation of system;
The 3rd, utilize the poor stream in Hall element detection branch to judge earthing position, Hall magnetic balance type element is easily subject to the impact of remanent magnetism, causes constantly drift about the zero point of device, easily causes the phenomenons such as wrong report.
Utility model content
The purpose of this utility model is to provide a kind of direct current leakage current detect warning device, monitoring accuracy is high, and can avoid maloperation, does not affect former loop, strengthened the anti-interference of tested ring current, infield is flexible, " changes and uses ", without " ground connection examination is drawn " with DC terminal, save manpower, it is convenient to change, can not have a power failure and safeguard (plug-in), can to Installed System Memory DC earthing make alarm memory.
In order to achieve the above object, the utility model is achieved through the following technical solutions: direct current leakage current detect warning device, be characterized in, and comprise:
The mutual inductor, filtering circuit, rectification circuit and the microprocessor that connect successively;
The voltage drive source being connected with mutual inductor, filtering circuit respectively;
Described voltage drive source is the excitation of mutual inductor provider wave voltage; And
For whole circuit provides the power module of electric energy;
Described microprocessor further connects warning indicating member;
Described mutual inductor detects after leakage current signal, through filtering circuit, rectification circuit, process, convert the discernible signal of microprocessor to, microprocessor carries out after computing, export result to warning indicating member, warning indicating member is made corresponding action according to corresponding instruction.
Described mutual inductor is single magnetic core direct current electricity leakage sensor.
Described mutual inductor adopts single magnetic core and simplex winding structure, and detection winding and excitation winding are united two into one, and magnetic core works in degree of depth state of saturation under square wave excitation voltage.
The magnetic core of described mutual inductor adopts permalloy material to roll and forms.
Described filtering circuit comprises the first amplifier, the first resistance, the low-pass filter connecting successively;
The negative input of the first described amplifier is connected with mutual inductor;
The positive input ground connection of the first described amplifier;
The output terminal of the first described amplifier and the negative input short circuit of the first amplifier;
One end of the first described resistance connects voltage drive source, and its other end connects mutual inductor;
Described low-pass filter one end connects the output terminal of the first amplifier, and its other end connects rectification circuit.
Described rectification circuit comprises full-wave rectification block and the inverter circuit connecting successively;
Described inverter circuit comprises the second resistance, the 3rd resistance, the 4th resistance and the second amplifier;
Second described resistance one end connects full-wave rectification block, and its other end connects the positive input of the second amplifier;
The 3rd described resistance one end connects the negative input of the second amplifier, and its other end connects the output terminal of the second amplifier;
The 4th described resistance one end connects the negative input of the second amplifier, its other end ground connection;
The positive input ground connection of the second described amplifier;
The output terminal of the second described amplifier connects the input end of microprocessor.
Described microprocessor connects host computer by RS485 bus interface.
Described microprocessor model is P89LPC938FD.
Described power module is DC power supplier, the voltage of output 5V, ± 12V.
Described warning indicating member comprises a hummer and a pilot lamp;
Described hummer is for carrying out auditory tone cues according to the instruction of microprocessor;
Described pilot lamp is for carrying out light prompt according to the instruction of microprocessor.
The utility model direct current leakage current detect warning device compared with prior art has the following advantages: adopt magnetic modulating to realize the detection to DC ground fault, good stability, detection sensitivity are high, and its accuracy of detection is up to lmA; Adopt the connected mode of terminal type (plug-in), " change and use " and do not affect former loop, strengthened the anti-interference of tested ring current, infield is flexible, without " ground connection examination is drawn ", save manpower, it is convenient to change, the maintenance that can not have a power failure, can to Installed System Memory DC earthing make alarm memory.
Accompanying drawing explanation
Fig. 1 is the one-piece construction schematic diagram of the utility model direct current leakage current detect warning device.
Fig. 2 is detection of electrical leakage alarm principle figure.
Fig. 3 A is DC leakage current mutual inductor figure.
Fig. 3 B is direct current creepage mutual inductor circuit theory diagrams.
Fig. 4 A magnetic core static magnetization curve.
Magnetization curve after Fig. 4 B linear fit.
Current waveform in Fig. 5 excitation voltage and winding.
The waveform of Fig. 6 A exciting curent when there is forward dc electric leakage.
The waveform of Fig. 6 B exciting curent when there is the electric leakage of negative sense direct current.
Fig. 7 direct current leakage current detect warning device and PC communication scheme.
Embodiment
Below in conjunction with accompanying drawing, by describing a preferably specific embodiment in detail, the utility model is further elaborated.
As shown in Figure 1, direct current leakage current detect warning device 100, comprises: the mutual inductor 1, filtering circuit 2, rectification circuit 3 and the microprocessor 4 that connect successively; The voltage drive source 5 being connected with mutual inductor 1, filtering circuit 2 respectively; Voltage drive source 5 is mutual inductor 1 provider's wave voltage excitation; And provide the power module 6 of electric energy for whole circuit; Microprocessor 4 further connects warning indicating member 7; Mutual inductor 1 detects after leakage current signal, through filtering circuit 2, rectification circuit 3, process, convert the discernible signal of microprocessor 4 to, microprocessor 4 carries out after computing, export result to warning indicating member 7, warning indicating member 7 is made corresponding action according to corresponding instruction.
Mutual inductor 1 is single magnetic core direct current electricity leakage sensor.Mutual inductor 1 adopts single magnetic core and simplex winding structure, and detection winding and excitation winding are united two into one, and magnetic core works in degree of depth state of saturation under square wave excitation voltage.The magnetic core of mutual inductor 1 adopts permalloy material to roll and forms.The coil of mutual inductor 1 need provide a square wave excitation voltage, and this need to design an oscillatory circuit and realize.Can reach ± 12V of power module 6 output voltage swings, the frequency of operation of the oscillatory circuit of design is 400Hz.
Filtering circuit 2 comprises a single order low-pass filter circuit and is connected with a second-order low-pass filter circuit and forms three rank low-pass filter circuits, the first amplifier 21, the first resistance 22(sampling resistor R that connect successively s), low-pass filter 23; The negative input of the first amplifier 21 is connected with mutual inductor 1; The positive input ground connection of the first amplifier 21; The negative input short circuit of the output terminal of the first amplifier 21 and the first amplifier 21; One end of the first resistance 22 connects voltage drive source 5, and its other end connects mutual inductor 1; Low-pass filter 23 one end connect the output terminal of the first amplifier 21, and its other end connects rectification circuit 3.
The signal obtaining after circuit 2 filtering is after filtering the voltage signal being directly proportional to actual leakage current, but because direct current leakage current has directivity, and the magnitude of voltage obtaining is also very little, therefore need to after overcommutation and amplifying circuit, just can send microprocessor 4 to carry out AD sampling and data processing, rectification circuit 3 parts have adopted full-wave rectifying circuit, and it consists of positive half-wave rectification circuit and phase inverter.
Rectification circuit 3 comprises full-wave rectification block 31 and the inverter circuit 32 connecting successively; Inverter circuit 32 comprises the second resistance 321, the 3rd resistance 322, the 4th resistance 323 and the second amplifier 324; Second resistance 321 one end connect full-wave rectification block 31, and its other end connects the positive input of the second amplifier 324; The 3rd resistance 322 one end connect the negative input of the second amplifier 324, and its other end connects the output terminal of the second amplifier 324; The 4th resistance 323 one end connect the negative input of the second amplifier 324, its other end ground connection; The positive input ground connection of the second amplifier 324; The output terminal of the second amplifier 324 connects the input end of microprocessor 4.
Microprocessor 4 connects host computer (PC) by RS485 bus interface 41.Microprocessor 4 models are P89LPC938FD.Power module 6 is DC power supplier, the voltage of output 5V, ± 12V.Warning indicating member 7 comprises a hummer 71 and a pilot lamp 72; Hummer 71 is for carrying out auditory tone cues according to the instruction of microprocessor 4; Pilot lamp 72 is for carrying out light prompt according to the instruction of microprocessor 4.
Concrete application: DC ground fault can simply be described as, the wiring of each DC load is to draw from positive and negative DC bus, when there is an earth point in this loop, owing to there being the earth point of establishing in DC system insulation monitoring device in system, so will produce one by ground short circuit current i in this loop.I 1, i 2it is the negative-phase sequence curent that flows through direct current leakage current detect warning device 100.When straight-flow system does not have ground connection normally to move (now in figure, A point does not have ground connection), i 1=i 2, there is not poor stream, direct current leakage current detect warning device 100 can not be reported to the police; While having earth fault to occur in straight-flow system, as shown in Figure 2, A point ground connection, will produce poor stream △ i, makes i 1be not equal to i 2; Now, due to ground connection, this load-side network also changes, and direct current leakage current detect warning device 100 just can detect to go on business and flow and the variation of impedance, sends warning, and testing staff just can know DC ground fault has occurred in straight-flow system.
The leakage current signal being detected by mutual inductor 1 is sent to after signal adjustment circuit, filtering circuit 2, rectification circuit 3 are processed, convert the discernible signal of microprocessor 4 to, enter the A/D convertor circuit of microprocessor 4, convert digital signal to, microprocessor 4 carries out, after computing, exporting result to warning indicating member 7, warning indicating member 7 is made corresponding action according to corresponding instruction, and pilot lamp (LED) is indicated corresponding duty.
Single magnetic core direct current electricity leakage sensor in the utility model, as shown in Fig. 3 A and 3B, the difference of it and traditional single magnetic core magnetic modulating current sensor is to have adopted single magnetic core and simplex winding structure, detection winding and field winding are united two into one, magnetic core works in degree of depth state of saturation, Rs under square-wave voltage excitation---sampling resistor;
Suppose that driving voltage U (t) is an ideal square wave, the loop equation of circuit is:
(1)
In formula, ψ for excitation winding institute chain around total magnetic linkage;
According to Ampère circuital theorem:
(2)
In formula, the average length of magnetic path of toroidal core, the number of turn of field winding, it is the momentary current in loop; Due to
(3)
(4)
Therefore (5)
Wherein, it is the dynamic relative permeability of magnetic core; being permeability of vacuum, is 4 π * 10-7Wb/ (Am); S is the sectional area of magnetic core;
The magnetic core of mutual inductor adopts the permalloy material of high magnetic permeability to roll and forms, the feature with high initial magnetoconductivity, low-coercivity and low remanent magnetism, its static magnetization curve as shown in Figure 4 A, non-linear due to magnetic core magnetic characteristic, so formula (5) is a nonlinear equation.For the ease of analyzing, can carry out piece-wise linearization matching to magnetization curve, as shown in Figure 4 B.Therefore formula (5) can be rewritten into
,j=1,2,3 (6)
In formula it is the relative permeability of positive and negative saturated section and linearity range on magnetization curve; When the leakage current in positive and negative busbar is zero, suppose that t=0 moment negative voltage just finishes, magnetic core is saturated in negative sense, and segmentation row write circuit equation is:
(7)
,j=1,2,3
In formula, for the peak-to-peak value of added square-wave voltage, self-inductance while being operated in positive and negative saturated section and linearity range for magnetic core, for linearity range zero hour, for linearity range cut-off time, j=1,2,3;
Solve
(8)
In formula, , ; electric current in sensor winding when reaching magnetic saturation, ; for the maximal value of electric current in winding, ;
As shown in (b) in Fig. 5, due to the symmetry of magnetic core working current, the current waveform in later half cycle can be tried to achieve by the current waveform of front semiperiod.Consider and , (transient process is enough short), so magnetic core current waveform can further be approximately as shown in (c) in Fig. 5, the cycle of current waveform depends primarily on rise time and the fall time of linearity range,
(9)
In having positive and negative busbar, there is a forward leakage current time, the magnetic field intensity in magnetic core is
(10)
Wherein, for the primary side number of turn, here =1;
Have
(11)
Due to what obtain on sampling resistor, it is the electric current in field winding , from formula (11), can find out effect be in fact equivalent to make along translation I0/ N2 under Y, as shown in Figure 6A; Similarly, when there is negative sense DC leakage current-I0, be equivalent to make along translation I0/ N2 on Y, as shown in Figure 6B.The sensing range that can obtain mutual inductor from figure is .
Because exciting curent is nonlinear periodic signal, therefore DC leakage current to be detected, just need to analyze the feature of signal, find out the characteristic quantity that can represent this electric leakage signal.Because the Fourier expansion formula of applied square wave excitation voltage is
(12)
While there is DC leakage current I0 in bus, by the superposition theorem of circuit, can be obtained
(13)
Can find out, in only contain DC component and odd harmonic component, and DC component is proportional to direct current leakage current , therefore can high fdrequency component filtering be obtained to direct current electric leakage signal by designing suitable low-pass filter.
In embodiment, microprocessor 4 has been chosen the P89LPC938 single-chip microcomputer that PHILIPS company produces, and cost performance is high, feature is outstanding, realized real-time demonstration and the system autodiagnosis function of direct current leakage current, and provide action report to the police, etc. multi-protective function; When mutual inductor 1 operation irregularity being detected or not connecting, the warning of also can sounding, to point out user to deal with problems as early as possible, ensures the reliability of its work.
P89LPC938 is the microcontroller of a monolithic encapsulation, is suitable for many high integration, occasions cheaply of requiring, and can meet many-sided performance requirement.P89LPC938 has adopted high performance processor structure, only needs 2 to 4 clock period instruction time, and 6 times to standard 80C51 device.Many system-level functions that P89LPC938 is integrated, can greatly reduce the cost of number, board area and the system of element like this.
The utility model can also connect host computer and understand by correspondence the ruuning situation of direct current leakage current detect warning device 100, and measured data, reports to the police etc.; At industrial circle, the application of the monitoring of tools management mode of master-slave mode more and more comes extensively.A host computer is monitored many slave computers (1: N), compare the pattern of a slave computer of an ipc monitor (1: 1), have more economy, convenience and ageing simultaneously.In the communication pattern of one-to-many, due to the physical location apart from each other between slave computer and host computer, slave computer and slave computer, running environment is complicated, interference is large, use RS232 serial communication (the longest 15 m) can not reach requirement completely, and communication distance (the longest 1 200 m) far away, RS485 serial port communicating protocol that antijamming capability is strong can be competent at electromagnetic environment complicated in industry completely.RS232 bus can only realize man-to-man communication, and RS485 bus can articulate 32 equipment, can carry out 1: the communication of N.And PC facility have stronger data analysis processing power, good man-machine interface and mass data storage space, can serve as host computer, is used for monitoring the operation conditions of slave computer.But, conventionally on PC machine, only have RS232C serial ports, realize 1 with RS485: N communication, RS232 communication protocol and RS485 communication protocol must be carried out to bi-directional conversion.
The master-slave communication control model of one-to-many, PC machine serves as main frame, and many slave computers serve as slave.Due to RS232 serial port logic level be-15~-3 V (logical one) and+3~+ 15 V (logical zero), transmitting range is 15 m to the maximum, and RS485 adopts the communication level of RS422A, for ± 2~± 6 V, when speed is 9 600 BPS, transmitting range can reach 1 500 m.Therefore, these two kinds of buses must be undertaken interconnected by a level converter.Simultaneously, because slave computer is used single-chip microcomputer as P89LPC938 chip, only have serial received (RXD), send (TXD) pin, only support TTL level, do not mate with RS485 bus level, therefore can not directly be connected with RS485 bus, in circuit design, needing to increase a SP3485 conversion chip drives, different from RS422, RS485 bus can only can not be carried out in semiduplex mode " receipts " and " sending out " simultaneously, and the mode of operation of system can only be a kind of " replying " mode of operation.System architecture is as shown in Fig. 7.
Although content of the present utility model has been done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to restriction of the present utility model.Those skilled in the art, read after foregoing, for multiple modification of the present utility model with to substitute will be all apparent.Therefore, protection domain of the present utility model should be limited to the appended claims.

Claims (10)

1. direct current leakage current detect warning device, is characterized in that, comprises:
The mutual inductor (1), filtering circuit (2), rectification circuit (3) and the microprocessor (4) that connect successively;
The voltage drive source (5) being connected with mutual inductor (1), filtering circuit (2) respectively;
Described voltage drive source (5) is the excitation of mutual inductor (1) provider's wave voltage; And
For whole circuit provides the power module (6) of electric energy;
Described microprocessor (4) further connects warning indicating member (7);
Described mutual inductor (1) detects after leakage current signal, through filtering circuit (2), rectification circuit (3), process, convert the discernible signal of microprocessor (4) to, microprocessor (4) carries out after computing, export result to warning indicating member (7), warning indicating member (7) is made corresponding action according to corresponding instruction.
2. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described mutual inductor (1) is single magnetic core direct current electricity leakage sensor.
3. direct current leakage current detect warning device as claimed in claim 1, it is characterized in that, described mutual inductor (1) adopts single magnetic core and simplex winding structure, and detection winding and excitation winding are united two into one, and magnetic core works in degree of depth state of saturation under square wave excitation voltage.
4. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, the magnetic core of described mutual inductor (1) adopts permalloy material to roll and forms.
5. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described filtering circuit (2) comprises the first amplifier (21), the first resistance (22), the low-pass filter (23) connecting successively;
The negative input of described the first amplifier (21) is connected with mutual inductor (1);
The positive input ground connection of described the first amplifier (21);
The output terminal of described the first amplifier (21) and the negative input short circuit of the first amplifier (21);
One end of described the first resistance (22) connects voltage drive source (5), and its other end connects mutual inductor (1);
Described low-pass filter (23) one end connects the output terminal of the first amplifier (21), and its other end connects rectification circuit (3).
6. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described rectification circuit (3) comprises full-wave rectification block (31) and the inverter circuit (32) connecting successively;
Described inverter circuit (32) comprises the second resistance (321), the 3rd resistance (322), the 4th resistance (323) and the second amplifier (324);
Described the second resistance (321) one end connects full-wave rectification block (31), and its other end connects the positive input of the second amplifier (324);
The 3rd described resistance (322) one end connects the negative input of the second amplifier (324), and its other end connects the output terminal of the second amplifier (324);
The 4th described resistance (323) one end connects the negative input of the second amplifier (324), its other end ground connection;
The positive input ground connection of described the second amplifier (324);
The output terminal of described the second amplifier (324) connects the input end of microprocessor (4).
7. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described microprocessor (4) connects host computer by RS485 bus interface (41).
8. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described microprocessor (4) model is P89LPC938FD.
9. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described power module (6) is DC power supplier, the voltage of output 5V, ± 12V.
10. direct current leakage current detect warning device as claimed in claim 1, is characterized in that, described warning indicating member (7) comprises a hummer (71) and a pilot lamp (72);
Described hummer (71) is for carrying out auditory tone cues according to the instruction of microprocessor (4);
Described pilot lamp (72) is for carrying out light prompt according to the instruction of microprocessor (4).
CN201420150469.9U 2014-03-31 2014-03-31 Direct-current electric-leakage monitoring and warning device Active CN203811737U (en)

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Application Number Priority Date Filing Date Title
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103995208A (en) * 2014-03-31 2014-08-20 国网上海市电力公司 Direct current leakage monitoring and alarming device
CN106199343A (en) * 2016-10-13 2016-12-07 国网四川省电力公司电力科学研究院 A kind of power system DC power supply monitor and monitoring method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103995208A (en) * 2014-03-31 2014-08-20 国网上海市电力公司 Direct current leakage monitoring and alarming device
CN106199343A (en) * 2016-10-13 2016-12-07 国网四川省电力公司电力科学研究院 A kind of power system DC power supply monitor and monitoring method

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