CN201054495Y - Online monitoring and over-current limit device for power transformer iron core ground current - Google Patents
Online monitoring and over-current limit device for power transformer iron core ground current Download PDFInfo
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- CN201054495Y CN201054495Y CNU200720101211XU CN200720101211U CN201054495Y CN 201054495 Y CN201054495 Y CN 201054495Y CN U200720101211X U CNU200720101211X U CN U200720101211XU CN 200720101211 U CN200720101211 U CN 200720101211U CN 201054495 Y CN201054495 Y CN 201054495Y
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Abstract
The utility model relates to an on-line monitoring and over-current limiting device for the iron core grounding current of a power transformer. The utility model has the technical proposal that the utility model consists of a current transformer, a signal processing circuit, a DSP, a current limiting resistor network and a control circuit; the current limiting resistor network comprises a group of resistors and four relays; the first resistor, the second resistor and the third resistor are connected with the normally closed contacts of the fourth resistor and the first relay to form a parallel circuit after being connected in series with a normally closed contact which controls the relays, and then the parallel circuit is connected in series with the iron core grounding loop of the transformer; the coils of the four relays are connected with the output end of the control circuit; and the input end of the control circuit is connected with the data output end of the DSP. The utility model not only monitors the iron core grounding current of the power transformer in real time, but also automatically limits the current within the regulated range so as to ensure the safe operation of the power transformer.
Description
Technical field
The utility model relates to a kind of can the monitoring in real time power transformer iron core grounding current, and can automatically it be limited in the device in the prescribed limit, belongs to the transformer technology field.
Background technology
Power transformer is one of electric equipment important in the electric power system, and its operation conditions is directly connected to the safety and stablization of power system operation.Statistical results show to Accident of Transformer, the iron core accident is occupied quite high ratio in the total accident of transformer, and the generation of iron core fault, major part is owing to multipoint earthing of iron core causes, when multipoint earthing appears in iron core, have sizable electric current and flow through iron core, cause the iron core local overheating, can cause localized burn when serious, so be necessary the electric current in the transformer core is monitored in real time.Both at home and abroad the monitoring method of power transformer iron core grounding current is concluded at present and is mainly contained following three kinds:
Method one: the tour personnel regularly utilize the electric current in the clamp on amperemeter measurement iron core grounding line, if find that electric current exceeds standard, generally are to be connected in series current-limiting resistance by the operations staff in grounded circuit temporarily, and there is the hysteresis quality of fault discovery and processing in clearly this method.
Method two: analog current table monitoring method.This method is directly to seal in the analog current table in the iron core grounding line of transformer, is used for the monitoring grounding electric current.After the tour personnel find that electric current exceeds standard, take further step again, as manually in grounded circuit, sealing in resistance, sometimes even make transformer out of service, carry out malfunction elimination.The disadvantage of this method is accurately to measure iron core grounding current, this is because in a single day multipoint earthing appears in transformer, electric current in its grounded circuit can reach tens peaces, therefore be used to monitor that the range of ammeter of core current is inevitable (be generally tens peaces very greatly, otherwise ammeter can blow because of electric current is excessive, cause the grounded circuit open circuit), and transformer under normal circumstances, electric current in its iron core grounding line is again very little (generally several milliampere to tens milliamperes), GB stipulates that the threshold value of its electric current can not surpass 100mA, and so little electric current does not almost have reading on the ammeter of wide range like this.In addition, there is the untimely problem of troubleshooting too in this method.
Method three: based on digitized measurement mechanism.This method is to utilize current sensor to gather current signal in the iron core grounding line, and signal is sent into PC or DSP or single-chip microcomputer after preliminary treatment, and PC or DSP or scm software carry out analyzing and processing to signal, provide alarm signal if exceed standard.This method can only play the effect that earth current is monitored and exceeded standard and report to the police, processing after electric current exceeds standard still can not be carried out automatically by manually finishing, there is the untimely problem of troubleshooting equally, and can not effectively carry out the preservation of data, be not easy to accident analysis afterwards, function ratio is more single.
Summary of the invention
The purpose of this utility model is to overcome the deficiencies in the prior art, provide a kind of can monitor in real time to power transformer iron core grounding current, and can automatically it be limited in power transformer iron core grounding current on-line monitoring and overcurrent limitting device in the prescribed limit.
Problem described in the utility model realizes with following technical proposals:
A kind of power transformer iron core grounding current on-line monitoring and overcurrent limitting device, by current transformer, signal processing circuit, DSP, current-limiting resistor network and control circuit thereof are formed, described current-limiting resistor network comprises one group of resistance and four relays, it is respectively first resistance R 1, second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, first relay, second relay, the 3rd relay and the 4th relay, described first resistance, second resistance and the 3rd resistance are with after the normally-closed contact of its control relay is connected in series, be connected into parallel circuits with the normally-closed contact J1-1 of the 4th resistance and first relay and be series in the transformer core grounded circuit, the output of the coil connection control circuit of four relays, the data output end of the input termination DSP of control circuit.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device, the ratio of the resistance of described first resistance, second resistance, the 3rd resistance and the 4th resistance is 1: 2: 4: 8, the span of described the 4th resistance is 1500～1800 ohm.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device are set up piezo-resistance YM and gas discharge tube FD1, and they all are connected in parallel with current-limiting resistor network.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device, described current transformer is provided with two, be respectively a small amount of journey current transformer CT1 and wide range current transformer CT2, they all are through on the transformer core earth connection, its signal output part connects signal processing circuit, described signal processing circuit comprises the small-signal pre-process circuit, large-signal pre-process circuit and A/D converter U2, the small-signal pre-process circuit is made up of isolating chip U5 and programmable amplifier U4, input+Vin of isolating chip U5 connects the output of journey current transformer CT1 in a small amount, its output end vo ut meets input+Vin of programmable amplifier U4, the output end vo ut of programmable amplifier U4 meets the CH1A end of A/D converter U2, its A0, the A1 end connects IOPE1 and the I0PE2 end of DSP respectively; The large-signal pre-process circuit is made up of isolating chip U6 and operational amplifier U7, the output signal of wide range current transformer CT2 meets input+Vin of isolating chip U6 behind two electric resistance partial pressures, operational amplifier U7 is connected into voltage follower, its in-phase input end meets the output end vo ut of isolating chip U6, the CH2A end of output termination A/D converter U2; Data output end D0～D13 of A/D converter U2 connects the D0 of DSP～D13 end through a level translator U1, its/CONVST and/the INT end connects IOPB4 and the XINT1 end of DSP respectively.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device, set up the voltage signal input circuit, it comprises voltage transformer pt and operational amplifier U8, voltage transformer is connected to the current-limiting resistor network two ends, its signal output part connects the in-phase input end of operational amplifier, operational amplifier is connected into voltage follower, the CH3A end of its output termination A/D converter U2.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device, described control circuit is made of chip for driving U3, input 1B, the 3B of chip for driving U3,5B, 7B connect IOPB0, IOPB1, IOPB2 and the IOPB3 end of DSP respectively, and its output 1C, 3C, 5C and 7C connect the coil of four relays respectively.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device are set up manual control model, and each relay is set up a hand control switch, switch by a change over switch between hand control switch and the DSP control circuit.
Above-mentioned power transformer iron core grounding current on-line monitoring and overcurrent limitting device are set up display, and the data input pin of display connects the data output end of DSP.
The utility model utilizes current transformer CT to gather the transformer iron core grounding current signal in real time, DSP can judge accurately whether earth current exceeds standard, when electric current exceeds standard, DSP is by the switching of four resistance of control, change the resistance of current-limiting resistor network, make within the scope that iron core grounding current is limited in stipulating all the time.Can also manually carry out switching to four resistance as required, DSP can preserve data, is convenient to afterwards to carrying out accident analysis.The utility model not only can be monitored in real time to power transformer iron core grounding current, and can automatically it be limited in the prescribed limit, guarantees the power transformer safe operation.
Description of drawings
The utility model is described in further detail below in conjunction with drawings and Examples.
Fig. 1 is an electric theory diagram of the present utility model;
Fig. 2 is an electrical schematic diagram;
Fig. 3 is a control flow chart.
Each label is among the figure: CT1, small current mutual inductor; CT2, great current mutual inductor; U1, level translator; U2, A/D converter; U3, chip for driving; U4, programmable amplifier; U5, U6, isolating chip; U7, U8, operational amplifier; R1～R6, resistance; J1～J4, relay; The normally-closed contact of J1-1～J4-1, relay; FD1, FD2, gas discharge tube; YM, piezo-resistance; K1～K4, hand switch; KZ1～KZ4, change over switch; DSP, microprocessor.
Embodiment
Transformer core is when operation, the electric field of coil makes each parts (comprising folder etc.) of iron core have different current potentials with the magnetic field acting in conjunction, if the unreliable ground connection of iron core, then may produce the intermittent discharge phenomenon because of current potential is different, damage its insulation, so transformer core must there be some reliable grounds; But then, if the multipoint earthing situation appears in transformer core, can form a closed-loop path between then per two earth points, wherein the magnetic flux of hinge will induce circulation in the loop, can make the iron core local overheating, can cause localized burn, multipoint earthing of iron core of transformer fault that Here it is when serious.Only during one point earth, the effective value that flows through transformer core current is tens milliamperes only to iron core, and iron core is safe from harm; But when multipoint earthing appears in iron core, the electric current that flows through in the iron core grounding line sharply increases (can reach tens amperes), stipulate according to GB, the electric current that flows through transformer core can not surpass 0.1A, after electric current surpasses 0.1A, think that promptly there is the multipoint earthing fault in iron core, multipoint earthing occurs at iron core obviously, under the situation that electric current exceeds standard, must take certain measure.Simultaneously, theory analysis also shows, though the electric current of this moment is very big, but the electromotive force that induces in the loop generally can not be higher than about 150V, so as long as in time sealing in current-limiting resistance in grounded circuit just can effectively be limited in electric current in the 0.1A, guarantee the safe operation of iron core, treat the maturation on opportunity, during as transformer stoppage in transit or overhaul, finally get rid of its multipoint earthing fault again.
Current transformer in the utility model becomes voltage signal with core current signal transformation, after signal processing circuit, send into DSP and carry out analysis and judgement, DSP judges according to size of current whether iron core has the multipoint earthing phenomenon, if have, then drop into suitable resistance automatically electric current is limited within the scope of GB regulation.Install in the time of timing also can being set and fault is arranged and preserve parameter function automatically, be convenient to accident analysis afterwards, system also can be equipped with lcd screen and LED light, can show abundant information, sets up wireless and wired communication interface, and realization and host computer is connected easily.This device runs directly in the transformer station scene, both can also can be connected with host computer by wireless network by independent operating, moves under the control of host computer, by the analysis software of host computer, can analyze in more detail the operation conditions of iron core.
Data acquistion and control system
Among Fig. 2, straight-through current transformer has been adopted in the extraction of electric current, is enclosed within the iron core grounding line, and transducer is output as voltage signal, output voltage is 1: 1 with the ratio of the amplitude of input current signal, has stronger anti-electromagnetic capability and have good linearty in measuring range.Because the electric current in the iron core grounding line only is tens milliamperes when single-point grounding, and when multipoint earthing, can reach tens of peaces, the excursion of electric current is big especially, be difficult to take into account simultaneously big or small electric current with a current sensor, this device seals in two current transformers on earth connection, divide two-way to measure current signal, wherein the measuring range of CT1 is 1mA～5A (the above core sataration of 5A), the measuring range of CT2 is 5A～30A, electric current is got first via signal when little electric current like this, gets the second road signal during big electric current.The pre-process circuit of first via current signal is made of isolation and amplifier, the voltage signal of CT1 output is input to isolating chip U5 earlier, the input and output voltage ratio of this chip is 1: 1, has good linearty, isolation voltage has reached 1500V, and input can bear 100V voltage, and this chip can effectively be avoided from the harm to collecting circuit board of the overvoltage signal of transducer output; Programmable amplifier U4 has adopted the PGA203 chip, the A0 of chip, A1 pin are controlled by the IOPB1 of DSP, IOPB2 pin, its multiplication factor is 1,2,4,8 fourth gear, DSP can select suitable multiplication factor automatically according to the power of current signal, and the signal of PGA203 output has been received the CH1A pin of A/D conversion chip MAK125.CT2 for wide range, at first utilized attenuator circuit that resistance R 5, R6 form with its signal attenuation within the acquisition range of A/D conversion chip (± 5V), because the input impedance of MAX125 is 10K Europe only, device has inserted the voltage follower that is made of operational amplifier U7, and then being input to the CH2A pin of MAX125, the effect of voltage follower mainly is the effect of playing a buffer.Voltage signal obtains from the two ends of current resistor network, and at first through the accurate PT step-down of a 220/6V, the voltage follower that constitutes through U8 is input to the CH3A pin of MAX125 to signal then.What be input to AD like this has two-way current signal and one road voltage signal, and under the control of DSP, this chip synchronous acquisition current and voltage signals can obtain the size of electric current like this after DSP calculates, can also obtain putting into simultaneously the resistance value in the iron core loop.
Master control chip DSP adopts TMS320LF2407 in the utility model, and U1 adopts SN74LVC16245, and U2 adopts MAX125, and U3 adopts ULN2803, and U4 adopts PGA203, and U5, U6 adopt ISO124, and U7, U8 adopt OP97.Because the pin of this DSP can only bear the voltage of 3.3V, and the digital signal of MAX125 output is 5V, and collecting circuit board has adopted SN74LVC16245 to realize the conversion of 3.3V and 5V level.MAX125 synchronous acquisition CH1A, CH2A, the analog signal of three passages of CH3A, chip internal has carried sampling hold circuit, its conversion accuracy is 14, the scope of input voltage is ± 5V, quantization error only is 0.12 millivolt, because being input to AD is power frequency component, so the sampling rate that device is set is 1KHz, that is to say and can gather 20 points within the one-period, so both guaranteed the slickness of the current-voltage waveform that host computer shows, reduce the time of each collection and signal processing again effectively, improved the real-time of system's control.DSP is under the control of software, the IOPB4 pin every 1ms with MAX125 /that the pin of CONVST is changed to low spot is flat, start AD and begin sampling, after AD has finished the signal sampling of 3 passages/INT pin output low level, cause that DSP interrupts, in interrupt routine, the data that DSP will temporarily be kept in the MAX125 internal RAM are read in three zones that are kept at outside RAM then successively, after treating that each passage has been gathered the signal of 10 cycles, this signals collecting finishes, change the analyzing and processing to signal over to, DSP reads in inside with the data in the external RAM, calculates the effective value and the resistance value of its electric current and voltage then.DSP is according to the value of electric current, judge and select to utilize the passage 1 or the current value of passage 2, when electric current exceeds standard, then pass through four I/O mouth (IOPB0 of DSP, IOPB1, IOPB2, IOPB3) come the switching of controlling resistance, because the I/O driving force of DSP is limited, device has added chip for driving ULN2803, the current drive capability of this chip can reach 1A, when the I/O of DSP mouth was high level, the triode of ULN2803 respective channel was in conducting state, then the relay closes of this passage, otherwise, when the I/O mouth is that low spot is flat, then the relay of this passage is opened, therefore, the height flat switching control that just can realize resistance of DSP by controlling four I/O mouths, thus current value is limited within the reasonable range.
The purpose of setting up current-limiting resistor network is when multipoint earthing appears in the iron core of transformer, iron core grounding current is limited, otherwise might burn out iron core.Current-limiting resistor network is formed in parallel by five branch roads altogether, is serially connected among the iron core grounding loop.R1 wherein, R2, R3, R4 are powerful aluminum hull resistance, its resistance value is respectively: 200 Europe, 400 Europe, 800 Europe and 1600 Europe; J2, J3, J4 are serially connected in resistance R 1, R2, on the R3 branch road, 4 of resistance R fixedly are connected in the loop, can control the folding condition of these relays by the I/O mouth of hand switch or DSP, and promptly can control these branch roads is on-state or resistance state.Obviously, just can change parallel resistor by the folding condition of controlling these relays and prop up way, thereby change the total resistance value that is sealed in the grounded circuit.
Above-mentioned wiring has the following advantages:
At first, reduced the probability of iron core grounding loop open circuit.The resistance of the 5th branch road connect with relay, but fixedly connected, like this with regard to avoided because of the misoperation under the manual mode or under automated manner the misoperation of DSP cause the possible of all branch roads open circuits.Next installs that resistance has adopted and the form of tie and do not adopt series wiring, and connect than serial connection and cause the probability of loop open circuit greatly to reduce, possibility is very little because open circuit (blow wiring as electric current is excessive, the loosening grade of the not firm wiring of mechanical connection caused open circuit) appears in each branch road simultaneously; The resistance of branch road has adopted powerful resistance in addition, has also reduced the probability of broken string.
Secondly, current-limiting resistance can be divided into many grades, and the resistance value of input is reasonable.When transformer core current exceeds standard, though its electric current of control that can adopt the mode that drops into a big resistance to settle at one go, this may cause having dropped into big resistance under the situation of resistance that there is no need to have high input, and might cause the lifting of iron core current potential.And adopt multiple branch circuit resistance parallel way, and making up by the parallel connection that can realize different branch of opening/close that changes relay, thereby reach the purpose of controlling the current limliting all-in resistance, resistance or small resistor according to actual needs can have high input.
Among Fig. 2, in order to take into account automatically and manual switching, this device is provided with automatically and the manual switchover control switch, can finish automatic and manual switching, and K1～K4 is a hand switch, and KZ1～KZ4 is a change over switch.
The throwing of resistance/cut control method:
As long as control relay J1, J2, J3, J4 open/close state just can control loop in total resistance, did but after electric current exceeded standard, this drop into great resistance and it could be limited in below the 0.1A? in addition, the earth fault of transformer is suspension earth fault sometimes, may can eliminate automatically through iron core fault behind the certain hour, this just requires this device to drop into automatically and can excise fault automatically.Behind the circuit structure of having analyzed multipoint earthing of iron core, this device has finally adopted to sound out step by step to be increased resistance and reduces electric-resistivity method, and the thinking of this method will be described below.
The theoretical analysis, transformer is when multipoint earthing occurring, its transformer inside can equivalence be the form that a voltage source and internal impedance are in series, this voltage is to the maximum about 150V (effective value) as can be known by analysis, internal resistance is transformer core body and the total impedance that causes the short circuit thing of multipoint earthing, the scope of its impedance probably several Europe between the hundreds of Europe, the earth point ground connection form of the magnitude of voltage of its induction and equiva lent impedance and core interior has very big relation.In actual applications, the occurrence of equivalent voltage source and internal impedance is unknown, can't judge this input or excise great resistance and electric current could be limited in below the 0.1A so install, based on above consideration, take progressively to increase or reduce the heuristic of resistance, its thinking is as follows:
By the structure of this current-limiting resistor network as can be known, when all relays are all closed, first relay is with all resistance short circuits, being equivalent to seal in the loop resistance is 0 Europe, first relay is opened, when all the other relays are all closed, be equivalent to four resistance parallel connections of branch road, obviously all-in resistance is the parallel connection value of four branch road resistance, open second relay, the 3rd relay and the 4th relay later on successively, then current-limiting resistance increases successively, but when closed the 4th relay successively, the 3rd relay, second relay and first relay, its resistance gradually reduces.According to the folding condition difference of each relay, corresponding current-limiting resistance such as table 1:
The current-limiting resistance of the folding condition correspondence of table 1 relay
(owing to resistance certain deviation is arranged in the reality, its parallel resistance value also has difference, but little with the theoretical value difference in the table)
| State | J1-1 | J2-1 | J3-1 | J4-1 | Loop current-limiting resistance (Europe) |
| 1 | Closed | Closed | Closed | Closed | 0 |
| 2 | Open | Closed | Closed | Closed | 107 |
| 3 | Open | Open | Closed | Closed | 229 |
| 4 | Open | Open | Open | Closed | 533 |
| 5 | Open | Open | Open | Open | 1600 |
Like this, after device monitoring exceeds standard to electric current, at first open first relay, the current-limiting resistance in loop is 107 Europe, if electric current also exceeds standard and will open second relay again, so go down up to the 4th relay is opened, after all relays were all opened, the resistance that seals in the loop was 1600 Europe, and the maximum induced voltage of considering the loop is probably at 150V, even so in this case, also can be below 0.1A with resistance limits.When needs reduce loop resistance, its process and to drop into resistance just the opposite, its change in resistance is followed successively by: 1600 Europe, 533 Europe, 229 Europe, 107 Europe, 0 Europe.
Prevent first relay method of switching repeatedly:
In the design of this device, when electric current greater than 100mA (operations staff can adjust in ± 10mA voluntarily), need to increase resistance, and work as electric current less than 20mA, need to reduce resistance, the repeatedly closed-ended question that has first relay in this process probably, especially under the very little situation of the inside of transformer equiva lent impedance, this is because device detects electric current and exceeds standard probably, after dropping into resistance, electric current is again less than the situation of 20mA, if directly press above-mentioned control method, will cause the switching repeatedly of first relay, above-mentioned phenomenon analysis is as follows:
Under the situation of main first relay, detect in closure electric current exceed standard (I＞100mA), the inner equiva lent impedance of its transformer is R, then install first relay opened after, electric current is in the iron core grounding line:
If hypothesis R=5 Europe, I=150mA, I '=6.7mA then, this value then is lower than the lower limit of threshold, control idea so routinely again, then install closed first relay, obviously, electric current will exceed standard again, and first relay will be opened, so go down to cause the switching repeatedly of first relay, this is unallowed at the scene certainly.In order to address the above problem, the software of this device has adopted the algorithm of Fig. 3.As can be seen from Figure 3, at regular intervals first relay closes is soundd out once, seen whether earth fault disappears, if disappear, then closed first relay, otherwise will open first relay once more.Even because first relay opens, its current-limiting resistance that seals in is 107 Europe, this value is little, so this device is set to sound out once through a talent at least, and the fate of its exploration can utilize the keyboard of this device to regulate within the specific limits by the user.
Though may there be repeatedly the problem of switching in first relay, can there be this problem in the throwing of other relay/cut then.Below just to state 3 conversions this problem to be described by state 2.As shown in Table 1, state 2 times, only first relay is opened, if the inner equiva lent impedance of its transformer this moment is R, when electric current exceed standard (I＞100mA), then device must be opened second relay to increase resistance, then second relay opens that electric current is in the iron core grounding line of back:
This function is an increasing function, if establish R ∈ (0, ∞), then I ' ∈ (0.47I, I) because electric current exceeds standard, I＞100mA obviously, so I '＞47mA, also promptly greater than the lower limit threshold value, so can closed once more second relay.The same analysis as can be known, the dress between other state are changed the problem of switching repeatedly that resistance can not appear in (increase resistance and reduce resistance).
Judge whether major loop opens a way:
If the major loop open circuit also is unallowed at the scene, the thinking that device is judged is under the situation of main contactor first relay closes, if (device is set to 3mA at present less than certain threshold value to monitor electric current, because the core current of the transformer in the actual motion is generally more than 10mA), think that then major loop may open a way, provide alarm.
The design of protective circuit:
Among Fig. 2, piezo-resistance YM and gas discharge tube FD1 are the overvoltage pressure limiting device.If too high voltage on current-limiting resistance, occurs; then the power of its current-limiting resistance will increase; though the resistance of this device has adopted high-power resistance; but to avoid this high voltage that occurs; for this this device in the parallel connection of the two ends of current-limiting resistance protection component piezo-resistance and gas discharge tube; its operation voltage is at 200V; like this; protective circuit can not impact system under general situation; after overvoltage occurring; then protection component action, automatically with voltage limit about general 200V.
Claims (8)
1. power transformer iron core grounding current on-line monitoring and overcurrent limitting device, it is characterized in that, it is by current transformer, signal processing circuit, DSP, current-limiting resistor network and control circuit thereof, described current-limiting resistor network comprises one group of resistance and four relays, be respectively first resistance (R1), second resistance (R2), the 3rd resistance (R3), the 4th resistance (R4), first relay (J1), second relay (J2), the 3rd relay (J3) and the 4th relay (J4), described first resistance, second resistance and the 3rd resistance are with after the normally-closed contact of its control relay is connected in series, be connected into parallel circuits with the normally-closed contact (J1-1) of the 4th resistance and first relay and be series in the transformer core grounded circuit, the output of the coil connection control circuit of four relays, the data output end of the input termination DSP of control circuit.
2. according to described power transformer iron core grounding current on-line monitoring of claim 1 and overcurrent limitting device, it is characterized in that, the ratio of the resistance of described first resistance, second resistance, the 3rd resistance and the 4th resistance is 1: 2: 4: 8, and the span of described the 4th resistance is 1500～1800 ohm.
3. according to claim 1 or 2 described power transformer iron core grounding current on-line monitoring and overcurrent limitting devices, it is characterized in that set up piezo-resistance (YM) and gas discharge tube (FD1), they are all in parallel with current-limiting resistor network.
4. according to described power transformer iron core grounding current on-line monitoring of claim 3 and overcurrent limitting device, it is characterized in that, described current transformer is provided with two, be respectively a small amount of journey current transformer (CT1) and wide range current transformer (CT2), they all are through on the transformer core earth connection, its signal output part connects signal processing circuit, described signal processing circuit comprises the small-signal pre-process circuit, large-signal pre-process circuit and A/D converter (U2), the small-signal pre-process circuit is made up of isolating chip (U5) and programmable amplifier (U4), input+the Vin of isolating chip (U5) connects the output of journey current transformer in a small amount, its output end vo ut meets input+Vin of programmable amplifier (U4), the output end vo ut of programmable amplifier (U4) meets the CH1A end of A/D converter (U2), its A0, the A1 end connects IOPE1 and the IOPE2 end of DSP respectively; The large-signal pre-process circuit is made up of isolating chip (U6) and operational amplifier (U7), the output signal of wide range current transformer meets input+Vin of isolating chip (U6) behind two electric resistance partial pressures, operational amplifier (U7) is connected into voltage follower, its in-phase input end meets the output end vo ut of isolating chip (U6), the CH2A end of output termination A/D converter (U2); Data output end DO～the D13 of A/D converter (U2) connects the DO of DSP～D13 end through level translator (U1), its/CONVST and/the INT end connects IOPB4 and the XINT1 end of DSP respectively.
5. according to described power transformer iron core grounding current on-line monitoring of claim 4 and overcurrent limitting device, it is characterized in that, set up the voltage signal input circuit, the voltage signal input circuit comprises voltage transformer (PT) and operational amplifier (U8), voltage transformer is connected to the current-limiting resistor network two ends, and its signal output part connects the in-phase input end of operational amplifier, and operational amplifier is connected into voltage follower, the CH3A end of its output termination A/D converter (U2), latter's output meets DSP.
6. according to described power transformer iron core grounding current on-line monitoring of claim 5 and overcurrent limitting device, it is characterized in that, described control circuit is made of chip for driving (U3), input 1B, the 3B of chip for driving, 5B, 7B connect IOPBO, IOPB1, IOPB2 and the IOPB3 end of DSP respectively, and its output 1C, 3C, 5C and 7C connect the coil of four relays respectively.
7. according to described power transformer iron core grounding current on-line monitoring of claim 6 and overcurrent limitting device, it is characterized in that, set up manual control model, each relay is set up a hand control switch, switches by a change over switch between hand control switch and the DSP control circuit.
8. according to described power transformer iron core grounding current on-line monitoring of claim 7 and overcurrent limitting device, it is characterized in that set up display circuit, the data input pin of display connects the data output end of DSP.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU200720101211XU CN201054495Y (en) | 2007-04-24 | 2007-04-24 | Online monitoring and over-current limit device for power transformer iron core ground current |
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| Application Number | Priority Date | Filing Date | Title |
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| CNU200720101211XU CN201054495Y (en) | 2007-04-24 | 2007-04-24 | Online monitoring and over-current limit device for power transformer iron core ground current |
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| CN201054495Y true CN201054495Y (en) | 2008-04-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNU200720101211XU Expired - Fee Related CN201054495Y (en) | 2007-04-24 | 2007-04-24 | Online monitoring and over-current limit device for power transformer iron core ground current |
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| Country | Link |
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| CN (1) | CN201054495Y (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102868140A (en) * | 2012-09-07 | 2013-01-09 | 常熟市森源电气科技有限公司 | Overload alarming device for power transformer |
| CN107526010A (en) * | 2017-09-30 | 2017-12-29 | 南京国电南自电网自动化有限公司 | A kind of distributed small current earthing wire-selecting method based on double CT samplings |
| CN110086141A (en) * | 2019-05-27 | 2019-08-02 | 福建和晔电气有限公司 | A kind of high voltage power cable sheath smart grounding device |
| CN110112712A (en) * | 2019-04-30 | 2019-08-09 | 广东电网有限责任公司 | Power distribution network earth protective device and its sampling control method with the configuration of double mutual inductors |
| CN110649586A (en) * | 2019-09-27 | 2020-01-03 | 上海锐开电气有限公司 | Iron core grounding current over-current suppression resistance circuit |
| CN116449252A (en) * | 2023-06-20 | 2023-07-18 | 国网山西省电力公司电力科学研究院 | Online positioning device and method for multipoint grounding faults of transformer core |
-
2007
- 2007-04-24 CN CNU200720101211XU patent/CN201054495Y/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102868140A (en) * | 2012-09-07 | 2013-01-09 | 常熟市森源电气科技有限公司 | Overload alarming device for power transformer |
| CN107526010A (en) * | 2017-09-30 | 2017-12-29 | 南京国电南自电网自动化有限公司 | A kind of distributed small current earthing wire-selecting method based on double CT samplings |
| CN110112712A (en) * | 2019-04-30 | 2019-08-09 | 广东电网有限责任公司 | Power distribution network earth protective device and its sampling control method with the configuration of double mutual inductors |
| CN110086141A (en) * | 2019-05-27 | 2019-08-02 | 福建和晔电气有限公司 | A kind of high voltage power cable sheath smart grounding device |
| CN110649586A (en) * | 2019-09-27 | 2020-01-03 | 上海锐开电气有限公司 | Iron core grounding current over-current suppression resistance circuit |
| CN116449252A (en) * | 2023-06-20 | 2023-07-18 | 国网山西省电力公司电力科学研究院 | Online positioning device and method for multipoint grounding faults of transformer core |
| CN116449252B (en) * | 2023-06-20 | 2023-09-19 | 国网山西省电力公司电力科学研究院 | Online positioning device and method for multipoint grounding faults of transformer core |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| EE01 | Entry into force of recordation of patent licensing contract |
Assignee: Baoding Jingyi Electric Power Technology Co. Ltd Assignor: North China Electric Power University Contract record no.: 2011130000041 Denomination of utility model: Device for online monitoring and overcurrent limiting power transformer iron core grounding current Granted publication date: 20080430 License type: Exclusive License Record date: 20110503 |
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| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20080430 Termination date: 20130424 |