CN106371049A - Current transformer secondary open circuit identification method - Google Patents
Current transformer secondary open circuit identification method Download PDFInfo
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- CN106371049A CN106371049A CN201610793873.1A CN201610793873A CN106371049A CN 106371049 A CN106371049 A CN 106371049A CN 201610793873 A CN201610793873 A CN 201610793873A CN 106371049 A CN106371049 A CN 106371049A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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Abstract
The invention provides a current transformer secondary open circuit identification method. Two sets of CT currents are introduced, an open circuit voltage of each phase of two CT sets is detected, when CT saturation does not occur, a formula |I1phi-I2phi|>K(|I1phi|+|I2phi|) is satisfied, and U1phi>Uset or U2phi>Uset, after T1 time delay, a phi-phase secondary current open circuit of a first path or a second path is determined, a CT open circuit blocking signal is sent to a protection device, after T2 time delay, a CT secondary open circuit device takes action to be in short connection with a first CT winding set or a second CT winding set, and a CT open circuit fault disappears. If conditions are not all satisfied, a sample is returned, and repeated determination is carried out. According to the method, two sets of sampling set currents and secondary open circuit voltages are combined, and a CT broken line fault can be rapidly and accurately determined. The method further belongs to the relay protection field.
Description
Technical field
The present invention relates to Current Transformer Secondary open circuit recognition methodss, belong to relay protection field.
Background technology
Current transformer (abbreviation ct) is widely used in power system, and its first winding is serially connected with high voltage circuit, and two
Secondary winding is connected with measuring instrumentss, protection device, is related to the accuracy of measuring, the reliability of protective relaying device and height
The safety of volt circuit.During normal work, ct secondary side is near short circuit state, and output voltage is very low, if being in operation two
Secondary winding open circuit can produce thousands of volts even overvoltage of volts up to ten thousand in secondary side, and this not only can make ct too drastic and scaling loss, or even
Jeopardize the life security of staff, and cause heavy economic lossess, therefore prevent Current Transformer Secondary from opening a way, research is effectively
Current Transformer Secondary open circuit recognition methodss significant.
Existing Current Transformer Secondary open circuit recognition methodss mainly have secondary current voltage block method and overvoltage protection method
Two big class.
1st, secondary current voltage identification method, predominantly relay protection producer adopt, by the electric current accessing protection device
Transformer secondary side three-phase current and three-phase voltage carry out logic discrimination, and the concrete criterion of each producer is not quite similar, and substantially adopts
With there being the discriminant approach of zero-sequence current no residual voltage.When certain phase current mutual inductor secondary side breaks phase, this phase current disappears, its
He is biphase normal, it will produce zero-sequence current, now once no ground fault, and residual voltage very little, by having zero-sequence current no
The method of residual voltage differentiates Current Transformer Secondary broken string.The method is load current is less or cannot judge during three-phase broken string
Ct second open circuit fault is it is impossible to ensure to determine the requirement of ct second open circuit in any case.
2nd, secondary overvoltage detection method, when mainly utilizing normal work, Current Transformer Secondary side is near short circuit shape
State, output voltage is very low, if can produce abnormal peak overvoltage in secondary side after the current transformer second open circuit that is in operation
Principle, by detect ct secondary side voltage judge whether occur ct second open circuit, if Current Transformer Secondary side voltage reaches
Setting value then overvoltage relay action it is believed that ct secondary side is opened a way.This method of discrimination can produce erroneous judgement to Lightning Over-voltage,
Erroneous judgement Current Transformer Secondary open circuit when causing normally to run.
As can be seen here, existing Current Transformer Secondary open circuit recognition methodss have certain limitation it is impossible to meet electric current
The actual requirement of transformer second open circuit real-time detection.
Content of the invention
It is an object of the invention to: a kind of Current Transformer Secondary open circuit recognition methodss are provided, mutual to solve existing electric current
Sensor second open circuit recognition methodss have certain limitation it is impossible to the reality meeting Current Transformer Secondary open circuit real-time detection will
The problem asked so that under any circumstance, can effectively detect Current Transformer Secondary open fault.
For solving the above problems, a kind of Current Transformer Secondary open circuit recognition methodss are provided, comprise the following steps:
(1) same current transformer has multigroup Secondary Winding, introduces two groups of different windings in Current Transformer Secondary side
Secondary current, a, b, c three-phase current is simultaneously introduced, and now can obtain current sample group i of two a, b, c three-phases1φAnd i2φ, with
When two windings of measurement every phase secondary voltage, the voltage of two a, b, c three-phases can be obtained using group u1φAnd u2φ, wherein i1Table
Show first group of current sample, i2Represent second group of current sample, u1φRepresent first group of open-circuit voltage sampling, u2φRepresent second group
Open-circuit voltage is sampled, and φ is the replacing representation of a, b, c three-phase；
(2) judge set of samples i1φAnd i2φWhether ct saturation, if ct saturation, return to step 1, if ct unsaturation, enter
Enter next step.During ct saturation, sampled value is the non-linear change of disease, and the electric current of different secondary winding output is different, does not have comparability.ct
Saturation can differentiate ct whether saturation with the secondary and triple-frequency harmonics content in secondary current.
(3) according to formula: | i1φ-i2φ|>k(|i1φ|+|i2φ|) judged, if formula is set up, enter next step,
If be false, return to step 1.In formula, k is coefficient of reliability, takes between 0.6-0.8.
(4) according to formula: u1φ>usetOr u2φ>usetJudged, if u1φ>usetSet up, then time delay t1 for a period of time
Judge that first via φ phase secondary current is opened a way afterwards, send ct open circuit block signal, time delay t2 for a period of time to protection device a simultaneously
Afterwards by ct first group of ct winding of second open circuit device action short circuit.If u2φ>usetSet up, then time delay judges after t1 for a period of time
Second road φ phase secondary current open circuit, sends ct open circuit block signal to protection device b simultaneously, time delay for a period of time after t2 by ct
Second group of ct winding of second open circuit device action short circuit.If above-mentioned two formulas are all false, return to step 1.U in formulasetFor two
Secondary open-circuit voltage setting value, takes between 0-600 volt, delay time t1 takes between the 0-30 second, and t2 took between the 0-5 second.
Compared with prior art, the electric current difference of current transformer difference winding is opened by the method for the invention with secondary side
Road voltage criterion combines, and solves that conventional second open circuit method of discrimination is little to current capacity, three-phase breaks simultaneously cannot be effective
Judgement and the problem of lightning surge erroneous judgement, are that Current Transformer Secondary open circuit provides new reliable method of discrimination.
Brief description
Fig. 1 is secondary open circuit detecting device of current transformer general structure schematic diagram of the present invention；
Fig. 2 is the flow chart of Current Transformer Secondary of the present invention open circuit recognition methodss.
Specific embodiment
For making the object, technical solutions and advantages of the present invention clearer, the present invention will be made further detailed below
Description,
Embodiment:
Secondary open circuit detecting device of current transformer population structure as shown in Figure 1, ct second open circuit detection means 1 is installed
The secondary current of two groups of different windings between ct Secondary Winding and protection device, is introduced in same Current Transformer Secondary side,
Wherein a phase Secondary Winding 7, b phase Secondary Winding 8, c phase Secondary Winding 9 constitute first group of secondary current, a phase Secondary Winding 4, b
Phase Secondary Winding 5, c phase Secondary Winding 6 constitute second group of secondary current, and two groups of secondary currents pass through ct second open circuit detection dress
Put 1 and separately flow into protection device a2 and protection device b3, while monitoring ct secondary winding electric current, ct second open circuit detection dress
Put 1 overvoltage also monitoring each Secondary Winding, the overvoltage between such as 1sa and 1san of monitoring a phase the first winding 7 both sides,
To judge to the step 4 in scheme.
The flowchart representation of Fig. 2 Current Transformer Secondary of the present invention open circuit recognition methodss, step is as follows:
(1) same current transformer has multigroup Secondary Winding, introduces two groups of different windings in Current Transformer Secondary side
Secondary current, a, b, c three-phase current is simultaneously introduced, and now can obtain current sample group i of two a, b, c three-phases1φAnd i2φ, with
When two windings of measurement every phase secondary voltage, the voltage of two a, b, c three-phases can be obtained using group u1φAnd u2φ, wherein i1Table
Show first group of current sample, i2Represent second group of current sample, u1φRepresent first group of open-circuit voltage sampling, u2φRepresent second group
Open-circuit voltage is sampled, and φ is the replacing representation of a, b, c three-phase.
(2) judge set of samples i1φAnd i2φWhether ct saturation, if ct saturation, return to step 1, if ct unsaturation, enter
Enter next step.During ct saturation, sampled value is the non-linear change of disease, and the electric current of different secondary winding output is different, does not have comparability.ct
Saturation can differentiate ct whether saturation with the secondary and triple-frequency harmonics content in secondary current.
(3) according to formula: | i1φ-i2φ|>k(|i1φ|+|i2φ|) judged, if formula is set up, enter next step,
If be false, return to step 1.In formula, k is coefficient of reliability, takes between 0.6-0.8, when being embodied as, k takes 0.6.
(4) according to formula: u1φ>usetOr u2φ>usetJudged, if u1φ>usetSet up, then time delay t1 for a period of time
Judge that first via φ phase secondary current is opened a way afterwards, send ct open circuit block signal, time delay t2 for a period of time to protection device a simultaneously
Afterwards by ct first group of ct winding of second open circuit device action short circuit.If u2φ>usetSet up, then time delay judges after t1 for a period of time
Second road φ phase secondary current open circuit, sends ct open circuit block signal to protection device b simultaneously, time delay for a period of time after t2 by ct
Second group of ct winding of second open circuit device action short circuit.If above-mentioned two formulas are all false, return to step 1.U in formulasetFor two
Secondary open-circuit voltage setting value, takes between 0-600 volt, delay time t1 takes between the 0-30 second, and t2 took between the 0-5 second.It is embodied as
When usetTake 300 volts, t1 takes 0.2s, t2 to take 0.1 second.
One given below uses example, is broken with first group of a phase ct, and other are normal, saturation do not occur, fault continue for
As a example 0.4 second.To first group, second group of electric current, voltage sample, obtain i1a、i2a、u1a、u2a.
Break in first group of a phase, in the case of other are normal, i1a=0, u is detected1aAnd its value is more than uset, i2aJust
Often, u2a=0.Step 3 is entered in the case of there is not ct saturation according to Fig. 2 it is clear that formula: | i1a-i2a|>0.6(|i1a|+|
i2a|) set up.Enter step 4, when first group of current transformer a phase broken string, high voltage can be produced in its secondary side, i.e. u1a>
usetMeet, time delay judges that first via a phase secondary current is opened a way for 0.2 second, send ct open circuit block signal to protection device a simultaneously,
Latch-up protection device is in order to avoid cause malfunction, then time delay 0.1 second is by ct first group of ct winding of second open circuit device action short circuit, and ct opens
Road failure vanishes.
Finally it should be noted that foregoing description is only the preferred embodiments of the present invention, the ordinary skill people of this area
Member, under the enlightenment of the present invention, without prejudice on the premise of present inventive concept and claim, can make table as multiple types
Show, such conversion each falls within protection scope of the present invention.
Claims (7)
1. a kind of Current Transformer Secondary open circuit recognition methodss are it is characterised in that comprise the steps:
(1) same current transformer has multigroup Secondary Winding, introduces the two of two groups of different windings in Current Transformer Secondary side
Primary current, a, b, c three-phase current is simultaneously introduced, and now can obtain current sample group i of two a, b, c three-phases1φAnd i2φ, survey simultaneously
The secondary voltage of every phase of two windings of amount, the voltage that can obtain two a, b, c three-phases is using group u1φAnd u2φ, wherein i1Represent the
One group of current sample, i2Represent second group of current sample, u1φRepresent first group of open-circuit voltage sampling, u2φRepresent second group of open circuit
Voltage sample, φ is the replacing representation of a, b, c three-phase；
(2) judge set of samples i1φAnd i2φWhether ct saturation, if ct saturation, return to step 1, if ct unsaturation, enter down
One step, ct saturation to be differentiated by the secondary and triple-frequency harmonics content in secondary current；
(3) according to formula: | i1φ-i2φ| ＞ k (| i1φ|+|i2φ|) judged, if formula is set up, enter next step, if
It is false then return to step 1, in formula, k is coefficient of reliability；
(4) according to formula: u1φ＞ usetOr u2φ＞ usetJudged, if u1φ＞ usetSet up, then time delay is for a period of time after t1
Judge that first via φ phase secondary current is opened a way, send ct open circuit block signal to protection device a, time delay is for a period of time after t2 simultaneously
By ct first group of ct winding of second open circuit device action short circuit；If u2φ＞ usetSet up, then time delay judges after t1 for a period of time
Second road φ phase secondary current open circuit, sends ct open circuit block signal to protection device b simultaneously, time delay for a period of time after t2 by ct
Second group of ct winding of second open circuit device action short circuit, if above-mentioned two formulas are all false, return to step 1, u in formulasetFor two
Secondary open-circuit voltage setting value.
2. according to claim 1 a kind of open circuit recognition methodss of Current Transformer Secondary it is characterised in that: k take 0.6-0.8 it
Between.
3. according to claim 2 a kind of open circuit recognition methodss of Current Transformer Secondary it is characterised in that: k takes 0.6.
4. according to claim 1 a kind of open circuit recognition methodss of Current Transformer Secondary it is characterised in that: uset0-600 is taken to lie prostrate
Between, delay time t1 takes between the 0-30 second, and t2 took between the 0-5 second.
5. according to claim 4 a kind of open circuit recognition methodss of Current Transformer Secondary it is characterised in that: usetTake 300 volts.
6. according to claim 4 a kind of open circuit recognition methodss of Current Transformer Secondary it is characterised in that: t1 takes 0.2 second.
7. according to claim 4 a kind of open circuit recognition methodss of Current Transformer Secondary it is characterised in that: t2 takes 0.1 second.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106877285A (en) * | 2017-03-24 | 2017-06-20 | 山东中实易通集团有限公司 | The station-service subsidiary engine CT thread-breakage protectings and relay system of differential protection are not configured |
| CN109932675A (en) * | 2019-03-27 | 2019-06-25 | 国家电网有限公司 | The method for detecting abnormality of current transformer loop |
| CN109932676A (en) * | 2019-03-27 | 2019-06-25 | 国家电网有限公司 | The method for detecting abnormality of voltage transformer circuit |
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| CN106877285A (en) * | 2017-03-24 | 2017-06-20 | 山东中实易通集团有限公司 | The station-service subsidiary engine CT thread-breakage protectings and relay system of differential protection are not configured |
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| CN109932675A (en) * | 2019-03-27 | 2019-06-25 | 国家电网有限公司 | The method for detecting abnormality of current transformer loop |
| CN109932676A (en) * | 2019-03-27 | 2019-06-25 | 国家电网有限公司 | The method for detecting abnormality of voltage transformer circuit |
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| CN106371049B (en) | 2023-09-26 |
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