CN112305373A - Power distribution network ground fault distance measurement method - Google Patents
Power distribution network ground fault distance measurement method Download PDFInfo
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- CN112305373A CN112305373A CN202011128523.6A CN202011128523A CN112305373A CN 112305373 A CN112305373 A CN 112305373A CN 202011128523 A CN202011128523 A CN 202011128523A CN 112305373 A CN112305373 A CN 112305373A
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- 238000000691 measurement method Methods 0.000 title abstract description 4
- 238000002347 injection Methods 0.000 claims abstract description 32
- 239000007924 injection Substances 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 15
- 238000005259 measurement Methods 0.000 claims abstract description 7
- 238000009795 derivation Methods 0.000 claims description 6
- 230000001131 transforming effect Effects 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims 1
- 230000007547 defect Effects 0.000 abstract description 2
- 230000005674 electromagnetic induction Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/11—Locating faults in cables, transmission lines, or networks using pulse reflection methods
Abstract
The invention relates to a power distribution network ground fault distance measurement method, which comprises the steps of injecting pulse signals into a fault phase and a non-fault phase at a low-voltage side of a power distribution transformer, transmitting the pulse signals to a high-voltage side through electromagnetic induction of a distribution transformer, transmitting the pulse signals into a line, and collecting traveling wave signals on the high-voltage side injection phase and the non-injection phase. After the signals acquired twice are compared, the first difference is caused by that the reflected wave generated after the injected traveling wave is transmitted to the fault point returns to the acquisition point, the propagation time of the traveling wave can be obtained, and the traveling wave is substituted into a distance measurement formula to calculate the fault distance. The method of the invention improves the safety compared with the prior high-voltage side injection by injecting the signal at the low-voltage side of the distribution transformer, and overcomes the defect that the prior signal injection device is often operated at the head end of the circuit, and the operation is often complicated if the injection position is changed.
Description
Technical Field
The invention relates to the field of electric power, in particular to a power distribution network ground fault distance measuring method.
Background
In an electric power system, an earth fault occurs in the electric power system due to the influence of the external environment and the failure of internal equipment. In the class C traveling wave method proposed for eliminating the ground fault, a pulse signal is injected into the power system on the high-voltage side in an off-line state, and a fault distance is calculated by identifying a fault point reflected wave.
However, the operation is cumbersome when injecting signals on the high voltage side, the positioning device needs to be connected to the 10kV distribution network, the device is usually installed in a substation, and the signal injection from other places is difficult to implement. Meanwhile, the signal is directly injected into a 10kv power distribution network, which brings threats to the safety of equipment and the personal safety of operators.
Disclosure of Invention
In order to solve the technical problem, the application provides a power distribution network ground fault distance measuring method, and the most common distribution transformer in a power distribution network is used, and a signal is injected at the low-voltage side of the distribution transformer, so that the advantage of adjustable injection place is realized. In addition, the low-voltage side injection signal reduces the threat to personal safety and equipment safety.
In order to achieve the purpose, the invention provides the following technical scheme:
a distribution transformer low-voltage side pulse injection-based distribution network ground fault distance measurement method comprises the following steps: step (1), when a line has a fault, acquiring a traveling wave signal at a high-voltage side corresponding to a fault phase after injecting a pulse into the fault phase at a low-voltage side of a distribution transformer;
after a line fails, acquiring traveling wave signals at a high-voltage side corresponding to a non-fault phase after injecting pulses into the non-fault phase at the low-voltage side of the distribution transformer;
subtracting the traveling wave signals obtained in the steps (1) and (2) to obtain difference data;
step (4), solving a second derivative of the difference signal obtained in the step (3), finding out a first point of which the second derivative is not zero, and obtaining traveling wave propagation time;
and (5) substituting the propagation time obtained in the step (4) into a distance measurement formula to obtain the fault distance.
Further, in the step (3), the following steps are performed:
Δu＝u1-u2；
wherein, u1 is when the line breaks down, collect the travelling wave signal at the high-pressure side corresponding fault phase after distributing and transforming the low-pressure side fault phase injection pulse; u2 is that after a line has a fault, a traveling wave signal is collected at a high-voltage side corresponding to a non-fault phase after a pulse is injected into the non-fault phase at the low-voltage side of the distribution transformer. After the injection phase and the non-injection phase are respectively injected after the fault, the signals of the injection phase and the non-injection phase corresponding to the high-voltage side are subtracted, so that the influence of irrelevant parameters on the distance measurement can be eliminated.
Further, in the step (4), the second reciprocal solution is performed as follows:
in the formula, Δ u "(t) is a second-order derivation result of Δ u (t), Δ u' (t) is a differential derivation result, Δ t is a sampling time interval, and Δ u (t) is difference data of fault phase voltage waveforms before and after a fault. t- Δ t is the last time that differs from the present time by a time interval.
Further, a relation between the difference signal and the traveling wave arrival time is established, a second derivative method can be adopted, and T corresponding to the first point with the value of |. DELTA.u "(T) | > 0 is the traveling wave arrival time.
Further, after obtaining the traveling wave propagation time, in step (5), the ranging formula is as follows:
in the formula: t is the traveling wave propagation time, and V is the traveling wave propagation speed.
And after the fault, injecting a pulse signal into the fault phase, using the first reflection signal as a reflection signal caused by the fault point, and using the first non-zero catastrophe point as the reflection information of the fault point. But the distribution network has many branches and the branches usually cause reflections of the pulsed signal. If the fault point is after the branch point, the first reflected signal will come from the branch point instead of the fault point, resulting in a ranging error.
Due to the symmetry of the line before the fault point, the voltage traveling waves obtained by fault phase injection and non-fault phase injection are equal before the fault point reflected wave arrives, the fault point causes the reflection of the fault phase and the reflection of the non-fault phase, and the first difference reflecting the difference value of the two groups of voltage traveling waves is the arrival time of the fault point reflected wave.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. according to the invention, the signal is injected at the low-voltage side of the distribution transformer, so that the safety is improved compared with the conventional high-voltage side injection;
2. the invention overcomes the defect that the operation of changing the injection position is complicated because the previous signal injection device is usually at the head end of a circuit.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a schematic diagram of fault phase pulse signal injection;
FIG. 3 is a schematic diagram of non-fault phase pulse signal injection;
fig. 4 shows the fault phase and non-fault phase voltage signals after pulse injection.
Fig. 5 shows that after a line has a fault, triangular pulses are injected into a non-fault phase at a low-voltage side of the distribution transformer, and traveling wave signals are acquired at a corresponding non-fault phase at a high-voltage side.
Detailed Description
The technical solutions in the embodiments will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the examples without making any creative effort, shall fall within the protection scope of the present invention.
Unless otherwise defined, technical or scientific terms used in the embodiments of the present application should have the ordinary meaning as understood by those having ordinary skill in the art. The use of "first," "second," and similar terms in the present embodiments does not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. "mounted," "connected," and "coupled" are to be construed broadly and may, for example, be fixedly coupled, detachably coupled, or integrally coupled; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. "Upper," "lower," "left," "right," "lateral," "vertical," and the like are used solely in relation to the orientation of the components in the figures, and these directional terms are relative terms that are used for descriptive and clarity purposes and that can vary accordingly depending on the orientation in which the components in the figures are placed.
Example 1
As shown in fig. 1, the distribution network ground fault location method based on distribution transformer low-voltage side pulse injection in this embodiment includes the following steps:
step (1), when a line has a fault, acquiring a traveling wave signal at a high-voltage side corresponding to a fault phase after injecting a pulse into the fault phase at a low-voltage side of a distribution transformer;
after a line fails, acquiring traveling wave signals at a high-voltage side corresponding to a non-fault phase after injecting pulses into the non-fault phase at the low-voltage side of the distribution transformer;
subtracting the traveling wave signals obtained in the steps (1) and (2) to obtain difference data; the method comprises the following steps:
Δu＝u1-u2；
wherein, u1 is when the line breaks down, collect the travelling wave signal at the high-pressure side corresponding fault phase after distributing and transforming the low-pressure side fault phase injection pulse; u2 is that after a line has a fault, a traveling wave signal is collected at a high-voltage side corresponding to a non-fault phase after a pulse is injected into the non-fault phase at the low-voltage side of the distribution transformer. After the injection phase and the non-injection phase are respectively injected after the fault, the signals of the injection phase and the non-injection phase corresponding to the high-voltage side are subtracted, so that the influence of irrelevant parameters on the distance measurement can be eliminated.
Step (4), solving a second derivative of the difference signal obtained in the step (3), finding out a first point of which the second derivative is not zero, and obtaining traveling wave propagation time; in the step (4), the second reciprocal is solved as follows:
in the formula, Δ u "(t) is a second-order derivation result of Δ u (t), Δ u' (t) is a differential derivation result, Δ t is a sampling time interval, and Δ u (t) is difference data of fault phase voltage waveforms before and after a fault. t- Δ t is the last time that differs from the present time by a time interval.
Establishing the relation between the difference signal and the traveling wave arrival time, adopting a second derivative method, wherein T corresponding to the first point with the value of |. DELTA. (T) | > 0 is the traveling wave arrival time.
And (5) substituting the propagation time obtained in the step (4) into a distance measurement formula to obtain the fault distance. After the traveling wave propagation time is obtained, in step (5), the ranging formula is as follows:
in the formula: t is the traveling wave propagation time, and V is the traveling wave propagation speed.
As shown in fig. 2, in the present embodiment, when a line fails, a traveling wave signal is collected at the high-voltage side corresponding to the failed phase after distributing the low-voltage side failed phase injection pulse. The traveling wave signal includes a branch point reflection signal and a fault point reflection signal.
In fig. 2, a, b, and c represent distribution transformer low-voltage side (phase rated voltage 400V), and high-voltage side rated voltage 10 Kv. The line lengths are respectively 5 km, 10km, wherein a point A is a line branch point which is 10km away from a distribution transformer, a point B is a distribution network branch tail end which is 10km away from the point A, a point C is a line fault point, and D is a line branch tail end. The sensor is placed at the outlet of the high-pressure side of the distribution transformer.
As shown in fig. 3, after a line fault occurs, a traveling wave signal is collected at the high-voltage side corresponding to a non-fault phase after a pulse is injected into the non-fault phase at the low-voltage side of the distribution transformer. Only branch point reflected signals are included in the traveling wave signal.
The collected fault phase and non-fault phase voltage signals after pulse injection are shown in fig. 4, the obtained fault phase and non-fault phase traveling wave signals are subtracted to obtain difference data, and the first point which is not 0 is the arrival time point of the fault point reflected signal.
And solving a second derivative of the obtained difference signal, and finding out the time corresponding to the first point with the second derivative not being zero to obtain the traveling wave propagation time delta t.
Substituting the obtained propagation time into a distance measurement formula to obtain a fault distance
As shown in fig. 5, after a line fault occurs, triangular pulses are injected into the distribution transformation low-voltage side non-fault phase, and traveling wave signals are collected on the high-voltage side corresponding to the non-fault phase. Only branch point reflected signals are included in the traveling wave signal.
The collected fault phase and non-fault phase voltage signals after pulse injection are shown in fig. 5, the obtained fault phase and non-fault phase traveling wave signals are subtracted to obtain difference data, and the first point which is not 0 is 33.4us of the arrival time point of the fault point reflection signal. And solving a second derivative of the obtained difference signal, finding out the time corresponding to the first point of which the second derivative is not zero, and obtaining the traveling wave propagation time delta t of 33.4 us.
And the method is proved to be effective when the distance is consistent with the set fault distance.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (5)
1. A power distribution network ground fault distance measuring method is characterized by comprising the following steps: step (1), when a line has a fault, acquiring a traveling wave signal at a high-voltage side corresponding to a fault phase after injecting a pulse into the fault phase at a low-voltage side of a distribution transformer;
after a line fails, acquiring traveling wave signals at a high-voltage side corresponding to a non-fault phase after injecting pulses into the non-fault phase at the low-voltage side of the distribution transformer;
subtracting the traveling wave signals obtained in the steps (1) and (2) to obtain difference data;
step (4), solving a second derivative of the difference signal obtained in the step (3), finding out a first point of which the second derivative is not zero, and obtaining traveling wave propagation time;
and (5) substituting the propagation time obtained in the step (4) into a distance measurement formula to obtain the fault distance.
2. The method of claim 1, wherein: in the step (3), the following steps are carried out:
wherein, u1 is when the line breaks down, collect the travelling wave signal at the high-pressure side corresponding fault phase after distributing and transforming the low-pressure side fault phase injection pulse; u2 is that after a line has a fault, a traveling wave signal is collected at a high-voltage side corresponding to a non-fault phase after a pulse is injected into the non-fault phase at the low-voltage side of the distribution transformer.
3. The method of claim 1, wherein: in the step (4), the second reciprocal is solved as follows:
in the formula (I), the compound is shown in the specification,
is composed of
The result of the second-order derivation of (c),
is the result of the differential derivation,
in order to sample the time interval between the samples,
difference data of fault phase voltage waveforms before and after fault;t-
is the last time that differs by a time interval from the present time.
4. The method of claim 3, wherein: non-viable cells
Corresponding to the first point for | 0 | > 0TIs the traveling wave arrival time.
5. The method of claim 1, wherein: after the traveling wave propagation time is obtained, in step (5), the ranging formula is as follows:
in the formula:Tin order to be the traveling wave propagation time,Vis the traveling wave propagation velocity.
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| CN103926511A (en) * | 2014-03-17 | 2014-07-16 | 四川大学 | Distance measurement method for power distribution network ground fault based on zero-mode travelling wave difference |
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| CN103926511A (en) * | 2014-03-17 | 2014-07-16 | 四川大学 | Distance measurement method for power distribution network ground fault based on zero-mode travelling wave difference |
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