CN113655261A - Novel nested micro-current transformer and use method thereof - Google Patents
Novel nested micro-current transformer and use method thereof Download PDFInfo
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- CN113655261A CN113655261A CN202111105907.0A CN202111105907A CN113655261A CN 113655261 A CN113655261 A CN 113655261A CN 202111105907 A CN202111105907 A CN 202111105907A CN 113655261 A CN113655261 A CN 113655261A
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- 238000000034 method Methods 0.000 title claims description 10
- 230000005294 ferromagnetic effect Effects 0.000 claims abstract description 59
- 238000004804 winding Methods 0.000 claims abstract description 45
- 238000001514 detection method Methods 0.000 claims abstract description 16
- 230000005291 magnetic effect Effects 0.000 claims description 9
- 230000035699 permeability Effects 0.000 claims description 4
- 238000005259 measurement Methods 0.000 abstract description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000005674 electromagnetic induction Effects 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
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- 239000000126 substance Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/181—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using coils without a magnetic core, e.g. Rogowski coils
Abstract
The invention discloses a novel nested micro-current transformer, which is characterized in that a Rogowski coil and a ferromagnetic current transformer are sequentially arranged from inside to outside, the Rogowski coil is embedded in the ferromagnetic current transformer, the ferromagnetic current transformer comprises two homodromous windings I, the two ends of a winding II of the Rogowski coil are reversely connected with the two ends of a winding I of the ferromagnetic current transformer through a connecting signal generator, the terminal voltages II at the two ends of the winding II are reversely connected to the two ends of the winding I of the ferromagnetic current transformer, the two ends of the other winding I of the ferromagnetic current transformer are connected with a signal detection module, and the signal detection module is used for detecting micro current. The novel nested micro-current transformer realizes the measurement of micro-current signals through the nesting of the ferromagnetic current transformer and the Rogowski coil, realizes the accurate measurement of micro-ampere leakage current under the background of kiloampere load current, and has simple structure and operation.
Description
Technical Field
The invention belongs to the technical field of micro-current signal detection, and particularly relates to a novel nested micro-current transformer and a using method thereof.
Background
The power cable is an important component of an urban power grid, a high-capacity central substation enters an urban area, and the incoming line of the high-capacity central substation is almost all medium-high voltage cables. After the cable breaks down, economic loss and adverse social influence can be caused, and the safe and stable operation of the urban power grid can be influenced, so that higher requirements are provided for the reliability of the power cable. In recent years, with the rapid development of regional economy and the rapid increase of power consumption, the number and the length of power cable lines are rapidly increased, and faults occur suddenly often without early warning, so that power failure accidents are caused. Partial discharge (called partial discharge for short) signals are often used as state parameters of cables, mainly aiming at the discharge action of insulation tiny defects, and the on-line partial discharge detection is mainly to measure the partial discharge quantity by connecting a detection sensing element (mainly a high-frequency current transformer) in a cable circuit under the power frequency voltage. Since the ordinary high-frequency current transformer can only measure at the monitoring point position, and inevitably generates the noise interference problem, the problem of separating a tiny current signal in a large background signal (inherent power frequency current signal + background noise) is involved in the online measurement, and the tiny current signal comprises a partial discharge current and a micro current related to insulation degradation.
Disclosure of Invention
In order to solve the problem of separation of micro current signals under large background noise, the invention provides a novel nested micro current transformer and a use method thereof.
In order to achieve the above purpose, the invention adopts a technical scheme as follows:
a Rogowski coil and a ferromagnetic current transformer are sequentially arranged from inside to outside, the Rogowski coil is embedded in the ferromagnetic current transformer, the ferromagnetic current transformer comprises two homodromous windings I, terminal voltages II at two ends of a winding II of the Rogowski coil are reversely connected to two ends of one winding I of the ferromagnetic current transformer through a connecting signal generator at two ends of the winding II, a signal detection module is connected to two ends of the other winding I of the ferromagnetic current transformer and used for detecting micro current;
further, the ferromagnetic current transformer and the rogowski coil satisfy the following relationship:
in the formula (1), R0Resistance of secondary side equivalent loop of ferromagnetic current transformer, N1、N2The coil turns of the winding I and the winding II corresponding to the ferromagnetic current transformer and the Rogowski coil respectively; a ═ pi r2Where l is 2 pi R, R and R are inner radius and outer radius of the corresponding Rogowski coil, and mu0Is a vacuum magnetic permeability.
Further, the terminal voltage i at two ends of another winding i of the ferromagnetic current transformer is:
E(t)＝U2(t)-V(t)； (2)
in formula (2), U2(t)＝I1(t)·N1·R0Represents the initial voltage of the ferromagnetic current transformer,
Representing terminal voltages II, I of the Rogowski coil1(t) represents a current input signal;
the invention also provides a use method of the novel nested micro-current transformer, which comprises the following steps:
s01, passing a current carrier to be measured through the circle center position of the novel nested micro-current transformer;
the magnetic current transformer comprises a Rogowski coil and a ferromagnetic current transformer which are sequentially arranged from inside to outside, the Rogowski coil is embedded in the ferromagnetic current transformer, the ferromagnetic current transformer comprises two homodromous windings I, two ends of a winding II of the Rogowski coil are reversely connected with two ends of a terminal voltage II at two ends of the winding II through a connecting signal generator to two ends of one winding I of the ferromagnetic current transformer, and two ends of the other winding I of the ferromagnetic current transformer are connected with a signal detection module;
s02, detecting the micro current by using a signal detection module.
Compared with the prior art, the technical scheme of the invention has the following advantages:
the invention provides a novel nested micro-current transformer and a use method thereof, the novel nested micro-current transformer utilizes a terminal voltage II corresponding to a Rogowski coil to offset the initial terminal voltage of a ferromagnetic current transformer through nesting of the ferromagnetic current transformer and the Rogowski coil, thereby avoiding the magnetic core saturation of the ferromagnetic current transformer; the novel nested micro-current transformer and the use method thereof realize the accurate measurement of microampere-level leakage current under the background of kiloamp-level load current.
Drawings
Fig. 1 is a schematic diagram of the operation of a ferromagnetic current transformer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the Rogowski coil according to an embodiment of the present invention;
fig. 3 is a structural diagram of a novel nested micro-current transformer in an embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, 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 embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The working principle of the ferromagnetic current transformer is mainly to convert current signals flowing in a coil into voltage signals at two ends of the coil by utilizing the electromagnetic induction principle. The circuit structure can be equivalent to a transformer, the schematic diagram of which is shown in fig. 1, and the transformer consists of a closed iron core and a winding. Current I to be measured1(t) is equivalent to the input of the primary winding of the transformer and generates an output voltage U at the secondary side of the transformer2(t) by measuring U2(t) and is based on the ratio of the number of turns of the coil (i.e., the ratio n of the primary and secondary windings of the transformer)1/n2) Obtaining the current I to be measured1(t) size. At the present stage, the method is mature, the precision of the measurement result is high, but the magnetic core is easily saturated when the large current is measured, and the large current is difficult to measure on the premise of ensuring the current precision.
The rogowski coil is another current transformer, and has a structural formula of a hollow annular coil, and the working principle of the rogowski coil is shown in fig. 2. When the current to be measured passes through the center of the rogowski coil along the axis, a correspondingly varying magnetic field is generated within the volume enclosed by the annular winding. According to the ampere loop theorem and Faraday's law of electromagnetic induction, it can be deduced that output voltage V (t) of Rogowski coil is proportional to the differential of the current to be measured, and the output voltage proportional to the primary current can be obtained by only passing the output through an integrator. The rogowski coil is suitable for measuring large current, but the accuracy is often inferior to that of a ferromagnetic current transformer.
The Rogowski coil is embedded into a ferromagnetic current transformer to form a nested micro-current transformer, as shown in FIG. 3, the Rogowski coil and the ferromagnetic current transformer are sequentially arranged from inside to outside, the Rogowski coil is embedded into the ferromagnetic current transformer, the ferromagnetic current transformer comprises two homodromous windings I, two ends of a winding II of the Rogowski coil are reversely connected to two ends of one winding I of the ferromagnetic current transformer through a connection signal generator to enable terminal voltages II at two ends of the winding II to be reversely connected to two ends of the other winding I of the ferromagnetic current transformer, two ends of the other winding I of the ferromagnetic current transformer are connected with a signal detection module, and the signal detection module is used for detecting micro current; the signal detection module can be equipment such as an ammeter, an acquisition card and an oscilloscope.
The output voltages of the terminals of the two current transformers are respectively U2(t) and V (t), since the current input signal is both I1(t)，U2(t) and V (t) are induced by currents of equal magnitude. For ferromagnetic current transformers, the output current I2(t)＝I1(t)·n2/n1At this time N1＝n2/n1，n11, the initial voltage U of the ferromagnetic current transformer2(t)＝I1(t)·N1·R0Wherein R is0Is the internal resistance of an ammeter, N1＝n2The number of turns of the winding I of the ferromagnetic current transformer is adopted. Rogowski coil portion, terminal voltages e (t) and I1The relationship of (t) is shown in the formula (1).
In the formula (3), A ═ π r2Where l is 2 pi R, R and R are inner radius and outer radius of the corresponding Rogowski coil, and mu0＝4π×10-7Is a vacuum magnetic permeability. The terminal voltage II of the Rogowski coil is the integral of e (t), as shown in formula (4).
In practice, 0 offset adjustment is often performed so that the constant C becomes 0. Let K be-AN2μ0L, then V (t) is I1(t). K. In the design of actual parameters, the initial voltage U of the ferromagnetic current transformer is enabled2(t)＝I1(t)·N1·R0Is equal to the terminal voltage II V (t) of the Rogowski coil, thereby obtaining the formula (5)
K＝R0·N1 (5)
Expanding the formula (5) to obtain the formula (1)
In the formula (1), R0Resistance of secondary side equivalent loop of ferromagnetic current transformer, N1、N2The coil turns of the winding I and the winding II corresponding to the ferromagnetic current transformer and the Rogowski coil respectively; a ═ pi r2Where l is 2 pi R, R and R are inner radius and outer radius of the corresponding Rogowski coil, and mu0Is a vacuum magnetic permeability.
In the field of chemical engineeringHaving U in case of thinking2(t) V (t), and in practice, U2The difference between (t) and v (t) is the precision deviation e (t) of the ferromagnetic current transformer from the rogowski coil, as shown in equation (2):
E(t)＝U2(t)-V(t)； (2)
in formula (2), U2(t)＝I1(t)·N1·R0Represents the initial voltage of the ferromagnetic current transformer,
Representing terminal voltages II, I of the Rogowski coil1(t) represents a current input signal;
an external circuit is designed, the external circuit comprises an arbitrary signal generator, the output voltage of the external circuit is ensured to be V (t), the signal is reversely injected into a terminal of a ferromagnetic current transformer, the output of the integrally nested micro-current transformer is E (t), and the value is a voltage signal corresponding to a target micro-current signal. Corresponding to micro current signal i (t) E (t)/R0. The use method of the novel nested micro-current transformer comprises the following steps:
s01, passing a current carrier to be measured through the circle center position of the novel nested micro-current transformer; in practice, the main test position is at the position of the metal protective layer grounding down lead;
s02, detecting the micro current by using a signal detection module.
The above examples are merely illustrative of several embodiments of the present invention, which are described in more detail and detail but are not to be construed as limiting the scope of the present invention. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. The utility model provides a novel little current transformer of nested formula, its characterized in that sets gradually roche coil and ferromagnetic current transformer from inside to outside, the roche coil is embedded inside ferromagnetic current transformer, ferromagnetic current transformer contains two syntropy windings I, II both ends of winding of roche coil are through connecting signal generator with II reverse access of terminal voltage at II both ends of winding to I both ends of winding of ferromagnetic current transformer, I both ends of another winding of ferromagnetic current transformer have connect signal detection module, signal detection module is used for detecting small electric current.
2. The novel nested micro-current transformer of claim 1, wherein the ferromagnetic current transformer and rogowski coil satisfy the following relationship:
in the formula (1), R0Resistance of secondary side equivalent loop of ferromagnetic current transformer, N1、N2The coil turns of the winding I and the winding II corresponding to the ferromagnetic current transformer and the Rogowski coil respectively; a ═ pi r2Where l is 2 pi R, R and R are inner radius and outer radius of the corresponding Rogowski coil, and mu0Is a vacuum magnetic permeability.
3. The novel nested micro-current transformer of claim 2, wherein the terminal voltage I across the other winding I of the ferromagnetic current transformer is:
E(t)＝U2(t)-V(t)； (2)
in formula (2), U2(t)＝I1(t)·N1·R0Represents the initial voltage of the ferromagnetic current transformer,
Representing terminal voltages II, I of the Rogowski coil1(t) represents a current input signal.
4. The use method of the novel nested micro-current transformer according to any one of claims 1-3, characterized by comprising the following steps:
s01, passing a current carrier to be measured through the circle center position of the novel nested micro-current transformer;
the magnetic current transformer comprises a Rogowski coil and a ferromagnetic current transformer which are sequentially arranged from inside to outside, the Rogowski coil is embedded in the ferromagnetic current transformer, the ferromagnetic current transformer comprises two homodromous windings I, two ends of a winding II of the Rogowski coil are reversely connected with two ends of a terminal voltage II at two ends of the winding II through a connecting signal generator to two ends of one winding I of the ferromagnetic current transformer, and two ends of the other winding I of the ferromagnetic current transformer are connected with a signal detection module;
s02, detecting the micro current by using a signal detection module.
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| CN202111105907.0A CN113655261B (en) | 2021-09-22 | 2021-09-22 | Nested micro-current transformer and use method thereof |
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