Current measuring device of high-voltage circuit
By combining a two-stage current transformer and an ammeter, the problem of inaccurate current measurement of small-power high-voltage motors in existing technologies is solved, and the ammeter pointer deflection is obvious, meeting the requirements for motor current measurement.
Patent Information
- Application Number
- CN202422772307.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-13
- Publication Date
- 2025-11-18
- Estimated Expiration
- 2034-11-13
AI Technical Summary
In the existing technology, the current measuring device for 10kV high-voltage motors cannot accurately read the current of small-power motors because the rated primary current of the current transformer is much larger than the rated current of the motor, causing the ammeter pointer deflection to be concentrated in a small range, which cannot meet the measurement requirements.
A combination of two-stage current transformers and ammeters is used. The first current transformer has a transformation ratio of 100/1, and the second current transformer has a transformation ratio of 0.5/1. They are connected in series to form a circuit. Combined with a through-type current transformer and a pointer-type ammeter, the current is amplified and measured.
It achieves a significant deflection of the ammeter pointer, enabling accurate reading of the circuit current of the high-voltage motor and meeting the measurement requirements of the actual operating current of the motor.
Smart Images
Figure CN223565768U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to high voltage motor technical field, in particular to a current measuring device of high voltage circuit. BACKGROUND
[0002] The current transformer is the instrument that converts the primary side big current into the secondary side small current to measure according to electromagnetic induction principle, is composed of closed core and winding. The current transformer should select according to rated voltage, rated current, dynamic stability, thermal stability and insulation level conditions, and the thermal stability check refers to the requirement of thermal stability under the action of the thermal effect of the current transformer when the short circuit fault occurs.
[0003] In the industrial power supply and distribution system, for the power distribution of 10kV high voltage motor, the site requires to set up the ammeter to display the actual running current of the motor.
[0004] As shown in the prior art, the industrial power supply and distribution system of 10kV high voltage motor, M represents the motor, QF is the main circuit breaker, and LHb is the current transformer for measurement. The current measurement of the high voltage motor is realized by connecting the primary winding of LHb and the power distribution circuit of the high voltage motor in series and connecting the ammeter in series on the secondary winding of the current transformer. Figure 1
[0005] However, the rated primary current of the current transformer is usually large, for example, when the short circuit current is 30kA, the rated primary current value of the selected current transformer is usually not less than 100A. If the power of the 10kV high voltage motor is small, its rated current is also small, for example, the power of a certain high voltage motor is 220kW, the power factor is 0.85, and the rated current is only 14.94A, which is far less than 100A. At this time, the reading of the ammeter is too small, even if a small range ammeter is used, the pointer deflection is concentrated in a small range of the ammeter, and the measurement requirement cannot be met. UTILITY MODEL CONTENTS
[0006] The utility model aims at providing a current measuring device of high voltage circuit to at least partially solve the above problems of prior art.
[0007] To achieve the above purpose, the utility model provides a current measuring device of high voltage circuit, comprising: a first current transformer, a second current transformer and an ammeter, wherein
[0008] The primary winding of the first current transformer is connected in series in the measured circuit, and the secondary winding of the first current transformer and the wire constitute a loop.
[0009] The primary winding of the second current transformer is the secondary winding of the first current transformer, and the secondary winding of the second current transformer and the ammeter are connected in series to form a loop through a wire;
[0010] The ammeter is connected in series with the secondary winding of the second current transformer to display the current in the circuit to be measured.
[0011] In a preferred embodiment, the first current transformer is a single-phase current transformer with a rated primary current of 100 A and a rated secondary current of 1 A, and a transformation ratio of 100 / 1.
[0012] In a preferred embodiment, the primary winding of the first current transformer is connected in series in the B-phase line of a high-voltage three-phase line.
[0013] In a preferred embodiment, the second current transformer has a rated primary current of 1 A, a rated secondary current of 1 A, and a transformation ratio of 1 / 1.
[0014] In a preferred embodiment, the second current transformer is a through-type current transformer, and the through core turns of the primary winding of the second current transformer are 2 turns.
[0015] In a preferred embodiment, the ammeter has a rated current of 1 A.
[0016] In a preferred embodiment, the rated current of the motor is not greater than 0.5 times the rated primary current of the first current transformer.
[0017] In a preferred embodiment, a second ammeter is connected in series in the loop formed by the secondary winding of the first current transformer and the wire.
[0018] In a preferred embodiment, the ammeter is a pointer ammeter.
[0019] Compared with the prior art, the utility model has at least the following advantages:
[0020] By using the current measurement device of the high-voltage circuit provided by the utility model, the ammeter pointer deflects obviously, the circuit current of the high-voltage motor can be easily read, and the measurement demand of the actual operating current of the motor is met. BRIEF DESCRIPTION OF DRAWINGS
[0021] Figure 1 The current measurement schematic diagram of the prior art 10kV high-voltage motor industrial power supply system.
[0022] Figure 2 The structure schematic diagram of the current measurement device of the high-voltage circuit provided by the utility model embodiment. DETAILED DESCRIPTION
[0023] In order to make the person skilled in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.
[0024] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances in order to understand the embodiments of the present application described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a product or device including a series of units does not have to be limited to only those units clearly listed, but can include other units not clearly listed or inherent to such products or devices.
[0025] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "transverse", "longitudinal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.
[0026] In addition, in addition to being used to indicate the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain attachment relationship or connection relationship in some cases. For the person skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific circumstances.
[0027] In addition, the terms "mount", "set", "provided with", "connected", "connected", "sleeved" should be broadly understood. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. For the person skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.
[0028] It should be noted that the embodiments in the utility model and the features in the embodiments can be combined with each other without conflict. The utility model will be described in detail below with reference to the drawings and in combination with embodiments.
[0029] Embodiment 1
[0030] The embodiment provides a current measuring device of a high-voltage circuit, Figure 1 A reference schematic diagram of the device is shown. As shown in the figure, Figure 2 The device comprises a first current transformer 10, a second current transformer 20 and an ammeter 30; wherein
[0031] The primary winding of the first current transformer 10 is connected in series in the circuit to be measured, and the secondary winding of the first current transformer and a wire form a loop;
[0032] The primary winding of the second current transformer 20 is the secondary winding of the first current transformer 10, and the secondary winding of the second current transformer 20 and the ammeter 30 form a loop through a wire in series;
[0033] The ammeter 30 is connected in series with the secondary winding of the second current transformer 20 and is used to display the current in the circuit to be measured.
[0034] In one example, the first current transformer 10 is a single-phase current transformer, the rated primary current is 100 A, the rated secondary current is 1 A, and the transformation ratio is 100 / 1. In other embodiments, the rated primary current and the rated secondary current of the first current transformer can be other values, and the transformation ratio can be 75 / 1, 150 / 1, 200 / 1, etc.
[0035] In one example, the primary winding of the first current transformer 10 is connected in series in the B-phase line of a high-voltage three-phase line. It is easy to understand that according to actual needs, the primary winding of the first current transformer 10 can also be connected in series in other phase lines of the high-voltage three-phase line.
[0036] The rated primary current of the second current transformer is 1 A, the rated secondary current is 1 A, and the transformation ratio is 1 / 1. The rated primary current of the second current transformer is determined by the rated secondary current of the first current transformer, and the rated secondary current of the second current transformer is usually the same as the rated current of the ammeter to avoid overloading of the ammeter.
[0037] In one embodiment, the second current transformer is a through-type current transformer (also known as a bus-type current transformer), and the number of through core turns of the primary winding of the second current transformer is 2 turns. At this time, the actual transformation ratio of the second current transformer is 0.5 / 1. Since the transformation ratio of the first current transformer 10 is 100 / 1 and the transformation ratio of the second current transformer 20 is 0.5 / 1, the ratio of the rated primary current of the first current transformer 10 to the rated secondary current of the second current transformer 20 is 50 / 1, i.e. the ratio of the rated primary current of the first current transformer 10 to the rated current of the ammeter is 50 / 1.
[0038] In one example, the power supply side short circuit current of a 10 kV high voltage motor is 30 kA, the rated power of the motor is 220 kW, the power factor is 0.85, and the rated current is 14.94 A. A pointer ammeter is used to measure the B-phase current of the high voltage motor, and the rated current of the ammeter is 1 A. The primary winding of a single-phase current transformer Tab is connected in the primary circuit of the 10 kV motor, and Tab is connected to the B-phase of the high voltage three-phase line for measuring the line current of the line, which is equal to the rated current of the motor under the rated state; at the same time, according to the thermal stability requirement, the rated primary current of Tab is selected to be 100 A, the rated secondary current is 1 A, and the transformation ratio is 100 / 1. The secondary winding of Tab is connected into a loop by a wire. The secondary winding of Tab is inserted into the window hole of a bus-type current transformer (i.e. a through-type current transformer) TA as the primary winding of TA, and the number of through core turns is 2 turns (the wire of the secondary winding loop is inserted into TA twice); the rated primary current of TA is selected to be 1 A, the rated secondary current is 1 A, and the transformation ratio is 1 / 1; since the number of through core turns of the primary winding of TA is 2 turns, the actual transformation ratio of TA in the loop is 0.5 / 1. The pointer ammeter on the motor field operating column is connected into the secondary winding loop of TA, and the loop is grounded; since the transformation ratio of Tab is 100 / 1 and the transformation ratio of TA is 0.5 / 1, the ratio of the rated primary current of Tab to the rated secondary current of TA is 50 / 1, and the rated primary current of Tab is the rated current of the motor, so the transformation ratio of the ammeter is 50 / 1; the rated current of the motor is 14.94 A, and 1.5 times the rated current is 22.41 A, and for the ammeter with a transformation ratio of 50 / 1, the pointer is close to the middle of the ammeter, which can meet the reading requirement of the ammeter.
[0039] In one example, the power supply side short circuit current of a 10 kV high voltage motor is 30 kA, the rated power of the motor is 220 kW, the power factor is 0.85, and the rated current is 14.94 A. A pointer ammeter is used to measure the B-phase current of the high voltage motor, and the rated current of the ammeter is 1 A. The primary winding of a single-phase current transformer Tab is connected in the primary circuit of the 10 kV motor, and Tab is connected to the B-phase of the high voltage three-phase line for measuring the line current of the line, which is equal to the rated current of the motor under the rated state; at the same time, according to the thermal stability requirement, the rated primary current of Tab is selected to be 100 A, the rated secondary current is 1 A, and the transformation ratio is 100 / 1. The secondary winding of Tab is connected into a loop by a wire. The secondary winding of Tab is inserted into the window hole of a bus-type current transformer (i.e. a through-type current transformer) TA as the primary winding of TA, and the number of through core turns is 2 turns (the wire of the secondary winding loop is inserted into TA twice); the rated primary current of TA is selected to be 1 A, the rated secondary current is 1 A, and the transformation ratio is 1 / 1; since the number of through core turns of the primary winding of TA is 2 turns, the actual transformation ratio of TA in the loop is 0.5 / 1. The pointer ammeter on the motor field operating column is connected into the secondary winding loop of TA, and the loop is grounded; since the transformation ratio of Tab is 100 / 1 and the transformation ratio of TA is 0.5 / 1, the ratio of the rated primary current of Tab to the rated secondary current of TA is 50 / 1, and the rated primary current of Tab is the rated current of the motor, so the transformation ratio of the ammeter is 50 / 1; the rated current of the motor is 14.94 A, and 1.5 times the rated current is 22.41 A, and for the ammeter with a transformation ratio of 50 / 1, the pointer is close to the middle of the ammeter, which can meet the reading requirement of the ammeter.
[0040] The scheme provided by the utility model is applied to the scene including: the rated current of the motor is not greater than 0.5 times the rated primary current of the first current transformer. Otherwise, the secondary current of the through-type current transformer will be greater than 1A, damaging the ammeter.
[0041] In an alternative embodiment, the second ammeter can be connected in series in the loop formed by the secondary winding of the first current transformer and the wire. At this time, the ammeter connected in series in the secondary winding of the through-type current transformer can be referred to as the first ammeter. If the reading of the second ammeter is not obvious, the first ammeter is used, and if the first ammeter fails, the second ammeter is used, increasing the robustness of the system. Moreover, the presence of the second ammeter increases the resistance of the loop in which the secondary winding of the first current transformer is located, which is beneficial to avoid the harm of short circuit.
[0042] By using the current measurement device of the high-voltage circuit provided by the utility model, the deflection of the ammeter pointer is obvious, the circuit current of the high-voltage motor can be easily read, and the measurement demand of the actual operating current of the motor is met.
[0043] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the utility model, but not to limit them. Those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced equivalently; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the utility model.
Claims
1. A current measuring device for a high voltage circuit, characterized in that The utility model relates to a current transformer, and more particularly to a current transformer for high-voltage circuit. The utility model relates to a current transformer, and more particularly to a current transformer for high-voltage circuit. The primary winding of the first current transformer is connected in series in the circuit to be measured, and the secondary winding of the first current transformer and a wire form a loop. The primary winding of the second current transformer is the secondary winding of the first current transformer, and the secondary winding of the second current transformer and the ammeter are connected in series through a wire to form a loop. The ammeter is connected in series with the secondary winding of the second current transformer to display the current in the circuit to be measured. The first current transformer is a single-phase current transformer with a rated primary current of 100 A, a rated secondary current of 1 A, and a transformation ratio of 100 / 1.
2. The current measurement device of a high voltage circuit according to claim 1, characterized in that, The primary winding of the first current transformer is connected in series in the B-phase line of a high-voltage three-phase line.
3. The current measurement device of a high voltage circuit according to claim 2, characterized in that The second current transformer has a rated primary current of 1 A, a rated secondary current of 1 A, and a transformation ratio of 1 / 1.
4. The current measuring device of a high voltage circuit according to claim 2, characterized in that, The second current transformer is a core-penetrating current transformer, and the core-penetrating turns of the primary winding of the second current transformer are 2 turns.
5. The current measuring device of a high voltage circuit according to claim 4, characterized in that, The ammeter has a rated current of 1 A.
6. The current measuring device of a high voltage circuit according to claim 5, characterized in that The high-voltage circuit includes a high-voltage motor circuit, and the rated current of the motor is not greater than 0.5 times the rated primary current of the first current transformer.
7. The current measuring device of a high voltage circuit according to claim 1, characterized by A second ammeter is connected in series in the loop formed by the secondary winding of the first current transformer and the wire.
8. The current measurement device of a high voltage circuit according to claim 1, characterized in that, The ammeter is a pointer ammeter.
9. The current measuring device for a high voltage circuit according to claim 1, characterized by