Portable current transformer ratio tester

Abstract

The utility model relates to power test equipment technical field provides a portable current transformer ratio tester, including host computer and branch, host computer and branch are used for measuring the voltage of current transformer primary side and secondary side respectively, its characterized in that, host computer and branch all are provided with shell body, and the voltage measurement loop is set up in the shell body, this tester is convenient to carry, and the overall weight of host computer and branch is within 2kg, simple one key operation, and the strong magnetic suction disc that is convenient to use when placing, and the telescopic detection line that is convenient to arrange, make operator improve work efficiency also alleviate the labor intensity. The charging lithium battery is 12V, 10AH, can reach 2 hours (7200 seconds) according to 5A test continuous discharge current calculation, and we normal use every test a phase ratio for 5 seconds and the test current is all less than 5A, therefore can completely undertake the ratio test of a large number of transformer substation.

Description

Technical Field

[0001] This utility model relates to the field of power testing equipment technology, and provides a portable current transformer ratio tester. Background Technology

[0002] A current transformer is a power device based on the principle of electromagnetic induction. It is mainly used to convert large currents in a power system into smaller currents for measurement, protection, and control. The following is a detailed explanation of current transformers:

[0003] I. Definition

[0004] A current transformer (CT) is a special type of transformer that uses the principle of electromagnetic induction to convert a large current on the primary side into a small current on the secondary side for use in measuring instruments, relay protection devices, and other equipment.

[0005] II. Working Principle

[0006] The working principle of a current transformer is based on electromagnetic induction. When current flows through the primary winding, a magnetic flux is generated in the iron core. This magnetic flux passes through the secondary winding, thereby inducing an electromotive force in the secondary winding. Because the secondary winding has more turns, the induced current is much smaller than the primary current, but the ratio between the two is constant, and this ratio is the turns ratio of the current transformer.

[0007] III. Structural Composition

[0008] A current transformer mainly consists of an iron core, a primary winding, a secondary winding, and insulating materials. The iron core is typically made of a high-permeability material to improve flux transmission efficiency. The primary winding has fewer turns and is connected in series in the circuit being measured; the secondary winding has more turns and is connected in series in measuring instruments or protection devices. The insulating material isolates the primary and secondary windings to prevent electrical interference and short circuits.

[0009] A current transformer ratio tester is a device specifically designed to measure the ratio of current transformers. It can accurately measure the ratio of current transformers of 35kV and below without disconnecting wires or interrupting power, making it an ideal tool for on-site online measurement of high and low voltage CT ratios.

[0010] Working Principle: The current transformer ratio tester uses the principle of magnetic flux balance to measure the transformer ratio. A stable voltage or current is applied to the primary side, and the voltage or current on the secondary side is measured by the signal processing circuit to calculate the transformer ratio. In actual testing, the tester typically uses a bridge circuit, adjusting the resistors to balance the bridge, thereby measuring the transformer ratio.

[0011] Key features: 1. Safe and convenient: The tester and primary clamp meter are powered by rechargeable batteries, requiring no external power supply. A single charge allows for several hours of continuous operation. Simultaneously, the primary current signal is transmitted wirelessly, ensuring operational safety. The primary clamp meter connects to a high-voltage insulating rod, enabling very convenient measurement of high-altitude current.

[0012] 2. Accurate Measurement: The tester has high precision and high stability, and can accurately measure the transformation ratio of current transformers, ensuring the accuracy and stability of current measurement in the power system.

[0013] 3. Powerful functions: In addition to measuring the turns ratio, the tester can also perform other related tests, such as polarity determination, secondary DC resistance measurement, and volt-ampere characteristic measurement.

[0014] 4. Easy to operate: The tester's interface is simple and intuitive; users can complete the test simply by following the prompts. Furthermore, the tester provides a detailed instruction manual and technical support to facilitate better use and maintenance.

[0015] Applications: Current transformer ratio testers are widely used in substations, power transmission and distribution equipment, and power generation enterprises in power systems. They can periodically test and calibrate the ratio of current transformers, ensuring the accuracy and stability of current measurements in power systems. The tester is also suitable for applications requiring current transformer ratio measurement in industrial automation, power testing, and instrumentation.

[0016] In summary, the current transformer ratio tester is an indispensable testing device in the power system, and it is of great significance for ensuring the safe and stable operation of the power system.

[0017] The existing current transformer ratio testers have the following shortcomings: During the substation renovation process, power companies may encounter the problem of incorrect CT ratio wiring during acceptance testing. It is time-consuming and labor-intensive to deal with problems caused by missing or illegible nameplates of some transformers and wiring errors. The CT testing instruments used by the repair and testing department are large in size and require AC power to simulate primary current and special personnel to operate them, which is not easy for the construction party to implement. In addition, sometimes it is only necessary to confirm that the three-phase ratios are the same, and there is no need to test parameters such as the inflection point voltage of the volt-ampere characteristic curve.

[0018] Chinese utility model patent CN201922400624.3 discloses a rapid on-site tester for the transformation ratio of current transformers, comprising a data acquisition device, an analysis device, and an extension rod. The data acquisition device and the analysis device are wirelessly connected. The data acquisition device includes a handheld end and a clamping end. The handheld end is equipped with a power button and an indicator light, and the clamping end includes a U-shaped clamp and a clamping plate. This technical solution designs the data acquisition device and the analysis device to be separate, exchanging data wirelessly to ensure reliable insulation and safe operation. It accurately measures the transformation ratio of current transformers of 35kV and below without disconnecting the wires or interrupting power. It also features peak hold, data hold, and data storage functions.

[0019] The aforementioned patents expand the versatility of current transformer ratio testers, but with the addition of transmitters, analysis devices, and other components, they still suffer from the technical drawbacks of being bulky and difficult to carry.

[0020] Chinese utility model patent CN202121708717.3 discloses a high and low voltage current transformer ratio tester, relating to the technical field of current transformer ratio testers. The tester includes a tester and a handle. Symmetrical clamp heads are movably connected to the upper side of the handle via a rotating shaft. A reset groove is provided on the outer side of the clamp heads, and a pulling structure is provided on the side of the reset groove. The pulling structure includes a reset plate, which is movably connected to the reset groove via a rotating shaft. Wire harness blocks are fixedly connected to both sides of the handle, and symmetrical wire harness wheels are provided on the lower side of the wire harness blocks. A slot is opened inside the handle, and symmetrical wire harness wheels are provided inside the slot. The pulling structure includes an insulated wire and a pull rod. By pulling the pull rod, the insulated wire can pull the clamp heads through the reset plate. Releasing the pull rod allows the clamp heads to reset under the action of a torsion spring, clamping the component to be tested. A restraining ring in the restraining structure compresses the component clamped inside the clamp jaws, thus preventing the component from being too small and thus preventing the clamp heads from clamping it properly.

[0021] The aforementioned patent describes a current transformer ratio tester that is applicable to both high and low voltage testing. It also features an additional pulling structure, indicating that the overall design is still quite bulky and complex, making it difficult to carry.

[0022] Chinese utility model patent CN201720880120.4 discloses a wireless high and low voltage current transformer ratio tester, including a high-voltage tester and a low-voltage tester. Both the high-voltage and low-voltage testers include independently configured ammeter bodies and clamps. Multiple clamps are provided, each with a current transformer of different inner diameter and a ring-shaped jaw. Each clamp is equipped with a plug-in connector of the same specification. The upper end of the current body has a socket for plugging and unplugging the aforementioned plug-in connectors. The high-voltage tester is used on the primary side of the current transformer under test, and the low-voltage tester is connected to the secondary side of the current transformer under test. The high-voltage tester is connected to a sub-unit with intelligent current signal detection and processing circuitry, and the low-voltage tester is connected to a main unit with intelligent current signal detection and processing circuitry. The main unit and the sub-unit communicate wirelessly. The purpose of this utility model is to provide a convenient, fast, safe, and suitable wireless high and low voltage current transformer ratio tester applicable to various types of wires.

[0023] Although the aforementioned patent achieves wireless signal transmission through the design of a sub-unit and a main unit, the addition of a wireless transmission module leads to a complex structure, high manufacturing costs, and the need for remote assistance for on-site testing, resulting in a complex workflow.

[0024] In summary, the existing improvement solutions are insufficient to overcome the technical problems that this invention aims to solve. Summary of the Invention

[0025] The purpose of this invention is to address the shortcomings of existing technologies by providing a portable current transformer ratio tester, which solves the following technical problems:

[0026] Existing mainstream equipment is large, difficult to carry, complex in structure, and expensive to manufacture. Furthermore, on-site testing requires remote assistance, making the workflow complex and the accuracy of testing needing improvement.

[0027] To achieve the above objectives, the present invention adopts the following technical solution: a portable current transformer ratio tester, comprising a main unit and a sub-unit, wherein the main unit and the sub-unit are respectively used to measure the voltage on the primary side and the secondary side of the current transformer, and both the main unit and the sub-unit are provided with an outer casing, wherein a voltage measurement circuit is provided inside the outer casing.

[0028] Furthermore, the outer casing is equipped with a strong magnetic chuck and a retractable detection line.

[0029] Furthermore, the voltage measurement circuit within the host is equipped with a time-delay disconnection circuit, an overcurrent protection circuit, and an AC oscillation circuit.

[0030] Furthermore, the voltage measurement circuit within the host is equipped with a power supply battery.

[0031] Furthermore, the power supply battery is connected to the overcurrent protection circuit and the AC oscillation circuit via a time-delay disconnection circuit.

[0032] Furthermore, the voltage measurement circuit within the host is also equipped with a buzzer and an AC digital voltmeter.

[0033] Furthermore, the voltage measurement circuit within the sub-unit is equipped with a ratio correction potentiometer, a ratio range switch, a mechanical pointer millivoltmeter, and a digital millivoltmeter.

[0034] Furthermore, the voltage measurement circuit within the sub-unit is also equipped with a power supply battery.

[0035] Furthermore, a charging circuit is also connected in parallel across the two ends of the power supply battery in the voltage measurement circuit within the sub-unit.

[0036] Furthermore, the voltage measurement circuit is a bridge-type measurement circuit.

[0037] The beneficial effects of this utility model are as follows: This tester is portable, with the main unit and sub-units weighing less than 2 kg. Its simple one-button operation, strong magnetic chuck for easy placement during use, and retractable test cable for easy organization all improve operator efficiency while reducing labor intensity. The rechargeable lithium battery is 12V, 10AH, and based on a continuous discharge current of 5 amps, it can last for 2 hours (7200 seconds). Since our normal use involves testing each phase ratio for 5 seconds and the test current is less than 5 amps, it can fully handle the large number of ratio tests in substations. Attached Figure Description

[0038] Figure 1 Schematic diagram of the U1 host circuit of this utility model;

[0039] Figure 2 This utility model presents a schematic diagram of the circuit principle of the U2 extension unit. Detailed Implementation

[0040] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0041] like Figure 1-2 A portable current transformer ratio tester mainly consists of two parts: a U1 main unit and a U2 sub-unit. The outer casings of the U1 main unit and the U2 sub-unit are equipped with strong magnetic chucks and telescopic detection lines.

[0042] U1 Unit Circuit Principle: Upon pressing the test button K, +12V power is supplied to the 5-second delay disconnect circuit through isolation diode D2. Simultaneously, the normally open contact of the delay relay J1 closes and holds (the delay time is 5 seconds, satisfying the transient to steady-state time process, ensuring stable readings, and also allowing the operator time to take the reading). While J1 is engaged, the +12V power supply powers the buzzer, the 5A overcurrent protection circuit, the AC digital voltmeter, and the 50Hz AC oscillation circuit. (The buzzer emits a beeping sound once per second, allowing the operator to clearly understand the time point for the test reading; the reading must be completed before the 5th beep. Because C...) The secondary side current of transformer T is rated at 5 amps. To ensure accuracy during CT testing and prevent overload of the lithium battery and oscillator board, a 5 amp overcurrent protection circuit is introduced. This is achieved by collecting the AC output current of the oscillator board and comparing it with a reference threshold. When the current exceeds 5 amps, overcurrent relay J2 engages, its normally closed contact opens, J1 releases, and the entire circuit is disconnected, thus achieving overcurrent protection. The 50 Hz AC oscillation is the core circuit for DC-to-AC conversion, implemented by four MOSFETs and an oscillating element. The maximum output current can reach 10 amps, with a large power margin, fully capable of meeting the conversion requirements. The purpose of introducing isolation transformer T1 is: 1. To avoid S1 A short circuit in the S2 test line caused an overload impact damage to the MOSFET in the oscillator board. The isolation transformer 2 is also a step-up transformer, converting AC 12V to AC 18V, which can increase the voltage by one-third. Correspondingly, the voltage on the P1P2 side also increases by one-third, thereby increasing the deflection angle of the mechanical millivoltmeter head and further improving the turns ratio range. The AC digital voltmeter is a 3.5-digit digital voltmeter with the same accuracy as a digital multimeter. It requires a 12V DC power supply to operate. When the 5-second delay time is reached, the relay release circuit disconnects and the test ends.

[0043] U2 circuit unit principle: When using an analog mechanical millivoltmeter to read the transformation ratio, the millivolt AC voltage on the P1P2 side passes through the normally closed contact of relay J1, then through the transformation ratio correction potentiometer W, and finally through the transformation ratio range switch K2 to the mechanical AC millivoltmeter B1 to achieve pointer deflection.

[0044] When reading the digital AC millivoltmeter, press switch K1, relay J1 will be energized, the normally open contact will close, and the digital AC millivoltmeter will also receive power. At the same time, the AC millivolt voltage on the P1P2 side will be sent to the digital AC millivoltmeter through the closed contact of the relay to achieve voltage display.

[0045] Application Example 1:

[0046] (1) According to the formula K=(U1 / U2) ×5:5

[0047] = (18.46 / 0.307) × 5:5

[0048] =60.13 × 5:5

[0049] =300.65:5

[0050] Therefore, the ratio (1S1-1S4) is 300:5.

[0051] Switch to direct reading test of mechanical meter head (1S1-1S3) with a ratio of 200:5.

[0052] Application Example 2:

[0053] As shown in the diagram above, according to the formula K=(U1 / U2) ×5:5

[0054] = (18.47 / 0.617) × 5:5

[0055] =29.935 × 5:5

[0056] =149.675:5

[0057] Therefore, the winding ratio of (S1-S2) is 150:5.

[0058] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A portable current transformer ratio tester, comprising a main unit and a sub-unit, wherein the main unit and the sub-unit are respectively used to measure the voltage on the primary side and the secondary side of the current transformer, characterized in that, Both the main unit and the sub-unit are equipped with an outer casing, and a voltage measurement circuit is installed inside the casing.

2. The portable current transformer ratio tester according to claim 1, characterized in that, The outer casing is equipped with a strong magnetic chuck and a retractable detection line.

3. A portable current transformer ratio tester according to claim 1 or 2, characterized in that, The voltage measurement circuit inside the host is equipped with a time-delay disconnection circuit, an overcurrent protection circuit, and an AC oscillation circuit.

4. A portable current transformer ratio tester according to claim 3, characterized in that, The voltage measurement circuit inside the host is equipped with a power supply battery.

5. A portable current transformer ratio tester according to claim 4, characterized in that, The power supply battery is connected to the overcurrent protection circuit and the AC oscillation circuit via a time-delay disconnection circuit.

6. A portable current transformer ratio tester according to claim 4 or 5, characterized in that, The voltage measurement circuit inside the main unit is also equipped with a buzzer and an AC digital voltmeter.

7. A portable current transformer ratio tester according to claim 1 or 2, characterized in that, The voltage measurement circuit within the sub-unit is equipped with a ratio correction potentiometer, a ratio range switch, a mechanical pointer millivoltmeter, and a digital millivoltmeter.

8. A portable current transformer ratio tester according to claim 7, characterized in that, The voltage measurement circuit within the sub-unit is also equipped with a power supply battery.

9. A portable current transformer ratio tester according to claim 8, characterized in that, The voltage measurement circuit inside the sub-unit is also connected to a charging circuit in parallel across the two ends of the power supply battery.

10. A portable current transformer ratio tester according to claim 5 or 9, characterized in that, The voltage measurement circuit is a bridge-type measurement circuit.

Images