A new polarity test tool for current and voltage transformers in substations

Abstract

The present invention discloses a new polarity testing tool for current and voltage transformers in substations. The tool comprises a signal generating device and a signal detecting device. The signal detecting device is connected to the secondary side of the current and voltage transformer. The signal generating device is provided with a plurality of N terminals connected to the signal input end of the current and voltage transformer and a three-phase output terminal. The signal generating device is provided with a rechargeable battery, the two poles of which are respectively connected to the N terminal circuit and the three-phase output terminal circuit. A signal generating unit and an optical coupling relay are connected in parallel to the two poles of the rechargeable battery circuit, and an oscillation signal generating unit is connected in parallel to the circuit connecting the rechargeable battery to the three-phase output terminal. The oscillation signal generating unit is controlled on and off by the signal generating unit via the optical coupling relay. This polarity testing tool can realize single-person, highly accurate, and efficient transformer polarity detection. It effectively reduces the workload of staff and improves the work efficiency of substation staff.

Description

Technical Field

[0001] The present invention relates to the technical field of live equipment detection, in particular to a new polarity testing tool for current and voltage transformers in a transformer substation. Background Art

[0002] After new construction, renovation, or wiring modifications are made to current and voltage transformers within a substation, polarity testing is required. Traditionally, this is performed by inspectors using a battery, test wiring, and an ammeter in a "point polarity" manner. This conventional "point polarity" method involves connecting test wiring from both ends of a battery to the primary side of the transformer, connecting a milliampere ammeter to the secondary side of the transformer, and generating a current by switching the primary test wiring on and off. The direction of the pointer change on the secondary milliampere ammeter is then monitored to determine if the transformer polarity is correct.

[0003] The traditional "point polarity" method for checking the polarity of a transformer presents two problems. First, it requires two people to perform this task simultaneously, working in close coordination and phase by phase. During the process, the two workers need to shout "connect" and "lift" to each other as a starting signal. In noisy environments, this reduces efficiency and is prone to errors. Second, the "break" process during the test generates an opposite induced current. Therefore, the secondary side milliammeter will also deflect in the opposite direction at the moment of break, which can easily lead to misjudgment. In severe cases, misjudging the transformer polarity can cause damage to the main substation equipment and even serious accidents such as personal injury to workers. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a novel polarity test tool for current and voltage transformers within substations. This tool enables single-person, highly accurate, and efficient polarity detection of current and voltage transformers within substations. This effectively reduces workload and improves the efficiency of substation personnel. Furthermore, compared to traditional DC detection methods, it provides more intelligent, convenient, and accurate polarity detection.

[0005] A new polarity testing tool for current and voltage transformers in a substation includes a signal generating device and a signal detecting device; the signal detecting device is connected to the secondary side of the current and voltage transformer; the signal generating device is provided with a plurality of N terminals and three-phase output terminals connected to the signal input ends of the current and voltage transformers; a rechargeable battery is provided in the signal generating device, and the two poles of the rechargeable battery are respectively connected to the N terminal circuit and the three-phase output terminal circuit; the two poles of the rechargeable battery circuit are connected in parallel to a signal generating unit and an optocoupler relay, and the circuit connecting the rechargeable battery to the three-phase output terminal is connected in parallel to an oscillation signal generating unit, and the signal generating unit is controlled to be on and off via the optocoupler relay.

[0006] Preferably, the signal generating unit includes a NE555 timer chip, a resistor R1, a resistor R2, an adjustable resistor R3, a capacitor C1 and a capacitor C2, wherein the resistor R1, the resistor R2, the adjustable resistor R3 and the capacitor C1 are connected in series in sequence; the first pin of the NE555 timer chip is connected to the N-terminal circuit and grounded, the second pin and the sixth pin of the NE555 timer chip are respectively connected to the resistance adjustment end of the adjustable resistor R3, the third pin of the NE555 timer chip is connected to the first pin of the optocoupler relay, the seventh pin of the NE555 timer chip is connected to the circuit between the resistor R1 and the resistor R2, the fourth pin and the eighth pin of the NE555 timer chip are respectively connected to the three-phase output terminal circuit, and the fifth pin of the NE555 timer chip is connected to the N-terminal circuit via the capacitor C2.

[0007] Preferably, the second pin of the optocoupler relay is connected to the N terminal circuit, and the third and fourth pins of the optocoupler relay are connected to the three-phase output terminal circuit and control the on and off of the oscillation signal generating unit.

[0008] Preferably, the oscillation signal generating unit includes an attenuation capacitor and a discharge resistor, wherein the attenuation capacitor is connected in series to the three-phase output terminal circuit, and the discharge resistor is connected in parallel to the two-pole circuit of the attenuation capacitor.

[0009] Preferably, the three-phase output terminals include A, B, and C three-phase output terminals, which are used for simultaneous detection of A, B, and C three phases. By setting different resistance values of the adjustable resistor R3, oscillating currents of different frequencies are generated, which are used to distinguish A, B, and C three phases during simultaneous detection.

[0010] Preferably, the signal detection device is a pointer-type DC milliammeter, the detection terminal of which is connected to the secondary side of the current and voltage transformer, and is used to detect the secondary current sensed by the current and voltage transformer, and to judge whether the polarity is correct by observing the positive or negative deflection of the pointer; and to judge whether the detected phase is A phase, B phase or C phase by the frequency of the pointer deflection.

[0011] The advantages and technical effects of the present invention are:

[0012] 1. The present invention is a new type of polarity test tool for current and voltage transformers in substations. It overcomes the characteristic of reverse deflection of the DC milliampere meter at the moment of disconnection in the traditional "point polarity" work, thus eliminating the possibility of misjudgment.

[0013] 2. This invention enables a single person to perform highly accurate and efficient polarity detection of current and voltage transformers within a substation during acceptance testing, reducing workload and improving the efficiency of substation personnel. Compared to traditional DC detection methods, this identification system can intelligently, conveniently, and accurately detect polarity. This overcomes the drawback of existing detection methods, which require two people to operate simultaneously and closely collaborate, effectively improving work efficiency and reducing on-site workload.

[0014] 3. The present invention has a simple principle, is easy to manufacture, and is easy to implement in field applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of circuit connections during detection of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of the A-terminal signal generating device of the present invention;

[0017] Figure 3 This is a schematic diagram of the structure of the signal detection device in the present invention. DETAILED DESCRIPTION

[0018] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings. It should be noted that the embodiments are illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereby.

[0019] A new polarity testing tool for current and voltage transformers in a substation includes a signal generating device and a signal detecting device; the signal detecting device is connected to the secondary side of the current and voltage transformer; the signal generating device is provided with a plurality of N terminals and three-phase output terminals connected to the signal input ends of the current and voltage transformers; a rechargeable battery is provided in the signal generating device, and the two poles of the rechargeable battery are respectively connected to the N terminal circuit and the three-phase output terminal circuit; the two poles of the rechargeable battery circuit are connected in parallel to a signal generating unit and an optocoupler relay, and the circuit connecting the rechargeable battery to the three-phase output terminal is connected in parallel to an oscillation signal generating unit, and the signal generating unit is controlled to be on and off via the optocoupler relay.

[0020] Preferably, the signal generating unit includes a NE555 timer chip, a resistor R1, a resistor R2, an adjustable resistor R3, a capacitor C1 and a capacitor C2, wherein the resistor R1, the resistor R2, the adjustable resistor R3 and the capacitor C1 are connected in series in sequence; the first pin of the NE555 timer chip is connected to the N-terminal circuit and grounded, the second pin and the sixth pin of the NE555 timer chip are respectively connected to the resistance adjustment end of the adjustable resistor R3, the third pin of the NE555 timer chip is connected to the first pin of the optocoupler relay, the seventh pin of the NE555 timer chip is connected to the circuit between the resistor R1 and the resistor R2, the fourth pin and the eighth pin of the NE555 timer chip are respectively connected to the three-phase output terminal circuit, and the fifth pin of the NE555 timer chip is connected to the N-terminal circuit via the capacitor C2.

[0021] Preferably, the second pin of the optocoupler relay is connected to the N terminal circuit, and the third and fourth pins of the optocoupler relay are connected to the three-phase output terminal circuit and control the on and off of the oscillation signal generating unit.

[0022] Preferably, the oscillation signal generating unit includes an attenuation capacitor and a discharge resistor, wherein the attenuation capacitor is connected in series to the three-phase output terminal circuit, and the discharge resistor is connected in parallel to the two-pole circuit of the attenuation capacitor.

[0023] Preferably, the three-phase output terminals include A, B, and C three-phase output terminals, which are used for simultaneous detection of A, B, and C three phases. By setting different resistance values of the adjustable resistor R3, oscillating currents of different frequencies are generated, which are used to distinguish A, B, and C three phases during simultaneous detection.

[0024] Preferably, the signal detection device is a pointer-type DC milliampere ammeter, the detection terminal of which is connected to the secondary side of the current and voltage transformer, and is used to detect the secondary current sensed by the current and voltage transformer, and to judge whether the polarity is correct by observing the positive or negative deflection of the pointer; and to judge whether the detected phase is A phase, B phase or C phase by the frequency of the pointer deflection.

[0025] In order to more clearly illustrate the specific embodiments of the present invention, several embodiments are provided below:

[0026] The mutual inductors of the electromagnetic coils in the substation are mainly current transformers and voltage transformers. The present invention is described by taking three current transformers A, B, and C to be inspected on site as an example.

[0027] Connect the three-phase output terminals (A, B, C) of the signal generator to the primary side three-phase output terminals (A, B, C) of the current transformer, and connect the N terminal to the N ends of the three current transformers.

[0028] Connect the connection terminals (x, n) of the signal detection device to the secondary terminals (a, n) of any current transformer.

[0029] When detection is required, turn on the power of the signal generating device, and the 3 oscillation signal generating part can generate an oscillating voltage signal, driving the 9 optocoupler isolation switch to regularly connect the circuit to charge the 6 attenuation capacitor. At the same time, current flows through the current transformer, and an induced current will be generated on the secondary side of the transformer.

[0030] Assume that the rechargeable battery voltage is 5V, fixed resistor R1 = 4.7kΩ, fixed resistor R2 = 68kΩ, adjustable resistor R3 = 0-150kΩ and set to 0kΩ, capacitor C1 = 5.1uF, capacitor C2 = 0.01uF, attenuation capacitor is set to 100uF, and discharge resistor is 470Ω.

[0031] Assuming that the rechargeable battery has a certain internal resistance, but it is very small, the primary DC resistance of the current transformer is ignored during the calculation process.

[0032] Calculations show that the oscillation signal generator generates a 5V square wave signal with a frequency of approximately 2Hz and a duty cycle close to 50% after power is applied. This oscillation signal drives the optocoupler isolator at a 2Hz frequency, meaning it switches from open to closed, or closed to open, every 0.25 seconds, effectively completing the circuit once every 0.5 seconds.

[0033] By calculating the discharge circuit composed of the attenuation capacitor and the discharge resistor, it can be obtained that its time constant t = 0.047 seconds and the four times time constant 4*t = 0.188s.

[0034] The signal generator operates as follows: When the optocoupler isolating switch is turned on, the rechargeable battery rapidly charges the attenuation capacitor, causing a transient, large positive current to flow through the primary side of the current transformer. This current is also sensed on the secondary side of the current transformer. The correct polarity of the current transformer can be determined by the direction of the ammeter pointer on the signal detector. Subsequently, the attenuation capacitor rapidly charges, and the forward current slowly decays to zero (this process takes much less than 0.25 seconds).

[0035] At the moment the optocoupler disconnector opens, the capacitor is fully charged and the current in the circuit is zero. Consequently, no primary current change occurs, and no current is sensed on the secondary side of the current transformer. This means the ammeter pointer on the signal detection device does not reverse. This eliminates the possibility of pointer reversal in conventional detection methods and eliminates the possibility of misjudgment by the tester.

[0036] During the opening period of the optocoupler isolating switch, the attenuation capacitor will be discharged through the discharge resistor with a time constant of t = 0.047 seconds, and will decay to zero at about 4 times the time constant of 0.188s.

[0037] The next time the optocoupler switch is turned on, the attenuation capacitor will be charged again, generating a transient large forward current.

[0038] While the above-mentioned current changes continue to occur on the primary side of the current transformer, the ammeter pointer connected to the signal detection device on the secondary side of the current transformer will deflect positively once every 0.5S. After connecting the signal generating device and the primary side of the current transformer, one person can hold the signal detection device to the secondary side of the current transformer to measure the polarity at any time.

[0039] As mentioned above, by setting the adjustable resistor R3 (0-150kΩ) in the other oscillation signal generating section of the signal generating device to 70kΩ and 150kΩ, respectively, an oscillation signal with a frequency of approximately 1Hz (duty cycle close to 50%) and an oscillation signal with a duty cycle close to 50% can be generated. This, in turn, generates primary currents of different frequencies. By distinguishing the frequency of the signal, the tester can distinguish the phase of the current transformer being tested.

[0040] The present invention has been tested in the laboratory and can be applied on site.

[0041] Finally, all the parts not described in the present invention adopt mature products and mature technical means in the existing technology.

[0042] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A new polarity test tool for current and voltage transformers in substations, characterized by: The invention comprises a signal generating device and a signal detecting device; the signal detecting device is connected to the secondary side of a current and voltage transformer; the signal generating device is provided with a plurality of N terminals and three-phase output terminals connected to the signal input end of the current and voltage transformer; a rechargeable battery is provided in the signal generating device, and the two poles of the rechargeable battery are respectively connected to the N terminal circuit and the three-phase output terminal circuit; the two poles of the rechargeable battery circuit are connected in parallel to a signal generating unit and an optocoupler relay, and the circuit of the rechargeable battery connected to the three-phase output terminal is connected in parallel to an oscillation signal generating unit, and the signal generating unit is controlled to be on and off via the optocoupler relay.

2. The new polarity test tool for current and voltage transformers in substations according to claim 1 is characterized by: The signal generating unit includes a NE555 timer chip, a resistor R1, a resistor R2, an adjustable resistor R3, a capacitor C1 and a capacitor C2, wherein the resistor R1, the resistor R2, the adjustable resistor R3 and the capacitor C1 are connected in series in sequence; the first pin of the NE555 timer chip is connected to the N-terminal circuit and grounded, the second pin and the sixth pin of the NE555 timer chip are respectively connected to the resistance adjustment end of the adjustable resistor R3, the third pin of the NE555 timer chip is connected to the first pin of the optocoupler relay, the seventh pin of the NE555 timer chip is connected to the circuit between the resistor R1 and the resistor R2, the fourth pin and the eighth pin of the NE555 timer chip are respectively connected to the three-phase output terminal circuit, and the fifth pin of the NE555 timer chip is connected to the N-terminal circuit via the capacitor C2.

3. The new polarity test tool for current and voltage transformers in substations according to claim 1 is characterized by: The second pin of the optical coupler relay is connected to the N terminal circuit, and the third and fourth pins of the optical coupler relay are connected to the three-phase output terminal circuit and control the on and off of the oscillation signal generating unit.

4. The new polarity test tool for current and voltage transformers in a substation according to claim 1, characterized in that: The oscillation signal generating unit includes a decay capacitor and a discharge resistor, wherein the decay capacitor is connected in series to the three-phase output terminal circuit, and the two-pole circuit of the decay capacitor is connected in parallel to the discharge resistor.

5. The new polarity test tool for current and voltage transformers in a substation according to claim 1, characterized in that: The three-phase output terminals include A, B, and C three-phase output terminals, which are used for simultaneous detection of A, B, and C three phases. By setting different resistance values of the adjustable resistor R3, oscillating currents of different frequencies are generated, which are used to distinguish A, B, and C three phases during simultaneous detection.

6. The new polarity test tool for current and voltage transformers in a substation according to claim 1, characterized in that: The signal detection device is a pointer-type DC milliampere ammeter, the detection terminal of which is connected to the secondary side of the current and voltage transformer, and is used to detect the secondary current sensed by the current and voltage transformer, and judge whether the polarity is correct by observing the positive or negative deflection of the pointer; and judge whether the detected phase is A phase, B phase or C phase by the frequency of the pointer deflection.

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