Sensors and detection devices for partial discharge detection in ultra-high voltage power grids

Abstract

This invention belongs to the field of partial discharge detection technology, specifically relating to a sensor and detection device for partial discharge detection in ultra-high voltage (UHV) flexible DC transmission systems. Addressing the shortcomings of existing partial discharge detection sensors for UHV flexible DC transmission systems, which suffer from low accuracy, this invention employs the following technical solution: The sensor for partial discharge detection in UHV flexible DC transmission systems includes: a magnetic core; a high-frequency coil; an RLC series circuit, including a resistor, an inductor, and a capacitor; a microcontroller; at least one of the resistor, inductor, and capacitor in the RLC series circuit is adjustable; the microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor. In this invention, the microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor, thereby adjusting the sensor and thus at least one of the sensing response center frequency, sensing response bandwidth, and sensing response sensitivity, thereby improving detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of partial discharge detection technology, specifically relating to sensors and detection devices for detecting partial discharge in ultra-high voltage power transmission. Background Technology

[0002] As a critical piece of equipment in ultra-high voltage (UHV) flexible direct current (DC) transmission projects, the condition of UHV converter transformers directly affects the safety of the entire system. A failure in a converter transformer can easily lead to converter valve closure, causing localized or even widespread power outages and resulting in incalculable economic losses. Surveys and statistics from CIGRE (International Conference on Large Electric Systems) show that 58.8% of DC transmission system failures are caused by converter transformer failures, with insulation failures accounting for approximately 50%. Partial discharge at weak points in the insulation, leading to insulation aging and failure, is the primary cause of these insulation failures. Therefore, systematic research on partial discharge detection technology for UHV large-capacity converter transformers under phased commissioning is crucial. This is of great significance for solving problems such as significant interference in field tests and difficulties in partial discharge detection, improving the detection level of converter transformer insulation performance, and ensuring the safe and reliable operation of the equipment.

[0003] However, the partial discharge detection of flexible DC transmission systems is affected by complex interference harmonics within the system. Because flexible DC transmission systems employ modular multilevel (MMC) converters, the harmonic interference levels in these systems differ significantly from those in traditional DC transmission systems. Currently, the mechanisms underlying the complex electromagnetic interference generated by IGBTs (Insulated-Gate Bipolar Transistors) during high-frequency switching and the in-station propagation characteristics of high-frequency interference under phased commissioning methods remain unclear.

[0004] One key challenge in partial discharge detection is effectively suppressing the unique noise interference of ultra-high voltage flexible DC transmission systems to improve detection accuracy. However, existing partial discharge detection sensors typically have fixed center frequencies, bandwidths, and sensitivities. Summary of the Invention

[0005] This invention addresses the shortcomings of existing partial discharge detection sensors in UHVDC flexible direct current transmission systems, which suffer from low accuracy. It provides a sensor for partial discharge detection in UHVDC flexible direct current transmission systems, where at least one of its sensing response center frequency, sensing response bandwidth, and sensing response sensitivity is adjustable. This effectively suppresses the unique noise interference of UHVDC flexible direct current transmission systems, improving the accuracy of partial discharge detection. This invention also provides a detection device using this sensor.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a sensor for partial discharge detection in an ultra-high voltage flexible direct current transmission system, the sensor comprising: magnetic core; High-frequency coil; An RLC series circuit includes a resistor, an inductor, and a capacitor; Microcontroller; Among them, the value of at least one of the resistor, inductor and capacitor connected in the RLC series circuit is adjustable; The microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor connected in the RLC series circuit, thereby adjusting at least one of the sensing response center frequency, sensing response bandwidth, and sensing response sensitivity.

[0007] The sensor for partial discharge detection in ultra-high voltage flexible DC transmission systems of the present invention includes a magnetic core, a high-frequency coil, an RLC series circuit, and a microcontroller. The value of at least one of the resistor, inductor, and capacitor in the RLC series circuit is adjustable. By adjusting the value of at least one of the resistor, inductor, and capacitor, the microcontroller can adjust at least one of the center frequency, bandwidth, and response sensitivity of the sensor filter, thereby improving the detection accuracy.

[0008] As an improvement, at least two of the resistors, inductors, and capacitors in an RLC series circuit are adjustable.

[0009] As an improvement, the RLC series circuit includes multiple inductors of different sizes that can be connected separately.

[0010] As an improvement, each inductor is connected to a relay controlled by a microcontroller.

[0011] As an improvement, the inductance values ​​of at least two inductors must satisfy: L1=m 2 L2 In the formula, L1 and L2 are the inductance values ​​of the two inductors, and m is an integer greater than 1.

[0012] As an improvement, the RLC series circuit uses a digital potentiometer as an adjustable resistor, which is controlled by a microcontroller.

[0013] As an improvement, the RLC series circuit includes multiple capacitors of different sizes that can be connected individually.

[0014] As an improvement, each capacitor is connected by a relay controlled by a microcontroller.

[0015] As an improvement, the center frequency of the sensor filter is expressed as: ω0 = 1 / sqrt(LC) In the formula, ω0 is the center frequency, L is the inductance value, and C is the capacitance value; The bandwidth of the sensor is expressed as: ω2-ω1=R / L In the formula, ω1 and ω2 are the lower cutoff frequency and the upper cutoff frequency, respectively, and R is the resistance value; The sensitivity of a sensor is expressed as: Q=(ω0L) / R=(1 / R)*sqrt(L / C)=1 / (ω0CR).

[0016] A detection device for partial discharge detection in ultra-high voltage flexible DC transmission systems includes: Main control unit; sensor; Coupling capacitor; Partial discharge instrument; Among them, the sensor is the aforementioned sensor used for partial discharge detection in ultra-high voltage flexible DC transmission systems; The main control unit communicates with the sensor, and the coupling capacitor is connected in series with the sensor. The coupling capacitor is located between the component to be detected and ground. The main control unit adjusts the center frequency and / or bandwidth of the sensor filter through a microcontroller.

[0017] The beneficial effects of the sensor for partial discharge detection in ultra-high voltage flexible DC transmission systems of the present invention are as follows: it includes a magnetic core, a high-frequency coil, an RLC series circuit and a microcontroller. The value of at least one of the resistor, inductor and capacitor in the RLC series circuit is adjustable. The microcontroller adjusts the value of at least one of the resistor, inductor and capacitor, thereby adjusting the center frequency and / or bandwidth of the sensor filter, thereby improving the detection accuracy.

[0018] The detection device for partial discharge detection in ultra-high voltage flexible direct current transmission systems of the present invention, which employs the sensor for partial discharge detection in ultra-high voltage flexible direct current transmission systems of the present invention, has all the beneficial effects of the sensor for partial discharge detection in ultra-high voltage flexible direct current transmission systems of the present invention. Attached Figure Description

[0019] Figure 1 This is a structural block diagram of the detection device according to Embodiment 1 of the present invention.

[0020] Figure 2 This is a structural block diagram of the sensor according to Embodiment 1 of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be explained and described below. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0022] See Figure 1 and Figure 2 The sensor for partial discharge detection in an ultra-high voltage flexible direct current transmission system according to an embodiment of the present invention includes: magnetic core; High-frequency coil; An RLC series circuit includes a resistor, an inductor, and a capacitor; Microcontroller; In the RLC series circuit, at least one of the resistor, inductor, and capacitor can be adjusted. The microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor.

[0023] The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to an embodiment of the present invention includes a magnetic core, a high-frequency coil, an RLC series circuit, and a microcontroller. The value of at least one of the resistor, inductor, and capacitor in the RLC series circuit is adjustable. The microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor, thereby adjusting the center frequency and / or bandwidth of the sensor filter, thereby improving the detection accuracy.

[0024] Example 1 See Figure 1 and Figure 2 The detection device for partial discharge detection in an ultra-high voltage flexible DC transmission system according to an embodiment of the present invention includes: Main control unit; sensor; Coupling capacitor; Partial discharge instrument; The main control unit communicates with the sensor, and the coupling capacitor is connected in series with the sensor. The coupling capacitor is located between the component to be detected and ground. The main control unit adjusts the center frequency and / or bandwidth of the sensor filter through a microcontroller.

[0025] In this embodiment, the sensor is grounded. The main control unit and the sensor communicate via optical fiber. Coupling capacitors are connected to the component to be detected (i.e., Figure 1 Partial discharge under test (partial discharge component) and sensor (i.e. Figure 1 (The CNC detection sensor in the middle).

[0026] In this embodiment, the sensor includes: Magnetic core (not shown in the figure); High-frequency coil; An RLC series circuit includes a resistor, an inductor, and a capacitor; Microcontroller; In the RLC series circuit, at least one of the resistor, inductor, and capacitor can be adjusted. The microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor.

[0027] In this embodiment, the resistance and inductance of the RLC series circuit are adjustable, while the capacitance is not. In other embodiments, other configurations are possible, such as adjustable resistance and capacitance, non-adjustable inductance, or adjustable resistance, inductance, and capacitance.

[0028] In this embodiment, the LC series circuit includes three inductors of different sizes (L1, L2, and L3) that can be connected separately. Each inductor is controlled by a relay (A, B, and C), which is controlled by a microcontroller. The relays are single-pole single-throw relays. The detection signal U0 is output from the capacitor.

[0029] In this embodiment, during detection, the microcontroller communicates with the main control unit via optical fiber and receives instructions from the main control unit to adjust the digital potentiometer and select the relay to turn on. The microcontroller adjusts the digital potentiometer to a certain resistance value according to the instructions, and at the same time turns on the corresponding relay according to the instructions to select an inductor.

[0030] In this embodiment, during detection, the transient pulse current generated when the partial discharge of the component under test occurs is converted into a voltage signal that can be measured and processed by subsequent instruments (such as a partial discharge analyzer). The partial discharge is measured in bands. The partial discharge signal is filtered and measured by the partial discharge analyzer to obtain a partial discharge signal with a certain center frequency and response bandwidth.

[0031] The principle behind the reliable filtering and improved detection accuracy of the scheme in this embodiment is explained below.

[0032] 1. Calculation of the center frequency of sensor filtering.

[0033] When the sensor is working, the digital potentiometer (which can be considered as a resistor R), the inductor L (one of L1, L2, and L3), and the capacitor C form an RLC series circuit. The detection signal U0 is output from the capacitor C. The relationship between U0 and frequency follows the amplitude-frequency characteristic of the RLC series resonant circuit. The frequency of the peak voltage U0 (i.e., the center frequency) is expressed as: ω0 = 1 / sqrt(LC) In the formula, ω0 is the center frequency (which is also the angular frequency when the circuit resonates), L is the inductance of the inductor connected to the RLC series circuit, C is the capacitance of the capacitor connected to the RLC series circuit; sqrt is the square root. After calculation, the main control unit transmits the inductor selection command to the microcontroller via optical fiber. Upon receiving the command, the microcontroller changes the level state of relays A, B, and C, causing one of the relays to conduct, thereby connecting the corresponding inductor to the RLC series circuit.

[0034] 2. Bandwidth calculation.

[0035] If the 3dB bandwidth in the amplitude-frequency response of the circuit is From the definition of the amplitude-frequency characteristic of Q, we have: ω2-ω1=R / L In the formula, ω1 and ω2 are the lower cutoff frequency and the upper cutoff frequency, respectively, and R is the resistance value of the resistor connected in the RLC series circuit. The above formula shows that the 3dB bandwidth of the detection signal depends only on the resistor R and the inductor L.

[0036] The above formula is the calculation formula for the filter bandwidth controlled by the main control unit. After calculation, the main control unit transmits the digital potentiometer command to the microcontroller via optical fiber. Upon receiving the command, the microcontroller adjusts the output pulse of the digital potentiometer, and the digital potentiometer is adjusted to the corresponding resistance value under the action of the adjustment pulse.

[0037] 3. Sensor sensitivity calculation.

[0038] According to the principle of RLC series circuit, the maximum voltage across the capacitor at circuit resonance is: =jQ

[0039] If the sensor voltage is K, then: K=U0 / U S =Q=(ω0L) / R The above formula shows that the sensor sensitivity Q is related to the filter center frequency (which is related to the connected inductor and capacitor), the selected inductor, and the resistance value of the digital potentiometer.

[0040] Therefore, the main control unit can calculate and balance the relationship between the filter center frequency, bandwidth, and sensor sensitivity according to the sensor measurement requirements.

[0041] Specifically, in a partial discharge test of a transformer using the pulse current method, the partial discharge frequency band used is 40kHz-300kHz. To accurately measure the partial discharge after the transformer is energized, it is necessary to eliminate external interference signals. The frequency band of the external interference signal can be determined by narrowing the measurement frequency band. The entire measurement frequency band is divided into two parts: 40kHz-200kHz and 200kHz-300kHz. The interference waveforms in these two narrowed frequency bands are observed and measured separately. If the interference is in the 200kHz-300kHz band, the 40kHz-200kHz band can be used for transformer partial discharge measurement. If the interference is in the 40kHz-200kHz band, then the interference must be eliminated before measurement.

[0042] The capacitor is 10nF. The inductance and digital potentiometer values ​​used in the existing scheme and this embodiment are calculated and shown in the table below:

[0043] In the table above, the left side represents the values ​​of existing non-adjustable sensors, while the middle and right sides represent the values ​​obtained by the solution in this embodiment. As can be seen from the table, this embodiment adjusts the center frequency and bandwidth of the sensor filter by adjusting the resistance and inductance connected to the RLC series circuit, enabling more accurate frequency-band measurements.

[0044] The beneficial effect of the detection device for partial discharge detection in ultra-high voltage flexible DC transmission system according to Embodiment 1 of the present invention is that by adjusting (or selecting) the value of the resistor and inductor connected to the RLC series circuit, the center frequency and bandwidth of the sensor filter are adjusted, and the relationship between the filter center frequency, bandwidth and sensor sensitivity is balanced, thereby ultimately improving the detection accuracy.

[0045] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A sensor for detecting partial discharge in ultra-high voltage flexible direct current transmission systems, characterized in that: Sensors used for partial discharge detection in ultra-high voltage flexible direct current transmission systems include: magnetic core; High-frequency coil; An RLC series circuit includes a resistor, an inductor, and a capacitor connected in series. Microcontroller; Among them, the value of at least one of the resistor, inductor and capacitor connected in the RLC series circuit is adjustable; The microcontroller adjusts the value of at least one of the resistor, inductor, and capacitor connected in the RLC series circuit, thereby adjusting at least one of the sensing response center frequency, sensing response bandwidth, and sensing response sensitivity.

2. The sensor for partial discharge detection in ultra-high voltage flexible DC transmission systems according to claim 1, characterized in that: In an RLC series circuit, at least two of the resistors, inductors, and capacitors are adjustable.

3. The sensor for partial discharge detection in ultra-high voltage flexible DC transmission systems according to claim 1, characterized in that: An RLC series circuit consists of multiple inductors of different sizes that can be connected individually.

4. The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to claim 3, characterized in that: Each inductor is connected to a relay controlled by a microcontroller.

5. The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to claim 4, characterized in that: At least two inductors have inductance values ​​that satisfy: L1=m 2 L2 In the formula, L1 and L2 are the inductance values ​​of the two inductors, and m is an integer greater than 1.

6. The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to claim 1, characterized in that: The RLC series circuit uses a digital potentiometer as an adjustable resistor, which is controlled by a microcontroller.

7. The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to claim 1, characterized in that: An RLC series circuit includes multiple capacitors of different sizes that can be connected individually.

8. The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to claim 7, characterized in that: Each capacitor is connected via a relay controlled by a microcontroller.

9. The sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system according to claim 1, characterized in that: The center frequency of the sensor filter is expressed as: ω0 = 1 / sqrt(LC) In the formula, ω0 is the center frequency, L is the inductance value, and C is the capacitance value; The bandwidth of the sensor is expressed as: ω2-ω1=R / L In the formula, ω1 and ω2 are the lower cutoff frequency and the upper cutoff frequency, respectively, and R is the resistance value; The sensitivity of a sensor is expressed as: Q=(ω0L) / R=(1 / R)*sqrt(L / C)=1 / (ω0CR).

10. A detection device for partial discharge detection in ultra-high voltage flexible DC transmission systems, characterized in that: include: Main control unit; sensor; Coupling capacitor; Partial discharge instrument; Wherein, the sensor is the sensor for partial discharge detection in an ultra-high voltage flexible DC transmission system as described in any one of claims 1 to 9; The main control unit communicates with the sensor, and the coupling capacitor is connected in series with the sensor. The coupling capacitor is located between the component to be detected and ground. The main control unit adjusts the center frequency and / or bandwidth of the sensor filter through a microcontroller.

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