Sensor arrangement method for partial discharge ultrahigh frequency sensing of a transformer

Abstract

The application provides a sensor arrangement method for partial discharge ultrahigh frequency sensing of a transformer. Based on a partial discharge test, the position of an ultrahigh frequency sensor in a test device is determined, and the ultrahigh frequency characteristics of a partial discharge signal in a transformer tank are explored. The method comprises the following steps: 1) a transformer partial discharge test model is built, a sub-nanosecond discharge tube is arranged in the model tank as a partial discharge source, and an actual defect in the transformer is simulated; 2) two ultrahigh frequency sensors, namely an internal ultrahigh frequency sensor and an external ultrahigh frequency sensor, are selected as detection devices at a detection point of the test model, the ultrahigh frequency electromagnetic wave signals of the transformer partial discharge model measured by the sensors are extracted by an ultrahigh frequency antenna using an oscilloscope, and then the signals are subjected to frequency spectrum analysis by a computer, so that the sensing of the partial discharge of the transformer is realized; the application provides a method for detecting the partial discharge fault of the transformer under the ultrahigh frequency, realizes the real-time monitoring and early warning of the partial discharge of the transformer, and is helpful for early discovery and solution of the transformer fault.

Description

Technical Field

[0001] This invention belongs to the field of electrical equipment and relates to uninterrupted power safety detection technology for high-voltage equipment, specifically to a sensor arrangement method for UHF partial discharge sensing of transformers. Background Technology

[0002] Electricity is the lifeblood of national economic development, and society's dependence on it has reached an unprecedented level. With the rapid growth in the number of users, not only is the demand for electricity increasing, but users' requirements for power quality are also rising. Faults in the power system can cause significant economic losses and even threaten human lives. To ensure a safe and reliable power supply, power grid companies invest heavily each year in necessary maintenance to maintain, restore, or improve their operational status. Scientific and reasonable maintenance methods are fundamental to ensuring power supply reliability and are also related to the operational efficiency and long-term development of power grid companies, making them a hot topic of research in the domestic and international power industries.

[0003] When partial discharge occurs inside a transformer, it excites and generates ultra-high frequency (UHF) electromagnetic wave signals. Due to the complexity of the transformer's insulation structure, the path of the electromagnetic wave propagating from the discharge point to the UHF sensor is uncertain, and it may encounter transformer oil, oil-paper insulation, or metal conductors. Thus, the electromagnetic wave undergoes multiple reflections and attenuations during propagation, increasing the difficulty of electromagnetic wave detection. If the discharge point inside the transformer is close to a certain gap, the signal strength measured by an external sensor at that gap will be much greater than the signal measured at other gap locations. Therefore, this method can be used to locate certain transformer faults. Thus, in-depth theoretical analysis and experimental research on the propagation mechanism of UHF electromagnetic waves generated by partial discharge are essential, as this is crucial for the coupling and reception of electromagnetic wave signals and the placement of UHF sensors. Summary of the Invention

[0004] This invention provides a sensor arrangement method for UHF partial discharge sensing in transformers. Based on the design and construction of a simulation test device for the UHF characteristics of partial discharge signals, the location of UHF sensors in the test device is determined. The propagation mechanism of UHF electromagnetic waves generated by partial discharge is theoretically analyzed and experimentally studied. The UHF characteristics of partial discharge signals in the transformer tank are explored, thereby determining the transformer fault state.

[0005] To achieve the above objectives, the propagation characteristics of ultra-high frequency electromagnetic waves generated by partial discharge were first experimentally studied. The experimental transformer model mainly consisted of a casing, bushings, sealing rings, and end covers. The dimensions and relative positions of the bushings and end covers were set according to the actual single-phase transformer. The partial discharge test included the following steps:

[0006] Step 1: Construct a transformer partial discharge test model. The transformer test model mainly consists of a tank, bushings, sealing rings, and end covers. The dimensions and relative positions of the bushings and end covers are set according to the actual single-phase transformer.

[0007] Step 2: The test model uses a sub-nanosecond discharge tube as a partial discharge power source inside the transformer tank. Its core is a discharge tube filled with high-pressure hydrogen gas to simulate actual defects in the transformer. The discharge power source is installed in the base of the high-voltage bushing.

[0008] Step 3: By setting voltage probes at the detection points, internal and external sensors are simulated. The internal sensor extends into the transformer through an oil valve. The UHF electromagnetic wave signal of the transformer partial discharge model measured by the sensor is extracted by an oscilloscope through an UHF antenna, and then subjected to spectrum analysis by a computer.

[0009] Specifically, the built-in sensor extends into the transformer through the oil valve. At the same time as the discharge occurs, the external sensor collects the leakage discharge signal along the transformer joint. The built-in sensor is selected as the reference to determine the position of the built-in sensor relative to the discharge source.

[0010] The built-in sensor is installed at the observation hole on the side of the transformer tank. The specific installation height is kept at the same horizontal line as the center point of the observation hole. The minimum horizontal distance from the installation point to the observation hole is calculated as follows:

[0011]

[0012] In the formula, h is the wall thickness of the box; a, b, and d are the length, width, and height of the box, respectively; c is the speed of light in a vacuum; and f is the frequency of the electromagnetic wave signal.

[0013] To avoid the discharge signal measured by the built-in sensor being affected by the reflection process inside the enclosure, the maximum horizontal distance from its installation point to the observation hole is calculated as follows:

[0014]

[0015] In the formula, L2 is the maximum horizontal installation distance of the built-in sensor.

[0016] The horizontal distance L from the mounting point of the built-in sensor to the observation hole must satisfy L1. <L<L2。

[0017] The beneficial effects of this invention are as follows: The transformer partial discharge sensing method described in this invention can realize real-time monitoring and early warning of transformer partial discharge, which helps to detect and resolve transformer faults early and avoid further expansion of the fault range and impact. This effectively improves the operational reliability and safety of the transformer. At the same time, these methods are based on uninterrupted power supply technology, eliminating the need to interrupt transformer operation and reducing the inconvenience and losses caused by power outages.

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0019] Figure 1 It is a test transformer model;

[0020] Figure 2 This is a diagram showing the internal power supply layout;

[0021] Figure 3 This is a sensor layout diagram.

[0022] In the diagram, 1 is the sleeve; 2 is the end cap; 3 is the observation hole; 4 is the gap; 5 is the power supply; 6 is the built-in UHF sensor; and 7 is the external UHF sensor. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a sensor arrangement method for UHF partial discharge sensing in transformers. Based on the design and construction of a simulation test device for the UHF characteristics of partial discharge signals, the location of UHF sensors in the test device is determined. The propagation mechanism of UHF electromagnetic waves generated by partial discharge is theoretically analyzed and experimentally studied. The UHF characteristics of partial discharge signals in the transformer tank are explored, thereby determining the transformer fault state.

[0025] To achieve the above objectives, a simulation experiment was first conducted on the ultra-high frequency characteristics of the partial discharge signal. The partial discharge experiment included the following steps:

[0026] Step 1: Construct a transformer partial discharge test model. The transformer test model mainly consists of a tank, bushings, sealing rings, and end covers. The dimensions and relative positions of the bushings and end covers are set according to the actual single-phase transformer with a rated voltage of 110kV and a rated capacity of 2000kVA. Among them, a = 1120mm, b = 1350mm, d = 1900mm, and the tank wall thickness h = 10mm. The sealing ring is located on the upper part of the tank, about 1cm away from the top cover of the tank, and the sealing ring thickness is 2mm. The test model is filled with transformer oil.

[0027] Step 2: The partial discharge signal inside the transformer is a pulse signal with an extremely steep rising edge. To simulate the propagation process of this signal, a pulse generator capable of producing a similar waveform can be used to replace the partial discharge power supply to study the propagation characteristics of pulsed electromagnetic waves. The experimental model uses a sub-nanosecond discharge tube inside the transformer tank as the partial discharge power supply. Its core is a discharge tube filled with high-pressure hydrogen. The pulse waveform is stable, with a rising edge of less than 500ps, a pulse width of less than 1ns, and an amplitude of over 4kV. It can excite a significant electromagnetic wave signal in the range of 500MHz to 1GHz, thereby simulating actual defects in the transformer and studying the performance of the UHF detection system and the UHF characteristics of the partial discharge signal in the transformer tank. The discharge power supply is installed in the base of the high-voltage bushing, with one end connected to the lead of the high-voltage bushing and the other end grounded through the transformer shell. When placing the discharge power supply, first pump the transformer oil level to be flush with the transformer cover plate, then open the observation hole on the side of the transformer. After fixing the partial discharge source and sealing the observation hole, fill the transformer with transformer oil.

[0028] Step 3: By setting voltage probes at the detection points, internal and external UHF sensors are simulated. The built-in UHF sensor extends into the transformer through an oil valve. The transformer tank provides good shielding for the built-in UHF sensor. At this time, the measured discharge signal mainly comes from inside the transformer. The amplitude of the UHF signal received by the sensor at different locations is different. The signal is stronger near the discharge source. Electromagnetic waves have difficulty passing through the transformer tank to the outside. They can only pass through gaps with sealing rings and other locations. Moreover, this propagation process will have a large attenuation. Therefore, the UHF sensor is built-in during detection. The UHF electromagnetic wave signal of the transformer partial discharge model measured by the sensor is extracted by an oscilloscope through an UHF antenna and subjected to spectrum analysis by a computer.

[0029] Specifically, according to the sensor arrangement method for UHF partial discharge sensing of a transformer described in step 3, the built-in sensor extends into the transformer through an oil valve. At the same time as the discharge occurs, an external sensor collects the leaked discharge signal along the transformer joint. The built-in sensor is selected as the reference. Due to the complexity of the transformer insulation structure, the path of electromagnetic waves from the discharge point to the UHF sensor is uncertain. It may encounter transformer oil, oil paper insulation or metal conductors, causing multiple reflections and attenuations when the electromagnetic waves propagate in them. Therefore, it is necessary to reasonably arrange the position of the built-in UHF sensor relative to the discharge source.

[0030] The built-in sensor is installed at the observation hole on the side of the transformer tank. The specific installation height is kept at the same horizontal line as the center point of the observation hole. The minimum horizontal distance from the installation point to the observation hole is calculated as follows:

[0031]

[0032] In the formula, h is the wall thickness of the box; a, b, and d are the length, width, and height of the box, respectively; c is the speed of light in a vacuum; and f is the frequency of the electromagnetic wave signal.

[0033] To avoid the discharge signal measured by the built-in sensor being affected by the reflection process inside the enclosure, the maximum horizontal distance from its installation point to the observation hole is calculated as follows:

[0034]

[0035] In the formula, L2 is the maximum horizontal installation distance of the built-in sensor.

[0036] The horizontal distance L from the mounting point of the built-in sensor to the observation hole must satisfy L1.

Claims

1. A sensor arrangement method for UHF partial discharge sensing in transformers, characterized in that, An experimental study was conducted on the propagation characteristics of ultra-high frequency electromagnetic waves generated by partial discharge; the method includes the following steps: Step 1: Construct a transformer partial discharge test model. The transformer test model mainly consists of a housing, bushings, sealing rings, and end covers. The dimensions and relative positions of the bushings and end covers are set according to the single-phase transformer. Step 2: The test model uses a sub-nanosecond discharge tube as a partial discharge power source inside the transformer tank. Its core is a discharge tube filled with high-pressure hydrogen gas to simulate actual defects in the transformer. The discharge power source is installed in the base of the high-voltage bushing. Step 3: By setting voltage probes at the detection points to simulate internal and external sensors, the built-in sensor extends into the transformer through an oil valve. The UHF electromagnetic wave signal of the transformer partial discharge model measured by the sensor is extracted by an oscilloscope through a UHF antenna, and then subjected to spectrum analysis by a computer. The built-in sensor extends into the transformer through an oil valve. At the same time as the discharge occurs, an external sensor collects the leakage discharge signal along the transformer joint. The built-in sensor is selected as a reference to determine the position of the built-in sensor relative to the discharge source. The built-in sensor is installed at the observation hole on the side of the transformer tank. The specific installation height is kept at the same horizontal line as the center point of the observation hole. The minimum horizontal distance from the installation point to the observation hole is calculated as follows: ； In the formula, h is the wall thickness of the box; a, b, and d are the length, width, and height of the box, respectively; c is the speed of light in a vacuum; and f is the frequency of the electromagnetic wave signal. To avoid the discharge signal measured by the built-in sensor being affected by the reflection process inside the enclosure, the maximum horizontal distance from its installation point to the observation hole is calculated as follows: ； In the formula, L2 is the maximum horizontal installation distance of the built-in sensor; The horizontal distance L from the mounting point of the built-in sensor to the observation hole must satisfy L1. <L<L2。

Images