CVT ferromagnetic resonance damper device and design method

Abstract

The present invention relates to a CVT ferromagnetic resonance damper device and a design method. The device comprises a damper body, which is connected in parallel to a 1a-1n winding in a secondary coil of an intermediate transformer, and comprises a series resistor, a parallel resistor and a saturable damping reactor, wherein the series resistor and the saturable damping reactor are connected in series and are then connected in parallel to the parallel resistor; one end of the parallel resistor and the series resistor are both connected to a 1a end of the 1a-1n winding, and the other end of the parallel resistor and the saturable damping reactor are both connected to a 1n end of the 1a-1n winding; and the rated magnetic flux density of the intermediate transformer satisfies Bm≤0.5 T; and the saturable damping reactor comprises a damping reactor core and a damping reactor coil, and the damping reactor core is made of a silicon steel sheet with a saturable magnetic flux density of 2.2 T. The present invention achieves a good damping performance, and can be applied to a system with non-effectively earthed neutral.

Description

A CVT ferromagnetic resonance damper device and design method Technical Field

[0001] The present invention relates to the field of capacitive voltage transformers, in particular to a CVT ferromagnetic resonance damper device and a design method thereof. Background Art

[0002] Capacitor Voltage Transformer (CVT) is a device that divides the primary high voltage (e.g. 220kV) on the transmission line into a lower intermediate voltage (e.g. 10kV) through a capacitor voltage divider, and then converts it into a standard secondary voltage (e.g. CVTs are widely used in power systems, primarily for voltage measurement, carrier communication, relay protection, telemetry, and monitoring systems. They also isolate the high-voltage primary and low-voltage secondary sides to protect the safe and stable operation of equipment, making them a crucial component of power grids. Compared to traditional electromagnetic voltage transformers (PTs), CVTs offer many advantages, including higher insulation reliability, lower cost, no ferromagnetic resonance caused by grid parameter mismatch, simpler daily operation and maintenance, and the ability to double as carrier communication devices.

[0003] As shown in Figure 13, a CVT typically consists of a capacitive voltage divider and an electromagnetic unit, which includes an intermediate transformer, compensating reactor, and a damper. The iron-core intermediate transformer, capacitor, and compensating reactor form a complete resonant circuit, but this also produces ferromagnetic resonance, necessitating a damper to suppress the resonance. Normally, the damper has a very high impedance. When ferromagnetic resonance causes overvoltage, the reactor in the damper is saturated before the intermediate transformer is affected, leaving only a resistive load. The resistor quickly absorbs the oscillation energy, rapidly reducing the overvoltage.

[0004] However, the damping of ferromagnetic resonance by the dampers of CVT products in the existing technology all works in conjunction with the compensating reactor and the overvoltage protection device. For example, some products connect a zinc oxide lightning arrester in parallel with the compensating reactor, and some products add a current-limiting resistor and a discharge tube to the reactor coil. However, these protection devices will fail if they are operated multiple times or for a long time, so they must be replaced in time. This increases the on-site maintenance work of the substation and is also prone to misjudgment.

[0005] In addition, the damper devices commonly used in CVT products in the existing technology are mostly fast-saturation reactance type (Permalloy or microcrystalline alloy). The iron core of the fast-saturation reactance type damper is expensive and large in size. In addition, under the condition of 1.22 to 1.24 times the rated voltage, the iron core saturation easily causes secondary output waveform distortion, and cannot be used in products with non-effective grounding of the neutral point. Moreover, the fast-saturation reactance type damper has a weak effect in damping ferromagnetic resonance when the rated voltage is low.

[0006] Furthermore, CVT manufacturers currently design the damping resistor of the damper based on past experience and then adjust the damping resistor value through experiments. This method is time-consuming, labor-intensive, and not accurate.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to provide a CVT ferromagnetic resonance damper device and design method, which can achieve excellent vibration reduction performance without reducing the transient response performance of the transformer, and is applicable to both neutral point effective grounding systems and neutral point non-effective grounding systems, while also improving design efficiency.

[0009] The object of the present invention is achieved through the following technical solutions:

[0010] A CVT ferromagnetic resonance damper device includes a damper body, and the damper body is connected in parallel with the 1a-1n winding in the secondary coil of the intermediate transformer. The damper body includes a series resistor, a parallel resistor and a saturation damping reactor, wherein the series resistor and the saturation damping reactor are connected in series and then connected in parallel with the parallel resistor, and one end of the parallel resistor and the series resistor are both connected to the 1a end of the 1a-1n winding, the other end of the parallel resistor and the saturation damping reactor are both connected to the 1n end of the 1a-1n winding, and the rated magnetic flux density B of the intermediate transformer is 1. m ≤0.5T, the saturated damping reactor comprises a damping reactor core and a damping reactor coil wound on the damping reactor core, and the damping reactor core is made of silicon steel sheet with a saturation magnetic flux density of 2.2T.

[0011] The damping reactor core is annular and is provided with a cardboard layer on the outside. A core insulation layer is provided on the outside of the cardboard layer, and the damping reactor coil is wound on the core insulation layer. An interlayer insulation layer is provided between adjacent layers of the damping reactor coil. An external insulation layer is provided on the outside of the damping reactor coil, and a shrink wrapping tape layer is provided on the outside of the external insulation layer. The starting and ending ends of the damping reactor coil are led out to form coil lead ends.

[0012] The paperboard layer includes an outer insulating paperboard for the core, an inner insulating paperboard for the core and an end insulating paperboard for the core. The core insulating layer, the interlayer insulating layer and the outer insulating layer are all made of polyester film. The outermost layer of the outer insulating layer is wrapped with a shrink tape to form the shrink wrapping tape layer.

[0013] The number of turns W of the damping reactor coil D Calculated according to the following formula:

[0014] In the above formula (2), F V. is the rated voltage factor, U sr is the rated secondary voltage, f r is the rated frequency;

[0015] The magnetic flux density B of the damping reactor core (3033) D Calculated according to the following formula:

[0016] In the above formula (3), A D is the cross-sectional area of ​​the damping reactor core (3033);

[0017] The inductance L of the saturated damping reactor (303) is calculated according to the following formula:

[0018] In the above formula (4), μ is the magnetic permeability; l is the average magnetic path length of the reactor core.

[0019] The temperature coefficient of the series resistor and the parallel resistor is 25ppm / K~100ppm / K, the insulation resistance of the series resistor and the parallel resistor to ground is ≥2000MΩ, and the power overload capacity of the series resistor requires a voltage overload of 10 times for 1s, a voltage overload of 5 times for 5s, and a voltage overload of 2 times for 3min.

[0020] The damper body is mounted on a damping device bracket, which includes a support plate, a support plate and a fixed plate, wherein the support plate includes a vertical plate and a horizontal plate, and a semicircular support plate is provided on one side of the vertical plate and a fixed plate is provided on the other side. The saturated damping reactor is supported by the support plate, the series resistor is provided on the horizontal plate, and the parallel resistor is provided on the vertical plate and between the saturated damping reactor and the series resistor.

[0021] The series resistors and the parallel resistors are respectively mounted on corresponding bases. The vertical plate and the horizontal plate are provided with a plurality of mounting screw holes, and the bases are fixed to a corresponding group of mounting screw holes by bolts.

[0022] One end of the damper body is provided with a first lead wire, which is connected to the ln terminal of the secondary coil of the intermediate transformer inside the oil tank. The other end of the damper body is provided with a second lead wire, and the second lead wire is connected to the F terminal on the secondary junction box of the oil tank. The F terminal is then connected to the 1a terminal on the secondary junction box through a connecting piece.

[0023] A design method of the CVT ferromagnetic resonance damper device includes the following steps:

[0024] Step 1: Determine the rated magnetic flux density B of the intermediate transformer m ≤0.5T, the calculation formula is as follows:

[0025] In the above formula (1), U sr is the rated secondary voltage; f r is the rated power; A Fe is the cross-sectional area of ​​the intermediate transformer core; W2 is the number of turns of the intermediate transformer secondary coil;

[0026] Step 2: Determine the parameters of the saturated damping reactor, wherein first determine the number of turns W of the damping reactor coil (3035) D , the calculation formula is as follows:

[0027] In the above formula (2), F V. is the rated voltage factor;

[0028] Then according to the number of turns W of the damping reactor coil D and the cross-sectional area A of the damping reactor core D Determine the magnetic flux density B of the damping reactor core at rated voltage D , the calculation formula is as follows:

[0029] Finally, determine the inductance L of the saturated damping reactor. The calculation formula is as follows:

[0030] In the above formula (4), μ is the magnetic permeability; l is the average magnetic path length of the reactor core.

[0031] Determine the impact of the inductance L on the voltage transformer error performance at rated voltage based on the above-mentioned inductance L;

[0032] Step 3: Determine the series resistor parameters in the damper body;

[0033] Step 4: Determine the shunt resistor parameters based on the secondary rated voltage and rated voltage factor at the connection between the damper body and the 1a-1n winding.

[0034] In step three:

[0035] Step 3.1: Determine the resistance R of the series resistor Fs Select the range and the calculation formula is as follows:

[0036] In the above formula (5), ω is the rated angular frequency, n is the number of subharmonics, U C is the rated voltage of the intermediate transformer (5), C1 and C2 are the rated capacitances of the intermediate transformer (5);

[0037] Step 3.2: Determine other parameter conditions of the series resistor, including that the temperature coefficient of the series resistor (301) is 25ppm / K to 100ppm / K, the insulation resistance of the series resistor to ground is ≥2000MΩ, and the power overload capacity of the series resistor requires that the overload lasts for 1s when the voltage is 10 times, lasts for 5s when the voltage is 5 times, and lasts for 3 minutes when the voltage is 2 times.

[0038] Step 3.3: Based on the conditions determined in Steps 3.1 and 3.2, use the transient program to perform ferromagnetic resonance transient simulation calculations on the CVT and ultimately determine the resistance value of the series resistor.

[0039] The advantages and positive effects of the present invention are:

[0040] 1. The present invention uses an intermediate transformer with a low rated magnetic flux density (rated magnetic flux density ≤ 0.5T) to match the damper body, and the damper body uses silicon steel sheets with a high saturation magnetic flux density (2.2T) to make the damping reactor core of the saturated damping reactor. When the damping reactor core is deeply saturated (greater than 2.2T), the magnetic permeability is close to 0, so the inductance of the saturated damping reactor is also close to 0, and the loop impedance is very small. At this time, the series resistor can be used to quickly consume a large amount of power to damp the ferromagnetic resonance overvoltage. Thus, the voltage can be restored to a normal level within a specified time. In addition, in addition to the fact that subharmonic oscillations can be quickly dissipated in the series resistor and the damper body, the damper body also has the characteristics of high impedance and low load for power frequency oscillations. Therefore, the present invention can effectively suppress ferromagnetic resonance oscillations, and this vibration reduction combination can achieve excellent vibration reduction performance without reducing the transient response performance of the transformer. At the same time, the present invention also solves the problem that the existing fast-saturation reactance damper has a weak ferromagnetic resonance damping effect when the rated voltage is low.

[0041] 2. Compared with the fast saturation reactance damper core (Permalloy or microcrystalline alloy) in the prior art, the damping reactor core of the present invention is made of silicon steel sheets with high saturation magnetic flux density (2.2T), which is lower in cost and smaller in size.

[0042] 3. The present invention can be used for CVT products of various voltage levels, and is applicable to both neutral point effective grounding systems and neutral point non-effective grounding systems (such as 35kY capacitive voltage transformers), thereby solving the technical problem that existing fast-saturation reactance dampers are only applicable to neutral point effective grounding systems.

[0043] 4. The present invention can determine the resistance value and power size of the series resistor by performing ferromagnetic resonance transient simulation calculation of the capacitive voltage transformer (CVT) through a transient program (ATP), thereby solving the problem that the existing fast-saturation reactance damper can only select the resistance value through past experience and adjust the damping resistor value through actual experiments. This not only improves the design efficiency, but also ensures the accuracy of the damping resistor design parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG1 is a schematic diagram of the structure of the electromagnetic unit of the present invention.

[0045] FIG2 is a front view of the electromagnetic unit in FIG1 ,

[0046] Figure 3 is a schematic diagram of the structure of the intermediate transformer inside the oil tank in Figure 1.

[0047] FIG4 is the AA view in FIG3 ,

[0048] FIG5 is a schematic structural diagram of the present invention,

[0049] FIG6 is a left side view of the present invention in FIG5 ,

[0050] FIG7 is a schematic diagram of the electrical principle of the present invention,

[0051] FIG8 is a front view of the saturated damping reactor in FIG5 ,

[0052] FIG9 is a BB view in FIG8 ,

[0053] FIG10 is a schematic diagram of the winding of the damping reactor coil in FIG8 ,

[0054] FIG11 is a schematic structural diagram of the damping device bracket in FIG6 ,

[0055] FIG12 is a view in the direction of I in FIG11,

[0056] FIG13 is a schematic diagram showing the electrical connection principle between the electromagnetic unit and the capacitive voltage divider in FIG1 ,

[0057] Figure 14 is a schematic diagram of the secondary terminal arrangement in Figure 13.

[0058] FIG15 is a secondary voltage waveform diagram of the ferromagnetic resonance simulation calculation when the present invention is applied to a 220kY capacitor voltage transformer.

[0059] FIG16 is a waveform diagram of a ferromagnetic resonance test when the present invention is applied to a 220kY capacitor voltage transformer.

[0060] FIG17 is a secondary voltage waveform diagram of the ferromagnetic resonance simulation calculation when the present invention is applied to a 35kY capacitor voltage transformer.

[0061] FIG18 is a waveform diagram of a ferromagnetic resonance test when the present invention is applied to a 35kY capacitor voltage transformer.

[0062] Among them, 1 is the oil tank, 2 is the compensation reactor, 3 is the damper body, 301 is the series resistor, 302 is the parallel resistor, 303 is the saturated damping reactor, 3031 is the shrink wrapping tape layer, 3032 is the coil lead end, 3033 is the damping reactor core, 3034 is the polyester film, 3035 is the damping reactor coil, 3036 is the core outer insulation cardboard, 3037 is the core inner insulation cardboard, 3038 is the core end insulation cardboard, 304 is the first lead wire, 305 is the second lead wire Wire, 306 is the terminal lug, 307 is the binding belt, 308 is the damping device bracket, 3081 is the support plate, 3082 is the support plate, 30821 is the vertical plate, 30822 is the horizontal plate, 3083 is the fixing plate, 309 is the base, 4 is the secondary junction box, 401 is the secondary junction board, 402 is the connecting piece, 5 is the intermediate transformer, 501 is the intermediate transformer primary coil, 502 is the intermediate transformer secondary coil, 503 is the intermediate transformer core, 504 is the intermediate transformer bracket, and 6 is the capacitor voltage divider. DETAILED DESCRIPTION

[0063] The present invention will be further described below in conjunction with the accompanying drawings.

[0064] As shown in Figures 1 to 18, the present invention includes a damper body 3, and as shown in Figure 13, the damper body 3 is connected in parallel with the 1a-1n winding in the secondary coil 502 of the intermediate transformer. As shown in Figures 5 to 10, the damper body 3 includes a series resistor 301, a parallel resistor 302 and a saturated damping reactor 303, wherein the series resistor 301 and the saturated damping reactor 303 are connected in series and then connected in parallel with the parallel resistor 302, and one end of the parallel resistor 302 and the series resistor 301 are both connected to the 1a end of the 1a-1n winding, and the other end of the parallel resistor 302 and the saturated damping reactor 303 are both connected to the 1n end of the 1a-1n winding.

[0065] First, the intermediate transformer 5 of the present invention needs to reduce the rated magnetic flux density. The rated magnetic flux density of the intermediate transformer of the CVT product in the prior art is generally selected between 0.7 and 0.8T. The rated magnetic flux density B of the intermediate transformer 5 is determined by calculation and product test verification. m≤0.5T. As shown in Figures 3 and 4, the intermediate transformer 5 includes an intermediate transformer primary coil 501, an intermediate transformer secondary coil 502 and an intermediate transformer core 503. This is a well-known technology in the art, wherein the intermediate transformer 5 is supported and installed in the oil tank 1 by an intermediate transformer bracket 504. The intermediate transformer core 503 is composed of two C-shaped cores relative to each other. According to the law of electromagnetic induction, the rated magnetic flux density B of the intermediate transformer 5 of the present invention is m Determined by the following formula:

[0066] In the above formula (1), B m is the magnetic flux density in the iron core, in T; U sr is the rated secondary voltage, in V; f r is the rated power, in Hz; A Fe is the cross-sectional area of ​​the intermediate transformer core 503, in cm2; W2 is the number of turns of the intermediate transformer secondary coil 502.

[0067] As can be seen from the application examples described below, the present invention has been verified through a large number of calculations and product tests. m When the value is ≤0.5T, the ferromagnetic resonance oscillation can be effectively suppressed by the combination of the low rated magnetic flux density of the intermediate transformer 5 and the damper body 3 of the present invention.

[0068] Secondly, the present invention requires that the damper body 3 has high impedance and low load for power frequency oscillation, and for subharmonic oscillation, it is required that the impedance becomes low after the saturated damping inductor 303 in the damper body 3 is saturated, so that the subharmonic oscillation will be quickly dissipated in the series resistor 301 and the saturated damping inductor 303. In addition, each resistor needs to have excellent thermal properties so that they can dissipate energy while maintaining a constant resistance.

[0069] In order to meet the above requirements, as shown in Figures 8 to 10, the saturation damping reactor 303 of the present invention includes a damping reactor core 3033 and a damping reactor coil 3035, wherein the damping reactor core 3033 is annular and is made of silicon steel sheets with high saturation magnetic flux density. The saturation magnetic flux density of such silicon steel sheets is 2.2T. The currently commonly used dampers are made of fast saturation reactance type core materials, which are usually Permalloy or microcrystalline alloy. However, the saturation magnetic flux density of these two materials is relatively low, namely: Permalloy 0.9T, microcrystalline alloy 1.5T, and with a certain number of turns W DThe damping inductor coil 3035 is evenly wound on the damping inductor core 3033. In this embodiment, the damping inductor coil 3035 is made of polyester enameled round copper wire, and the principle for selecting the number of turns of the damping inductor coil 3035 is that when the primary voltage is FVUpr (rated voltage factor multiplied by the rated primary voltage), when the damping inductor core 3033 is not saturated, the entire damping unit will not reduce the accuracy level of the CVT.

[0070] The number of turns W of the damping reactor coil 3035 D Calculated by the following formula:

[0071] In the above formula (2), F V. is the rated voltage factor, U sr is the rated secondary voltage in V, f r is the rated frequency in Hz.

[0072] In addition, as shown in Figures 8 to 10, the damping reactor core 3033 must be annealed, and a cardboard layer is provided on the outside of the damping reactor core 3033. In this embodiment, the cardboard layer includes an outer insulating cardboard 3036 of the core, an inner insulating cardboard 3037 of the core, and an end insulating cardboard 3038 of the core provided on the upper and lower end surfaces of the core. Then, two layers of polyester film 3034 are half-stacked on the outer side of the cardboard layer as the core insulation layer. Then, the number of turns W is determined according to the above formula (2). D Polyester enameled round copper wire is wound on the damping reactor core 3033 to form the damping reactor coil 3035, and the number of turns determines the number of winding layers. The interlayer insulation layer of the damping reactor coil 3035 is made of two half-folded layers of polyester film 3034. After the winding is completed, the entire coil is wrapped with three layers of polyester film 3034 to form an external insulation layer, and then the outermost layer of the external insulation layer is half-folded with a shrink tape to form a shrink wrapping tape layer 3031. The beginning and end of the damping reactor coil 3035 are led out from the insulating tube to form the coil lead end 3032.

[0073] The present invention needs to determine the parameters of the damper body 3, wherein the damper body 3 is connected in parallel to the 1a-1n winding terminals of the intermediate transformer secondary coil 502. When the product is operating normally, the power consumption of the damper is very small and has basically no effect on the voltage error. In the ferromagnetic resonance state, the overvoltage multiple of the electromagnetic unit inside the product can reach up to 3-4 times the rated voltage. The damping inductor core 3033 of the damper body 3 is in deep saturation (at this time, the magnetic flux density of the damping inductor core 3033 is greater than 2.2T), and the inductance of the saturated damping inductor 303 drops sharply. Connecting the series resistor 301 to the loop can consume sufficient power to damp the ferromagnetic resonance. Therefore, this is also the reason why the inductor is called a saturated damping inductor 303.

[0074] The present invention can be realized according to the number of turns W of the damping reactor coil 3035 of the saturated damping reactor 303. D , the cross-sectional area of ​​the damping reactor core 3033 and the law of electromagnetic induction determine the magnetic flux density B of the damping reactor core 3033 at rated voltage D , calculated as follows:

[0075] In the above formula (3), A D is the cross-sectional area of ​​the damping reactor core 3033, in cm 2 .

[0076] The inductance L of the saturated damping reactor 303 can be calculated according to the following formula:

[0077] In the above formula (4), μ is the magnetic permeability, unit is H / m; l is the average magnetic path length of the reactor core, unit is m.

[0078] It can be seen from the calculation of the application example of the present invention described later that since the present invention selects silicon steel sheets as the damping reactor core 3033, the saturated damping reactor 303 of the present invention has very little error with the voltage transformer under the rated voltage (or 1.2 times the rated voltage), and under a resonant overvoltage of 2 times or higher, the magnetic flux density of the damping reactor core 3033 can reach deep saturation (greater than 2.2T). At this time, the magnetic permeability of the damping reactor core 3033 is close to 0, so the inductance L of the saturated damping reactor 303 is also close to 0, and the loop impedance is very small. At this time, the series resistor 301 can be used to quickly consume a large amount of power consumption to damp the ferromagnetic resonance overvoltage and enable the voltage to return to a normal level within a specified time.

[0079] The resistance R of the series resistor 301 Fs The selection range is calculated as follows:

[0080] In the above formula (5), ω is the rated angular frequency, n is the number of subharmonics, U C is the rated voltage of the intermediate transformer 5, and C1 and C2 are the rated capacitances of the intermediate transformer 5.

[0081] In addition, for the series resistor 301 and the parallel resistor 302, since a large amount of power is absorbed and a large amount of heat is generated when damping ferromagnetic resonance, their structural heat dissipation performance is required to be good, and at the same time, the change of their resistance value should be within a very small range at any temperature, so that they can effectively damp ferromagnetic resonance, that is, the resistance is required to have a low temperature coefficient. The present invention requires that the temperature coefficient of the series resistor 301 and the parallel resistor 302 is 25ppm / K~100ppm / K. In addition, in order to meet the ground insulation requirements, the ground insulation resistance of the series resistor 301 and the parallel resistor 302 is ≥2000MΩ. At the same time, in order to make the damper body 3 have an excellent ferromagnetic resonance damping effect, the resistor is also required to have a strong power overload capacity. Therefore, the power overload capacity of the series resistor 301 and the parallel resistor 302 of the present invention requires that the voltage is overloaded by 10 times for 1s, the voltage is overloaded by 5 times for 5s, and the voltage is overloaded by 2 times for 3min.

[0082] Furthermore, as will be seen from the application examples described below, the resistance and power of the series resistor 301 of the present invention can be calculated by performing CVT ferroresonance transient simulation calculations using a transient program (ATP). The simulation results are consistent with actual test results, thereby simplifying the design process.

[0083] As shown in Figures 5-6 and Figures 11-12, in this embodiment, the damper body 3 is installed on a damping device bracket 308, and the damping device bracket 308 includes a support plate 3082, a support plate 3081 and a fixing plate 3083, wherein the support plate 3082 is L-shaped, including a vertical plate 30821 and a horizontal plate 30822, and a semicircular support plate 3081 is provided on one side of the vertical plate 30821, and a fixing plate 3083 is provided on the other side. The saturated damping reactor 303 is supported by the support plate 308, the series resistor 301 is provided on the horizontal plate 30822, and the parallel resistor 302 is provided on the vertical plate 30821 and is provided between the saturated damping reactor 303 and the series resistor 301. The damping device bracket 308 as a whole is fixed at a corresponding position in the oil tank 1 by the fixing plate 3083. In this embodiment, the series resistors 301 and parallel resistors 302 are respectively mounted on corresponding bases 309, which are fixed to the damping device bracket 308 via bolts. Multiple sets of mounting screw holes can be provided on the vertical plate 30821 and the horizontal plate 30822 as needed to facilitate adjustment of the positions of the series resistors 301 and parallel resistors 302. Once the positions of the series resistors 301 and parallel resistors 302 are determined, the bases 309 are fixed to the corresponding sets of mounting screw holes via bolts. Furthermore, in this embodiment, the damping device bracket 308 is made of aluminum alloy or steel plate with excellent heat dissipation properties.

[0084] As shown in Figures 1-2, 5-7 and 14, in this embodiment, one end of the damper body 3 is provided with a first lead-out wire 304 which is connected to the ln terminal of the secondary coil of the intermediate transformer 5 inside the oil tank 1, and the other end of the damper body 3 is provided with a second lead-out wire 305, and the second lead-out wire 305 is first led out to the secondary wiring board 401 on the secondary wiring box 4 of the oil tank 1 and connected to the F-end terminal, and the F-end terminal is then connected to the 1a terminal through a connecting piece 402. The connecting piece 402 is made of copper and is tin-plated or nickel-plated on the surface. This structure facilitates the installation and connection of the damper body 3 and the 1a-1n winding of the secondary coil 502 of the intermediate transformer, and it should be noted that when the product is in operation, the F terminal must be firmly connected to the 1a terminal through the connecting piece 402.

[0085] As shown in Figure 5 , in this embodiment, the ends of the first lead wire 304 and the second lead wire 305 are each provided with a terminal lug 306 for easy connection. Furthermore, as shown in Figure 6 , in this embodiment, the lower side of the saturated damping reactor 303 is supported by the support plate 3081 and secured to the damping device bracket 308 using a binding strap 307 with an insulating tube attached to the outside.

[0086] As shown in Figures 1-2 and 13-14, the capacitive voltage divider 6 used in conjunction with the present invention includes capacitors C1 and C2, and the compensating inductor 2, intermediate transformer 5 and damper body 3 of the present invention used in conjunction with the present invention are all arranged in the oil tank 1. The electrical connection relationship between the above-mentioned various parts is shown in Figure 13, which is a well-known technology in the art.

[0087] The working principle of the present invention is:

[0088] The present invention comprises the following steps when being designed:

[0089] Step 1: Design the intermediate transformer 5. Determine the rated magnetic flux density B of the intermediate transformer 5. m ≤0.5T, the calculation formula is as follows:

[0090] In the above formula (1), U sr is the rated secondary voltage; f r is the rated power; A Fe is the cross-sectional area of ​​the intermediate transformer core 503; W2 is the number of turns of the intermediate transformer secondary coil 502.

[0091] Step 2: Design the saturated damping reactor 303 in the damper body 3 and determine its relevant parameters.

[0092] The saturation damping reactor 303 includes a damping reactor core 3033 and a damping reactor coil 3035, wherein the damping reactor core 3033 is annular and is made of silicon steel sheets with high saturation magnetic flux density, and the saturation magnetic flux density of the silicon steel sheets needs to be 2.2T, specifically:

[0093] First determine the number of turns W of the damping reactor coil 3035 D , the calculation formula is as follows:

[0094] In the above formula (2), F V. is the rated voltage factor.

[0095] Then according to the number of turns W of the damping reactor coil 3035 D The magnetic flux density B of the damping reactor core 3033 at rated voltage is determined by the cross-sectional area AD of the damping reactor core 3033. D , the calculation formula is as follows:

[0096] Finally, the inductance L of the saturated damping reactor 303 is determined, and the calculation formula is as follows:

[0097] In the above formula (4), μ is the magnetic permeability; l is the average magnetic path length of the reactor core.

[0098] In addition, the inductive reactance of the reactor can be obtained through the above-mentioned inductance L, and then the power consumption of the secondary damper circuit can be determined based on the inductive reactance, and then the impact on the error performance of the voltage transformer under rated voltage can be determined. This is a well-known technology in the field.

[0099] Step 3: Determine the parameters of the series resistor 301 in the damper body 3.

[0100] Step 3.1: Determine the resistance R of the series resistor 301 Fs Select the range and the calculation formula is as follows:

[0101] In the above formula (5), ω is the rated angular frequency, n is the number of subharmonics, U C is the rated voltage of the intermediate transformer 5, and C1 and C2 are the rated capacitances of the intermediate transformer 5.

[0102] Step 3.2: Determine other parameter conditions of the series resistor 301, including that the temperature coefficient of the series resistor 301 is 25ppm / K to 100ppm / K, the insulation resistance of the series resistor 301 to ground is ≥2000MΩ, and the series resistor 301 is overloaded for 1 second at 10 times the voltage, for 5 seconds at 5 times the voltage, and for 3 minutes at 2 times the voltage.

[0103] Step 3.3: Based on the conditions determined in Steps 3.1 and 3.2, a transient simulation calculation of ferromagnetic resonance is performed on the CVT using a transient program (ATP), thereby ultimately determining the resistance value of the series resistor 301. Using the transient program (ATP) to perform a ferromagnetic resonance transient simulation calculation on a CVT is a well-known technique in the art.

[0104] Step 4: Determine the resistance and power of the parallel resistor 302 based on the secondary rated voltage and rated voltage factor at the connection between the damper body 3 and the windings 1a-1n. This is known in the art. The parallel resistor 302 must meet a temperature coefficient of 25ppm / K to 100ppm / K, an insulation resistance to ground ≥ 2000MΩ, and withstand an overload of 10 times the voltage for 1 second, 5 times the voltage for 5 seconds, and 2 times the voltage for 3 minutes.

[0105] Two application examples are listed below for further explanation.

[0106] Application example 1: 220kY capacitor voltage transformer ferromagnetic resonance damper device.

[0107] The parameters of this application example are detailed in Table 1 below:

[0108] Table 1 Parameters of 220kV capacitor voltage transformer

[0109] This application example first determines the rated magnetic flux density of the product's intermediate transformer core. The rated primary voltage of this product is kV, and the voltage is divided by a capacitive voltage divider. The rated medium voltage is 10kV, that is, the rated primary voltage of the intermediate transformer of the electromagnetic unit is 10kV. In order to ensure that the turn potential of the coil is ≤1V under the rated voltage of the intermediate transformer and the magnetic flux density in the iron core is relatively low, the cross-section of the intermediate transformer core is first selected as AFe=90.2cm2, and the number of secondary turns is W2=60 turns.

[0110] Substituting the above known parameters into the above formula (1), the magnetic flux density of the intermediate transformer core at rated voltage is calculated to be B m =0.5T.

[0111] Then the damper parameters are determined. The product first calculates the number of turns W of the damping reactor coil according to the above formula (2): D = 193 turns, and determine the cross-section AD of the reactor core to be 10.2 cm2, then substitute it into the above formula (3) to calculate the magnetic flux density B of the reactor core at rated voltage D =1.38T.

[0112] The core material of the damping reactor selected by the present invention is silicon steel sheet, which has the following properties: D=1.38T, the magnetic permeability is 0.04125H / m. Substituting it into the above formula (4), the inductance L of the reactor is calculated to be 5.52H, and the inductive reactance is 1732Ω. The inductive reactance is very large, and the power consumption of the secondary damper circuit is correspondingly very small, about 1.8VA. Therefore, at the rated voltage, it has no effect on the error performance of the voltage transformer.

[0113] In addition, the magnetic flux density B of the reactor core of the damper at rated voltage D =1.38T, then under a resonant overvoltage of 2 times or higher, the magnetic flux density in the iron core can reach deep saturation, that is, much greater than 2.2T. At this time, the magnetic permeability of the iron core is close to 0, so the inductance of the inductor is also close to 0, and the impedance of the loop is very small. At this time, the series resistor 301 can be used to quickly consume a large amount of power and damp the ferromagnetic resonance overvoltage, and the voltage can return to normal level within the specified time.

[0114] According to the above formula (5), the resistance R of the series resistor 301 is calculated as Fs In this application example, according to the actual situation, the ferromagnetic resonance waveform is 1 / 3 harmonic, so n=3 in the above formula (5). Substituting other parameters into the above formula (5), we can calculate R Fs ≤5.2Ω. Obtain the resistance R of the series resistor 301 Fs After the selection range is determined, the transient program (ATP) is used to perform ferromagnetic resonance transient simulation calculation on the CVT, and finally the damping resistance value of the series resistor 301 is determined.

[0115] This application example uses the transient program (ATP) to simulate the ferromagnetic resonance transient of a capacitive voltage transformer (CVT) using a series resistor 301. Simulations are performed at 0.8, 1.0, 1.2, and 1.5 times the rated primary voltage, and the damping resistor value is selected. This method is fast and accurate. This simulation method is consistent with the actual core resonance test method, using a secondary terminal short circuit for a time greater than 0.1s to simulate the waveforms before and after the secondary short circuit, allowing for checking the duration of ferromagnetic resonance after the short circuit is closed. This application example calculates four primary voltages: 0.8Upr, 1.0Upr, 1.2Upr, and 1.5Upr. For each primary voltage, 40 simulated waveforms are calculated, each with a closing time of 0.001s after the secondary short circuit, for a total of 160 waveforms calculated for the four voltages. Due to the large number of graphs, only one waveform is listed under each voltage in this application example. FIG15 is a secondary voltage waveform diagram of the ferromagnetic resonance simulation calculation of the 220kY capacitor voltage transformer, and FIG16 is an actual ferromagnetic resonance test waveform diagram of the 220kY capacitor voltage transformer. Comparison of the two graphs shows that the present invention can obtain a product that meets the requirements through simulation calculation, and the present invention no longer needs to rely on past experience to select the resistance value and then conduct actual test adjustment, but can directly obtain the resistance value accurately through simulation, thereby improving design efficiency.

[0116] Application example 2: 35kY capacitor voltage transformer ferromagnetic resonance damper device.

[0117] The parameters of this application example are detailed in Table 2 below.

[0118] Table 2 Parameters of 35kV capacitor voltage transformer

[0119] For this 35kY capacitor voltage transformer product, the neutral point grounding mode of its operation is non-effective grounding mode, and the rated voltage factor is 1.9 times / 8 hours, which is much larger than the rated voltage factor (1.5 times / 30s) of the 220kY capacitor voltage transformer in application example 1. In order to ensure the product's error performance and suppress the ferromagnetic resonance performance, the magnetic flux density in the intermediate transformer core is further reduced. While maintaining the cross-section of the intermediate transformer core (AFe = 90.2cm 2 ) remains unchanged, the number of secondary turns is adjusted to W2 = 70 turns. According to the above formula (1), it can be calculated that at the rated voltage, the magnetic flux density in the core of the intermediate transformer of this application example is 0.43T.

[0120] Then, the damper parameters are determined. The core cross-section of the saturated damping reactor in this application example is consistent with that in the previous application example. According to the above formula (2), the number of turns of the damping reactor coil W is determined by substituting the known parameters. D = 244 turns, so in actual production, according to the secondary voltage Usr And the overvoltage factor F V , just need to adjust the number of coil turns.

[0121] According to the above formula (5), the series resistor R can be obtained by substituting the parameters into Fs The selection range is ≤2.56Ω, and then the transient program (ATP) is used to perform ferromagnetic resonance transient simulation calculation to finally determine the resistance value of the damping resistor.

[0122] The simulation method of this application example is the same as that of application example 1, but this application example simulates and calculates four cases: 0.8Upr, 1.0Upr, 1.2Upr, and 1.9Upr (application example 1 is 1.5Upr). Figure 17 is a secondary voltage waveform diagram of the ferromagnetic resonance simulation calculation of the 35kY capacitor voltage transformer, and Figure 18 is an actual ferromagnetic resonance test waveform diagram of the 35kY capacitor voltage transformer. Comparison of the two figures shows that the present invention can obtain a product that meets the requirements through simulation calculation and improves design efficiency.

Claims

1. A CVT ferromagnetic resonance damper device, characterized in that: The invention comprises a damper body (3), and the damper body (3) is connected in parallel with the 1a-1n winding in the secondary coil of the intermediate transformer (5), and the damper body (3) comprises a series resistor (301), a parallel resistor (302) and a saturated damping reactor (303), wherein the series resistor (301) and the saturated damping reactor (303) are connected in series and then connected in parallel with the parallel resistor (302), and one end of the parallel resistor (302) and the series resistor (301) are both connected to the 1a end of the 1a-1n winding, and the other end of the parallel resistor (302) and the saturated damping reactor (303) are both connected to the 1n end of the 1a-1n winding, and the rated magnetic flux density B of the intermediate transformer (5) is m ≤0.5T, the saturated damping reactor (303) comprises a damping reactor core (3033) and a damping reactor coil (3035) wound on the damping reactor core (3033), and the damping reactor core (3033) is made of silicon steel sheets with a saturation magnetic flux density of 2.2T.

2. The CVT ferromagnetic resonance damper device according to claim 1, characterized in that: The damping reactor core (3033) is annular and is provided with a paperboard layer on the outside, an iron core insulation layer is provided on the outside of the paperboard layer, and the damping reactor coil (3035) is wound on the iron core insulation layer, an interlayer insulation layer is provided between adjacent layers of the damping reactor coil (3035), an external insulation layer is provided on the outside of the damping reactor coil (3035), and a shrink wrapping tape layer (3031) is provided on the outside of the external insulation layer, and the start and end of the damping reactor coil (3035) are led out to form a coil lead outlet (3032).

3. The CVT ferromagnetic resonance damper device according to claim 2, characterized in that: The paperboard layer comprises an outer insulating paperboard (3036) of the core, an inner insulating paperboard (3037) of the core and an end insulating paperboard (3038) of the core. The core insulating layer, the interlayer insulating layer and the outer insulating layer are all made of polyester film (3034). The outermost layer of the outer insulating layer is wrapped with a shrink tape to form the shrink wrapping tape layer (3031).

4. The CVT ferroresonant damper device according to claim 2, characterized in that: The number of turns W of the damping reactor coil (3035) D Calculated according to the following formula: In the above formula (2), F V is the rated voltage factor, U sr is the rated secondary voltage, f r is the rated frequency; The magnetic flux density B of the damping reactor core (3033) D Calculated according to the following formula: In the above formula (3), A D is the cross-sectional area of ​​the damping reactor core (3033); The inductance L of the saturated damping reactor (303) is calculated according to the following formula: In the above formula (4), μ is the magnetic permeability; l is the average magnetic path length of the reactor core.

5. The CVT ferroresonant damper device according to claim 1, characterized in that: The temperature coefficient of the series resistor (301) and the parallel resistor (302) is 25ppm / K-100ppm / K, the insulation resistance of the series resistor (301) and the parallel resistor (302) to ground is ≥2000MΩ, and the power overload capacity of the series resistor (301) requires that the voltage is overloaded 10 times for 1 second, the voltage is overloaded 5 times for 5 seconds, and the voltage is overloaded 2 times for 3 minutes.

6. The CVT ferroresonant damper device according to claim 1, characterized in that: The damper body (3) is mounted on a damping device bracket (308), and the damping device bracket (308) includes a support plate (3082), a support plate (3081) and a fixing plate (3083), wherein the support plate (3082) includes a vertical plate (30821) and a horizontal plate (30822), and a semicircular support plate (3081) is provided on one side of the vertical plate (30821), and a fixing plate (3083) is provided on the other side, the saturated damping reactor (303) is supported by the support plate (3081), the series resistor (301) is provided on the horizontal plate (30822), and the parallel resistor (302) is provided on the vertical plate (30821) and is provided between the saturated damping reactor (303) and the series resistor (301).

7. The CVT ferroresonant damper device according to claim 6, characterized in that: The series resistor (301) and the parallel resistor (302) are respectively mounted on corresponding bases (309); a plurality of groups of mounting screw holes are provided on the vertical plate (30821) and the horizontal plate (30822); and the base (309) is fixed to a corresponding group of mounting screw holes by bolts.

8. The CVT ferroresonant damper device according to claim 1, characterized in that: One end of the damper body (3) is provided with a first lead wire (304) which is connected to the 1n terminal of the secondary coil of the intermediate transformer (5) inside the oil tank (1); the other end of the damper body (3) is provided with a second lead wire (305), and the second lead wire (305) is connected to the F terminal on the secondary junction box (4) of the oil tank (1); the F terminal is further connected to the 1a terminal on the secondary junction box (4) via a connecting piece (402).

9. A design method for a CVT ferroresonant damper device according to claim 1, characterized in that: The steps include: Step 1: Determine the rated magnetic flux density B of the intermediate transformer (5) m ≤0.5T, the calculation formula is as follows: In the above formula (1), U sr is the rated secondary voltage; f r is the rated power; A Fe is the cross-sectional area of ​​the core of the intermediate transformer; W2 is the number of turns of the secondary coil of the intermediate transformer; Step 2: Determine the parameters of the saturated damping reactor (303), wherein the number of turns W of the damping reactor coil (3035) is first determined. D , the calculation formula is as follows: In the above formula (2), F V is the rated voltage factor; Then according to the number of turns W of the damping reactor coil (3035) D and the cross-sectional area A of the damping reactor core (3033) D Determine the magnetic flux density B of the damping reactor core (3033) at rated voltage D , the calculation formula is as follows: Finally, the inductance L of the saturated damping reactor (303) is determined, and the calculation formula is as follows: In the above formula (4), μ is the magnetic permeability; l is the average magnetic path length of the reactor core. According to the above inductance L, determine the influence on the error performance of the voltage transformer at rated voltage; Step 3: Determine the parameters of the series resistor (301) in the damper body (3); Step 4: Determine the parameters of the parallel resistor (302) according to the secondary rated voltage and rated voltage factor at the connection between the damper body (3) and the 1a-1n windings.

10. The design method of the CVT ferroresonant damper device according to claim 9, characterized in that: In step three: Step 3.1: Determine the resistance R of the series resistor (301) Fs Select the range and the calculation formula is as follows: In the above formula (5), ω is the rated angular frequency, n is the number of sub-harmonics, and U is C is the rated voltage of the intermediate transformer (5), C1 and C2 are the rated capacitances of the intermediate transformer (5); Step 3.2: Determine other parameter conditions of the series resistor (301), including that the temperature coefficient of the series resistor (301) is 25ppm / K to 100ppm / K, the insulation resistance of the series resistor (301) to ground is ≥2000MΩ, and the power overload capacity of the series resistor (301) requires that the overload lasts for 1s when the voltage is 10 times, lasts for 5s when the voltage is 5 times, and lasts for 3min when the voltage is 2 times. Step 3.3: According to the conditions determined in step 3.1 and step 3.2, a transient program is used to perform ferromagnetic resonance transient simulation calculation on the CVT, and finally determine the resistance value of the series resistor (301).

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