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Flexible DC wall bushing monitoring device, monitoring method and fault judgment method

A wall bushing and flexible direct current technology, applied in the field of power transmission and transformation of power systems, can solve problems such as multi-screen aluminum foil electrode breakdown, electric field distortion of accessories at fault points, and large short-circuit current

Active Publication Date: 2022-05-17
EXAMING & EXPERIMENTAL CENT OF ULTRAHIGH VOLTAGE POWER TRANSMISSION COMPANY CHINA SOUTHEN POWER GRID
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The process of failure inside the bushing is as follows: First, one screen of the internal aluminum foil electrodes breaks down. After the screen breaks down, the voltage of other capacitive screens is redistributed, and the aluminum foil electrodes close to the breakdown screen are affected by the electrothermal effect of the fault point. Insulation Gradually deteriorating, and the electric field distortion near the fault point may cause breakdown of multi-screen aluminum foil electrodes, resulting in an increase in the probability of breakdown of the remaining intact capacitive screens
If the main insulating capacitive screen of the bushing is completely broken down, it will cause a penetrating discharge of the high voltage of the bushing to the ground, and a large short-circuit current will flow.
[0003] Patent No. CN106896257B is an electrical state detection system for ultra-high voltage wall bushings. It mainly detects the voltage of the external capacitor and the current of the external current transformer to monitor the state of the wall bushing. When the screen is open, the failure cannot be effectively judged, which may cause misjudgment

Method used

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  • Flexible DC wall bushing monitoring device, monitoring method and fault judgment method
  • Flexible DC wall bushing monitoring device, monitoring method and fault judgment method
  • Flexible DC wall bushing monitoring device, monitoring method and fault judgment method

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Embodiment 1

[0020] according to figure 2 As shown, this embodiment proposes a flexible DC wall bushing monitoring device, including a current transformer CT, the primary side of the current transformer CT is used to connect to the bushing main capacitor CTH of the flexible DC wall bushing, and the current The secondary side of the transformer CT is connected in parallel with the last screen-to-ground capacitor CTL, monitoring capacitor C1, monitoring capacitor C2, monitoring capacitor C3, discharge resistor R1 and varistor R2, the last screen-to-ground capacitor CTL is grounded separately, and the monitoring capacitor C1 , the monitoring capacitor C2, the monitoring capacitor C3, the discharge resistor R1 and the varistor protection resistor R2 share a common ground.

Embodiment 2

[0022] A method for monitoring harmonic voltage and capacitance of a flexible DC wall-piercing bushing, which is used in the flexible DC wall-piercing bushing monitoring device described in Embodiment 1, comprising the following steps:

[0023] Establish the analytical formula of the ground voltage of the flexible DC wall bushing;

[0024] figure 1 The analytical formula of the ground voltage of the wall-piercing bushing is:

[0025]

[0026] gamma h =hγ vx

[0027]

[0028] Among them, U dc is the DC component, U ac is the total AC harmonic component, k is any positive integer, N is any positive integer, h is the harmonic order, γ vx is the initial phase of any phase modulation wave, x=A / B / C, s is the total number of level transitions in the first 1 / 4 period, θ i is the electrical angle corresponding to the i-th level transition.

[0029] Obtain the capacitance of monitoring capacitor C1, monitoring capacitor C2, and monitoring capacitor C3, and set the capacita...

Embodiment 3

[0060] A method for judging a fault of a flexible DC wall-piercing bushing, which is used in the method for monitoring the harmonic voltage and capacitance of the flexible DC wall-piercing bushing described in Embodiment 2, and iteratively calculates the voltage of each phase at each time according to the relationship expression of each phase voltage Proportional change, the proportional change of each phase voltage at each time is compared with the breakdown capacitance of the flexible DC wall bushing to determine the fault phase of the flexible DC wall bushing.

[0061] by figure 1 Take the circuit topology as an example, the flexible DC wall bushing is installed between the converter valve and the bridge arm reactor, and the voltage here is:

[0062] where U dc / 2 is the DC component, is the total harmonic component,

[0063] Taking a flexible straight system as an example, the DC component and harmonic content of the voltage U at the flexible DC wall bushing are show...

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Abstract

The invention discloses a flexible DC wall bushing monitoring device, a monitoring method and a fault judgment method. The fault judgment method iteratively calculates the proportional change of each phase voltage at each time according to the voltage relationship expression of each phase, and calculates the proportional change of each phase voltage at each time. The proportional change of the voltage is compared with the breakdown capacitance of the flexible DC wall bushing to determine the fault phase of the flexible DC wall bushing. The beneficial effects of the present invention are: using the voltage harmonic component of the flexible DC wall bushing, using a capacitive coupling device to monitor the voltage of the end screen of the bushing in real time, and comparing the variation of the voltage value of the end screen of the three-phase flexible DC bushing at different times , to calculate the change ratio of the three-phase bushing capacitance, so as to judge whether the bushing capacitive screen is faulty.

Description

technical field [0001] The invention relates to the technical field of power transmission and transformation in electric power systems, in particular to a monitoring device, a monitoring method and a fault judgment method for a flexible DC wall bushing. Background technique [0002] The flexible DC wall bushing is used between the bridge arm reactor and the converter of the flexible DC transmission project. The operating current is the superposition of DC current and the AC circulating current of the converter, and the operating voltage is the superposition of DC voltage and circulating AC voltage drop. Taking a flexible DC project as an example, the position of the wall bushing in the flexible DC system is as follows: figure 1 The position of the ellipse is shown. The capacitor core of the flexible DC through-wall bushing adopts an epoxy resin impregnated paper structure, and the function of the aluminum foil electrode is to uniform the axial and radial electric field dist...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/50G01R19/165G01R27/26
CPCG01R31/50G01R19/165G01R27/2605Y02E60/60
Inventor 张晋寅韦晓星潘志城周海滨楚金伟邓军梁晨杨旭
Owner EXAMING & EXPERIMENTAL CENT OF ULTRAHIGH VOLTAGE POWER TRANSMISSION COMPANY CHINA SOUTHEN POWER GRID
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