Simulation Study on the Effects of DC Electric Field on Insulator Surface Pollution Deposit
Abstract
:1. Introduction
2. Analysis of Insulator String Electric Field and Electric Force
2.1. Electric Field Simualtion
2.2. Electric Force Calculation
3. Effects of the DC Electric Field on the Pollution Particle’s Motion
- (1)
- Under DC electric field, their horizontal moving speed vpx does not change much, the increasing rate is only within 5%. The lower the wind speed, the higher the Δvpx values of particles. This is mainly because when wind velocity is low, the function of air drag force on the particles is weakened, in which case the electric force is relatively distinct and easily accelerates the particle motion.
- (2)
- Particles’ vertical velocity component is greatly affected by the DC electric field. The vertical component of the end speed increased by 0.5–23 times when dp is within 1–50 μm, obviously higher than that of the horizontal component. The smaller the particle diameter, the more outstanding the particle velocity increases in the vertical direction. The increasing rate drops rapidly when dp increases from 1 to 20 μm, and then remains gentle. This is mainly because gravity is proportional to the third power of dp, while the electric force is proportional to the square of dp.
- (3)
- The end speed of particles moving across electric field is associated with the colliding position. The increasing rate of the particles’ end speed is higher if the colliding position is closer to the insulator string (such as A1). This is because it takes a longer time and distance for particles to get closer to the insulator string, in which case the electric force will have a greater effect on the particles’ motion.
4. Effects of DC Electric Field on the Insulator Pollution Degree
- (1)
- The ratio ck presents a decreasing trend with the increment of wind speed, which means the higher the wind speed, the weaker the DC electric field aggravating pollution degree. This is due to higher wind speed, resulting in larger air drag force, which obscures the electric field force.
- (2)
- Additionally, the ratio ck varies obviously with particle diameter dp. The value of the particle capture coefficient ratio ck when dp is 50 μm is always the lowest compared to other conditions (dp = 1 μm, 5 μm, 10 μm, 20 μm), meaning that the DC electric field has less of an effect on the pollution increment when the particle diameter is larger, which is in good accordance with previous analyses. Combined with the results shown in Figure 5, it can be deduced that the critical particle diameter when the air flow field controls the pollution particle deposition more than the DC electric field may be close to 20 μm.
- (3)
- The particle capture coefficient ratio ck is in the range of 1.04 to 1.98 when dp is within 1–50 μm and the wind velocity within 1–5 m/s, very close to the field measurement results of the DC pollution ratio k (within 1.2–1.7), as shown in Table 2. In such a case ck can be used to reflect the pollution degree increment of insulators under DC. In this way the complicated field measurement work can be saved to some degree.
5. Conclusions
- (1)
- The main function of the electric field on insulator contamination is that it changes the particles’ vertical motion during its deposition process from outside to the insulator’s surface, especially when dp is within 1–20 μm. The particle’s vertical speed can increase to 0.5–23 times by electric force, which significantly accelerates the particles’ deposition process and benefits contamination.
- (2)
- The particle capture coefficient ratio ck of DC to non-energized conditions is in the range of 1.04 to 1.98 when dp is within 1–50 μm and wind velocity is within 1–5 m/s, very close to the one-year period field test results of the DC pollution ratio k (within 1.2–1.7) for the ±800 kV line.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Insulator Type | Structure Height (mm) | Shed Diameter (mm) | Creepage Distance (mm) |
---|---|---|---|
XP-160 | 155 | 255 | 305 |
Tower Number | DC-Energized String | Non-Energized String | DC Pollution Ratio k | |||
---|---|---|---|---|---|---|
ESDD | NSDD | ESDD | NSDD | By ESDD | By NSDD | |
No. 1 | 0.075 | 0.245 | 0.049 | 0.165 | 1.52 | 1.48 |
No. 2 | 0.031 | 0.097 | 0.024 | 0.119 | 1.24 | 0.81 |
No. 3 | 0.055 | 0.195 | 0.035 | 0.115 | 1.58 | 1.69 |
Wind Velocity | Particle Capture Coefficient Ratio ck | ||||
---|---|---|---|---|---|
dp = 1 μm | dp = 5 μm | dp = 10 μm | dp = 20 μm | dp = 50 μm | |
VC = 1 m/s | 1.28 | 1.47 | 1.76 | 1.98 | 1.26 |
VC = 2 m/s | 1.17 | 1.42 | 1.72 | 1.62 | 1.13 |
VC = 5 m/s | 1.11 | 1.14 | 1.26 | 1.12 | 1.04 |
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Zhang, D.; Zhang, Z.; Jiang, X.; Shu, L.; Wu, B. Simulation Study on the Effects of DC Electric Field on Insulator Surface Pollution Deposit. Energies 2018, 11, 626. https://doi.org/10.3390/en11030626
Zhang D, Zhang Z, Jiang X, Shu L, Wu B. Simulation Study on the Effects of DC Electric Field on Insulator Surface Pollution Deposit. Energies. 2018; 11(3):626. https://doi.org/10.3390/en11030626
Chicago/Turabian StyleZhang, Dongdong, Zhijin Zhang, Xingliang Jiang, Lichun Shu, and Bin Wu. 2018. "Simulation Study on the Effects of DC Electric Field on Insulator Surface Pollution Deposit" Energies 11, no. 3: 626. https://doi.org/10.3390/en11030626