Lightning Impulse Breakdown Characteristics and Electrodynamic Process of Insulating Vegetable Oil-Based Nanofluid

Abstract

Insulating vegetable oils are considered environment-friendly and fire-resistant substitutes for insulating mineral oils. This paper presents the lightning impulse breakdown characteristic of insulating vegetable oil and insulating vegetable oil-based nanofluids. It indicates that Fe 3 O 4 nanoparticles can increase the negative lightning impulse breakdown voltages of insulating vegetable oil by 11.8% and positive lightning impulse breakdown voltages by 37.4%. The propagation velocity of streamer is reduced by the presence of nanoparticles. The propagation velocities of streamer to positive and negative lightning impulse breakdown in the insulating vegetable oil-based nanofluids are 21.2% and 14.4% lesser than those in insulating vegetable oils, respectively. The higher electrical breakdown strength and lower streamer velocity is explained by the charging dynamics of nanoparticles in insulating vegetable oil. Space charge build-up and space charge distorted filed in point-sphere gap is also described. The field strength is reduced at the streamer tip due to the low mobility of negative nanoparticles.

Influence of Monodisperse Fe3O4 Nanoparticle Size on Electrical Properties of Vegetable Oil‐Based Nanofluids

“…For positive lightning-impulse, nanoparticles in nanofluids will weaken the field strength and extremely increase positive breakdown voltages. However, the effect is inconspicuous for negative lightning-impulse [4]. Our results point out an opposite tendency with the breakdown behavior that has been observed in mineral oil-based nanofluids [1,8].…”

“…Recent research works have shown that conductive and semiconductive nanoparticles can be dispersed in mineral and vegetable insulating oils to enhance dielectric strength or thermal conductivity of the insulating oils. Magnetic Fe 3 O 4 nanoparticles have been proved of increasing the AC breakdown voltage of insulating oils for the case that the nanoparticles were well dispersed in oil [1][2][3][4][5]. It is also documented that both mineral and vegetable insulating oils are possible to show enhanced AC breakdown voltages and partial-discharge-inception voltages after the oils are modified by semiconductive TiO 2 nanoparticles [6,7].…”

Enhanced Electrical Insulation and Heat Transfer Performance of Vegetable Oil Based Nanofluids

“…The increase in positive impulse breakdown voltage of the nano-oil was larger than the negative one. This phenomenon can be explained by space charge theory [23,29]. In the positive polarity model (Figure 11), some electrons near the positive-electrode were captured by nanoparticles.…”

“…Compared with mineral oil, vegetable insulating oil has a higher AC and DC breakdown voltage [22]. The addition of a certain amount of magnetic conductive nanoparticles, Journal of Nanomaterials such as Fe 3 O 4 , to either vegetable insulating oil, improves its positive (∼37.4%) and negative (∼11.8%) lighting impulse breakdown voltages [23]. In addition, nanoparticles can form negatively charged particles in a short time period and consequently affect the development of the streamer.…”

Nanofluids in the Service of High Voltage Transformers: Breakdown Properties of Transformer Oils with Nanoparticles, a Review

“…Li et al [111] studied nanoparticles of Fe 3 O 4 with a modified surface by oleic acid suspended in vegetable oil (rapeseed oil). The average size of used nanoparticles was 30 nm in diameter.…”