Page 499 - Book Hosokawa Nanoparticle Technology Handbook

13 ENHANCEMENT OF THE PERFORMANCE OF INSULATING MATERIALS APPLICATIONS
particles, as seen in Fig. 13.4. This phenomenon was
reportedly attributable to the existence of submicron-
Positive electrode
sized void-like defects near the nanoparticles, which
enlarged the damage process zone at the tip of the
Negative electrode
electric tree and hindered the tree progress.
Tip electric field (kV/mm) 600 (a)
700
500
400
300
(a) In case of micron particles 200 (b)

Negative electrode Positive electrode 100 1 10 100 1000 10000
Lifetime (h)

Figure 13.2
Withstand voltage characteristics of epoxy resin dispersed
with TiO particles [4]: (a) Nanoparticles, (b) micron particles.
2
Time until electrical breakdown (s) 1000 6

(b) In case of nanoparticles 4 2

Figure 13.1
Distributions of voltage, electric charge and field of epoxy 4
resin dispersed with TiO particles [3]. (V: Electric voltage 2
2
3
[kV], : Electric charge[C/m ], E: Electric field [kV/mm]). 100
Following the withstand voltage test, conducted on 0wt% 5wt%
2 3
the above-mentioned sample under an alternating Al O particle addition
voltage of 60 Hz, the lifetime was extended about 100
times using nanoparticles compared to the case where Figure 13.3
micron particles were used at a voltage of 400 Time to reach the electrical breakdown of epoxy resin with
kV/mm, as seen in Fig. 13.2 [4]. This is regarded as Al O particle addition [5].
2
3
attributable to the reduction of internal charge, which
causes insulating materials to deteriorate at the inter- 12000
face between the resin and particles. znO, 1 μm
znO, 65 nm
On the other hand, there is a report where Al O 3 10000
2
particles 10nm in size were added to epoxy resin [5].
Following the withstand voltage tests, conducted on 8000
the material under the alternating voltage of 60 Hz,
the time required to reach the insulation breakdown Time until electrical breakdown (min) 6000
was found to nearly double with the addition of 5 wt%
Al O compared with the epoxy resin, as shown in 4000
2
3
Fig. 13.3. This was explained by the progress of the
electric trees being hindered by the nanoparticles. 2000 Sample age = 10 days
In another report [6], the properties were measured AC voltage = 10 kV
using two kinds of ZnO, of particle sizes 1 m and 0
65 nm, which were added to epoxy resin. The with- 0.0 0.2 0.4 0.6 0.8 1.0
stand voltage test under an alternating voltage of ZnO particle loadings (wt %)
50 Hz showed that the time to the insulation
breakdown increased with the increasing addition of Figure 13.4
ZnO and that it doubled when nanosized particles Time to reach the electrical breakdown of epoxy resin with
were used, compared to the case using micron-sized ZnO particle addition [6].
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