|
| Property |
Transformer
Oil | Cable Oil |
Capacitor
Oil | Askarels |
Silicone Oils |
|---|
| Breakdown strength
(20 C, 2.5mm sphere
gap) | 150 |
300 |
200 |
200-250 |
300-400 |
|---|
| Relative Permittivity
(50Hz) | 2.2-2.3 |
2.3-2.6 |
2.1 |
4.8 |
2-73 |
|---|
| Loss Tangent (50Hz) |
.001 |
.002 |
0.25E-3 |
0.60E-3 |
.001 |
|---|
| Loss Tangent (1 kHz) |
.0005 |
.0001 |
0.10E-3 |
0.50E-3 |
0.1E-3 |
|---|
| Resistivity (Ohm -cm) |
1e12-1e13 |
1e12-1e13 |
1e13-1e14 |
2e12 |
3e14 |
|---|
| Specific Gravity at 20
C | 0.89 |
0.93 |
0.88-0.89 |
1.4 |
1.0-1.1 |
|---|
| Viscosity at 20 C
(cStokes) | 30 |
30 |
30 |
100-150 |
10-1000 |
|---|
| Refractive Index |
1.4820 |
1.4700 |
1.4740 |
1.6000 |
1.5000-1.6000 |
|---|
| Saponification |
0.01 |
0.01 |
0.01 |
<0.01 |
<0.01 |
|---|
| Thermal Expansion |
7e-4/deg |
7e-4 |
7e-4 |
7e-4 |
5e-4 |
|---|
| Max permissible
Water content (ppm) |
50 | 50 |
50 |
<30
negligble | <30
negligible |
|---|
Pure Liquids
Pure liquids often have much higher breakdown strengths than commercial liquids. For instance, the
addition of 0.01% water to insulating oil reduces its breakdown strength to 20% of the "dry" value.
Compare, for example, the breakdown for Transformer Oil is usually taken as 150 kV/cm (see
above table), but when highly purified, it is almost 8 times that, or 1000 kV/cm.
|
Liquid |
Max Breakdown Strength
MV/cm |
|---|
| Hexane | 1.1-1.3 |
| Benzene | 1.1 |
| Transformer Oil | 1.0 |
| Silicone | 1.0-1.2 |
| Liquid Oxygen | 2.4 |
| Liquid Nitrogen | 1.6-1.9 |
| Liquid Hydrogen | 1.0 |
| Liquid Helium | 0.7 |
| Liquid Argon | 1.10-1.42 |
|