Cores and secondary windings are located inside the head of the transformer. High voltage insulation is entirely obtained in SF6 gas instead of paper-oil.
Considerable and numerous advantages are gained thanks to this solution:
- The dielectric quality no longer depends on complex and lengthy treatments then followed by delicate checks. In particular, monitoring partial discharges has become meaningless, since the only solid dielectric medium which might be subject to ageing is the external porcelain insulator;
- The internal discharges can practically be excluded because of the coordination selected for insulation and the gaseous nature of the internal dielectric medium. The specific characteristics of SF6 gas are such as to considerably limit the consequences of any discharges;
- The presence of a device with a pre-set rupture point protects the transformer against overpressures;
- The level of internal insulation can be continuously monitored remotely by means of a densimeter with contacts, fitted with an alarm and trip threshold for minimum SF6 gas pressure.
These many kinds of TG are available
| Type | Maximum System voltage |
| TG 72.5 | 72,5 kV |
| TG 145 | 145 kV |
| TG 170 | 170 kV |
| TG 245 | 245 kV |
| TG 362 | 362 kV |
| TG 420 | 420 kV |
| TG 550 | 550 kV |
| TG 800 | 800 kV |
Technical characteristics
| System voltages | 72.5 kV - 800 kV |
| Insulation level | up to 2100 kV |
| Rated primary current | up to 4000 A *) |
| Rated secondary current | 1 A or 5 A |
| Rated short-circuit current | Thermal (1 s) = up to 63 kA *) - Dynamic = up to 170 kA *) |
| Accuracy | All IEC and IEEE metering and protection classes, including special cores type TPS, TPX, TPY and TPZ. |
*) Depends on number of primary turns. Please refer to our TG brochure for detailed technical data.