Inductive Current Transformer JOF
Oil-paper insulated outdoor current transformers type JOF are used in high voltage networks within the 24-550 kV range. They transform high current into standardised values for meters, measuring and protection devices.
The active part of the current transformer is located in the head housing. Based on customer specifications, the optimum design is calculated and the corresponding head housing is determined.
The high voltage insulation is based on oil-paper technology. High-grade, PCB-free mineral oil is used. The fine graded bushing is inside the insulator.
The expansion bellows made from stainless steel is located above the head housing of the current transformer. This unit acts as volume compensation for the oil in case of temperature variations. The oil level is indicated by a mechanical system in the window of the bellows cover.
All metal housings and flanges are made from a special aluminium alloy. These parts can be colour coated on request.
All current transformers have either a high-quality porcelain or a high-grade silicone composite insulator. Different creepage distances are available according to the different pollution classes, as specified in the standards.
The hermetic sealed housing protects the oil-paper insulation against atmos- pheric influences.
The generously sized terminal box has a cover which can be opened sidewards. This allows easy connection of the secondary cables. The terminal box has a flange without holes by default. Cable glands, circuit diagram and individual safety instructions can be preinstalled on request.
Features
- Precise electric field control and prevention of local partial discharges through fine graded bushing
- Higher safety through prevention of subsequent arcing
- High operating safety as there are no active parts in the insulator
- Minimum oil volume through optimised design
Specifications and Downloads
Technical Specifications
Dimensions
Technical data
Type JOF | 24 | 36 | 72 | 123 | 145 | 170 | 245 | 362 | 420 | 550 | |
| Standard | IEC / IEEE | ||||||||||
| Highest voltage for equipment | kV | 24 | 36 | 72.5 | 123 | 145 | 170 | 245 | 362 | 420 | 550 |
| Rated power-frequency withstand voltage | kV | 50 | 70 | 140 | 230 | 275 | 325 | 460 | 510 | 630 | 680 |
| Rated lightning impulse withstand voltage | kV | 125 | 170 | 325 | 550 | 650 | 750 | 1050 | 1175 | 1425 | 1550 |
| Frequency | Hz | 16.7 / 50 / 60 | |||||||||
| Primary rated current | A | ≤ 4000 | |||||||||
| Secondary rated current | A | 1 / 5 | |||||||||
| Rated short-time thermal current [Ith] | kA / 1s | ≤ 63 | |||||||||
| Rated dynamic current [ldyn] | kA | ≤ 160 | |||||||||
| Accuracy class | 0.1-3; 0.2S; 0.5S; P; PR; PX; PXR; TPX; TPY; TPZ | ||||||||||
| Max. number of CT cores | 7 | ||||||||||
Type JOF | 24 | 36 | 72 | 123 | 145 | 170 | 245 | 362 | 420 | 550 | ||
| Height of unit* | A | mm | 1632 | 1632 | 1782 | 2256 | 2532 | 2631 | 3912 | 4440 | 4944 | 5644 |
| Height to primary terminal* | B | mm | 1186 | 1186 | 1336 | 1810 | 2086 | 2185 | 3248 | 3776 | 4280 | 4980 |
| Depth of unit including terminal box | C | mm | 725 | 725 | 725 | 725 | 725 | 725 | 851 | 851 | 851 | 851 |
| Depth of unit base | D | mm | 500 | 500 | 500 | 500 | 500 | 500 | 650 | 650 | 650 | 650 |
| Width of unit base | E | mm | 500 | 500 | 500 | 500 | 500 | 500 | 700 | 700 | 700 | 700 |
| Distance between screw holes at base | F | mm | 450 | 450 | 450 | 450 | 450 | 450 | 600 | 600 | 600 | 600 |
| Min. creepage distance* |
| mm | 1340 | 1340 | 1950 | 3080 | 3900 | 4394 | 8250 | 10230 | 11600 | 15260 |
| Approximate weight* |
| kg | 220 | 220 | 230 | 285 | 295 | 300 | 830 | 800 | 900 | 1000 |
*with standard composite silicone insulator, creepage distance 25 mm/kV
