Inductive Combined Transformer EJOF
Combined instrument transformers type EJOF are used in high voltage networks within the 24-170 kV range. They transform high voltage and high current into standardised values for meters, measuring and protection devices.
The inner construction of a combined instrument transformer is similar to the construction of the current and voltage transformer. The current transformer is located in the head and the voltage transformer in the bottom housing of the combined instrument transformer. The fine graded bushings are inside the insulator.
The high voltage insulation is based on oil-paper technology. High-grade, PCB-free mineral oil is used.
The expansion bellows made from stainless steel is located above the head housing of the combined instrument 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 combined instrument 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 atmospheric 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
- Reduced transport costs with one unit instead of two
- Less space needed with just one footprint
- Lower material costs due to a reduced number of supports and fewer primary connections
- Lower installation effort as only one unit has to be installed instead of two
Specifications and Downloads
Technical Specifications
Dimensions
Technical data
Type EJOF | 24 | 36 | 72 | 123 | 145 | 170 | |
| Standard | IEC / IEEE | ||||||
| Highest voltage for equipment | kV | 24 | 36 | 72.5 | 123 | 145 | 170 |
| Rated power-frequency withstand voltage | kV | 50 | 70 | 140 | 230 | 275 | 325 |
| Rated lightning impulse withstand voltage | kV | 125 | 170 | 325 | 550 | 650 | 750 |
| Frequency | Hz | 16.7 / 50 / 60 | |||||
| Primary rated current | A | ≤ 5000 | |||||
| Secondary rated current | A | 1 / 5 | |||||
| Rated short-time thermal current [Ith] | kA / 1s | ≤ 63 | |||||
| Rated dynamic current [Idyn] | kA | ≤ 160 | |||||
| Accuracy class CT part | 0.1-3; 0.2S; 0.5S; P; PR; PX; PXR; TPX; TPY; TPZ | ||||||
| Accuracy class VT part | 0.1-3; 3P; 6P | ||||||
| Rated thermal limiting output VT part | VA | ≤ 1500 | ≤ 3000 | ||||
| Max. simultaneous burden (cl. 0.2) | VA | 200 | 300 | ||||
| Max. number of CT cores | 7 | ||||||
| Max. number of VT windings | 5 | ||||||
Type EJOF | 24 | 36 | 72 | 123 | 145 | 170 | ||
| Height of unit* | A | mm | 1591 | 1591 | 1791 | 2484 | 2659 | 2929 |
| Height to primary terminal* | B | mm | 1145 | 1145 | 1345 | 2038 | 2203 | 2503 |
| Depth of unit including terminal box | C | mm | 526 | 526 | 526 | 710 | 710 | 730 |
| Depth of unit base | D | mm | 360 | 360 | 360 | 500 | 500 | 500 |
| Width of unit base | E | mm | 360 | 360 | 360 | 520 | 520 | 520 |
| Distance between screw holes at base | F | mm | 310 | 310 | 310 | 450 | 450 | 450 |
| Min. creepage distance* |
| mm | 1040 | 1040 | 1900 | 3080 | 3770 | 4394 |
| Approximate weight* |
| kg | 295 | 295 | 470 | 500 | 515 | 550 |
*with standard composite silicone insulator, creepage distance 25 mm/kV
