Place of application 
Current transformers are used as large-scale current converters and also for supplying standard, usable currents in various monitoring, measuring and protection installations and, at the same time, for isolating protective and measuring equipment from high system voltages.
Execution
- Unom: from 110 to 750 kV
- Inom: up to 6000 A
- Short circuit: up to 100 kA (Idyn: 250 kA peak)
- Secondary cores: up to 8
- All measuring and protective accuracy classes
Primary winding
The advantage of the top-core design is that the primary winding is evenly and symmetrically positioned around the cores. This way local saturation is avoided and reactance is kept to a minimum.
In addition, this design results in minimal losses in the primary winding.
Different transformation ratios are provided through switching either on the primary (HV) or secondary (LV) winding. Switching on both sides is also possible.
When the primary winding consists of one turn, it is in the form of a rod wire. When more turns are needed, external or internal wires are used. Cores and secondary windings Up to 8 cores of different sizes and materials can be placed in the transformer.
The cores are made, depending on the required accuracy class, from cold-rolled grain-oriented magnetic steel, soft magnetic materials and non-crystal alloys.
High-quality enameled wire is evenly wound around the core to ensure minimal reactance, which, in turn, allows for accurate computer calculations of the behavior of CTs in transient states of the network (IEC accuracy classes: PR, TPS, TPX, TRU and TPZ).
Paper-oil insulation
The primary high voltage side is separated from the secondary low voltage side by paper impregnated with high dielectric strength oil.
Insulator
External insulation can be porcelain or composite. Porcelain insulators are made from the highest quality C130 alumina porcelain, and composite insulators consist of a glass fiber reinforced rubber pipe and a silicone skirt.
The creepage distance of the insulator is based on the level of ambient air pollution and is specified in the request.
Frame
The transformer body consists of a base, an insulator, a head and a bellows protective cap.
The active part of the transformer is located inside the die-cast aluminum head and is designed in such a way that the amount of oil is minimal.
The transformer base is made from high quality steel, protected by hot-dip galvanizing, and optionally repainted for long-term corrosion resistance, or from aluminum casting. A secondary terminal box is installed on the base, along with other accessories such as identification plates, an oil sample valve, lifting lugs, grounding clamps, a dissipation tangent clamp and an optional oil pressure indicator.
Clamps
Primary clamps are made of aluminum or tinned copper. The shapes and types of clamps are designed according to transformation ratios and current standards.
Standard secondary clamps are M8 threaded bolts made of stainless steel.
The secondary clamps, along with the safety devices and the custody transfer clamp seal, are located in the secondary clamp box. Glands or plates for access to the box are designed according to customer requirements.
The standard connection is screw (M12x35) or in the form of a twisted conductive copper clamp made from galvanized steel plates.
Main technical and metrological characteristics
| Characteristics | AGU-123 | AGU-170 | AGU-245 | AGU-362 | AGU-420 | AGU-765 | |
| Rated primary current: | possible options are shown in the table below | ||||||
| Rated secondary current, A | 1 and/or 5 | ||||||
| Voltage class, kV | 110 | 170 | 220 | 330 | 400 | 750 | |
| Number of secondary windings | 1 to 8 | 1 to 8 | 1 to 8 | 1 to 8 | 1 to 8 | 1 to 8 | |
| For measuring winding: | 0.2S or 0.2 | 0.5S or 0.5 | |||||
| - accuracy class / KBnom | 5 or 10 | 5 or 10 | |||||
| - rated load, VA | 2 or 5 or 10 or 20 or 30 | 10 or 20 or 30 or 40 or 50 | |||||
| For protection circuits: | 5R or 10R | ||||||
| - accuracy class | 20 or 30 | ||||||
| - maximum multiplicity | 20 or 30 or 40 or 50 or 60 or 75VA | ||||||
| - rated load, VA | |||||||
| Rated frequency, Hz | 50 | ||||||
| Operating temperature range, °C | from -60; -45; -35 to +40 | ||||||
| Temperature range during transportation, °C | from - 45 to +50 | ||||||
Standard overall and installation dimensions
| Type | Voltage class | Transformer height | Height to clamp | Fixing dimensions | Oil weight | Transformer weight | Ud. creepage distance min |
| kV | mm | mm | mm | kg | kg | mm | |
| AGU-123 | 110 | 2400 | 1925 | 400x400 | 75 | 340 | 3150 |
| AGU-170 | 170 | 2850 | 2350 | 520x520 | 85 | 420 | 4250 |
| AGU-245 | 220 | 3700 | 3050 | 520x520 | 200 | 740 | 6300 |
| AGU-362 | 330 | 4700 | 3940 | 650x650 | 320 | 1150 | 9050 |
| AGU-420 | 400 | 5400 | 4600 | 650x650 | 380 | 1300 | 10500 |
| AGU-765 | 750 | 8130 | 6940 | 900x900 | 800 | 3100 | 20000 |
The indicated informative dimensions refer to standard versions of transformers with porcelain insulators.
The final dimensions and weights of transformers depend on the specific electrical, mechanical and environmental characteristics specified in the customer's request.
Additional features
In the upper part of the current transformer type AGU-362, AGU-525 and AGU-765 you can install:
- the fixed part of the disconnector (item 1) type RPD-330; RPD-500; RPD-750
- fixed part of the ground electrode (item 2) type ZRO-330-3; ZRO-500-2; ZRO-750-2
