Inductive voltage transformers from 110 to 500 kV type VPU

Place of application

Voltage transformers are used as large-scale voltage converters and also for supplying standard, usable voltages in various monitoring, measuring and protection installations and, at the same time, for isolating protective and measuring equipment from high system voltages. 

Main features

• Unom: from 110 to 500 kV
• Up to 6 secondary windings
• All measuring and protective accuracy classes
• Unique open-circuit design provides resistance to ferroresonance
• Explosion-proof design
• Maintains the required accuracy class throughout the entire service life
• High quality paper-oil insulation
• Oil expansion compensation system with stainless steel bellows
• Hermetically sealed
• Standard climatic version -45 to +40 °C (more extreme climatic versions on request)
• Porcelain or composite insulators of the highest quality
• Extensive experience in application in seismically active regions
• Low-oil version without PCBs - does not harm the environment
• Corrosion resistance
• Maintenance free
• No partial discharges at power frequency test voltages

Additional options

Clamp for measuring the dielectric dissipation tangent
Oil indicator
Fuses or microswitches for protecting secondary windings (optional)
Secondary terminals for custody transfer can be separately sealed
Transport shock indicators (standard for Unom ≥ 330 kV, optional for other voltage classes)
Internal overpressure indicator ( to choose from)

Quality assurance

KONCAR voltage transformers are manufactured in accordance with all current international standards GOST, IEC and others.
The quality of products is ensured by a certified quality system - ISO 9001, covering all aspects of development, production and testing.
Koncar-Instrument transformers Inc. has ISO 14001 and OHSAS 18001 certificates, certifying compliance with environmental and labor protection standards.

Magnetic core and secondary windings

The rod-type magnetic core is made of sheets of electrical steel. The design of the open magnetic circuit ensures linear magnetization characteristics of the transformer, thereby eliminating the possibility of ferroresonance within the network.
The secondary windings, made of high-quality enameled copper wire, are wound directly around the magnetic core and ensure uniform distribution of the magnetic field along the height of the magnetic core. In addition, the large cross-section of the windings makes the transformer resistant to short circuits, which makes it even more explosion-proof. The design of the active part allows the provision of up to 6 secondary windings of any accuracy class for measurement and/or protection. Double transformation ratios can be achieved through taps on the secondary windings.

Paper-oil insulation

The primary high voltage side is separated from the secondary low voltage side by paper impregnated with high dielectric strength oil.
A significant number of conductive capacitive screens are laid within layers of paper insulation to provide suitable distribution of high frequency surges. The paper insulation is then dried in a high vacuum and impregnated with high quality inhibited and degassed (moisture content less than 2 pm) mineral oil.
Oil-paper insulation is hermetically sealed without contact with the surrounding air. A stainless steel bellows compensates for the thermal expansion of the oil and also indicates the oil level in the transformer.

Primary winding

The advantage of the open-circuit design is that the primary winding consists of many sections stacked vertically along the height of the transformer. This ensures a controlled distribution of dielectric stresses on the internal and external insulation.
The fact that the primary winding consists of independent and insulated sections makes the primary winding resistant to defects occurring within its turns. In the unlikely event of an interturn defect or a defect between layers of the primary winding, the defect remains localized within one section without spreading to other sections and does not cover the entire primary winding. This property makes the VPU type voltage transformer explosion-proof.

Insulator

According to the client's request, the external insulation can be made of porcelain or composite. Porcelain insulators are made from the highest quality alumina porcelain C130, and composite insulators consist of a fiberglass-reinforced rubber pipe and a silicone skirt.
The creepage distance of the insulator is based on the ambient air pollution level and must be specified in the request.
The inductive voltage transformer type VPU has successfully passed all seismic resistance tests in accordance with all requirements of the IEEE 693-2005 standard.

Standard overall and installation dimensions

The indicated informative dimensions refer to standard versions of inductive transformers with porcelain insulators.

 Main technical and metrological characteristics