10 kV SC(B)10/SC(B)11/SC(B)12 Series Cast Resin Dry-Type Transformers

10 kV SC(B)10/SC(B)11/SC(B)12 Series Cast Resin Dry-Type Transformers Overview

The SC(B)10, SC(B)11 and SC(B)12 series cast resin dry-type transformers provide a reliable and environmentally friendly alternative to oil-immersed distribution transformers. They are ideally suited for urban power networks and demanding applications such as high-rise buildings, commercial centers, healthcare facilities, transportation hubs, underground substations and other critical infrastructure.

Product Features

• Economical Design

1. Compact footprint
2. No special safety systems required, such as fire detection equipment
3. Maintenance-free operation
4. Long service life
5. Installation close to load centers, reducing cable losses and feeder length
6. Optimized design through continuous innovation and advanced materials

• Safety and Environmental Performance

1. Environmentally friendly design
2. No risk of leakage of flammable or polluting substances
3. Safe and clean manufacturing process in a closed production system
4. Suitable for humid and polluted environments
5. No fire hazard
6. Flame-retardant and self-extinguishing insulation system
7. Excellent short-circuit withstand capability
8. High overload capability

• Extremely low partial discharge levels

• Special coil finishing process for a smooth winding surface

• No hazardous gas emission in the event of fire or arcing

• Step-lap core design for low no-load loss, low no-load current and low noise

• Special segmented cylindrical winding design

• LV windings manufactured from copper foil conductors

• High overload capability enabled by superior thermal capacity

• Class F insulation system with an average winding temperature rise not exceeding 100K

Structural Features

The core features a fully mitred step-lap construction, ensuring low losses, low noise and optimized magnetic performance. Automated cutting and stacking processes provide high dimensional accuracy and consistent assembly quality.

Core Performance

1. High-permeability grain-oriented silicon steel with low magnetostriction is used to minimize operating noise.
2. All core laminations are processed on fully automated cutting lines for maximum precision. SC(B) transformers incorporate a single-sheet, four-step step-lap core design, further reducing losses and noise.
3. An advanced steel tie-plate and banding structure replaces conventional clamping systems, providing uniform core compression and enhanced mechanical stability. Disc springs maintain constant clamping force throughout the transformer’s service life.
HV windings are manufactured using a segmented cylindrical winding process and vacuum-cast with epoxy resin. The robust winding design
provides superior mechanical strength.

Winding Design

1. The HV windings are made of high-quality oxygen-free copper conductors, reinforced with glass fiber and cast with resin-filled insulation. Embedded resin cooling ducts are provided. The windings are vacuum impregnated and cast, then cured according to a defined temperature profile. The HV winding adopts a special sectional cylindrical structure with multi-layer axial cooling ducts for efficient heat dissipation.
2. The LV winding adopts a foil-type structure and is manufactured using the same process.

Winding Manufacturing Process

1. The LV winding is made of copper foil and resin-prepreg insulation layers. After winding, the coil is cured in an oven to form a mechanically robust winding with excellent short-circuit withstand capability.
2. The efficient design, high-quality materials and advanced casting technology of our cast resin dry-type transformers ensure low partial discharge performance.
3. The windings are preheated to the specified casting temperature, while the resin mixture is prepared in a continuous processing system. The resin components are mixed only immediately before casting. The preheated windings are then transferred to the vacuum casting chamber. Once the specified vacuum level is reached, the resin is poured into the mould. At this stage, the mixed resin has very low viscosity, allowing it to fill fine gaps and minimize partial discharge. After casting, the windings are cured to achieve optimal electrical and mechanical properties.

Winding Performance

1. Impulse Withstand Capability: For SC(B) transformers, the HV winding adopts a special sectional cylindrical structure. Optimized interlayer voltage distribution improves withstand capability against lightning and switching impulse overvoltages, delivering higher performance than conventional sectional cylindrical windings.
2. Electric Field Distribution: Wire-wound cast resin windings use high-quality oxygen-free copper conductors cold-drawn into rectangular profiles. Rounded conductor edges eliminate sharp points and burrs, ensuring uniform electric field distribution and low field distortion. Together with the vacuum casting process, this optimized conductor design enables low partial discharge performance
of ≤5 pC.
3. Heat Dissipation: High-purity resin and glass fiber composite insulation provides excellent electrical and mechanical strength. With a surface insulation thickness of only 3mm~4mm, SC(B) series windings achieve efficient heat dissipation. Multi-layer axial cooling ducts provide effective cooling surfaces for the conductors, ensuring balanced heat generation and heat dissipation throughout the winding.
4. Short-Circuit Withstand Capability: SC(B) transformers use wire-wound sectional cylindrical or cylindrical windings. During vacuum casting, resin fully penetrates the layers, turns and sections in a single process. After curing, the resin, conductors and glass fiber form a solid integrated structure, providing excellent short-circuit withstand capability.

Overload Capability

The service life of a dry-type transformer is closely related to the overload conditions experienced during operation. Overloads may cause temperature fluctuations and accelerate thermal aging of the winding insulation.
When the normal load is below rated capacity, the transformer can withstand certain overload conditions without affecting its service life. The permissible overload level and duration depend on the initial load factor and average ambient temperature.
The transformer is designed and manufactured in accordance with IEC 60726 and GB 1094, and is suitable for operation at rated power under the following normal ambient conditions:

• Max. temperature: +40°C
• Daily avg. temperature: +30°C
• Annual avg. temperature: +20°C
• Unless otherwise specified, the reference ambient temperature is +20°C.

Accessories

Enclosure

Standard dry-type transformers are supplied without an enclosure, with a protection degree of IP00. Upon request, IP20 or IP23 enclosures can be provided for enhanced safety and protection.
The IP20 enclosure is designed to prevent accidental contact with live parts and the ingress of solid objects larger than 12mm. Perforated steel panels are used in the upper and lower ventilation areas to ensure effective cooling airflow.
The IP23 enclosure provides additional protection against water drops falling at an angle of up to 60° from the vertical. It features perforated ventilation panels and a solid steel top cover. All enclosures are made of coated steel sheets. Front and rear access doors allow easy connection of HV tapping links, while cable entry openings are provided on the base plate for convenient installation.

Overtemperature Protection

Each transformer is equipped with a temperature monitoring and protection device to protect the windings against overheating. Temperature sensors embedded in the LV winding provide signals to the digital temperature controller. When the winding temperature changes, the controller displays the updated temperature and automatically controls fan start/stop and overtemperature alarm functions, ensuring reliable transformer protection.

Forced-Air Cooling

Upon request, the transformer can be equipped with low-noise axial fans. When the fans are in operation, the transformer output capacity can be increased by up to 50%, making it suitable for extended intermittent overload operation. To avoid frequent fan starts, fan operation is automatically controlled by the temperature controller.