| Brand | ROCKWILL |
| Series | S |
| Rated Voltage(kV) | 24/36 |
| Rated Power (kVA) | 50/100/160 |
| Frequency (Hz) | 50 |
| Vector Group | Yzn11; Dyn11 |
ROCKWILLElectric strives to bring our customers the latest technology and competitive pricing and best service for distribution automatic. With the development of the power industry, the constraints of installation space and environmental conditions, as well as the specific needs of some developing countries, efficient and flexible power distribution equipment is the future trend.
Drawing on years of electrical design experience and incorporating the world’s most advanced technical design concepts, Rockwill has developed a low-voltage bushing side-out transformer (namely, the H61 distribution transformer). The H61 is a specially designed distribution transformer with its low-voltage bushings (output terminals) located on the side of the transformer, rather than the traditional top. This design is typically used for single-pole installation and can directly supply power to users. It is widely used in West Africa, including countries such as Cameroon, Togo, Benin, Niger, Guinea, Burkina Faso, Chad, and others.
24kV Electrical Characteristics
| Rated Power (kVA) | 50 | 100 | 160 | |
| Rated Voltage (kV) | Primary voltage 15/20kV, 22kV, 24kV Secondary voltage 0.38kV, 0.4kV, 0.41kV,0.42kV |
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| High Voltage Insulation Level (kV) | 24 | |||
| Tapping (%) | ±2*2.5% | |||
| Vector Group | Yzn11; Dyn11 | |||
| Frequency (Hz) | 50 | |||
| Impedance Voltage at 75℃ (%) | 4 | 4 | 4 | |
| Losses (W) | No-load | 145 | 210 | 460 |
| Load(75℃) | 1350 | 2150 | 2350 | |
| Efficiency at Full Load (%) | cosΦ=1 | 97.10 | 97.69 | 98.27 |
| cosΦ=0.8 | 96.40 | 97.13 | 97.85 | |
| Efficiency at 75% Load (%) | cosΦ=1 | 97.65 | 98.14 | 98.54 |
| cosΦ=0.8 | 97.07 | 97.69 | 98.18 | |
36kV Electrical Characteristics
| Rated Power (kVA) | 50 | 100 | 160 | |
| Rated Voltage (kV) | Primary voltage 30kV, 33kV, 36kV Secondary voltage 0.38kV, 0.4kV, 0.41kV, 0.42kV |
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| High Voltage Insulation Level (kV) | 36 | |||
| Tapping (%) | ±2*2.5% | |||
| Vector Group | Yzn11; Dyn11 | |||
| Frequency (Hz) | 50 | |||
| Impedance Voltage at 75℃ (%) | 4.5 | 4.5 | 4.5 | |
| Losses (W) | No-load | 250 | 380 | 530 |
| Load(75℃) | 900 | 2200 | 3200 | |
| Efficiency at Full Load (%) | cosΦ=1 | 97.75 | 97.48 | 97.72 |
| cosΦ=0.8 | 97.21 | 96.88 | 97.17 | |
| Efficiency at 75% Load (%) | cosΦ=1 | 98.02 | 97.89 | 98.10 |
| cosΦ=0.8 | 97.54 | 97.37 | 97.63 | |
1.HV Bushing 2.Tap changer 3.Radiator 4.LV bushing 5.Nameplate 6.Oil drain valve 7.Ground terminal 8.Lifting lug 9.Thermometer 10.Oil level gauge 11.Suspension device
H61 is a small-capacity (≤160kVA) hermetically sealed pole-mounted distribution type with epoxy plug‑in bushings and no oil conservator, while H59 is its upgraded version, covering 50–800kVA+ with improved insulation and heat dissipation.
Replacement cannot be performed while the unit is live (due to personal safety risks). However, they can be swapped via a simple plug-in/out process once the transformer is de-energized, without the need to drain the transformer oil. In contrast, traditional bolted bushings typically require oil draining (or at least lowering the oil level) during replacement, which is a much more complex procedure. Therefore, plug-in bushings significantly reduce maintenance time and workload.
Yes. A hermetically sealed maintenance-free design (like the H61 structure) can be combined with high-efficiency cores (amorphous alloy or high-quality silicon steel sheets) to produce models such as "SH21" or "S20 Sealed Type." However, standard H61 models on the market do not typically prioritize extreme energy efficiency.
If you require both "hermetically sealed maintenance-free" and "Level 1 energy efficiency," you can request a custom build from the manufacturer. These models are usually designated as SH22-M (Sealed Amorphous Alloy) or S22-M (Sealed Electrical Steel), both complying with the Level 1 standards of GB 20052.
H61 feature epoxy resin plug-in bushings that require no oil draining for replacement and offer anti-pollution flashover and UV aging resistance, making them ideal for long-term outdoor service. Their hermetically sealed design without an oil conservator isolates the oil from air, eliminating the need for periodic silica gel replacement and achieving true maintenance-free operation. Additionally, they are equipped with a dedicated gas relay specifically optimized for sealed tanks, providing higher protection sensitivity.
Choose H61 for outdoor installation, limited budget, or high overload capacity needs. Choose SCB dry-type transformers for indoor use where fire safety is critical and budget allows. Both are maintenance-free, but SCB offers flame-retardant oil-free safety, while H61 provides lower cost and stronger overload capability.
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