ANSI 1.2kV 125A Transformer Bushing
Low Voltage Porcelain Bushing | 30kV Lightning Impulse Withstand | ANSI C76 Compliant
Rated Voltage: 1.2 kV | Rated Current: 125 A | Creepage Distance: ≥25 mm | BIL: 30 kV
This ANSI standard low voltage transformer bushing is engineered for the LV side of distribution transformers, pad-mounted transformers, and substation auxiliary transformers. Rated at 1.2kV and 125A continuous current, it delivers a lightning impulse withstand voltage of 30kV and a dry power-frequency withstand voltage of 10kV. The wet-process porcelain insulator provides high mechanical strength, UV resistance, and long-term reliability in outdoor and indoor service conditions. Flange mount design ensures oil-tight installation on transformer tanks. Direct OEM replacement compatible.
Technical Specifications
| Parameter | Value |
|---|---|
| Rated Voltage | 1.2 kV |
| Rated Current | 125 A |
| Creepage Distance | ≥25 mm |
| Lightning Impulse Withstand Voltage (BIL) | 30 kV peak (1.2/50μs waveform) |
| Power-Frequency Withstand Voltage (Dry) | 10 kV rms (1 minute) |
| Applicable Standard | ANSI C76 / IEEE C57.19.01 |
| Insulation Material | Wet-process porcelain (high-grade) |
| Mounting Type | Flange mount with gasket groove |
| Terminal Type | Plain stud (standard) / Pad connector (optional) |
| Gasket Material | Neoprene (standard) / Silicone (optional) |
| Installation Orientation | Vertical or horizontal (within 15°) |
| Ambient Temperature Range | -40°C to +55°C |
| Altitude | Up to 1000m (derating above) |
Electrical Withstand Capability – Engineering Summary
| Test Type | Applied Voltage | Duration / Waveform | Result Requirement |
|---|---|---|---|
| Lightning Impulse Withstand | 30 kV peak | 1.2/50 μs | No flashover or puncture |
| Power-Frequency Dry Withstand | 10 kV rms | 1 minute | No breakdown |
| Leak Test (Flange Seal) | 50 kPa air pressure | 1 minute | No leakage |
Key Engineering Features
ANSI C76 / IEEE C57.19.01 compliant – Full traceability to North American standards
30kV BIL – Provides adequate impulse margin for 1.2kV systems (typical system BIL requirement is 30kV for exposed LV bushings)
≥25mm creepage distance – Suitable for normal pollution environments (indoor and protected outdoor)
10kV dry withstand – Confirms insulation integrity under clean, dry conditions
Wet-process porcelain – Dense, non-porous, high dielectric strength, resistant to tracking and erosion
Flange mount with gasket groove – Oil-tight seal on transformer tank cover or wall
OEM interchangeable – Dimensional match to standard 1.2kV 125A bushings from major transformer manufacturers
-40°C to +55°C operation – Suitable for most North American and international climates
Dimensional Data (Typical – Confirm with Datasheet)
| Dimension | Typical Value (mm) | Typical Value (inches) |
|---|---|---|
| Overall Length | 160 – 190 mm | 6.3 – 7.5 in |
| Flange Diameter | 75 – 85 mm | 3.0 – 3.3 in |
| Flange Bolt Circle | 55 – 65 mm | 2.2 – 2.6 in |
| Mounting Holes | 2 or 4 holes, 8mm diameter | 5/16 in |
| Creepage Distance (external) | ≥25 mm | ≥1.0 in |
| Stud Size (standard) | M10 or 3/8″-16 | — |
For certified dimensional drawings, request the product datasheet.
Compliance & Testing
Each 1.2kV 125A transformer bushing is factory tested per ANSI C76. A Factory Acceptance Test Report (FAT) is included with each shipment, covering:
Visual and mechanical inspection
Dimensional verification (critical mounting and sealing dimensions)
Power-frequency dry withstand test (10kV, 1 minute)
Lightning impulse withstand test (30kV, 1.2/50μs, 3 positive and 3 negative impulses)
Flange seal leak test (50kPa air pressure, 1 minute)
Porcelain surface integrity check (dye penetrant on sample basis)
Third-party witness testing: SGS, TÜV, Bureau Veritas, or Intertek – available upon request.
Ordering Information
To place an order or request a quote, please specify:
| Ordering Parameter | Options |
|---|---|
| Rated Current | 125A (fixed for this model) |
| Rated Voltage | 1.2kV (fixed) |
| Terminal Type | Plain stud (M10 / 3/8″-16) / Pad connector (specify hole spacing) |
| Gasket Material | Neoprene (standard) / Silicone / Viton |
| Quantity | Single piece / 10 pieces / 50 pieces / 100+ pieces |
| Packaging | Standard export carton / Palletized |
| Certification Required | Standard FAT / Third-party inspection (specify agency) |
Typical lead time: 15–30 days depending on quantity (stock units available for small quantities)
Typical Applications
Low voltage side of single-phase distribution transformers (1.2kV class)
Pad-mounted transformers – LV termination
Substation station service transformers
Oil-filled switchgear – LV bushing entry
Transformer repair and maintenance – direct OEM replacement
Re-bushing projects for aging distribution transformers
Cross-Reference Information
This bushing is dimensionally compatible with standard 1.2kV 125A bushings originally supplied on:
ABB / Cooper (formerly McGraw-Edison)
ERMCO
Howard Industries
Eaton (Cooper Power series)
Siemens
Delta Star
Virginia Transformer
For cross-reference verification, please provide the OEM part number or a sample drawing.
