35KV Pad Mounted Transformer

Sarah Electric offers high-quality, durable 35KV Pad Mounted Transformers. Featuring a safe, enclosed design, this equipment is suitable for long-term, continuous operation and offers excellent protection and weather resistance.

What is a 35kV Pad Mounted Transformer?

A 35kV pad mounted transformer is an outdoor, enclosed distribution transformer designed for medium-voltage distribution systems. It is installed on a concrete pad and connected to the medium-voltage grid via underground cables, stepping down 35kV medium-voltage power to low-voltage power for end-user consumption.

Its operational flow is as follows: 35kV grid → high-voltage cable input → high-voltage switching and protection → voltage step-down by the transformer → low-voltage distribution output → user equipment.

During operation, the process proceeds as follows:

1. The 35kV power supply enters the unit via underground cables.

2. High-voltage side switchgear provides control and protection.

3. The transformer steps down the voltage.

4. The low-voltage side supplies power to the user.

Technical Specifications

Product Features

1. Fully Enclosed Safety

All live parts of the 35kV pad-mounted transformer are fully enclosed within a grounded metal housing. No additional fencing is required; the unit can be installed directly in public areas such as sidewalks, green belts, or parking lots, ensuring that pedestrians and children cannot come into contact with live components.

2. Dead-Front Design

The high-voltage side utilizes elbow-type separable connectors. All terminals are fully shielded and sealed, ensuring that personnel do not come into contact with live parts during operation and maintenance.

3. Compact Footprint

Compared to traditional pole-mounted transformers or civil-constructed substations, the pad-mounted transformer has a small footprint and an aesthetically pleasing appearance that harmonizes with the urban environment.

4. Underground Cable Compatibility

Designed specifically for underground distribution systems, both high- and low-voltage cables enter and exit from the bottom. There are no overhead lines, making the system immune to the effects of severe weather.

5. Integrated Protection

The unit integrates a high-voltage load-break switch and dual-fuse protection, enabling ring-main power supply capabilities and fault isolation.

6. Rapid Installation

The product is fully prefabricated at the Sarah Electric factory; on-site installation requires only placement on the base and cable connection to put the unit into operation.

How to Perform Routine Maintenance on a 35kV Pad-Mounted Transformer?

1. Quarterly/Annual Routine Inspections

● Oil level and temperature checks: Visually inspect the oil level gauge and temperature indicator. If the oil level is low, check for leaks; if the oil temperature is abnormally high, verify the load current.

● Enclosure appearance and corrosion protection: Inspect the transformer enclosure's paint finish for scratches or rust; in coastal areas with salt spray, regularly clean accumulated salt from the enclosure surface.

● Security and sealing: Check the front door locks, safety interlock pins, and sealing gaskets to ensure they are intact and provide protection against rain and animal intrusion.

2. In-depth inspection every 2–3 years

● Oil sample analysis (DGA – Dissolved Gas Analysis): Extract oil samples to measure the content of gases such as acetylene and hydrogen, helping to detect potential internal incipient partial discharge or overheating.

● Fuse inspection: Inspect the exterior of the Bay-O-Net fuse and the internal backup fuse to ensure there are no signs of moisture ingress or thermal erosion.

● Elbow connector and bushing condition: Inspect the insulation of the high-voltage elbow connectors for signs of aging or corona discharge.

Quick Troubleshooting Guide for Common Faults

FAQ

Q: Can a 35kV pad-mounted transformer be installed indoors?

A: Yes, provided the following conditions are met:

1. Good indoor ventilation and an ambient temperature not exceeding 40°C.

2. Floor load-bearing capacity sufficient to support the transformer's weight.

3. Provision of an emergency oil pit or oil containment facilities (for oil volumes > 1000L).

4. Unobstructed fire access routes and equipped with fire-extinguishing facilities.

5. Natural ester oil-filled units are more suitable for indoor installation.

Q: Can 35kV pad-mounted transformers operate in parallel?

A: Yes, provided the following parallel operation conditions are met:

1. Identical rated voltage ratios (deviation ≤ ±0.5%).

2. Identical vector groups (e.g., both Dyn11).

3. Similar impedance voltages (deviation ≤ ±10%).

4. Capacity ratio not exceeding 3:1.

Q: Which international standards do Sarah Electric's 35kV pad-mounted transformers meet?

A: Our entire product line is manufactured in strict accordance with US standards, including IEEE C57.12.00, IEEE C57.12.34, and IEEE C57.12.28 / C57.12.29.

Comprehensive third-party type test reports are available for the products.