1000 KVA Bess Transformer -34.5/0.48 KV

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer side instrument box with grounding shield

2500 kVA BESS Pad-Mounted Transformer for America, 34.5/0.48 kV, with DOE High Efficiency

01 General

1.1 Project Description

In 2026, a U.S. energy infrastructure contractor ordered a 1000 kVA pad mounted transformer for BESS system applications as part of a community battery energy storage project connected to a 34.5 kV underground utility distribution network. Although the transformer nameplate follows conventional pad-mounted transformer voltage labeling, the unit was specifically engineered and operated as a BESS step up pad mounted transformer for utility-scale underground grid interconnection.

In this BESS application, power enters the BESS transformer from the 0.48 kV low-voltage side through the battery inverter system and is stepped up to 34.5 kV for connection to the underground loop-feed utility network. This low-voltage input and high-voltage output configuration enables stable energy export from the battery energy storage system to the local utility grid.

To satisfy the operational requirements of modern energy storage infrastructure, the BESS transformer integrates FR3 insulating fluid, a three-phase five-leg core structure, DOE high-efficiency performance up to 99.43%, and a 5.32% impedance design for stable inverter-connected operation. Additional configurations of the pad mounted transformer for BESS system include static shielding, lightning protection, side-mounted gauge box, terminal box, monitoring instruments with alarm contacts, and a powder-coated white enclosure (RAL 9003), supporting safe outdoor operation, remote monitoring capability, and improved thermal performance in utility-scale BESS installations.

1.2 Technical Specification

1000 kVA underground distribution transformer specification and data sheet

Delivered to	America
Year	2026
Type	Three phase pad mount transformer
Standard	IEEE Std C57.12.34-2022
Rated Power	1000KVA
Frequency	60HZ
Feed	Loop
Front	Dead
Phase	three
Cooling Type	KNAN
Liquid insulant	FR3 Oil
Primary Voltage	34.5 kV
Secondary Voltage	0.48 kV
Vector Group	YNyn0
Winding Material	Aluminum
Impedance	5.32%
Efficiency and Losses Standard	DOE Efficiency 99.43%
Tap Changer	NLTC
Tapping Range	±2*2.5%
No Load Loss	1.3 kW
On Load Loss	6.94 kW
Accessories	side instrument box

1.3 Drawings

1000 kVA underground distribution transformer drawing and nameplate

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer drawing

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer nameplate

02 Manufacturing

2.1 Three-Phase Five-Leg Core

The BESS transformer adopts a three-phase five-limb core structure designed to improve magnetic flux balance, reduce zero-sequence effects, and enhance operational stability under inverter-based energy storage loading conditions. The core design supports DOE high-efficiency performance up to 99.43%, helping the transformer maintain stable long-term operation in battery energy storage system applications.

1000 kva, 34.5 kv to 0.48 kv three‑phase five‑column bess transformer iron core with workers inserting iron yoke

2.2 Low-Loss Winding

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer transformer winding

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer final assembly

The BESS step up pad mount transformer uses aluminum windings designed for 34.5 kV / 0.48 kV YNyn0 operation with 5.32% impedance configuration, providing stable voltage transformation between the battery inverter system and the utility grid interface. The winding structure is optimized for thermal reliability and continuous cycling operation in BESS applications.

2.3 Static Shield

The sealed pad-mounted tank structure of the pad mounted transformer for BESS system is designed for FR3 insulating fluid and integrates static shielding to improve insulation stability and reduce electrical interference associated with inverter-based energy storage systems. The enclosure adopts a powder-coated white finish (RAL 9003) to improve outdoor durability and thermal performance in utility-scale BESS installations.

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer in the workshop

2.4 Terminal Box

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer Terminal Box

1000 kva 34.5 kv to 0.48 kv three-phase five-column bess transformer Terminal Box door open

The pad mounted transformer for BESS system integrates both a dedicated terminal box and a side-mounted gauge box to support organized signal wiring, monitoring integration, and maintenance accessibility. This configuration improves field installation efficiency and simplifies operational management for BESS step up pad mount transformer applications in utility-scale energy storage projects.

2.5 Monitoring Instruments with Alarm Contacts

Monitoring Instruments with Alarm Contacts-2

To support unattended operation and remote monitoring, the BESS transformer is equipped with a top oil thermometer, an oil level gauge, and vacuum pressure gauge with alarm contacts. These monitoring devices allow operating signals and abnormal conditions to be transmitted directly to SCADA or BESS control systems, improving operational visibility and protection coordination in energy storage applications.