1000 KVA Railroad Transformer-66/11 KV | South Africa 2025

Seamless Integration Starts with the Right Power Transformer.

01 General

1.1 Project Description

1000kVA power transformer was delivered to South Africa in 2025. The rated power of the transformer is 1000 kVA with ONAN cooling. The primary voltage is 66 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 11 kV, they formed a vector group of Dyn11.

The transformer ensures efficient heat dissipation, with a maximum winding temperature rise of 60℃ and top oil temperature rise of 55℃ to maintain optimal operating conditions.

With an impedance of 5% and impressive efficiency-reaching 98.789% at full load (1.0 PF) and 98.49% at 0.8 PF (both measured at 75℃)-it minimizes energy loss during power transmission. Equipped with essential safety and monitoring components, including a Buchholz relay for fault detection, oil and winding temperature indicators (with contact support and 4-20mA/RS485 output), oil level monitors, and pressure relief valves, it offers comprehensive protection against overheating, oil leakage, and excessive pressure. Additional functional parts such as off-circuit tap changers, draining/filling valves, oil sampling devices, and lifting lugs enhance operational convenience and maintenance accessibility.

Weighing 7700kg in total (transportation weight: 5700kg) with a robust tank and accessory design, this transformer is engineered for reliability in industrial power distribution and grid transmission scenarios. It integrates precise regulation (1.07% at 1.0 PF, 3.78% at 0.8 PF full load) and multiple safety safeguards, making it a dependable solution for medium-to-high voltage power conversion needs.

1.2 Technical Specification

1000 kVA railroad transformer specification and data sheet

1.3 Drawings

1000 kVA railroad transformer diagram drawing and size.

02 Manufacturing

2.1 LV Bushing

The porcelain bushing on the transformer’s low-voltage side provides the insulated exit for the LV winding connections. This traditional design features a high-strength ceramic insulator known for excellent durability and weather resistance. It houses a central conductor and serves as the critical interface, ensuring safe electrical isolation from the tank and a reliable connection point for external busbars or cables.

2.2 HV bushing

The porcelain bushing on the transformer’s high-voltage side provides the insulated exit point for the incoming HV winding connection. Constructed with a high-strength ceramic insulator, it features a longer creepage distance and a more complex internal insulation system to withstand significantly higher electrical stresses. Its primary functions are to ensure safe isolation at high voltage from the grounded tank and to provide a reliable sealed interface for the external HV connection. The glazed surface offers excellent pollution resistance for outdoor service.

2.3 Control Box

The control box, typically a weatherproof enclosure mounted on the transformer tank, houses the protection, monitoring, and control devices. It contains components such as protective relays, tap changer controls, temperature and oil level gauges, and alarm contacts. Its primary function is to provide a centralized, accessible interface for managing transformer operation, issuing warnings for abnormal conditions, and facilitating remote supervision and control.

2.4 BCT Junction Box

The BCT (Bushing Current Transformer) junction box is a compact enclosure located near the transformer’s bushings. It houses the secondary terminals of the current transformers that are encapsulated within the bushing insulation. This box provides the protected and accessible connection point for routing the instrument-level current signals to external meters, protective relays, and monitoring devices.

2.5 Winding Thermometer

The winding thermometer monitors the temperature at the hottest spot within the transformer winding. It consists of a sensing bulb inserted into a dedicated pocket near the top of the winding, connected via a capillary tube to a remote dial gauge typically mounted on the control box. This direct measurement is critical for thermal protection, enabling load management, issuing over-temperature alarms, and initiating cooling system controls to ensure safe and reliable transformer operation.

2.6 Buchholz Relay

The Buchholz relay is a gas-activated protection device mounted in the oil pipe between the transformer’s main tank and conservator. It detects internal faults by responding to the accumulation of gas from slow insulation degradation (triggering an alarm) or to the sudden oil surge caused by a major fault (triggering an immediate trip). This provides critical early warning and protection against incipient and serious internal faults.

03 Testing

Frequency Response Analysis (FRA) is a diagnostic technique that assesses the mechanical integrity of transformer windings. By injecting a low-voltage sinusoidal signal across a wide frequency range at one terminal and measuring the response at another, it creates a unique “fingerprint” of the winding’s transfer function. Deviations in this signature from a previous baseline or a sister winding indicate potential mechanical damage, such as deformation, displacement, or loosened components within the core and windings.

04 Packing and Shipping

4.1 Packing

4.2 Shipping

05 Site And Summary

In summary, this 1.0MVA railroad transformer integrates IEC 60076-compliant design, high operational efficiency (up to 98.789%), robust safety safeguards, and stable performance, perfectly suited for medium-to-high voltage power distribution and grid transmission. Engineered for low-loss, reliable power conversion, it serves as a trusted energy solution for industrial needs-connect with us for customization or further technical support.