420 Units of 11 kV Automatic Reclosers for Dhaka Grid Upgrade

01 General Overview: Dhaka 11 kV Distribution Grid Upgrade

1.1 Project Background

Bangladesh is currently undergoing a period of rapid economic and industrial development, and the growing demand for electricity has placed immense pressure on the local distribution networks. However, the country's existing 11 kV backbone distribution lines are facing severe equipment aging issues. The original switchgear suffers from serious mechanical wear, resulting in not only high failure rates but also sluggish response times. Furthermore, due to historical reasons, the network is a mix of equipment from various brands with incompatible communication protocols. This has led to a severe "information silo" phenomenon, making it impossible for the background SCADA system to achieve global, unified monitoring.

To completely resolve these pain points in the June 2024 Dhaka distribution network upgrade project, Rockwell Energy Company acted as the core equipment manufacturer. We customized and delivered 420 units of 11 kV intelligent Automatic Circuit Reclosers in bulk to the state-owned utility of Bangladesh. This comprehensive replacement of retired equipment aims to reshape the power supply reliability and automation level of the local backbone distribution network.

1.2 Technical Specification

Tailored to the actual operating conditions of the 11 kV distribution network in Bangladesh, the equipment delivered utilized high-standard main circuit parameter designs to ensure powerful breaking capacity and high insulation withstand levels.

1.3 Drawings

We provided the customer with a comprehensive set of engineering drawings, including dimensional drawings of the recloser main unit, internal electrical schematic diagrams of the control box, and standardized mounting bracket hole layouts. This not only offered precise data support for early-stage scheme reviews but also laid a solid foundation for standardized on-site construction.

02 Manufacturing Quality for 11 kV Intelligent Reclosers

The core manufacturing processes for this batch of equipment strictly adhere to international standards, aiming to build a highly reliable hardware foundation adaptable to harsh tropical climates.

2.1 Vacuum Interrupter (VI)

The main circuit adopts a high-performance Vacuum Interrupter (VI), completely eliminating the environmental hazards associated with greenhouse gases like SF6. At a 16 kA short-circuit current, the equipment fully complies with the rated short-circuit breaking capacity requirements stipulated by IEC 62271-111; at the rated operating current, it achieves an extremely long electrical operational lifespan, perfectly meeting the demanding requirements of frequent reclosing in distribution networks.

2.2 Single-Coil Magnetic Actuator

To thoroughly resolve the chronic issue of "refusal to operate/maloperation due to mechanical wear" inherent in old spring mechanisms, the equipment is equipped with an advanced single-coil magnetic actuator. This mechanism utilizes permanent magnets to maintain the open/close states and features very few moving parts, completely eliminating complex latches and mechanical transmission chains. This minimalist design elevates the mechanical lifespan to an extremely high level, achieving truly "maintenance-free" operation.

2.3 Intelligent Controller & High IP Enclosure

• Intelligent Brain: A built-in dedicated microcomputer controller for the recloser features a powerful advanced protection matrix (including 3-stage overcurrent, phase/zero-sequence fast and slow curve TCC, and Sensitive Earth Fault SEF protection). It also deeply integrates with protocols like IEC 60870-5-104 (IEC 104) and DNP3.0, breaking down communication barriers.
• Physical Protection: Bangladesh experiences high temperatures and humidity year-round. Tailored to the tropical monsoon climate of this project, the delivered recloser main body is configured with an IP65 protection rating (upgradable to IP67). The control cabinet utilizes a high IP54 protection rating (standard is IP43) and has undergone C4-level heavy-duty multi-layer anti-corrosion coating, compliant with ISO 12944 for industrial/coastal environments (customizable to C5), effectively preventing the ingress of rainwater, salt spray, and dust.

2.4 Final Assembly

In the final assembly stage, the Vacuum Interrupter (VI), magnetic actuator, high-precision current/voltage sensors, and intelligent control box are precisely integrated on a standardized, dust-free production line. Digital torque wrenches are used for torque control during assembly to ensure highly consistent mechanical characteristics for every single recloser.

03 Rigorous Testing: Ensuring IEC & IEEE Compliance

Rockwell Energy Company strictly relies on the ISO 9001 Quality Management System and ISO 14001 Environmental Management System for full-process production control. Before mass delivery, this series of intelligent automatic reclosers passed comprehensive Type Tests at an internationally authoritative third-party laboratory, fully complying with the dual standards of IEC 62271-111 / IEEE C37.60. These tests included the 95 kV BIL lightning impulse withstand voltage test and the 16 kA short-circuit breaking test, fully verifying the equipment's design margins under extreme conditions.

For the 420 units delivered in this project, rigorous Routine Tests were 100% executed before leaving the factory to ensure the delivery quality of each unit:

• Insulation and Withstand Voltage Tests: Power frequency withstand voltage tests were performed on both the primary and secondary circuits to verify insulation consistency under mass manufacturing.
• Mechanical Operation and Characteristic Tests: Continuous mechanical action cycle tests were conducted on the single-coil magnetic actuator to precisely verify its operation time, synchronicity, and mechanical stability.
• Secondary Circuit and Functional Joint Tests: A professional test platform was used to conduct secondary circuit verification and full-function joint commissioning on the control box. This included verifying advanced protection logic actions and performing deep data interaction testing of multi-protocol communications (e.g., IEC 60870-5-104, DNP3.0), ensuring the equipment could seamlessly integrate into the customer's SCADA system upon site arrival.

04 Packing and Secure Shipping to Bangladesh

For the cross-border delivery of large batches of precision power equipment, we formulated the highest-standard safe logistics plan.

4.1 Packing

Considering the high humidity and salt spray erosion during transit through tropical waters, both the recloser main body and control box were vacuum-sealed in thickened moisture-proof bags with an ample amount of industrial desiccant placed inside. The exterior utilized heavy-duty, fumigation-free solid wood crates that meet international export standards, providing robust physical support.

4.2 Shipping

During the ocean freight container loading process, customized anti-shock lashing straps were used for rigid securing, and anti-tilt and anti-shock labels were affixed to the exterior of key wooden crates. This end-to-end transportation plan ensured that the 420 units of equipment arrived completely intact at the customer site after enduring long-distance ocean voyages and inland transportation bumps in Bangladesh.

05 Installation and SCADA Integration Summary

5.1 Site Installation

The on-site deployment of the equipment was extremely efficient. The recloser adopts a standardized pole-mounting bracket design, and the connection between the control box and the main body uses a plug-and-play, heavy-duty aviation plug cable. This eliminates complex on-site wiring and secondary commissioning, drastically shortening the installation and outage time for a single unit.

5.2 Summary

The successful grid connection of 420 units of 11 kV intelligent automatic reclosers completely broke the long-standing "communication silo" in the Bangladesh distribution network. The equipment relies on the zero-maintenance architecture of the "Vacuum Interrupter (VI) + Single-Coil Magnetic Actuator." Combined with the millisecond-level advanced protection matrix and multi-protocol plug-and-play technology, it reduces traditional line fault troubleshooting and isolation times from hours down to milliseconds. This qualitative leap in fault handling efficiency will significantly improve the System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI) performance of the regional distribution network, laying a solid physical and data foundation for the Bangladesh grid to comprehensively move towards automation and self-healing.

06 Lifecycle Services

As a senior power equipment manufacturer with global delivery capabilities, Rockwell Energy Company not only provides high-quality physical equipment but is also committed to offering customers systematic service guarantees covering the equipment's entire lifecycle:

• Technical Consultation and Customization: Providing professional grid protection logic customization and protocol docking schemes in the early stages of the project.
• Spare Parts Guarantee: Establishing a dedicated spare parts warehouse for customers in Bangladesh to ensure a rapid-response supply of core wearing parts such as vacuum interrupters and controller plug-ins.
• Software Iteration and Upgrades: As the customer's SCADA system evolves, providing free underlying software upgrade services for the controller to continuously optimize the communication protocol stack and protection algorithm curves.
• Long-Term Technical Support: Providing 24/7 remote diagnostic support and regular localized technical training for engineering personnel, ensuring the grid O&M team always masters the latest equipment debugging and maintenance skills.

For more details, please feel free to contact us. We are ready to provide you with exclusive solutions and highly efficient response services!