CASA1000 HVDC Interconnector: Powering Regional Connectivity

The CASA1000 project is a landmark 1,300MW High Voltage Direct Current (HVDC) interconnector, developed to link the power grids of Tajikistan and Pakistan. This pioneering infrastructure has been designed to enhance regional energy cooperation, enabling efficient transfer of surplus hydroelectric power from Central Asia to South Asia.

Project Overview

A classic bipole HVDC configuration has been implemented, supporting reliable, high-capacity long-distance power transmission. Advanced control systems and a fibre-optic communications platform have been integrated to ensure secure, real-time system operation.

• Classic Bipole HVDC Interconnection:
  Engineered as a ±500kV bipole system to maximize transmission efficiency and reliability over long distances. The configuration incorporates metallic return and earth electrode operation for redundancy, ensuring secure and stable operation even during monopolar faults.

• Control & Protection System:
  A fully digital, redundant control and protection system was deployed, utilizing a high-speed optic communications platform. This fibre optic system supports critical input/output (I/O) traffic between control devices and field equipment, enabling deterministic response times for interlocking, fast protection signaling, and real-time closed-loop control. Integrated control algorithms manage power flow, fault ride-through, and system stability, while advanced protection schemes safeguard against DC and AC faults.

Commissioning and Integration

Commissioning on the CASA1000 project required not only technical expertise and adaptability, but also resilience in the face of challenging site conditions. Unique regional factors made standard activities—such as equipment testing, subsystem integration, and system testing with international partners—significantly more complex. Flexible methods and solutions were developed to overcome these hurdles, ensuring the project was delivered safely and efficiently.

• Key subsystems delivered and commissioned include:
  • Harmonic Filter Banks: Installed on the AC side to support reactive power compensation.
  • HV Transformers: Commissioned converter transformers, with on-load tap changers for continuous operation.
  • Switchgear: AC circuit breakers and AC and DC disconnectors installed for rapid fault isolation, busbar transfer, and maintenance switching.
  • External Interfaces: Integration with external control systems, local SCADA and protection systems.