PCS-9550 HVDC Control & Protection System

Line Commutated HVDC (LCC) transmission technology is used for long distance bulk power transmission through overhead lines or submarine cables. It is also used in asynchronous interconnection to AC networks.

  • Overview
  • Structure
  • Redundancy

The control and protection system is the key to the overall performance of HVDC transmission system. It guarantees safe and steady system operation, provides flexible operating modes and accurate control effects, helps to clear fault and assists in system recovery during system disturbances.

A well-designed control and protection system can maximally exert the advantages of HVDC transmission technology in the following aspects:

  • Long distance bulk power transmission
  • Underground or underwater cables transmission
  • Asynchronous interconnection of AC system
  • Offshore transmission
  • Multi-terminal systems
  • Power delivery to large urban areas

A complete PCS-9550 HVDC control and protection system can be divided into the following subsystems:

  • Interface with remote control center
    This sub-system consists of tele-control workstations and Remote Terminal Units (RTUs) for point-to-point communication with remote control centers.
  • Operator control system
    Operator control system is so called SCADA system. It consists of station LAN, operator workstations (OWS), engineer workstations (EWS), SER terminals, system servers, station clock and etc.
  • station control system
    AC/DC station control system consists of main computers and distributed I/O. In hardware realization, the DC station control is assembled with the pole control system.
  • DC control system
    DC control system implement the control of bipolar, pole and converter unit. It consists of main control computers, distributed field buses and distributed I/O.
  • DC protection system
    DC protection system ensures the safe operation of whole HVDC system. It includes DC protection (PPR), DC filter protection (DFP), converter transformer protection (CTP) and AC filter protection (AFP).

The design of HVDC control and protection system aims at 100% availability and the whole system is built in redundant structure. The reliable and complete duplicate design ensures that the normal operation of HVDC system can be immune to any single failure.

For the redundant control system, one system is active and the other is on hot standby. System self supervision and automatic switch-over functions are used to ensure that the relative healthy system is active. Operators may also manually select the system operating state.