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Voltage Control Scheme

For this client, AEE developed the control strategies for the switching of five 33 kV filter capacitor banks located at three substations placed approximately 10 km apart on a feeder circuit.

Two independent control strategies were devised:

  • a PLC based scheme which relied on fibre optic communications for the correct coordination between the capacitor banks,
  • a hardwired control scheme that was programmed into each of the capacitor banks’ protection relays. This scheme was designed to provide control during outages of the PLC or the fibre optic communications.

Both schemes were to be permanently enabled.

The control strategy priorities were to:

  • Ensure that both HV and LV voltage profiles remained within acceptable limits to promote a high availability of electrical infrastructure & to
  • minimise the number of unwanted capacitor bank switching operations.

By inputting electrical parameters including power and voltage, and in the case of the PLC, mine operational data such as conveyor belt speeds, the schemes were able to meet these objectives.

As part of their earlier studies for this client, AEE carried out the complete range of harmonic studies to specify filter bank characteristics that would eliminate harmful resonant conditions associated with the high penetration of VVVF conveyor drives employed at the mine.

AEE also attended site to supervise the commissioning of the schemes.