Fluvial Design Guide - Chapter 11

River and canal structures

11.6 Power supplies

11.6.1 Selection of power supplies

The main sources of electrical power for operating equipment are as follows:

  • mains electrical power from local power supply company;
  • local generation using diesel or petrol generators;
  • renewable sources of power such as wind or solar generation.

11.6.2 Mains electrical power

Mains electrical power is the most usual means of providing power for most of the larger gates or pumping installations. Normally the mains supply is very reliable and is adequate for most applications. Where additional security of supply is required, duplicate supplies from separate circuits can sometimes be obtained or, where this is not possible, a standby generator is normally installed, which would start automatically in the event of a mains failure.

In most instances, the source of power for operating equipment is to take a supply from the local electricity supply company.

For small installations where there is already an existing low-voltage (400V three-phase 50Hz) distribution system, a metered supply could be made available in the same manner as any other commercial consumer.

Where the power demand is much higher (such as a large drainage pumping station or where the location of the equipment is some distance from any existing low voltage distribution network), the local electricity supply company would provide a high voltage (HV) supply, probably at either 33kV or 11kV. This would normally require a local transformer (substation) to reduce the voltage to 400V.

On large drainage pumping stations where power demand is high, the probability is that the driving motors would require a HV supply. In general, it is more economic to use HV motors at 3.3kV or 11kV for any drive in excess of 350kW. In such cases, it may be possible to operate the drive motors at the supply voltage in order to avoid having a large substation. It would still be necessary to provide a small substation to provide low voltage supplies to ancillary equipment and for single phase small power, lighting and heating.

11.6.3 Local generation

Local generation is usually uneconomic for continuous operation, due to the high costs of providing fuel, as well as increased maintenance. But where equipment is located a long way from an existing power supply and the cost of installing a mains supply becomes prohibitively expensive, local generation should be considered.

Small diesel, petrol or even gas-fuelled generator sets can be used to provide power at remote locations.

Where occasional operation is required (such as an adjustment to a regulating gate or emergency drainage pump), the generator can be arranged to:

  • start automatically whenever the gate or pump is required to operate;
  • shut down when the equipment is no longer needed.

Local generation is never as reliable as mains power and requires considerably more maintenance and manual intervention.

11.6.4 Renewable energy

Although renewable energy sources such as wind and solar energy are becoming more widespread as the technology advances, their use is usually limited to low wattage applications such as instrumentation, monitoring equipment, and associated remote telemetry outstations. Their use for providing power for operating electrical drives is still very limited.

Renewable energy sources are ideal for remote instrumentation such as level and condition monitoring. They can also been used to operate small drives such as small pumps and gate drives, though the problem is in providing sufficient storage capacity in batteries to ensure reliable operation.


11.6.5 Motor control panels

If power is provided to a site of a pumping station or gate installation, local controls are required to operate the equipment.

Where simple manual operation is required, a local panel is required containing the necessary protective devices as well as manual controls to enable the equipment to be operated. This can be as simple as on/off pushbuttons or switches.

Where simple automatic operation is required, the control system is incorporated in the control panel. This automatically starts pumps or alters gate positions depending on signals from level sensors or flow controllers. The panel also provides manual override of the automatic controls for testing or other operational reasons.

On sophisticated installations where a number of parameters are monitored and controlled, a local programmable logic controller (PLC) might be incorporated to provide the necessary functionality. The PLC might also be integrated into a global system control and data acquisition (SCADA) system, whereby a number of installations can be controlled from a central control room using telemetry systems.

Examples of motor control panels are shown in Figures 11.16 to 11.18.

Figure 11.16 Typical examples of motor control panels

Figure 11.17 Control desk at small pumping station

The local control desk provides the facility to manually operate the plant locally in the pumping station. It also interfaces with the automatic controls.

 

Figure 11.18 Central control room for larger scheme

This control room covers the remote operation of a number of pumping installations. Overall status is shown on the wall mounted mimic diagram that gives the operators an overview of the entire system.


 

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