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Power electronic control in electrical systems 27

1.5.5 Non-linear loads

Many power plant components have the ability to draw non-sinusoidal currents and,
under certain conditions, they distort the sinusoidal voltage waveform in the power
network. In general, if a plant component is excited with sinusoidal input and
produces non-sinusoidal output, then such a component is termed non-linear, other-
wise, it is termed linear (Acha and Madrigal, 2001). Among the non-linear power
plant components we have:
. power electronics equipment
. electric arc furnaces
. large concentration of energy saving lamps
. saturated transformers
. rotating machinery.

Some of the more common adverse effects caused by non-linear equipment are:
. the breakdown of sensitive industrial processes
. permanent damage to utility and consumer equipment
. additional expenditure in compensating and filtering equipment
. loss of utility revenue
. additional losses in the network
. overheating of rotating machinery
. electromagnetic compatibility problems in consumer installations
. interference in neighbouring communication circuits
. spurious tripping of protective devices.

1.6 The role of computers in the monitoring, control
and planning of power networks

Computers play a key role in the operation, management and planning of
electrical power networks. Their use is on the increase due to the complex-
ity of today's interconnected electrical networks operating under free market
principles.

1.6.1 Energy control centres

Energy control centres have the objective to monitor and control the electrical net-
work in real-time so that secure and economic operation is achieved round the clock,
with a minimum of operator intervention. They include:
. `smart' monitoring equipment
. fast communications
. power systems application software
. an efficient database
. mainframe computers.