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The TCLAS software has been developed in the context of water
distribution systems but it is of potential use to other public
utilities industries such as electric power or gas. TCLAS is a
stand-alone package that can be used off-line or be interfaced
to an operational decision support system.
The RTTS group would be pleased
to undertake a consultancy work in applying TCLAS to specific industrial
problems.
Meter Placement Design - Case Study
The sample network consists of 65-nodes and 92 pipes and
it is supplied from five sources: two
boreholes, one high-pressure zone inlet and two interlinked reservoirs
which ate replenished from an external source. All supplies to the
network are measured with +-5% accuracy and a reference pressure in one
of the reservoirs (top left corner on the diagram) is measured with an
accuracy +-0.02m. The consumption estimates in nodes fitted with
off-line meters (large consumers)
were created by apportioning an appropriate fraction of a daily
consumption according to a diurnal consumption pattern. These were
assumed to be accurate to within +-10%. The estimates of consumptions in
all other nodes were obtained by dividing the reminder of the total
supply in proportion to the population count associated with a given
node. Such estimates were believed to be much less accurate, with
accuracies ranging from +-20% for nodes with large volume of
consumptions to +-70% for nodes with small volume of consumptions.
The result of the Confidence Limit Analysis on this network is
illustrated in
Figure 1.
The red error blocks, associated with each
node, indicate that the corresponding pressures calculated by any
simulation software cannot be more accurate than approx. +-1m Aq, and
indeed, in some nodes it will be less accurate than +-2m Aq.
This is a very significant result since the pressure difference
between the highest- and the lowest-pressure node in this network is
also 2m Aq. The
"zoom-1"
display gives numerical detail of flows
and pressures with their associated confidence limits in the vicinity of
a selected node 22.
To investigate the effect of additional metering, a pressure meter has
been added in node 22. The assumed accuracy of this meter is +-0.03m Aq
which improves on the previous error bound for the pressure of
+-1.28m Aq. The new confidence limits calculated by TCLAS are
displayed in
Figure 2.
It can be seen that a number of nodes, in the
neighbourhood of node 22, have benefitted from the addition of this
meter and now they have blue error blocks indicating maximum
inaccuracies of +-0.02 to +-0.2m Aq. Additionally, a number of nodes
that lie further away from the node 22 had their error bounds reduced
to below +-1.0m Aq (partially filled red blocks). It is interesting to
note however, from the
"zoom-2"
display, that the addition of a single
pressure meter did not significantly improve the confidence limits on
flows. Consequently, it can be concluded that additional meters are
needed.
The design of a telemetry system proceeds as an iterative
process aiming at achieving acceptable error bounds with a minimum
number of meters. Such an iterative design has a distinct
advantage that the design engineer gains an in-depth knowledge of the
effects of individual meters thus assisting in planning of various
contingencies.
The result of the Confidence Limit Analysis on this network is illustrated in Figure 1. The red error blocks, associated with each node, indicate that the corresponding pressures calculated by any simulation software cannot be more accurate than approx. +-1m Aq, and indeed, in some nodes it will be less accurate than +-2m Aq. This is a very significant result since the pressure difference between the highest- and the lowest-pressure node in this network is also 2m Aq. The "zoom-1" display gives numerical detail of flows and pressures with their associated confidence limits in the vicinity of a selected node 22.
To investigate the effect of additional metering, a pressure meter has been added in node 22. The assumed accuracy of this meter is +-0.03m Aq which improves on the previous error bound for the pressure of +-1.28m Aq. The new confidence limits calculated by TCLAS are displayed in Figure 2. It can be seen that a number of nodes, in the neighbourhood of node 22, have benefitted from the addition of this meter and now they have blue error blocks indicating maximum inaccuracies of +-0.02 to +-0.2m Aq. Additionally, a number of nodes that lie further away from the node 22 had their error bounds reduced to below +-1.0m Aq (partially filled red blocks). It is interesting to note however, from the "zoom-2" display, that the addition of a single pressure meter did not significantly improve the confidence limits on flows. Consequently, it can be concluded that additional meters are needed.
The design of a telemetry system proceeds as an iterative process aiming at achieving acceptable error bounds with a minimum number of meters. Such an iterative design has a distinct advantage that the design engineer gains an in-depth knowledge of the effects of individual meters thus assisting in planning of various contingencies.
TCLAS - Screen Dumps
Figure 1: Confidence limits for a network with
a reference pressure measurement only
Zoom-page for the selected node 22
(reference pressure only)
Figure 2: Confidence limits for a network with
one additional pressure measurenent in node 22
Zoom-page for the node 22
(with an additional pressure measurement in node 22)
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