  Reactive power has been proposed as a method of voltage control for
distribution networks, providing a means of increasing the amount of energy
transferred from distributed generators to the bulk transmission network. The
value of reactive power can therefore be measured according to an increase in
transferred energy, where the transferred energy is defined as the total
generated energy, less the total network losses. If network losses are ignored,
an error in the valuation of a given amount of reactive power will be observed
(leading to reactive power provision being under- or over-valued). The
non-linear analytic solution of a two-bus network is studied, and non-trivial
upper and lower bounds are determined for this `valuation error'. The
properties predicted by this two-bus network are demonstrated to hold on a
three-phase unbalanced distribution test feeder with good accuracy. This allows
for an analytic assessment of the importance of losses in the valuation of
reactive power in arbitrary networks.
