  This paper proposes a novel and simple linear model to capture line losses
for use in linearized DC models, such as optimal power flow (DC-OPF) and
security-constrained economic dispatch (SCED). The \textit{Line Loss Outer
Approximation} (LLOA) model implements an outer approximation of the line
losses lazily and typically terminates in a small number of iterations.
Experiments on large-scale power systems demonstrate the accuracy and
computational efficiency of LLOA and contrast it with classical line loss
approaches. The results seem to indicate that LLOA is a practical and useful
model for real-world applications, providing a good tradeoff between accuracy,
computational efficiency, and implementation simplicity. In particular, the
LLOA method may have significant advantages compared to the traditional loss
factor formulation for multi-period, stochastic optimization problems where
good reference points may not be available. The paper also provides a
comprehensive overview and evaluation of approximation methods for line losses.
