This document was prepared, within the UIC Infrastructure Forum by the Energy and Electric Traction experts of the Technology Support Group, to provide all the railways with guidelines for testing, monitoring and diagnosing the OCL conditions and performance, on the basis of uniform criteria and common objectives. All the needs regarding the checking and testing of the OCL characteristics, depending upon the required or expected performance, were investigated by analysing the relevant context and the objectives to be attained. In particular the main parameters that characterise the behaviour of the OCL in static or dynamic conditions were enhanced, together with the methods to be applied, the procedures to be followed and the diagnostic systems to be adopted.