This part of IEC 61788 covers a test method for the determination of the residual resistance ratio (RRR) of a composite superconductor comprised of Nb-Ti filaments and Cu, Cu-Ni or Cu/Cu-Ni matrix. This method is intended for use with superconductors that have a monolithic structure with rectangular or round cross-section, RRR less than 350, and cross-sectional area less than 3 mm2. All measurements are done without an applied magnetic field. This second edition cancels and replaces the first edition published in 2001. It constitutes a technical revision. The main revisions are the replacement of "accuracy" by "uncertainty" and a change in Figure 1, where the relationship between temperature and voltage is changed to the relationship between temperature and resistance.