@Marla The CT class is 10P150F20 which is from an old CT standard (Australian Standard 1675). The modern equivalent to IEC 60044 would be class 10P20 7.5VA, i.e. accuracy will be within spec so long as the burden is less than 7.5 VA. That 7.5 A includes the load itself as well as the burden of the secondary wiring (can be substantial for long runs of cabling.)