The New Zealand power system, with a number of large rectifier loads and extensive use of audiofrequency power system signalling (ripple control) for load management, presents particular problems to the designers of harmonic-control measures. The approach adopted in the Limitation of Harmonic Levels Notice differs from that adopted in other standards and guidelines in a number of areas, in particular in its adoption of individual current and voltage limits for the transmission system, the use of psophometrically weighted limits for both current and voltage, the provision of a detailed measurement schedule, and the approach to the equitable sharing of available harmonic capacity. In parallel with the standard, a specially designed monitoring system has been developed to gather information on system harmonic behaviour, and to present this information to a user. A primary role of this equipment will be in the monitoring of power system harmonic conditions, to assess the influence of the legislation in controlling harmonic levels.