In accordance with the IEC 61000-3-6, the evaluation of the harmonic emissions requires an accurate harmonic impedance representation of the system. However, the assessment of a harmonic impedance is understood to be a very complex problem and that the available methods are not entirely satisfactory. Yet, utilities and other network users are expected to prove compliance to apportioned emission limits. To enable the online assessment of harmonic emissions, this paper proposes the use of prevailing phasors to enable the monitoring of the network's harmonic impedance. The proposed method has been validated using network simulations and practical measurements at a windfarm were used for offline assessments