This study proposes a novel measurement method to assess the disturbances in the electrical grid for the CISPR Band A (9-150 kHz), as no normative grid measurement method for these frequencies exists yet. Compatibility levels (CL) in IEC 61000-2-2 in this frequency range are defined based on the CISPR 16-1-1 method using the quasi-peak (QP) detector. However, this method is not directly applicable for grid measurements as it was originally designed for laboratory conditions and for measuring radio disturbances and immunity. The method proposed in this article (Light-QP method) overcomes these limitations, along with lower complexity, computational burden, and memory requirements than CISPR 16-1-1. The Light-QP method uses a digital QP detector that processes root mean square (rms) values of spectral components, calculated by adapting the IEC 61000-4-7 standard to the CISPR Band A. The proposed Light-QP method is applied to real measurements from a low-voltage (LV) distribution grid and compared to the QP outputs from a digital implementation of the CISPR 16-1-1 method. The results are comparable and can be used for assessment against CL. The Light-QP method has been presented to IEC SC77A/WG9 for its potential inclusion as a normative measurement method in a new version of the IEC 61000-4-30 standard.