  As more and more renewable intermittent generations are being connected to
the distribution grid, the grid operators require more flexibility to maintain
the balance between supply and demand. The intermittencies give rise to
situations which require not only slow-ramping flexibility capability but also,
fast-ramping flexibility capability from a variety of resources connected at
the MV and LV distribution grids. Moreover, the intermittencies may increase
the costs of grid reinforcement. Therefore, to defer the reinforcement of the
grid assets, the grid needs to be operated optimally. This paper proposes - a)
such an optimal operational methodology for the MV and LV grids; and b) an
aggregated flexibility estimation methodology estimated separately for fast and
slow services at the primary substation (TSO interface). The methodologies
based on model-based MV grids and a sensitivity coefficients-based model-less
LV grids are suitable for LV grids where an up-to-date and accurate model and
topology are not always available. The approaches of the paper use the
synchronised and accurate measurements from grid monitoring devices located at
the LV distribution grids. It is assumed that the implementation of the
methodology is centralised, where a grid monitoring device or a central
platform is capable to host grid aware algorithms and to communicate control
setpoints to DERs. The approaches have been validated on a real MV and LV
networks of a Swiss DSO equipped with grid monitoring devices. The results, in
terms of technical losses, grid violation costs and flexibility capability
curve, show the efficacy of the optimal operation and flexibility estimation
methodologies and therefore, can be easily deployed.
