Fluctuations in voltages and power mismatches are common in modern power grids due to the dynamic changes in the load and generation levels. Ancillary services are provided by specialized engineering firms to assist the market operators in operating the power networks and to manage the power mismatches. Ancillary services require a lot of data including the load data, system data, and control device data to take appropriate decisions based on standardized computational processes. This chapter introduces the overall process of determining the required reactive power flows based on load data aggregation in low voltage (LV) networks. The proposed method utilizes the adjustment of DER inverter reactive power using the IEEE 1547 standard reactive power control mode, constant-reactive mode (Cons-VAr), and voltage-reactive power mode (Volt-VAr). The suggested process is applied to a modified IEEE 5-bus network. ETAP software is used simulations for 12-month period.