The K3YM400VSY20 monitoring relay is a product of the KAPPA series. It has the function of monitoring the voltage of 3-phase and 1-phase networks, and can monitor the deviation, phase failure and asymmetry of the voltage. The product can choose different functions through a rotary switch, including undervoltage monitoring, undervoltage and phase sequence monitoring, monitoring between the maximum and minimum voltage values, and monitoring between the maximum and minimum voltage values and phase sequence monitoring.