# Evaluating Effects of Electric Vehicle Chargers on Residential Power Infrastructure
## 4 Impact on the Electrical System
### Impact of Phase Imbalance Induced by EV Charging  
The first observed effect concerns the imbalanced phase conditions arising from the operation of EV chargers. These chargers are capable of functioning in both single- and three-phase modes. However, the single-phase charging most associated with Phase-1 tends to dominate due to user convenience and constraints inherent in the existing electrical infrastructure. This leads to asymmetric loading among the phases, resulting in an elevated current in the neutral conductor. While no direct temperature measurements were performed in this study, such imbalanced loading is theoretically known to  
Figure 7: Average power in each phase during charging operation. increase the risk of conductor heating, which could lead to insulation degradation or fire hazards if not properly managed. Furthermore, current imbalance can lead to voltage fluctuations, thereby impairing power quality and potentially disrupting the operation of sensitive equipment. In addition to current imbalance, voltage unbalance was analyzed to quantify the degree of asymmetry in the phase voltage during charger operation. The unbalance percentage was calculated based on the maximum deviation of each phase voltage from the average, relative to the average value. This method is suitable for datasets that contain average voltage values without phasor information. As shown in Figure 8, periods of EV charging usually coincide with noticeable increases in voltage unbalance. While the average unbalance across the monitoring period was 0.535%, the peak value reached 2.18% during active charging. These values, though generally within acceptable limits, demonstrate the dynamic impact of EV charger loads on system symmetry. The data obtained from the experiment, as shown in Figure 9, indicate the maximum current of each phase (I\({}_{\text{n,max}}\)) relative to the charging state at each time. It was found that, during charging periods, the current in the neutral wire was significantly higher, especially during single-phase charging. For three-phase charging, the neutral current also increased, but to a lesser extent. Additionally, there were periods with current in the neutral wire even outside the recorded usage times, potentially caused by device malfunction or charger installation issues. It is necessary to consider the impact during non-charging periods, as the current generated can be as high as that generated during charging. Figure 8: Comparison of voltage unbalance with and without EV charging activity. Figure 9: Neutral current variation corresponding to EV charging activity. The root causes of phase imbalance observed in this study are attributed to user-driven charging behaviors, unrestricted phase selection, and limitations associated with retrofitted electrical systems in existing condominium developments. In such contexts, the absence of coordinated load balancing or phase allocation control inevitably results in disproportionate phase utilization. Voltage unbalance can adversely affect the performance and lifespan of electrical equipment. Induction motors operating under unbalanced voltage may experience increased copper losses, reduced torque, excessive vibration, and shortened service life. A voltage unbalance as small as 2% can result in temperature rises, significantly accelerating insulation degradation. In addition, power electronic devices, such as converters and adjustable-speed drives (ASDs), are particularly sensitive to unbalanced conditions. These devices may suffer from current distortion, component overheating, and the premature triggering of protective elements. In new construction projects where EV charger deployment is anticipated, it is recommended that the electrical system design incorporates infrastructure provisions that facilitate a balanced load distribution, such as dedicated three-phase supplies or phase rotation scheduling algorithms.