1. Increased line losses: The load losses of distribution transformers vary with the load current and are directly proportional to the square of the load current. When three-phase loads are unbalanced, the active losses of the transformer increase. Additionally, power losses occur in the conductors. The greater the imbalance, the higher the line losses.

2. Increased energy losses of distribution transformers: Distribution transformers are primary equipment in low-voltage power grids. When they operate under conditions of three-phase load imbalance, it results in increased losses in the transformer. This is because the losses of the distribution transformer vary with the degree of load imbalance.

3. Reduced output of distribution transformers: Distribution transformers are designed based on balanced load conditions, with windings designed to have nearly identical performance and equal rated capacities for each phase. The maximum allowable output of the transformer is limited by the rated capacity of each phase. If the transformer operates under conditions of three-phase load imbalance, the phase with a lighter load will have surplus capacity, leading to reduced transformer output. The extent of output reduction is dependent on the degree of three-phase load imbalance. The greater the imbalance, the more the output decreases. Consequently, when distribution transformers operate under conditions of load imbalance, their output capacity cannot reach the rated value, and their reserve capacity also decreases, reducing overload capability. Operating distribution transformers under overload conditions can lead to overheating and, in severe cases, transformer damage.

4. Generation of zero-sequence currents: When distribution transformers operate under conditions of three-phase load imbalance, zero-sequence currents are generated. The magnitude of these currents varies with the degree of three-phase load imbalance. Larger imbalances result in larger zero-sequence currents. When zero-sequence currents pass through steel components, they induce hysteresis and eddy current losses, leading to localized heating of transformer steel components and accelerated aging of winding insulation, thereby reducing equipment lifespan.

5. Impact on the safe operation of electrical equipment: Distribution transformers are designed to operate based on balanced three-phase load conditions, with the resistance, leakage reactance, and magnetizing impedance of each phase winding being nearly identical. When distribution transformers operate under balanced three-phase loads, the three-phase currents and internal voltage drops are nearly equal, resulting in balanced three-phase output voltages. However, under conditions of three-phase load imbalance, the output currents of each phase are unequal, leading to unequal internal three-phase voltage drops in the transformer and consequently unbalanced three-phase output voltages. Additionally, when distribution transformers operate under conditions of three-phase load imbalance, different currents flow through the neutral line, resulting in impedance voltage drops and causing neutral point displacement, which can lead to fluctuations in phase voltages, posing a serious risk to the safe operation of electrical equipment.

6. Decreased motor efficiency: Operating distribution transformers under conditions of three-phase load imbalance results in unbalanced output voltages. When motors are supplied with such unbalanced voltages, negative-sequence voltages are produced, generating a rotating magnetic field opposite to that produced by positive-sequence voltages, which acts as a braking force. However, since the positive-sequence magnetic field is much stronger, the motor continues to rotate in the direction of the positive-sequence magnetic field. Nevertheless, the braking effect of the negative-sequence magnetic field reduces the output power of the motor, leading to decreased motor efficiency.

Moreover, motor temperature rise and reactive losses also increase with the degree of three-phase voltage imbalance. Therefore, operating motors under conditions of three-phase voltage imbalance is highly uneconomical and unsafe.