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For some large electrical equipment, many people only pay attention to the quality. In the usual life, there are few accidents caused by the imbalance of electrical equipment. So, is there no harm if the power is not balanced? of course not.
For some large electrical equipment, many people only pay attention to the quality. In the usual life, there are few accidents caused by the imbalance of electrical equipment. So, is there no harm if the power is not balanced? of course not.
1. Hazard to the oil-immersed transformer itself.
Under normal circumstances, oil-immersed transformers have two losses of iron loss (no-load loss) and copper loss (load loss). The iron loss generally does not change, and the copper loss changes according to the load. When the three-phase load is unbalanced, the load loss of the oil-immersed transformer can be regarded as the sum of the load losses of the three single-phase oil-immersed transformers. This may have serious consequences for the oil-immersed transformer. If the balance is unbalanced, the phase current will be too large (three times), which will cause overheating of the winding and oil-immersed transformer oil. The winding is overheated and the insulation aging is accelerated; the oil-immersed transformer oil is overheated, causing oil quality deterioration, rapidly reducing the insulation performance of the oil-immersed transformer, and reducing the life of the oil-immersed transformer (for every 8 °C increase in temperature, the service life will be reduced by half) ), even burning the windings. At the same time, the oil-immersed transformer operating under the three-phase unbalanced condition produces zero-sequence magnetic flux, and the zero-sequence magnetic flux flows through the circuit composed of the metal components of the oil-immersed transformer, which is the heat of the oil-immersed transformer, which also affects the operation safety of the oil-immersed transformer. .
2. Impact on oil-immersed transformer related circuits.
As mentioned above, the three-phase unbalance will produce zero-sequence flux, and the zero-sequence flux will become neutral current on the neutral line, so that not only the phase line will be lost, but also the neutral line will also cause loss. It will increase the loss of the grid line. On the other hand, in the three-phase four-wire system, the line loss is minimum when the three-phase is balanced; when the phase load is heavy, the line loss is small when the two-phase load is light; The load of one phase is light, and the load of the third phase is larger than that of the average load. When the load of one phase is light, the increase of the line loss will be the largest when the load of the two phases is heavy. When the three-phase load is unbalanced, the current imbalance is greater and the line loss increment is larger regardless of the load distribution.
3. Impact on electrical equipment.
The imbalance between the phases can lead to a shortened service life of the electrical equipment, and the frequency of replacement of the acceleration components increases the cost of equipment maintenance. For distribution transformers, when operating under three-phase load imbalance conditions, the output currents of the phases are unequal, which results in unequal internal three-phase voltage drops, resulting in three-phase unbalance of the output voltage. At the same time, the distribution substation equipment operates under the condition of three-phase load unbalance, and the output current of the three phases is different, resulting in current passing through the neutral line. As a result, the neutral line generates an impedance voltage drop, which causes the neutral point to drift, causing the phase voltages to change. The voltage of one phase of the load is reduced, while the voltage of one phase of the load is increased. In the case of voltage imbalance, the power supply is easy to cause the user of one phase of the high voltage to burn out, and the user of the low voltage one phase may not be used. Therefore, when the three-phase load is unbalanced, the safe operation of the electrical equipment will be seriously jeopardized. For the motor, the three-phase voltage imbalance also increases the reverse torque in the motor, which causes the temperature of the motor to rise, the efficiency to decrease, the energy consumption to increase, the vibration to occur, and the output to be depleted. For the circuit breaker, the three-phase unbalance will reduce the allowable current of the circuit breaker, and it is prone to overload and short circuit when the load is changed or alternated.
Therefore, the manufacturer must strictly control the quality control in the production of oil-immersed transformers, ensure the three-phase voltage balance of the oil-immersed transformers produced, and minimize damage to equipment and lines. Ziguang Electric is a professional electrical equipment manufacturer and power supplier. Engineering installation service manufacturers, each piece of equipment has undergone strict factory inspection, customers can rest assured to buy.
To find out more, click on the Ziguang Electric website or follow the Ziguang Electric blog.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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