What are the effects of a high power factor in low-voltage capacitor banks?
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Our low-voltage capacitor banks have a power factor of around 0.99 – what impact will this have on the circuit? I checked online, and everyone said that a value around 0.95 is considered normal; moreover, devices often shut down due to sudden spikes in voltage
As you mentioned, the issue is likely due to too few inductive loads (when few capacitors are used for inductive loads, the voltage tends to rise); furthermore, there may be a problem with the reactive power controller.
There are two reasons for improving the power factor: one is to improve the quality of the power grid, reduce energy losses, and at the same time increase the efficiency of energy utilization. Second, it allows companies to win rewards from the power supply authority. But 0.95 is the highest reward possible.
I can be sure that for this marine customer, the power factor of the low-voltage capacitor bank remains around 0.99, so it won’t have any impact on the circuit. Generally speaking, low-voltage systems do not have overvoltage protection; I’m not sure what kind of low-voltage protection you are using – this feature can definitely be removed! If there is power factor reactive power compensation on the high-voltage side, it is generally not necessary to use it on the low-voltage side as well. Of course, reactive power compensation on the low-voltage side can also be used for adjustment, so as to keep the power factor on the high-voltage side above 0.95 and thereby obtain a 0.75% discount on electricity bills from the power supply company. Additionally, regarding the frequent overvoltage tripping incidents, I suggest that you check whether the voltage on the low-voltage bus is too high, i.e., whether it exceeds 400 V (for 380 V systems). If it does, I recommend that you adjust the tap changer of the low-voltage distribution transformer as soon as possible to reduce the voltage on the low-voltage side of the transformer to below 400 V. Excessively high voltage not only affects the lifespan of low-voltage components, such as lighting fixtures, contactor coils, and rectifiers.
The power factor of the capacitor bank remains around 0.99, which has no impact on the circuit; however, it should not exceed 1； The electricity utility offers the highest reward for values above 0.95; the amount of the reward depends on whether you are a type of customer that falls under the 0.85 or 0.9 threshold ； If the capacitance compensation exceeds 1, it will result in reverse reactive power being sent upstream, and the electricity utility will still charge a fee for this ；
The low-voltage level is around 390V, and the overvoltage protection serves as a soft-start function for the motor; it activates when the voltage exceeds 120%. Currently, the soft start of all 5 motors often triggers overvoltage protection, but this overvoltage is likely an instantaneous phenomenon; everything is normal at other times. Previously, it was considered whether a sudden increase in voltage was caused by capacitor switching; now that 4 groups of capacitors have been removed, the power factor has dropped to 0.96, but the aforementioned problem still exists. I have a headache
Dear sea friend, perhaps your overvoltage setting is too low! I checked the instructions for relevant soft starters. For AB soft starters, overvoltage is characterized by two parameters: level and delay. By increasing the delay slightly, for example to 3–5 seconds, it is generally possible to avoid such overvoltage-induced malfunctions. Of course, in fact many soft starters do not have this feature, such as brands like ABB and SCHNEIDER. Additionally, if the SIEMENS brand is chosen, it may not be possible to modify the delay; in such cases, we can increase its overvoltage setting to +15%, or alternatively change the power supply voltage from 380V to 400V.