Is it normal if the sampling current of the reactive power compensation controller is less than 20A and the displayed power factor is 1?

During the operation of the reactive power compensation system, the power factor value displayed by the controller is an important basis for evaluating the compensation effect. When the sampled current is less than 20A, the power factor displayed as 1 (indicating a fully compensated state) requires a comprehensive analysis from multiple aspects such as measurement principles, system characteristics, and equipment parameters. So, is this situation considered a normal phenomenon?

I. Analysis of Measurement Principles and Technical Characteristics

Modern reactive power compensation controllers usually measure the power factor using vector calculation methods, and their accuracy is directly related to the size of the sampled current. When the load current is lower than 20A, it may enter the critical working area of the measurement device, and at this time, the measurement error will significantly increase. Some controllers will automatically switch the measurement mode in the low current state, which may cause the displayed value to remain fixed at 1.

II. Relationship between System Conditions and Measurement Accuracy

Under light-load conditions (current < 20A), the reactive component of the system may indeed be very small, and a power factor close to 1 at this time is a normal phenomenon. However, a comprehensive judgment should be made by considering parameters such as voltage waveform and harmonic content. If there is harmonic interference in the system, the fundamental power factor may show as 1 while the actual total power factor may be lower. It is recommended to use a professional power quality analyzer for comparative measurement to verify the authenticity of the controller's display value.

III. Discussion on Equipment Parameter Settings

Improper setting of controller parameters is a common cause of abnormal display. Incorrect setting of current ratio will cause deviation in the measurement system's perception of the actual current; improper selection of power factor calculation method (such as using displacement factor instead of true power factor) can also lead to abnormal display. In addition, some controllers have a minimum action current threshold (usually within the range of 5-30A), and when the sampled current is lower than this value, it may remain in the last state unchanged.

IV. Analysis of Hardware Failure Possibilities

The occurrence of abnormal display could be a signal of hardware failure: Open circuit or short circuit on the secondary side of the current transformer may lead to measurement failure; Faults in the signal processing circuit may cause data locking; Damage to the A/D converter on the motherboard will make the values remain constant. Hardware issues can be identified through methods such as comparing three-phase measurement values, checking historical data curves, and conducting analog signal tests. It is worth noting that some controllers will default to displaying a power factor of 1 when the self-check fails, which is a protective design.