The condition of incoming power has a direct impact on the electrical reliability of a plant. As the conditions surround electrical equipment they are often disregarded as a high rate of failure of a particular brand of VFD, computer, server, transformer, electric motor, PLC, IoT device, and similar. However, the impact of these conditions have dire consequences. Where a bad bearing might shut down a machine, the loss of a single transformer can take down an entire production facility. While a replacement bearing has a nuisance delivery time of a few hours, a replacement oil or dry type distribution transformer is measured in double-digit months or more than a year.
There is also the question of the impact to power quality surrounding clean energy applications. The data science project surrounding this initial project relates to several months data from a facility in which the local and bulk grid are primarily traditional power sources (coal – local, nuclear, natural gas) which rely upon distribution corrective systems to maintain voltage control. In another project we will post similar data from another facility that is serviced by a distribution system that also has a solid mixture of base generation but also has a high mixture of wind, solar and storage.
The Jupyter notebook (DataAnalytics-WorkingCopy.ipynb) and database (trans.MDB) and details (readme.md) can be found at MotorDoc1/energydata (github.com). It consists of 10,000 records per table collected every 15 minutes. Data collected at a revenue meter with an ECMS-1 (https://empathcms.com).
As noted at the top of this article (Figure 1), the allowable deviation from the nominal voltage of 12,460 volts AC is +/- 10%. In this case, over 13% of the time the voltage deviates over 10%. Over 50% of the time the voltage deviates over and under +/- 5%, which is the recommended upper and lower limit to maintain efficiency.
When considering the additional impact, Figure 2 shows the voltage unbalance which has a maximum of 5% and a recommended 2% to maintain optimal operation of equipment. As noted, unbalances of up to 13.5% occur over 50% of the time and over 2% over 75% of the time. While in-plant power conditioning will provide some improvement to that equipment, the associated primary transformers are having to manage these conditions. The impact on electric motor temperatures resulting from unbalance can be found: Voltage Unbalance and Motor Temperature – MotorDoc LLC
This is in addition to power factor, load, and harmonic distortion, which impacts the loading of the transformers and power factor, as well. The condition of voltage at the meter, however, is directly related to the stability of the local and bulk grid in that area.
