When adding new loads to an existing electrical service or set of feeders, the first thing to determine is whether the existing system is capable of supporting the new loads. In other words, what is the highest load the system carries?
What you need to know
To determine existing equipment capacity, factor in the incoming conductor size, the ratings of the equipment, and space for new circuits. To determine present loading, you’ll need to either precisely calculate the existing loads, or measure them. How these calculations are performed across the globe varies but typically some measurement of the consumed current and energy will be used in developing a safe reliable result to the problem. In order to conduct a load study, you must first ensure that you meet local requirements. Once you’ve done that, you can follow these simple steps to conduct a 30-day load study.
Five simple steps to perform a load study with the Fluke Power or Energy Logger
- Hook up the feeders or service
Using proper personal protective equipment, connect the Fluke Logger to line power and secure the area so no one will tamper with your setup. Ensure the instrument is powered as you don’t want to come back to an instrument that has used up all its battery power after a short time. For a 3-phase wye system. There will be seven or eight connections:
- Three phase voltages
- Neutral voltage
- Three phase currents
- Neutral currents
- Set power system parameters
Set the Network Topology to wye or delta to match the system you are recording. Verify that the nominal voltage (mains voltage) and line frequency is correct. The Fluke Logger includes displays that make it easy to check everything is connected correctly –there’s even an automatic configuration and correction tool to ensure you are connected and set up correctly. Additionally, the waveform and phasor display provide detailed information about the setup.
- Set the recording time
Set the Fluke Logger to 15-minute averaging intervals and a 30-day recording duration. The 15-minute average time is specified in the NEC 220 as the designated period.
- Record the data
On the Power display the Fluke Logger will display a min, max, and average of these values every 15 minutes:
- Power in Watts for each phase and total
- Reactive Power in vars for each phase and total
- Apparent Power in Vas for each phase and total
- Power Factor for each phase and average
- Averages of Energy in kWh and Reactive Energy in kvarh
A live trend screen will appear when selected and plot a new minimum, maximum and average on the display every fifteen minutes, moving from left to right.
The Fluke Logger can also be set to monitor the 15-minute period in terms of power demand. This demand period is often used by utilities to charge industrial and commercial consumers variable rates. Minimizing this demand can save users money based on their electricity tariff agreement.
During the 30-day measurement period (or designated local period) it’s possible to collect the data for review from the instrument on screen or, when using the Fluke loggers, simply by plugging a USB memory stick into the USB port on top of the instrument, to download the partial data without interrupting the long term study. Additionally, some Fluke Power and Energy Loggers allow you to view and review data wirelessly vis a vis the Fluke Connect ® mobile app and desktop software.
The data can be reviewed on the instrument using the basic statistics provided and the stored detailed trends. After 30 days, or when you are satisfied you have the information needed, disconnect the Fluke Logger from the source, download the data using either transfer to the USB stick or by connecting your computer to the associated product software included with the units.
- Download and review the measurements
For 30 days of recording, with a measurement every 15 minutes, you will have 2880 sets of measurements. Use application software to graph this data, find the maximum current or power on each phase, compare the three phases and report the largest number.
Application software packages usually have a built-in report generator that includes graphs of current and real power, as well as maximum average current on a bar chart. Your report can range from a single current or power number, to a full-blown document with graphs and tables. The ultimate goal is still the same –get an accurate picture of the system load, help design a safety upgraded system and satisfy electrical authorities.
With Fluke Power and Energy Loggers, you can determine the load capacity of your existing electrical service or set of feeders with the accuracy and ruggedness you’ve come to expect from Fluke tools.
(article used by permission from Fluke Corporation)
JM Test Systems sells and rents Fluke Power and Energy Loggers. For more technical information please visit our website dedicated entirely to Fluke Predictive Maintenance. Also for all Electrical Safety Testing and PPE sales/services visit our Electrical Safety Lab Website. Contact us today at 800-353-3411 or [email protected] for a quote.