What could be worse than arriving at a site to install a meter only to find that you are not equipped with the appropriate current transformer (CT)? As the saying goes, a craftsman is only as great as his tools; not having the right ones is not only a waste of time but also money. However, itentirely avoidable if you pre-plan this the right way.
Today you can easily find a current transformer available in a variety of sizes, styles, and amperage ranges. Some of them also vary in terms of accuracy and output as well. With so many variables, it is often challenging to choose the right transformer for a project.
However, selecting the right current transformer can be simplified by answering a few questions about your goals, site, and the project in hand. In fact, you may be able to straighten out of some of these details even before checking out a project site! That said, let us look at some basic questions that you must answer to choose the right option and save yourself plenty of troubles down the road!
What Power Meter Are You Using?
You need to understand that because a CT agrees with a meter doesn’t mean that it is your best option. In fact, your meter choice has a considerable impact on your CT choice.
So, you need to check if your meter is better for mV output CT or amp output? You must also check if the meter will be installed permanently, or are you planning to move the meter from one location to another?
How Many Amps Do You Want To Measure?
Another important consideration is to know the number of amps that will be measured. This is something you are likely to know before you visit your site because it is something determined by the goals of your project. For example, if your purpose is to measure a lighting load in a small office, then the CT requirement will be relatively smaller compared to the one for a large establishment.
It is also important to keep in mind that CT performs best when the current flow is anywhere between 10-100% of the CT full-scale value. It would help if you also considered Rogowski coils that are easy to install and work with a wide range. It is also critical to keep in mind that you get the maximum CT accuracy when the load operates to CT’s full rating possible. If the load is under 20A, then it is not advisable to use Rogowski coil because it will be too huge for the load.
If you be moving the meter between multiple loads, then the best solution is to keep at least two different sets of CTs in your repository – one for the small load and one for a large load. This way you will remain covered for all kinds of project settings.
What Are Your Project Types And Goals?
If you are thinking about your project type and goals, then it is essential to know the purpose of the end data. For instance, if you are planning to do a measurement and verification project (M&V), then a standard accuracy meter will be enough to reach your project requirements. However, if you use a revenue-grade meter for tenant submetering, then you need a maximum amount of accuracy. This is when a revenue grade CT would be a perfect choice.
What Is The Duration Of Your Project?
If you are planning to move the meter around a lot, then split-core, clamp-on, and Rogowski coil CTs can be a bit inconvenient to uninstall. In any case, regardless of the CT you choose, it is always advisable to first de-energize the circuit and follow complete safety precautions in your manual to move the CT safely.
If you have read enough and still feel unsure about the best CT for your project, then don’t hesitate to take help from an expert. Just discuss your project requirements and let them help you choose the right CT tailored to your needs.