There are several factors to consider when evaluating equipment requiring a new installation of power distribution equipment.
Typically, these decisions will start at the utility to understand what they can support for large load connections. It is important to make educated recommendations for the proper voltage design as it impacts the project as things progress. For this article we will focus on three general areas:
- Driven load
- Supporting Resources
While there are other areas that can be evaluated in the decision-making process expanding on these should help give an understanding of how to act.
Electric motors consume nearly half of energy generated for industry in the US so making the right decision on large driven loads is important. Considering this use of energy and how end users are charged for this usage could have a significant impact. Considering a 500 HP motor for example would show significantly different current usage results for a 480 V system as compared to a 4160 V system. As motor loads increase in size the design of the motors changes as well. Medium voltage assets are typically designed with a form coil winding design which can provide better cooling and more reliability for the end user.
While evaluating the driven load itself it’s important to consider the way in which the load will be energized and controlled. Most systems will have either an across the line start, soft or reduced voltage starting, or variable frequency drives installed. While each has its strengths and weaknesses it’s important to choose the right starting device that the utility will support and that will meet the need of the driven load in the application. Some applications will determine the starting device which narrows the selection process for the application engineer – example if speed control is important a variable frequency drive will be the only option to meet the need.
Let’s face it, many of the power experts within organizations are retiring or may be focused in other areas of the business. When power systems make the switch to medium voltage from low voltage the knowledge pool of people with comfort in these decreases significantly. We’ve all met the E&I technician who works with low voltage gear but when asked to evaluate something in the medium voltage lineup they hesitate. This is no fault of their own as many have not had the opportunity to learn the proper procedures and protocols that comes with the higher voltage designs. As an electrical power systems owner, you need to take into consideration the comfort level and expertise of the local team that will be installing and supporting the equipment can provide. You don’t want to find yourself in a situation where the only capable people that can assist with this equipment are outside of your organization. In the time that we live in now where minutes of production are calculated for efficiency, being self-sufficient is extremely critical.
Costs for projects vary due to the needed equipment. As you evaluate low voltage systems versus medium voltage a few items rise for immediate evaluation. First you need to consider the cost of the gear itself. Medium voltage systems tend to have a premium associated as the design requirements are more robust in order to safely manage the voltage levels of the system. However, with a medium voltage system the conductors needed to complete the installation could yield cost savings as the overall diameter for the current carrying capacity would be smaller. These are up front costs that you as the owner would need to consider. Operating costs would have the primary variable of energy usage. For a MV system, depending on rates negotiated with the utility, the operating cost may prove to be significantly lower. Both systems would require a level of maintenance to support the safe operation and the variables between those costs would be minimal.
For an engineer tasked with projects such as this you should consider these factors before making the overall recommendation of one system over another. Driven load, supporting resources and costs are all factors that will come into play when making the right decision for your application.
Let the EECO Power Team help you navigate decisions and projects such as this. We have experience on our team to help you with your modernization strategy. Feel free to reach out to us at any time by filling out the form below.