Choosing convenience over serviceability increases costs over the long term.
By: Allan Evora
I want to talk about the pros and cons associated with installing submetering within your electrical switchgear. When I say switchgear, I’m talking about low voltage substations, panel boards, switch boards… any type of equipment within your electrical distribution system.
To understand why we’re even talking about this, you need to be aware of NFPA 70E. NFPA stands for the National Fire Protection Association, and their 70E standard is for electrical safety in the workplace. Developed on OSHA’s request, NFPA 70E protects companies and employees by reducing the exposure to major electrical hazards like shock, arc flash, and arc blast.
What to think about when installing an electric submeter within switchgear
Before making any decisions about where to install your submeter, you really need to take into consideration these three points:
The main reason you probably want to install an electric submeter within switchgear is convenience. By locating the meter inside the switchgear, you won’t have to provide a separate enclosure. In addition, the wiring will probably be self-contained within the switchgear, which means that’s where you’ll locate the CTs.
Simple, right? Not so fast.
Certainly one of the aspects you’ll need to weigh against convenience is serviceability. Instead of reducing costs over the long term, the convenience factor may actually make serviceability suffer.
What happens when you need to access the electric submeter after its installed? What if you’re having a meter malfunction, or need to troubleshoot meter readings? In many cases, you’re going to have to access the back of the meter.
Based on NFPA 70E rules, and the actual location of the meter, you may not be able to do that in a timely or efficient manner while the panel is energized. Suiting up in PPE can make troubleshooting or viewing the instrument very challenging.
Your other option is deenergizing the panel.
If you’re not able to access the panel or open the deadfront of the piece of switchgear where your meter is installed, you’ll have to remove the electricity from the panel, also known as deenergizing.
The feasibility to deenergize a piece of switchgear where your electric submeter is located totally depends on your environment. In data centers, hospitals, and energy plants, equipment deenergization may not be possible, may require a lot of paperwork, and will represent a high cost.
The industry trend toward compact devices has facilitated this concern. Rope CTs and small faceless meters are made specifically to be put in small, cramped places such as switchgear.
Our recommendation is this: pause and think about the future long-term serviceability and access requirements before automatically choosing the most convenient route. Think about troubleshooting, connecting to the network, modifications, enhancements, and additions. Will the cost of downtime justify the convenience?
Consider installing your meter external to the switchgear in a more controlled environment where NFPA 70E rules are less stringent, or require less PPE in order to access the meter. Sometimes the easiest or most obvious way isn’t always the best way.
It requires a lot of planning to think about the total cost of installation. We’d be happy to share our experience and provide guidance on potential installations of electric submeters.
Allan D. Evora is a leading expert in control systems integration and president of Affinity Energy with over 20 years of industry experience working in every capacity of the power automation project life cycle. With a background at Boeing Company and General Electric, Allan made the decision to establish Affinity Energy in 2002. Allan is an alumnus of Syracuse University with a B.S. in Aerospace Engineering, graduate of the NC State Energy Management program, and qualified as a Certified Measurement & Verification Professional (CMVP).
Throughout his career, Allan has demonstrated his passion for providing solutions. In 1990, he developed FIRST (Fast InfraRed Signature Technique), a preliminary design software tool used to rapidly assess rotary craft infrared signatures. In 2008, Allan was the driving force behind the development of Affinity Energy's Utilitrend; a commercially available, cloud-based utility resource trending, tracking, and reporting software.
Allan has been instrumental on large scale integration projects for utilities, universities, airports, financial institutions, medical campus utility plants, and manufacturing corporations, and has worked with SCADA systems since the early ‘90s. A passion for data acquisition, specialty networks, and custom software drives him to incorporate openness, simplicity, and integrity into every design in which he is involved.