If you’re a PV solar producer who is not home for a week, the PV may fill up your battery storage and send too much current to the grid, possibly violating NEC or other rules. If this is likely to happen, a new Power Control System (PCS) that regulates the flow, timing and direction of power comes in handy.

PCS are described in the 2020 NEC 705.13 code for the first time.

A current transformer, a part of a PCS, can throttle down your PV system so it’s not sending too much current to the grid, explains Sean White, instructor of HeatSpring’s 40-hour NABCEP Advanced PV Certification Training and CEUs course.

Protective Measures that Allow for More Solar PV

“With power control systems, you could have a bigger PV system with protective measures so you don’t send too much current in any direction at any one time,” says White, who was the 2014 Interstate Renewable Energy Council Trainer of the Year. He is an IREC Certified Solar PV Master Trainer and has written several books about solar.

White covers PCS such as current transformers in his 40-hour NABCEP course.

Using such controls, homeowners and businesses can regulate flows to and from solar PV, electric cars and energy storage systems, meeting regulations from the NEC, the utility or local building department.

Meeting Power Flow Regulations, Allowing for More Distributed Energy

With PCS, it’s possible to meet these guidelines while adding more distributed energy to your home or business.

“Even with a smaller connection to the grid, you can put more solar on your roof by controlling the flow of power, slowing down the export to the grid or sending power to batteries,” he says. Such systems are not required but are a smart option for solar PV users. “With power control systems, we can control where we export and where we put breakers,” says White.

Smart Breakers More Powerful than Traditional Breakers

A PCS can work with a smart breaker that provides wireless connectivity and computing power, allowing utilities and building owners to monitor the interplay among grid-supplied power and solar PV, batteries or electric vehicles–and take action. Smart breakers replace the more traditional electromechanical devices that aren’t active very often. They’re more powerful, allowing for more control, which paves the way for more solar PV, storage or other distributed resources.

“Smart breakers will tell you what the current is doing and throttle down the solar system if needed,” says White. “You might have a house with a smaller, 100-amp connection to the grid. If you have two electric cars and want to charge both cars and do laundry at the same time, it would control the timing and direction of the flow of power,” he says.

The NEC Tackles Power Control Systems

The 2020 version of the NEC addresses power control systems. For example, section 705.13, entitled Power Control Systems, says that such systems should be evaluated to control the output of one or more power production sources, energy storage systems, EV-to-grid or other equipment.

“The PCS shall limit current and loading on the busbars and conductors supplied by the PCS,” the section says.

The NEC guidelines can get pretty complex quickly, but White’s course includes material that will help students demystify the new code requirements for these game-changing systems. His course will also help students learn how to use them, even before they become common.

“It may be a decade before these systems become mainstream,” he says.

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