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Electrical control panels for facilities with solar-to-grid connections


Electric utility companies in the U.S. have by-laws for solar power systems that are connected to electrical grids. To meet those requirements, commercial facilities that use solar power need to add an integrated protective relay (IPR) to their photovoltaic (PV) system.

A solar power installation company based in Pennsylvania serves end users in the Northeast, Midwest, and South. Some of these end user facilities—including a farm, glass manufacturer, printing company, and hospital—use solar power to offset the needs of electricity from the grid.

The solar power installer needed an integrator who could work with an engineering firm to design and build IPR systems to meet solar requirements set by local electric utility companies. 


DenTech worked with an electrical engineering firm and local electric utilities to design the control system, determine functional specifications, and select appropriate components based on power requirements from the electric utility company. The design was evaluated and approved by a professional engineer. Our team built the electrical control panel in a NEMA 4 enclosure.

The control system monitors the service voltage, amperage, and power quality of the premises where the system is installed. When the IPR system detects that grid power is lost or detects any deviation from power quality standards, the system isolates the PV power inverters from the utility’s distribution lines.

DenTech tested the electrical control panel in-house for point-to-point testing. We also performed testing at the end user’s facility, in several stages over the course of the project.

As components were installed and brought online, they were tested individually. After hardware installation and connection to the utility service, the whole system was tested for operation.

DenTech performed start-up and testing procedures. Our customer commissioned the PV system. The electric utility company uploaded the IPR settings. A third party tested and verified equipment operation. All parties jointly tested and verified system performance.  

Test points included:

  • Relay acceptance tests and calibration of settings
  • Current transformer tests
  • Current transformer saturation tests
  • Current circuit verification
  • Potential circuit verification
  • Control circuit tests
  • In-service verification tests


The solar power installer is now able to provide grid-tied and net-metering PV systems with their low- and medium-voltage solar installations.

Although the concept of the IPR system is the same for each location, we modified the electrical control panels based on each facility’s voltage, feed circuit, power requirements, solar power amount, and utility company’s requirements. 

As the solar power market grows on the east coast and in the northeast, companies will have an increasing need for PV inverters to contribute to grid stability and services. DenTech works in commercial-sized solar installations with low- and medium- voltage and net metering. Relay manufacturers we currently work with are Basler and Schweitzer, and we could work with others in the future, too.

Collaboration among electric utility companies, engineering firms, and integrators like DenTech is key to ensuring we build safe control systems to manage electric and solar power.

Capabilities in this Project:

  • Electrical control panel design, assembly, and testing
  • Programming the integrated protective relay system
  • Start-up and testing procedures

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