Interconnection of Utility-Scale Solar PV to Distribution

This course is self-paced, so you don’t need to be logged in at any specific time. You can get started immediately after you enroll and the course materials will remain in your account with minimum guaranteed access for 12 months (1 year) after enrollment.

The overview of Generation and Transmission systems provides context around utility-scale solar interconnections to T&D systems. This week we take a look at the different types of generation on utility systems, including central station (steam) thermal types of generation; an overview of the different types of renewables generation; and a discussion on utility transmission systems, including concepts, architectures, and operating principles.

There are some basic electric fundamentals that anyone working with solar and utility systems needs to know. This week covers topics such as voltage, current, and power; impedance; watts, vars, and volt-amps; power factor; single-phase and three-phase circuits; and grounding.

In the next week-and-a-half, we look at the common characteristics of North American style utility distribution systems. This knowledge is intended to give you background on the historic context of distribution systems, and why it can sometimes be challenging to connect large amounts of solar PV to it. This includes basic design and operating concepts, architectures, voltage levels, equipment, and operating principles. We'll look at the impact that distribution characteristics have on the location and quantity of solar on the system, including source impedance; radial, looped, and networked systems; minimum and peak feeder loads; feeder sectionalizing; and system stiffness.

In this week, we'll finish the material on distribution systems and then progress into the first part of Utility-Scale Solar PV Interconnection.

In this module, we start with the basics of solar PV farms on distribution, before we get into more detail in the coming weeks. We start by looking at common solar PV issues on distribution. We also look at topics such as interconnection requirements including equipment and its function, inverters and their functionality with respect to the grid, grounding, SCADA connection and communications, and transformer winding configurations.

Distribution voltage control/regulation, as well as reactive power control, is one of the most important design and operating principles that a utility must consider. With the introduction of IEEE 1547-2018, solar plants are facing new voltage control requirements. During this week, we'll look at voltage requirements that utilities must provide their customers; voltage drop that occurs on distribution feeder primaries and secondaries; utility voltage control equipment; common impacts of solar installations on utility voltage supply; and possible solutions to voltage issues created by solar installations, including smart inverter controls impacting voltage and reactive power. We also discuss voltage flicker and sags, and inverter ride-through capability.

Short-circuits and overcurrent protection is a key design consideration for utility systems, with considerations on solar plant design and operation. This week we'll look at the nature of distribution system faults, overcurrents, and key design principles including instantaneous and time-delayed tripping, reclosing, and post-fault restoration practices. We'll discuss over/under voltage and frequency events on the system, and how they impact the solar PV plant. We'll also look at the potential for unintentional islanding and ground fault overvoltages, and possible mitigation measures, including 3Vo protection and DTT (Direct Transfer Trip).

Estimating what the impacts of new solar PV farms on distribution systems is important for utility engineers as well as developers. In this section, we look at some Hosting Capacity studies and maps which some public service commission and distribution organizations now use, some additional technical screens, and an overview of distribution interconnection procedures.

This is our last module but you still have access to the all of course materials for 12 months (1 year), so keep working and you'll be able to complete the course at your own pace. After your year of access expires you can optionally extend access with a HeatSpring Membership. Enjoy the course and keep in touch!