Bulk Power System or Bulk Electric System

By John Helme, USV Technical Coordinator

If you listen to many presentations related to NERC or FERC, you will occasionally hear the terms Bulk Power System (BPS) and Bulk Electric System (BES). These terms may seem to be used interchangeably. An example of this is in a 2017 document where an Independent System Operator stated “Electricity transferred over transmission lines is often known as bulk power, and the collection of transmission lines and associated equipment is referred to as the transmission system or bulk electric system.” This was written after the NERC definition of BES was effective.

Why BPS and BES Are Confused in NERC Compliance

Here are a few of the reasons that there is confusion with these two terms.

• The meaning of the terms is inconsistent when used by NERC, FERC and others.
• The FERC Glossary of terms does not include definitions for either term but includes the acronyms for both.
• The NERC Glossary of terms includes definitions for both BES and BPS but only the acronym for BES.
• The meaning of the BPS term included in Section 215 of the Federal Power Act uses different language than the NERC definition of BPS.
• The meaning of the BPS term in the Federal Power Act is derived from Section 201, 205, 206, 210, 215, and 222.
• Both the BES and BPS terms were used for decades before they were officially defined by NERC. (BES, 7/1/2014) (BPS, 7/1/2016)
• FERC has a definition of “Distribution” but NERC does not.
• Last of all, sometimes the wrong term is used by industry experts.

How BPS, BES, and Distribution Relate in the NERC Glossary

For those who like pictures better than words, here is a simplified explanation of how the terms relate.
Starting from the bottom of the relationship, distribution is whatever it takes to provide power to a retail customer. Generation can be non-BPS if no portion of the generation output reaches Transmission. BES is a subset of the BPS. The systems that meet the exclusions which are a part of the NERC BES definition may still be BPS or they may be distribution, depending on the specifics of that system.

Navigating NERC Compliance with Utility Services

Understanding the distinction between BPS and BES is critical for navigating NERC compliance requirements. The Utility Services team is glad to help guide you through these complexities. If you have any questions or need clarification on how these terms apply to your facilities, don’t hesitate to reach out.

Related Resources

• NERC Compliance Program Development – Learn how Utility Services can help build and maintain your compliance program.