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Intro to Relays #3 – What does SEL stand for?

Protective Relays are an advanced area of electrical engineering and contracting that can be intimidating, but they don’t have to be! This series of 3 articles will introduce basic relaying to the non-engineers in the solar and energy storage industries.

Intro to Relays #1 – What are Relays, CTs, & PTs?

Intro to Relays #2 – ANSI/IEEE Relay Device Numbers

Intro to Relays #3 – What does SEL stand for? (below on this page)


What does SEL stand for?

If you’re in a conversation about protective relaying, it’s likely that you will hear the term “SEL” about every third sentence.

The Company Name

SEL is an acronym for Schweitzer Engineering Laboratories. They are the top manufacturer of utility-grade relays and other protection, monitoring, & control devices. They are ubiquitous across the electrical industry. If you are using a relay in a solar or energy storage project, it’s probably a Schweitzer.


SEL Logo


GE, Basler, and Beckwidth are other popular manufacturers of protective relays in Solar, but we see and use SEL more than all the others combined.


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Model Numbers

The term SEL is also used in their Model Numbers, which is convenient, so you know both the manufacturer and model in a short number.

All of Schweitzer’s relays start with SEL- followed by three numbers and sometimes a letter.

SEL-751 – Feeder Protection Relay (most frequently used by Pure Power) and for more than just feeder protection.

SEL-351 – Protection System Relay

SEL-551 – Overcurrent relay

SEL-587 – Overcurrent Differential Relay

SEL-651R – Recloser control


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Schweitzer makes more than just protective relays, such as:

SEL-735 – Power Quality and Revenue Meter (When you want to pair your relay with a top-notch meter)

SEL-3530 – Real-Time Automation Controllers (Pure Power uses this RTAC for dynamic control & curtailment of a solar system)


At a high level, the concept of relay device numbers is simple. It is a slippery slope that quickly gets more complicated. However, developers and project managers don’t need to be experts in relays if they have Pure Power on the job. Our experienced engineers will ensure your relays are designed, fabricated, programmed, and commissioned fast and cost-effectively.

If you need help with the relays on your project, click here to learn more or reach out to us today at info@purepower.com.