Protective relays are a complex and advanced field within electrical engineering, often seen as intimidating. But they don’t have to be! This three-part series is designed to introduce the basics of relay systems to non-engineers working 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)**
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**What Does SEL Stand For?**
If you're involved in discussions about protective relaying, you'll likely hear the term "SEL" more often than not. But what exactly does it mean?
**The Company Name**
SEL stands for **Schweitzer Engineering Laboratories**, a leading manufacturer of utility-grade relays and other protection, monitoring, and control devices. Their products are widely used across the electrical industry, and if you're working on a solar or energy storage project with a relay, there's a good chance it’s made by SEL.
Here's a quick look at the SEL logo:
While companies like GE, Basler, and Beckwith also produce protective relays, SEL is the most commonly used in our projects — more than all others combined.
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**Model Numbers**
The term "SEL" is also part of their model numbers, making it easy to identify both the manufacturer and the specific product. All SEL relays start with "SEL-" followed by three digits and sometimes a letter.
- **SEL-751** – A versatile feeder protection relay, often used by Pure Power.
- **SEL-351** – A general-purpose protection system relay.
- **SEL-551** – An overcurrent relay.
- **SEL-587** – An overcurrent differential relay.
- **SEL-651R** – A recloser control unit.
Here are some examples of SEL relays in action:
Beyond relays, SEL also offers other critical equipment, such as:
- **SEL-735** – A power quality and revenue meter.
- **SEL-3530** – A real-time automation controller (used by Pure Power for dynamic solar system control).
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**Conclusion**
At a high level, understanding relay device numbers may seem straightforward, but the details can quickly become complex. However, developers and project managers don't need to be experts in relays — especially when working with a team like Pure Power. Our engineers specialize in designing, programming, and commissioning relays efficiently and cost-effectively.
If you need assistance with your project's relay systems, contact us today to learn more. We’re here to help ensure your system is safe, reliable, and built to last.
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