Protective relays represent a complex yet essential field within electrical engineering and contracting, often perceived as daunting. But fear not—this series of three articles aims to demystify the basics of relaying for those in the solar and energy storage sectors who aren't engineers.
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**Introduction to Relays #1 – What Are Relays, CTs, & PTs?**
**Introduction to Relays #2 – ANSI/IEEE Relay Device Numbers**
**Introduction to Relays #3 – What Does SEL Stand For? (Below on This Page)**
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**What Does SEL Stand For?**
If you find yourself in discussions about protective relaying, you'll likely encounter the term "SEL" cropping up quite frequently.
**The Company Name**
SEL stands for **Schweitzer Engineering Laboratories**, a leading manufacturer of high-quality utility-grade relays and associated protection, monitoring, and control equipment. Their products are everywhere in the electrical industry. When working on solar or energy storage projects involving relays, there's a good chance you're dealing with a Schweitzer product.
Other notable relay manufacturers include GE, Basler, and Beckwidth, but SEL dominates the market in solar applications. We see and use SEL far more than any other brand combined.
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**Model Numbers**
The term SEL is also integrated into their model numbers, making it easy to identify both the manufacturer and the specific model. All of Schweitzer’s relays begin with **SEL-**, followed by three digits and occasionally a letter.
- **SEL-751** – Feeder Protection Relay (frequently used by Pure Power)
- **SEL-351** – Protection System Relay
- **SEL-551** – Overcurrent Relay
- **SEL-587** – Overcurrent Differential Relay
- **SEL-651R** – Recloser Control
Schweitzer offers more than just protective relays. Here are some examples:
- **SEL-735** – Power Quality and Revenue Meter (ideal for pairing with a premium meter)
- **SEL-3530** – Real-Time Automation Controller (Pure Power uses this RTAC for dynamic control and curtailment in solar systems)
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**A Closer Look at Schweitzer's Range**
While protective relays form the core of Schweitzer's offerings, they also provide solutions beyond relays. Their equipment spans everything from power quality meters to automation controllers, ensuring comprehensive support for solar and energy storage projects.
Take a look at these images showcasing some of their hardware:
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**Why Choose SEL?**
Schweitzer Engineering Laboratories has set the gold standard in reliability and innovation. Their products are designed to withstand harsh environments while maintaining precision and accuracy. Whether you're managing large-scale solar farms or smaller installations, SEL provides solutions tailored to meet your needs.
For example, the **SEL-751** is one of the most versatile relays in the industry, offering features that go beyond traditional feeder protection. Meanwhile, the **SEL-3530 RTAC** ensures seamless integration and control within complex solar systems.
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**A Note to Engineers**
Attention Engineers!
If you enjoy diving deep into technical topics like this, consider joining Pure Power. Our team of 80 engineers designs over 2,000 commercial and industrial (C&I) and utility-scale solar projects annually. Being surrounded by such expertise can significantly boost your career trajectory.
Explore our open positions [here](#).
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**Conclusion**
At its core, understanding relay device numbers is straightforward. However, delving deeper reveals layers of complexity. While developers and project managers may not need to master every detail, having Pure Power on the job ensures that your relays are handled efficiently, from design to commissioning.
If you require assistance with relays on your project, feel free to [learn more](#) or contact us directly.
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This introduction should provide a solid foundation for anyone looking to grasp the basics of protective relays. Stay tuned for future articles exploring additional concepts in this fascinating field!
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