Protective relays are a complex and crucial part of electrical engineering, especially in the solar and energy storage sectors. While they may seem intimidating at first, they don’t have to be! This three-part series is designed to break down the basics of relaying for non-engineers working in the renewable energy space.
**Intro to Relays #1 – What Are Relays, CTs, and 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 protective relay discussions, you’ll likely hear the term “SEL†quite often — maybe every third sentence. But what exactly does it mean?
**The Company Name**
SEL stands for **Schweitzer Engineering Laboratories**, a leading manufacturer of utility-grade relays and protection, monitoring, and control devices. Their products are widely used across the electrical industry, and if you're working with a relay in a solar or energy storage project, it's very likely that it's from SEL.
Here’s a look at their iconic logo:
While companies like GE, Basler, and Beckwith also produce high-quality protective relays, SEL is by far the most commonly used in our projects.
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**Model Numbers**
In addition to being the company name, "SEL" is also part of their product model numbers, making it easy to identify both the manufacturer and the specific device.
All SEL relays start with **SEL-** followed by three digits and sometimes a letter. Here are some common models:
- **SEL-751** – Feeder Protection Relay (often used by Pure Power)
- **SEL-351** – Protection System Relay
- **SEL-551** – Overcurrent Relay
- **SEL-587** – Overcurrent Differential Relay
- **SEL-651R** – Recloser Control
Here are some examples of SEL relays in action:
Beyond relays, SEL offers a wide range of products, including:
- **SEL-735** – Power Quality and Revenue Meter
- **SEL-3530** – Real-Time Automation Controller (used by Pure Power for dynamic solar system control)
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**Conclusion**
At a high level, relay device numbers are 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 experienced teams like ours. Our engineers specialize in designing, programming, and commissioning relays efficiently and cost-effectively.
If you need help with your next solar or energy storage project, reach out today to learn how we can support your relay needs. Let’s make sure your system is protected, reliable, and built right the first time.
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