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Simplicity for the Modern Substation

Time-Domain Link (TiDL) Technology for Digital Secondary Systems

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The inherent simplicity, the sampling rate, the cybersecurity, the protection—nothing comes close to Time-Domain Link (TiDL) technology. TiDL is a point-to-point digital secondary system solution that improves safety by removing high-energy cables from the control house. It saves you money by limiting the amount of copper wiring needed. And it saves you time by significantly reducing the amount of wiring installation, maintenance, and documentation needed.  

This is how you save copper, save time, save money, and save lives.

One and Done

No network engineering. No external time source. No Ethernet switch. With TiDL, all you need is one direct fiber connection between each of the field modules and the relay in your control house. Done.

In the TiDL system, the SEL-2240 Axion acts as the field module, digitizing analog signals into deterministic fiber communications. This simple, point-to-point architecture transports power system data with embedded time synchronization over fiber-optic cable to the TiDL-enabled SEL-400 series relay in the control house. That’s simplicity.

SEL Time-Domain Link (TiDL) Technology

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An Isolated Network

Because of the nonroutable protocol and the direct fiber connection between field modules and the relay in the control house, there’s no need for switches or routers. This security-minded architecture and protocol prevents remote access and eliminates the need for managing port access. Due to the isolated network architecture of TiDL, your communications are deterministic and your system is more cybersecure. 

TiDL Product Location
Axion 421

Higher Sampling. Proven Protection.

Using TiDL technology, the Axion samples power system data remotely and sends the data to the SEL-400 series relay, providing uncompromised protection for your power system. 

In addition, the point-to-point architecture of TiDL means you’ll have lower latency and lower jitter—the Axion nodes sample within ±100 ns of each other, ensuring analog sampling coherency.

The New Solution You Already Know

If you’re thinking that TiDL sounds great but will require all-new product training, think again. TiDL is based on the proven protection of the SEL-400 series relays, which means your relay algorithms, schemes, and configuration in the control house remain the same and you get consistency throughout your modernized substation.


SEL-421 Protection, Automation, and Control System


SEL-451 Protection, Automation, and Bay Control System


SEL-487B Bus Differential and Breaker Failure Relay


SEL-487E Transformer Protection Relay

Committed to a Simpler, Faster, More Secure Future

Other Substation

As we continue with our commitment to develop higher sampling rates, time-domain principles, and other innovative technologies, expect more TiDL-enabled solutions in the future. The journey starts here.

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