Who makes relays for AI data centers

A protection relay is the judgement in a high-voltage system. It watches current and voltage on a circuit, decides in a fraction of a cycle whether what it sees is a fault or normal behaviour, and tells the breaker to open. The breaker is the muscle; the relay is what decides, and the quality of that decision is the difference between clearing a fault and taking a substation offline. Selectivity is the whole design problem. A fault should be cleared by the nearest device upstream of it and nothing else, so relays are coordinated in a scheme where each one waits just long enough to let the device closer to the fault act first. Get that coordination wrong and a single cable fault takes out a whole campus feed. Modern relays are computers with communications, which brings both better schemes and a cyber-security surface that did not exist in electromechanical designs. AI campuses interact with this in a specific way: they are very large loads connected at high voltage, often behind a customer-owned substation, so the operator now owns protection engineering it would previously have left to the utility. What to look for is whether protection is engineered by the switchgear vendor or independently, how the coordination study is maintained as the site expands, and how relay settings and firmware are controlled — a setting change is a configuration change to a safety system.