Electrical power distribution systems designed for data centers are complex. To achieve near-flawless uptime, power systems are designed with multiple sources and redundancy. Data center electrical power monitoring systems (EPMS) must provide pertinent data about normal operations as well as forensics when abnormal conditions are detected. To ensure reliable power, root-cause analysis is used to understand the sequence of events—not only for disaster recovery—but to diagnose any abnormal condition, long before these lead to a total outage.
Sequence of Events Recording Systems. Sequence of Events Recording (SER) systems provide high-speed logging of power system events, time-stamped to 1-ms accuracy. Typically, a GPS antenna and receiver obtains a highly accurate time reference, and this is distributed to SER devices using PTP (IEEE 1588) or a legacy protocol such as IRIG-B or DCF77. SER devices then maintain their own clocks synchronized to this time, allowing recorded events to be compiled and analyzed from all devices in the system, not simply in isolation.
Advance Warning of Slow Breakers. Another benefit of having 1ms-accuracy time-stamping of events is being able to calculate circuit breaker operating times and identify "slow" breakers. Over the lifetime of medium and low-voltage power breakers, contact wear, temperature and mechanical stresses can result in longer opening and closing times. These can affect automatic transfer operations and selective time-current coordination. In addition, arc-flash energy is proportional to time, and so longer opening times increase arc-flash hazard. By recording the time of an open, close or trip command (manual switch, relay trip coil, etc.) as well as the resulting confirmation (breaker a, b or trip contacts), breaker operating times are measured and recorded. You need to know which breakers are slow or stuck—before they take down your data center!