Microgrids and Alternative Energy
Microgrids are electrical power distribution systems specifically designed to be operated independently from the electric power grid. Often these include alternative energy sources such as wind and solar power, with storage batteries and means to ensure system stability while connected to the grid or in "island" mode. These complex power networks require challenging engineering and dynamic controls. To ensure reliable power, root-cause analysis is needed to understand the sequence of events—not only for disaster recovery—but to diagnose any abnormal condition, long before these lead to instability or outages.
Sequence of Events Recording Systems. Sequence of Events Recording (SER) systems provide high-speed logging of power system events, time-stamped to 1ms 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 Slowing Breaker Operation. 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 both medium and low-voltage power breakers, contact wear and mechanical stresses can result in longer opening and closing times. These can affect proper selective time-current coordination as well as arc-flash calculations. 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. Historical trend plots of this data will reveal trouble spots—before they take down your microgrid!