brownouts

A brownout is a drop in electrical power that reduces the voltage supplied to customers, causing lights to dim and equipment to operate at reduced performance. Unlike a blackout, a brownout preserves some electrical power rather than a complete loss of supply. Brownouts can be intentional, used by utilities to prevent wider outages during periods of high demand or limited generation, or they can occur unintentionally due to equipment faults, transmission constraints, or weather-related damage.

Causes: They include load shedding during peak demand, generation shortfalls, transmission line congestion, protection schemes that automatically reduce voltage to protect equipment, and faults that trigger voltage-reduction in parts of the grid. Brownouts may be scheduled as rolling events in which different areas experience reduced voltage for limited times.

Effects: Reduced voltage can cause lights to flicker or dim, motors to run poorly or overheat on restart, and electronic devices to reset or malfunction. Some equipment is more sensitive to under-voltage; prolonged brownouts can degrade motors and cause heat-related wear. Voltage levels considered as brownouts vary, but reductions of roughly 5-20% from nominal for extended periods are typical.

Mitigation: Utilities use voltage regulators, tap-changing transformers, capacitor banks, and demand-response programs to prevent or shorten brownouts. On the consumer side, uninterruptible power supplies, voltage regulators, good surge protection, and appropriate equipment sizing help reduce risk from voltage sag events. Long-term solutions include grid modernization, energy storage, and diversified generation to increase reliability.