Power Outages – Causes and Remedies

4 Jun

Power loss incidents cause tremendous damages to computers and data, in industry, communication and data center facilities, which are well equipped to provide Uninterrupted Power. Failures in sensitive locations, although related to grid malfunction in harsh and stormy season, occur mainly due to transformer failures, standby generator starting troubles, cable malfunctions, and other victims of poor maintenance that can be avoided.

Excessive summer heat overloads electricity supply due to tremendous growth in air conditioning, causing power interruptions due to load shedding or tripping of overload switches. 

Normally, during the dry period, contamination which includes electrically conductive materials is collected on power line insulators. First rains and storms close the electric path causing shorts and arcs, tripping line breakers. Sometimes utility poles catch fire due to the electric arcs.  

Salt is used in some areas as part of winter road treatment, increasing the amount of contamination spread by road vehicles kicking up salt from the roadway. This creates more potential for electric arcs near freeways and major roads.  

Trees are also a leading cause of power failures in winter. Winds and snow cause trees to fall. The falling trees cut power lines. Some power lines create electric shorts and arcs between adjacent power lines or from power lines to ground.  

Till late eighties, year by year, the arrival of first autumn storm or summer power outages was accompanied by collapsing of defective Uninterruptible Power Systems (UPS) and particularly worn out backup batteries. No UPS Company had enough staff, or enough batteries to deal with all irate calls from customers. The chaos stopped when microprocessor based UPS control was introduced in early nineties, enabling automatic testing of UPS systems including batteries, by performing periodic power outage simulation exercises. The exercising enabled detection of defective systems, correction of the UPS and replacement of defective and weak batteries. All these preventive actions were performed when mains power was still available, before the stormy weather season. 

Recent studies indicate that installations equipped with Uninterruptible Power Supply systems, do not normally fail. In most cases the power failure occurred after depletion of UPS batteries.  

Similarly to the described initial experience with UPS systems, most of the studied power equipment, which failed during harsh seasons was revealed to be already defective, and did not perform within its designed limits. Lightning and switching voltages generated in the grid are generally attenuated and clamped to the insulation levels of line isolators and surge protective devices. Healthy transformers and cables should be able to withstand these voltage levels, and backup generators should start when needed.  

Performing proper preventive maintenance can solve major failure problems. Simple, cost effective monitors based on technologies such as Partial Discharge (PD) and Infrared tomography are able to detect transformer defects, and allow scheduling corrective actions in time. Power outage simulation exercising can reveal generator’s starting problems. PD methods, Power Factor measurements, as well as other monitoring methods, offered by test instruments manufacturers, can alarm before the stormy season about defective underground cables, which require treatment.  

Thus, power outage studies indicate that most incidents are due to defective equipment, which fails in harsh environment. Such outages, do not happen due to acts of God but due to negligence of humans, and can be avoided.  Proper preventive maintenance service, regular periodic maintenance schedule, exercising and monitoring can foresee possible problems, which can be solved before the storms come.



Source by Meir Portnoy

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