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Business DomainNecessity for maintenance

In order to prevent system failures and assure stabilized operation, maintenance services by professional engineers are indispensable. These engineers are required to possess sufficient technical expertise in regard to equipment and facilities.

Failure statistics

Present failures in electrical systems

  1. 1.Causes are classified into the categories of unsatisfactory maintenance, intentional actions, errors, and imperfect facilities.
  2. 2.In more than half of all cases, failure spots are mostly located in circuit breakers and switches.
  3. 3.The phenomena of failures result from the reduction of insulation, ground faults, and burning.
 

Examples of failures and deterioration

The following photos show typical accidents of each equipment.

Power reciving substation facilities

Busbar short-circuiting caused by dust contamination in switchgear
Insulation breakdown caused by intrusion of rainwater in an oil-immersed transformer
Overheating and burning caused by insufficient tightening in the MCB

Excerpt from consideration of reliability in long-used incoming and transforming facilities by The Japan Electrical Manufacturers’ Association (JEMA), Fiscal 1999

Rotating machine facilities

Intrusion of cooling water caused by deterioration in the packin
Stator winding ground fault in a steam turbine generator
Stator winding ground fault in a cage-rotor type induction motor
Tracking in stator winding of a cage-rotor type induction motor
Burning in a current collector of a wound-rotor type induction motor
Burnout of a stator winding of a regular-use engine generator

These are examples of failures caused by deterioration.

Conductor silver plating peel-off is caused by sulfuric corrosion.

Conductor with peel-off (contact side)
Conductor surface cross-section ×200

Short-circuiting in printed circuit board caused by copper migration

Transistor through-hole part ×10 times
Short-circuiting section ×50 times

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