Reliability Articles

Switchgear Failure Modes: How to Identify and Prevent Them!

Switchgear is a distribution panel which distributes electricity load to smaller capacity panel. Switchgear is a switch/breaker components and its support in one integrated unit, so could be utilized as switcher, breaker, and protector for 2 sides of circuit. Switchgear’s main role on power plant is as power generator, transmission, distribution and power conversion, opening and closing, control and electrical equipment protection. Switchgear contains of main circuit, load switch, transformer, protection equipment and other components.

Switchgear classification method contains of detachable and fixed switchgear. Meanwhile different cabinet structure divided into open switchgear, metal closed switchgear, and steel closed switchgear. And for different volt level it is divided into high voltage switchgear, middle voltage switchgear, low voltage switchgear, etc. It mainly applies to power plant, substation, petrochemical industries, metallurgy rolling, mild and textile industries, mining, residence, high building etc.

Switchgear functions as:

  • Switches and disconnects electrical power source from load
  • Switches and disconnects power source from other electrical equipment
  • Switches electrical grid with the branch
  1. Switching function: through circuit breaker, load breaker switch or disconnecting switch
  2. Protection function: switchgear is equipped with fuse or protection load relay such as overcurrent, overload, reverse power, under/over voltage, etc.
  3. Measurement function: switchgear is equipped with measuring tool for large measurement electrical load such as current, voltage, kwh, frequency, power factor etc.
  4. Monitoring function: switchgear is equipped with pilot indicator/monitoring facilities to monitory on/off status or abnormal/trip condition. This should also apply to do remote monitoring through PLC/DCS/SCADA

Switchgear Components

  1. Bus Bar compartment
  2. Switchgear compartment
  3. Cable compartment
  4. Other operational supporting such as PT, CT, Relay Protection

The main elements for switchgear is switch/disconnect protection equipment:

  1. Switch/disconnecting switch (S/DS)
  2. Load Breaker Switch (LBS)
  3. Breaker (CB)
  4. Dissolving Breaker (Fuse)

Switchgear Failure Mode

Bus bar Compartment

Damaged Isolation Bushing, cause by dirty bushing, worn out mechanical breaker, damaged seal breaker to low isolation endurance effect and reduce life time bushing. These are the activities that can be done to prevent previous matter:

  • Partial Discharge Check
  • Visual Check
  • Cleaning Isolation Bushing
  • Voltage Function Test
  • Isolation replacement Bushing if damaged
Switch and Breaker Compartment

Breaker doesn’t move normally or lost contact because contact breaker is unsterile or leakage from breaker. The effects are the reducing of life time breaker and switchgear will be unable to operate. These are the activities that can be done to prevent previous matter:

  • Infrared Themography
  • Function Test (breaker open/closed)
  • Breaker condition Visual Check
  • Greasing Contact Breaker with Contact grease

On switch and breaker compartment usually bolt, nut, and ring breaker become loose because breaker moves in and out of panel many times, and breaker also moves to one cubicle to another cubicle and operates open/closed. These are the activities that can be done to prevent previous matter:

  • Partial Discharge
  • Infrared Thermography
  • Visual Check
  • Function Test (breaker open/closed)
Applied to All Compartments

Arcing Contact caused by short circuit that usually happens because damaged isolation, unbalanced phase, unsterile breaker contact, and also loss contact. This effects to short circuit, disconnection of supply and also makes the equipment unable to operates. These are the activities that can be done to prevent previous matter:

  • Partial Discharge (for compartment above 3,3kV)
  • Infrared Themography
  • Visual Check
  • Cleans switchgear regularly
  • Contact endurance and resistance test when it’s open
  • Function Test (breaker open/closed)