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Commissioning Substation and Medium Voltage Switchgear Equipment and Some Lessons Learned

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Commissioning Substation and Medium Voltage Switchgear Equipment and Some Lessons Learned

Commissioning a substation or medium voltage switchgear line-up both safely and on schedule requires significant planning, documentation, and effort, as discussed by Bowen. Most new switchgear is assembled and tested in the factory. However, some equipment suppliers may claim to test the switchgear but in fact may not truly perform comprehensive testing. The switchgear is disassembled for shipment, and then reassembled at the job site. The result may be the creation of many mechanical and electrical problems. Start-up lists and test procedures, including IEEE standards, testing organization procedures, electric utility procedures, and equipment manufacturer guidelines, exist to help discover these problems. However, many times the electric system was designed correctly, constructed with the best intentions, but not thoroughly inspected and tested by qualified personnel before being placed in service.

Over the course of an average day, somewhere in the world a major electrical failure occurs at a petro-chemical plant. For many outages due to corrosion, heat build-up, insulation failures (some accelerated by contamination or humidity), animals, improperly prepared terminations, or mis-operation, the cause is quickly identified and corrected, and the equipment is placed back in service. With properly designed, installed, and maintained protection systems, damage is usually limited in scope. However, in cases with extensive and possibly collateral damage, the cause may not be found until a thorough analysis and investigation is complete. Unfortunately, the conclusion is never appealing. Often, the equipment or system:

  • was designed incorrectly,
  • was installed incorrectly, or
  • did not perform as designed.

Furthermore, the cause of many failures in Commissioning a substation is either inconclusive or misdiagnosed. For those instances when the system did not perform as designed, there are two common causes:

  • Lack of maintenance
  • Improper commissioning

This paper is not a complete treatise on the subject of testing and inspection required prior to or after energizing medium voltage switchgear and substation equipment. It does, however, discuss many important aspects of ensuring the protection systems for substation or medium voltage switchgear are, from an electrical standpoint, ready to be placed in service. The following sections discuss:

  • Important items to be considered in the commissioning planning stage
  • Practical methods for checking protective device circuits
  • Common commissioning oversights and avoiding them

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Some Lessons Learned From Commissioning Substation and Medium Voltage Switchgear Equipment