Transformers

CEC 450

1-SYSTEM BONDING JUMPER

2-EQUIPMENT GROUNDING CONDUCTOR

3-SUPPLY-SIDE BONDING JUMPER

4-GROUNDING ELECTRODE CONDUCTOR

5-TERMINAL CONNECTOR TO ENCLOSURE

ALWAYS USE EXTREME CAUTION DURING THE INSPECTION OF ELECTRICAL EQUIPMENT, DO NOT PUT YOUR HAND INSIDE THE TRANSFORMERS, AND ALWAYS ASSUME IT IS ENERGIZED!!!

  • TRANSFORMERS SHOULD BE LABELED WITH CLEARANCES (< 112.5KVA 12” FROM COMBUSTIBLES UNLESS A BARRIER IS PROVIDED)
  • DRY TRANSFORMERS ARE NOT REQUIRED TO BE READILY ACCESSIBLE

DISCONNECTING MEANS CEC450.14

  • LOCATED WITHIN SIGHT OR REMOTE LOCATION
  • REMOTE DISCONNECT REQUIRED TO BE LOCKABLE
  • IF THE DISCONNECT IS REMOTE, THE LOCATION OF THE DISCONNECT SHALL BE MARKED ON THE TRANSFORMER

OVERCURRENT PROTECTION CEC450.3

PRIMARY CALC BELOW (PRIMARY EXAMPLE IS 480 VOLT)

  • OCPD RATED AT 125% OF THE LOAD
  •  X 1.25 = LOAD
  • YOU CAN THEN USE THE NEXT HIGHEST RATING OVERCURRENT PROTECTION DEVICE/BREAKER.  (OR USE ADJUSTABLE RATE BREAKER)
  • EXAMPLE 45KVA=45,000:
  • YOU CAN THEN USE THE NEXT HIGHEST RATING OVERCURRENT PROTECTION DEVICE/BREAKER.  (OR USE ADJUSTABLE RATE BREAKER)
  • NEXT HIGHEST=70AMP

SECONDARY CALC BELOW (SECONDARY ON EXAMPLE IS 240 VOLT)

  • EXAMPLE 45KVA=45,000  
  • YOU CAN THEN USE THE NEXT HIGHEST RATING OVERCURRENT PROTECTION DEVICE/BREAKER.  (OR USE ADJUSTABLE RATE BREAKER)
  • NEXT HIGHEST = 150 AMP BREAKER
  • IN ALL CASES THE CONDUCTORS SHALL BE SIZED BASED ON THE OVERCURRENT PROTECTION DEVICE/BREAKER

GROUNDING CEC 250.30

  • SEE EQUIPMENT GROUND SIZED PER TABLE 250.122
  • SEE GROUNDING ELECTRODE CONDUCTOR PER TABLE 250.66
  • Grounding electrode: A common grounding electrode conductor for multiple separately derived systems shall be permitted. A grounding electrode conductor tap shall then be installed from each system CEC 250.30.6

BONDING CEC250.104

  • BOND METAL WATER PIPE CEC 250.104.A
  • BOND OTHER METAL PIPING CEC 250.104.B
  • BOND STRUCTURAL METAL CEC 250.104.C
  • BONDING BUSHING CEC250.9

Transformer Vault: CEC450.42 (typical for large oil/askarel insulated transformers)

  • 3 HOUR CONSTRUCTION  (1hr if sprinkler/fire protection system) (note: 3hr is typically 6” reinforced concrete)
  • 4” CONCRETE SLAB (if floors below approved by E OR)
  • OUTSWING DOOR WITH PANIC HARDWARE (3hr rated fire if interior)
  • STUD AND WALLBOARD CONSTRUCTION ARE NOT PERMITTED
  • SILL OR CURB ≥ 4”
  • DOORS SHALL BE LOCKED (ACCESS BEING ALLOWED BY QUALIFIED PERSONS)