Substation upgrade and new main switchboard for a packaging plant

What arrived without paperwork

The plant had run for 28 years on original switchgear, electromechanical relays and an earthing mesh with no measurement record at all. The three 13.8 kV incoming feeds had no coordination criterion: a fault on one low-voltage board took the whole line down, and maintenance found the reason later, opening cover after cover. The utility had flagged the power factor while on-peak demand kept climbing each cycle.

Measure before drawing

• Circuit-by-circuit inventory: steady current, demand factor and harmonics on each feeder
• Mesh continuity and resistance with a four-terminal earth tester, using the 62% method
• Thermography of 18 busbars and 6 motor starters under nominal load, at the end of the shift
• Trip curves of the existing relays photographed before replacement so the history was kept

1. A new single-line diagram, with thermal and time-graded discrimination between the 13.8 kV relay and the feeder fuses
2. The 750 kVA transformer replaced by a 1,500 kVA unit with forced ventilation and a conservator tank
3. Four low-voltage boards with copper busbars, selective residual current devices and class II surge protectors
4. Mesh recalculated for the assumed fault current, with numbered inspection pits and test boxes

The work was split into three-hour shutdown windows agreed with production. Three cycles after handover, metered on-peak demand had fallen 22% and the power factor left the notification band — the outcome of switching and corrections, logged in a spreadsheet, not a contractual promise.