500-230kV Transformer Replacements

SECo replaced two banks of single phase autotransformers configured for 525-230/13.8kV, 600/800/1000MVA transformers operation at an existing ring bus substation.   

The primary, secondary and tertiary bus arrangements, including disconnect switches and the lightning arresters, were reconfigured to match the new bushing positions.  This included new structural steel supports and foundations.  Although the existing foundations were reused due to the lighter and smaller transformers that were purchased, the existing oil containment and firewalls were not satisfactory for the new units. 

The existing earth containment berms were removed and replaced with a new concrete basin and walls.  The height of the existing five (5) firewalls was increased by five feet (5’) to provide adequate protection between the units.  This required sixteen (16) new helical piers per firewall to be installed to provide adequate support and anchoring for the extension. 

Additionally, each of the firewalls was refurbished with a new fireproofing sealant.  The transformers’ control and protection systems had been upgraded recently, but they did require modification to accommodate the units’ new features and capabilities, such as on-line dissolved gas analysis (DGA).