Transformer down. No OEM part. G-10 replacements in two days.
Orlando Utilities Commission cracked a CT secondary wiring passthrough block while tightening terminal connections during installation. The block was brittle aged phenolic — the replacement they had sourced cracked just like the original. The transformer stayed down. They called Southern Switch.
The original OEM block — gray cast phenolic. 35 pins, lettered A through HH. Material becomes brittle with age and cracks under terminal torque.
What broke and why
CT secondary wiring passthrough blocks carry the current transformer leads through the transformer tank wall, with one pin end inside the oil and the other exposed for field terminations. The OEM blocks on older power transformers are cast phenolic or early polyester resin — materials chosen for their dielectric properties in the 1960s and 70s that become progressively more brittle as the polymer cross-links further over decades of thermal cycling.
When a utility technician tightens a terminal nut on a degraded block, the torque concentrates at the pin interface and the housing cracks. OUC had sourced a replacement block — presumably an aftermarket or surplus phenolic unit — and it cracked during installation the same way the original did. Same material, same failure mode. The transformer was down and there was no second spare.
Why G-10 fiberglass
G-10 is a NEMA-grade laminate of woven fiberglass cloth and epoxy resin. Unlike phenolic, it does not embrittle with age — the epoxy matrix remains tough over the service life of the component. G-10 has excellent dielectric properties, handles continuous oil and thermal exposure, and machines cleanly to tight tolerances. It does not crack when you torque a terminal nut. Every CT passthrough block SSC makes uses G-10.
How we did it in two days
OUC sent us the old block as a sample. We measured every dimension — pin spacing, pin diameter and thread, mounting hole pattern, block thickness, flange geometry, overall diameter — and programmed the machining from those measurements. There was no drawing. There was no OEM print. The block itself was the specification.
The only thing that slowed us down was material: OUC’s block was a large-diameter configuration we don’t stock in G-10 sheet. We sourced it and had both replacement blocks machined, pinned, and ready to ship in two days. For standard sizes we keep G-10 on hand and can move faster.
The result
Two G-10 passthrough blocks, dimensionally identical to the OEM configuration, delivered to OUC in 48 hours. The transformer went back into service. The G-10 blocks will not crack under terminal torque. When OUC needs to tighten a termination in the future, they won’t be back to square one.
OEM block — gray cast phenolic. Cracks under terminal torque after decades of thermal cycling.
SSC G-10 replacements for OUC — machined to the same pin pattern and flange geometry as the original. Two blocks, 48-hour turnaround.
Send us the old block — or the dimensions if you have them — and we’ll quote a G-10 replacement. Transformer-down jobs go to the front of the line.
A fractured OEM casting reverse-engineered and machined from billet, then installed by our crew.
Precision machining of utility components from sample, drawing, or model number. No minimums.
How SSC reverse-engineers discontinued components from customer samples — no drawing required.