Presentation on theme: "CENTERPOINT ENERGY Materials Used in Sea Spray Environments Presented by William R. Grimes Field Inspections and Pictures by Glenn Smith & Roderick Jefferson."— Presentation transcript:
CENTERPOINT ENERGY Materials Used in Sea Spray Environments Presented by William R. Grimes Field Inspections and Pictures by Glenn Smith & Roderick Jefferson
CenterPoint Energy’s H.O.C./Brazosport Service Area, along the Gulf Coast, Surfside, Texas
18 miles long and the majority of circuit within 350 feet of the Gulf of Mexico, and steady coastal winds. Typically there are no structures to block wind.
GALVESTON ISLAND: 29 Miles long effected by sea spray drops off as you move inland
3 Failure Modes and General Solutions 1) Flashover during electrical storms due to lightning. Maintain high CFO target = 300 CFO, Arrestors 2) Flashovers from leakage currents: Salt collects on equipment – light rains or high humidity create saline solution – leakage currents – flashovers occur as moisture evaporates Longer leakage distances, Hydrophobic surface (surface that expels water) verses hydrophilic surface (surface that attracts water), moisture breads VS spreading or sheen Leakage resistance surfaces (polymer insulators and covering), “ hidden, unexposed” skirts (fog bowl insulators), 3) Atmospheric & dissimilar metal corrosion of metal components Loss of hardware strength – damage to equipment Corrosion resistant metals: Stainless steel, copper, bronze, aluminum, Sacrificial coatings: zinc galvanized, zinc silicate Paints & Coatings- Teflon, Wax Tape
Before 1986: Fog Bowl Pin Insulators (110 CFO) on wood crossarms Hot dipped Galvanized nuts, bolt, steel brackets (both fabricated steel and ductile iron cast), Stainless housing, banding and hardware for tanked equipment
WOOD X-ARM, STEEL PINS, and PORCELAIN FOG BOWL PIN INSULATORS
WOOD BRACE ENDS & HARDWARE DISINTEGRATED, ESPECIALLY BOLTS
Circa 1986: Post Insulators 210 kv BIL, 29” leakeage Distance on fabricated steel brackets Brackets bonded to system ground Hot dipped Galvanized nuts, bolts, steel brackets (both fabricated and ductile iron cast),
GALVESTON: * 35 kV DOUBLE CIRCUIT CONSTRUCTION. * FABRICATED BRACKETS WITH PORCELAIN LINE POST INSULATORS 29” LEAKAGE DISTANCE.
Circa 1999: Fog Bowl Pin Insulators (110 CFO) on polymer covered fiberglass brackets bonded to system ground. Aluminum fabricated or casting preferred over of hot dipped galvanized ductile iron casting or fabricated steel brackets, Stainless steel bolts (with bronze nuts), washers, spring washers. Stainless Steel guy wires and grips.
Fog Bowl Pin Insulators (110 CFO) on polymer covered fiberglass insulated brackets bonded to system ground.
Aluminum casting Stainless Steel Spring Washer Fabricated Steel Brackets Galvanized ductile iron
Guy wire and grip study (2000 -2004) Status quo: “B” zinc thickness grade on guy wire and grips – ‘C” grade is just a heavier coating of the same material. – Mischmetal is 95% zinc coating with 5% aluminum. The manufacturer claims this coating will outlast “C” grade two-to-one. – Stainless Steel- Much more expensive but out performed the other two products.
RECENT (2005-2009): Aluminized (aluminum extruded over steel core) – steel guy wire and grips, – grips #2aaac, 4/0aaac and 600aac. Zinc-silicate coatings on nut, bolts and small hardware Teflon coatings on nut, bolts, small hardware and brackets Silicone Rubber Insulators: – Post insulators on fiberglass crossarms and – Post insulators for jumper support (trunnion top). Silicone Polymer housed MOV arrestors with 17” leakage distances (vs 13” for standard arrestors), Wax tape applied to anchor eyes and grips
Aluminized Steel aluminum extruded over steel core
Aluminized preformed grips #2aaac, 4/0aaac and 600aac
Location 2: Blue Water Hwy near Down guy graveyard – rotated 90 degrees, and taken from direction of sea breeze. Compare A and C phases to B (center) phase. Black teflon confirmed by line mechanic was flaking and corroding off the 24” brackets. Why? HARDWARE COATINGS: 1) HOT DIP GALVANIZED STUD BOLTS 2) BLACK TEFLON COATED 5/8 INCH BOLT 4) STAINLESS STEEL 5/8 INCH BOLT 3) ZINC-SILICATE FLAT WASHER