Nameplate Accuracy for New SF6 Gas Circuit Breakers

Todd Irwin, Keith McLaughlin, Michael Broglio

SF6 Nameplate Accuracy

§ Materials Tolerances

§ Factory Measuring

§ Site Accuracy

Example Baseline

§ DT1-72.5 FKF1

§ 72.5kV

§ 3000A

§ 40kA, 3 cycles

§ SF6 Gas Insulated

§ FK3-1 Spring/Spring Operating mechanism

§ Gang Operated

NEMA SF6 Coalition

“…the nameplate is meant to indicate the approximate mass of SF6 that the GIE will hold once it is filled to the proper density.”

https://www.nema.org/Products/Documents/Sf6-ReportingChallenges.pdf

SF6 Pressure Curve

1 – Nominal (67)2 – Alarm (52) 3 – Lockout (48) 4 – Liquefaction Curve

Gas Nameplate Weight

29 Pounds

IEEE C37.04-2018

IEEE C37.04-2018

CARB sf6-gis-discussion-draft-20190815

5% of 29lbs = +/-1.45 lbs

Aluminum Tank: +/- 0.5mm to 2mm

Porcelain Insulator: +/- 6mm

Component Tolerances – 72.5kV

Variables§ Tank § Bushing Insulators§ Bushing Conductors§ Solid Insulation§ Interrupter Components

Calculated Weight (79.32 lb/m3 67psig @ 20°C)§ Minimum = 28.43 lbs§ Nominal = 29.17 lbs§ Maximum = 29.91 lbs

§+/- 0.74 lbs§+/- 2.53%

Achievable Nameplate Accuracy

§ For Theoretical Nameplate Weight

§ +/- 2.5% may be reasonable for lower voltage CB

§ Larger volume may display wider manufacturing tolerance

§ +/- 5% anticipated in California regulation is reasonable.

Other Variables

§ Temperature (expansion/contraction)• Relatively stable in factory environment

§ Atmospheric Pressure

§ Gas temperature normalization period• Especially when filling from liquid

Factory Measurement Equipment

§ Pressure Gauge

§ Temperature Gauge

§ Scales

§ Mass Flow

§+/-1%

Site FillingMeasuring

§ Pressure Gauge (+/- 0.5%)

§ Temperature Gauge (+/- 1°)

§ Scales/Mass Flow (+/- 0.1 lb)

+/- 1.5 psi @ 70°F+/- 2.4 % (67 psig)+/- 3% @ min/max temp

+/- 1% @ 70°F+/- 2.5% @ min/max temp

Site Conditions

§ Ambient Temperature, Gas Temperature

§ Atmospheric Pressure

+/- 1% @ 70°F

Summary

§ Nameplate weight is a theoretical ideal• Dependent on manufacturing tolerances

§ Factory mass flow can yield +/-1% accuracy (with extra time/cost)• Installed accuracy dependent on site-filling

§ High Accuracy site filling = best installed accuracy.

Questions