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E E 6372

E E 6372. High Voltage Engineering. Generation and Transmission. Started with DC Edison in NYC in 1882 Holburn in London in 1882 Low voltage DC cannot deliver much power due to voltage drop Utilization had to be at low voltage

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E E 6372

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  1. E E 6372 High Voltage Engineering

  2. Generation and Transmission • Started with DC • Edison in NYC in 1882 • Holburn in London in 1882 • Low voltage DC cannot deliver much power due to voltage drop • Utilization had to be at low voltage • No effective method to alter voltage levels (until solid-state switching developed a century later)

  3. Generation and Transmission • AC Systems developed later • Nikola Tesla filed 7 patents in 1887 for inventions including the transformer, AC generator and motor. • Tesla backed financially by George Westinghouse • 10 kV system at Depford transmitted power 28 miles to London in 1890 • Tesla/Westinghouse exhibit at World’s Fair in 1893 in Chicago led the USA development

  4. Generation and Transmission • Power transmitted is proportional to V2/ZL where V is the voltage and ZL is the surge impedance. • Typical ZL = 250  • A voltage of 100 kV would allow 40 MW • A voltage of 1000 kV would allow 4 GW

  5. Generation and Transmission • This incentive led to higher voltages such as current levels of 345 kV, 500 kV and 765 kV. • New technologies (solid-state high voltage and high power switches) allow better utilization of existing ROW’s: • Static VAR compensators • DC transmission lines • Underground cable systems better with DC

  6. Voltage Stresses • Normal operating voltages not a threat unless • Pollutants/contaminants compromise insulation • Structural damage to insulation • External voltages (mainly lightning) • Less important at higher voltages • Internal voltages • Mainly switching and faults • Load & generator fluctuations

  7. Voltage Stresses • The balance between stress on insulation and dielectric strength is called insulation coordination. • Voper_level < Vprot_action < Vinsul_rating • In classical approach, Safety Margin = Vinsul_rating – Vprot_action

  8. Testing Voltages • Must test for over-voltages as well as rated ac and dc levels • Simulate switching surges & lightning strikes • AC voltage tests: 1 minute at rated frequency • Dry test only for indoor equipment • Wet and dry tests for outdoor equipment • “Standard rain” used for wet tests

  9. Lightning Impulses • Short rise time: 1 ms – 10’s of ms • Standard: 1.2 ms rise with half peak at 50 ms 1.2 ms 50 ms t

  10. Switching Impulses • Equipment vulnerable to slow rise times at around 100 – 300 ms. • Standard test pulse is 250 ms rise time to half peak at 2.5 ms.

  11. DC Test Voltages • Hard to test cables due to large capacitance • Use DC test voltages • Some premature failures due to dc testing • Now use very low frequency (VLF) at about 1 Hz

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