Ehv places new demands on power circuit breaker insulation levels

Journal Article · Mon Jun 29 00:00:00 EDT 1964 · Electr. World; (United States)

OSTI ID:6676932

Bednarek, R E; Johnson, I B; Simmons, Jr, H O

For voltage levels of 345 kV and below, effectively grounded systems have allowed application of 80% arresters for insulation requirements. At 500 kV, for greater system operating flexibility and economy of design, the protective levels provided by an 85% arrester become the logical basis for design and coordination of breaker insulation. This leads to the derivation of a wet switching surge withstand level of 1250 kV crest line-to-ground. Tests show that the wet switching surge strength of external insulation can be equivalent to the crest of the wet 60 c/s flashover strength and that BIL strength at ehv tend to be at least twice the wet rms hipot value. Consideration must also be given to protecting the breaker against voltages which exceed proposed withstand values. The preferred solution is the provision a line side arrester or gap near but not part of the breaker. Improvements in breaker restriking performance and the effect of modern core steels in transformers on current chopping has minimized the concern about switching surges from these sources. Attention is focused on surges from the ordinary energization or reclosing of lines. Investigations have shown that voltages in the order of 3.0 per unit of phase-to-neutra..gamma..l crest voltage are possible when picking up lines from a stiff bus. Voltages well over 3.0 per unit are possible on reclosing operations. Through a proper combination or resistor size, pole closing span and resistor shorting time maximum voltages can be limited to the order of 2.0 per unit for line lengths up to 200 miles.

• OSTI ID: 6676932
• Journal Information: Electr. World; (United States), Vol. 161
• Country of Publication: United States
• Language: English

Related Subjects

24 POWER TRANSMISSION AND DISTRIBUTION
CIRCUIT BREAKERS
ELECTRICAL INSULATION
EHV AC SYSTEMS
POWER TRANSMISSION LINES
DESIGN
ELECTRICAL FAULTS
PERFORMANCE TESTING
SPECIFICATIONS
SURGES
AC SYSTEMS
ELECTRICAL EQUIPMENT
EQUIPMENT
EQUIPMENT PROTECTION DEVICES
POWER SYSTEMS
TESTING
200301* - Power Transmission & Distribution- AC Systems
EHV & UHV- (-1989)