Transcript Lighting Arresters and their Application

Lightning Arresters and Their Application
(System Reliability Enhancement)
2011 SWEDE Conference
Steve Brewer
Hubbell Power Systems/Ohio Brass
SWEDE Conference - April 2011
Outline
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Disconnector Reliability
Line Insulator Protection
Practical/Safety Topics
Track Resistant Bracket
SWEDE Conference - April 2011
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Disconnector Reliability
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Proper Isolator Operation
• Ground lead separated
• Normal overcurrent
sequence
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–
–
–
Protection operates
System re-energized
Voltage holds
Service to end user restored
• Visual indication of failure
SWEDE Conference - April 2011
Improper Isolator Operation
• Ground lead remains intact
• Normal overcurrent
sequence
–
–
–
–
Protection operates
System re-energized
System trips until lock-out occurs
Service to end user NOT restored
• No visual indication of failure
SWEDE Conference - April 2011
Resistor Graded Disconnector Time-Current Curve
10
Time (s)
1
0.1
0.01
10
100
1000
Current (A)
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Capacitor Graded Disconnector Time-Current Curve
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Line Insulator Protection
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The Enemy
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Traveling Wave/ Overvoltage Protection
• Lightning hits mid-span
• Current divides and then
propagates
• V=IxR
Surge Arresters - Concept
• Surge causes traveling voltage wave
• Voltage would be enough to flash-over insulation
• Surge arrester high resistance at L-G voltage
• Surge arrester low resistance at surge voltage
• Surge is diverted to ground
• Surge arrester high resistance again after surge
• Conduction time is too short for breakers to react
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Case Histories
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National Grid
• Champion International Paper Co.
– Operates 363 days/year, 24 hours/day
– One interruption costs $50-100k
• No. 2 line - 115 kV, 70 years old
– Hired PTI
– Installed new OHSW
– Improved footing resistances
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National Grid 115 kV Line without Surge
Arresters
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National Grid 115 kV Line with Surge Arresters
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Suspended Line Arrester Configuration
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Typical Dead-End Line Arrester Configuration
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Practical/Safety Topics
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Practical Issues
• Must use right rating and type
– Too large as bad a too small
• Lead length affects protection
• Conductor Size - Min. # 6 AWG
– Ground lead must be flexible
• Reuse of arresters
– Not recommended
• Testing of Arresters
– Thermal Imaging holds most promise
• DOT shipping considerations
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Safety Issues
• Porcelain arresters
– Most dangerous if do not blow up
• Disconnector operation
– Brings line voltage to base of unit
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Track Resistant Bracket
SWEDE Conference - April 2011
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