Ground%20Fault%20Protection[1].ppt
Transcript of Ground%20Fault%20Protection[1].ppt
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Grounding
Ground Fault Protection
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Ground Fault Protection
Course Objectives:Upon completion of this course, you will be
able to:• Define the ground fault protective schemes
utilized in the industry today for simple radial schemes• Define the ground fault protective schemes
utilized in the industry today for complex
systems
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Ground-Fault Systems
Types of Ground Fault Protective Schemes Ground Strap
Zero Sequence
Residual
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Ground Strap System
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Ground Strap Operation
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Ground Strap System
Disadvantages
* Can only be used on main disconnect
* ust be the only neutral ground ! " can lead to nuisance trippings
" desensiti#ed tripping under an actual
faulted condition
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Ground Strap System
Disadvantages
* desensiti#ed tripping due to groundedneutrals
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Zero Sequence System
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Zero Sequence System
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Zero Sequence System Operation
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Zero Sequence System Operation
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Zero Sequence System
Advantages
**can be used on both the main and feeder brea$ers
Disadvantages**do%nstream grounds can cause nuisance trippings
**improperly centered conductors can also causenuisance trippings
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Residual System
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Residual System
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Residual System
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Residual System Operation
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Residual System
Advantages
&sed on main and feeder brea$ers
'eutral grounds on line side have no effect
'o control po%er required
(ne)pensive if purchased %ith brea$er
'eutral C only e)ternal device
Disadvantages
'o do%nstream grounds
'ot economical for fused s%itches
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Complex Systems
Ground Fault Protection
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Multi-Leel Ground Fault- ProtectionSystems
Ground Fault Protection
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!ou"le-#nded Su"station
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!ou"le-#nded Su"station $it% Fault
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Single Point Ground System
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Modi&ied !i&&erential Sc%eme
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Modi&ied !i&&erential $it% Residual System
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#mergency Systems
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#mergency Systems $it% S$itc%ed 'eutral
irst !lternative
Utilize four"pole
#ransfer $witch
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#mergency Systems
$econd !lternative
%emove the &ain
'onding (umper
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#mergency Systems
#hird !lternative
)mploy a Differential
$cheme
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Ground Fault
*+ hat are the two schemes often employed to provide
ground"fault protection on double"ended substations-
.+ hat is the major disadvantage of the
single"point"grounding scheme for ground" fault
protection when the tiebrea/er is closed-0+ hat are the three different types of ground"fault systems-
1+ here is the ground"fault sensor located for a ground
strap system-
2+ hat is the only disconnect device that can use a ground strap system-
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Ground Fault
*+ hat are the two schemes often employed to provide
ground"fault protection on double"ended substations-
3source ground sensing
3modified differential scheme
.+ hat is the major disadvantage of the
single"point"grounding scheme for ground" fault
protection when the tiebrea/er is closed-
++!ll unbalanced single"phased loads from the remote halfof the switchboard are 4seen5 as fault current 6 which may
cause nuisance trippings+
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Ground Fault
0+ hat are the three different types of ground"fault systems-
3ground strap 7also called neutral ground strap8
3zero se9uence
3residual
1+ here is the ground"fault sensor located for a ground
strap system-
3located on the main bonding jumper
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Ground Fault
2+ hat is the only disconnect device that can use a
ground strap system-
3ground strap system can only be used on the main
disconnect
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Ground Fault
Comments or uestions-