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Earth Fault Protection |
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  May 8 2007, 08:58 AM
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#1
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Member  Group: Full Member Posts: 61 Joined: 17-December 05 Member No.: 1,308  |
 hi everybody we have a 520kw dc motor (arm voltage 550v amps 1008) controlled by dc drive of siemens make. The incoming supply of this drive is through transformer 3.3kv/550v .the neutral is unearthed. can anyone suggest earth fault protection of motors and cables(dc /ac side). ram |
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Mar 21 2008, 05:18 PM
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#2
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Junior Member Group: Full Member Posts: 7 Joined: 19-March 08 Member No.: 4,399 |
AC SIDE EF protection for unearthed sys is tough, Now a days high sensitive CBCT 's are used to detect earth faults in such systems which measure cable capacitive disc. currents to the fault. DC SIDE Ground fault sensing cards are available , but i do not know whether those can be applied for DC drives. |
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Mar 28 2008, 02:02 PM
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#3
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Junior Member Group: Members Posts: 3 Joined: 15-March 08 Member No.: 4,391 |
QUOTE (ram14375 @ May 8 2007, 08:58 AM)  hi everybody we have a 520kw dc motor (arm voltage 550v amps 1008) controlled by dc drive of siemens make. The incoming supply of this drive is through transformer 3.3kv/550v .the neutral is unearthed. can anyone suggest earth fault protection of motors and cables(dc /ac side). ram for DC it require an instrument to detect +,- cable's current balancing,also a shunt trip is need for the motor's supply circuit breaker. for AC it just need 3 nos CTs ,1 no earth fault IDMT,ciruit breaker of the AC side should provide a shunt trip. QUOTE (lau @ Mar 28 2008, 02:00 PM) for DC it require an instrument to detect +,- cable's current balancing,also a shunt trip is need for the motor's supply circuit breaker. for AC it just need 3 nos CTs ,1 no earth fault IDMT,ciruit breaker of the AC side should provide a shunt trip. |
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