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Switchgear Riddle No.27 - Circuit breaker with two trip coils
What is the criteria or norm for a circuit breaker to have double trip coil?
Author : Julio Navas - From: Venezuela
 
#1
Wed, July 22nd, 2015 - 09:11
You can refer to:
IEEE PSRC, WG I 19 (Redundancy Considerations for Protective Relaying Systems)

For the protection of Interconnected Power Systems, the requirement for redundant protection systems is not only necessary to avoid major system disturbance, but also may be compulsory as part of regulatory obligations. For the protection of systems of lesser importance, the redundancy can be optional provided that the power system elements are adequately and reasonably protected. Therefore, in determining whether the protection redundancy should be made compulsory or optional, one should consider the following questions:

The cost of providing redundant protection systems is justifiable
The loss of the power system, due to a single contingency failure of the protection system, is deemed an acceptable risk
Regulatory organizations may require redundancy for Interconnected Power System
Protection system without redundancy could adversely impact maintenance frequency and interval criteria
Protection system without redundancy could adversely impact safety of equipment, facilities, and the public
Redundant communications scheme may be necessary if a protection system uses
communications, i.e. for transfer tripping upon a breaker failure condition, can the backup relays provide remote backup protection for a loss-of-communications or out-of-service communications condition and/or can a local breaker failure isolate the infeed so that remote relays sense all faults in adjacent lines?

When required, a fully redundant protection system can be realized using separate and independent sensing devices, trip modules, protective relays, and batteries. The following system and design requirements may then be considered:
Separate current transformers for each protection group
Separate voltage transformers or at least dual voltage supply (one voltage transformer with separate secondary windings) for each protection group
Each independent protection system may be mounted on separate panels or segregated on a single panel
Independent and separate battery systems (A and B)
Maintain routing of cables from instrument transformers as separate as possible
Dual trip coils for circuit breakers
Provide separate communication channels for teleprotection and transfer trips

 
Author : Hamid - From: Iran
 
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