Circuit breakers and fuses are commonly used in power systems in order to protect valuable power systems assets such as conductors, transformers, motors, generators, switchgear assemblies etc… against both sustained overloads and short circuit currents. In such events, it is important to isolate the affected section swiftly and reliably while ensuring that the rest of the system remains operational.
In a well-co-ordinated protection scheme, protective devices are selected and adjusted such that the occurrence of false trips and equipment damage are prevented, giving you robust and reliable electrical protection.
In a protection co-ordination study, time current curves (TCCs) of various protective devices are constructed and analysed against each another on Log-Log plots. Overlapping of TCCs from various devices represent poor co-ordination. These issues are then addressed by adjusting the curves until appropriate grading and protection is achieved.
There is also a regulatory requirement under “The Electricity at Work Regulations 1989” to ensure that Electrical Systems are properly protected from excess current.
Regulation 4 Systems, work activities and protective equipment States in (1) All systems shall at all times be of such construction as to prevent, so far as is reasonably practicable, danger.
The safety of a system depends upon the proper selection of all the electrical equipment in the system and the proper consideration of the inter-relationship between the individual items of equipment. For example, electrical protection
against overloads and earth faults etc may need to be provided in one part of a system to protect another, possibly remote, part of the system.
Regulation 11 Means for protecting from excess of current: States efficient means, suitably located, shall be provided for protecting from excess of current every part of a system as may be necessary to prevent danger.
Carrying out a protection study will certainly help to demonstrate compliance with these Regulations.
You can now ensure that your valuable assets are protected against damage caused by short circuits and overloads while minimizing production loss caused by unnecessary plant down time. In addition, the interrupting ratings of all protective equipment, conductors, and switches are checked for adequacy in coordination studies ensuring compliance with legislation. Inadequate equipment ratings can result in either extensive damage to the equipment during faults and system operation and may introduce hazards to plant operating personnel.
With Protective Device Coordination Analysis, Electrical Safety (UK) will ensure that you achieve the optimum balance between equipment protection and selective isolation that is consistent with the operating requirements of the overall power system.