Coordinacion De Protecciones

Why specify a Short Circuit and Coordination Study?
A Short Circuit and Coordination Study is critical for the safe, efficient, and economical operation of any electrical distribution system. A Short Circuit Study will help to ensure that personnel and equipment are protected by establishing proper interrupting ratings. When an electrical fault exceeds the interrupting rating of the protectivedevice, the consequences can be devastating, including injury, damaged electrical equipment, and costly downtime. A Coordination Study maximizes power system selectivity by isolating faults to the nearest protective device, as well as helping to avoid nuisance operations that are due to transformer inrush or motor starting operations. NFPA 70B maintains that a Short Circuit and Coordination Studyis a very important, yet sometimes an overlooked step after the initial design and before the implementation of an electrical distribution system. The NEC addresses the importance of this type of study in articles 110-9, 110-10, 240, and 517.17. It is clear that a thirdparty, independent study performed during/after the equipment submittal process, can prove to be invaluable. A Short Circuit andCoordination Study serves to incorporate all the system changes that come about after the initial design. Some examples of factors that commonly change in the implementation of a system are: the utility available fault level, size and/or transformer impedance values, conductor size/type, addition of motors, and the system operating parameters. The following is an example of a complete shortcircuit/coordination, motor starting, harmonics, and load flow study project specification. Please review this specification for possible use in your next electrical design project to protect and maximize the operating efficiency of your power system design. If you would like this specification on a disc formatted in Microsoft Office (Word), please call CPE at (401) 694-9494, fax your request to (410)694-0085, or e-mail carl@cpeinc.net
======================================================================+++++++====================== TECHNICAL SPECIFICATIONS SHORT CIRCUIT ANALYSIS AND COORDINATION STUDY PART 1 – GENERAL 1.1 A. SUMMARY An Engineering Analysis and Coordination Study shall be performed on the electrical distribution system. The analysis shall include a short-circuit analysis withprotective device evaluation, a protective device coordination study, a motor starting study, load flow/voltage drop study and a harmonics analysis. A one-line diagram of the system shall also be included. The final report shall be bound in a three-ring binder. SCOPE OF PROJECT The project shall begin at the 34.5kV utility service at the facility, continue through the corresponding 15kV system,down through the 480V unit substation to all downstream distribution and branch panelboards, motor control centers, and significant motor locations. The project shall include the new generator and all associated emergency power distribution equipment, including automatic transfer switches and generator ground fault protection.

1.2 A.

B.

1.3 A.

PREPARER Engineering Analysis andCoordination Study shall be performed by Coordinated Power Engineering, Inc. or an approved, acceptable and qualified equal. Local Representative: Coordinated Power Engineering, Inc. 1340-G Charwood Road Hanover, Maryland 21076 Voice: 410-694-9494 Fax: 410-694-0085 Attention: Carl Rager

1.4 A.

SHORT-CIRCUIT ANALYSIS WITH PROTECTIVE DEVICE EVALUATION Systematically calculate fault currents based on theavailable fault current at the facility service entrance. Study preparer shall obtain the available fault current from the local utility. Short-circuit calculations shall be prepared by means of a digital computer utilizing a commercially available software package. Motor contribution shall be incorporated in determining fault levels. Results of short-circuit calculations shall be presented in...