VA 26 05 71-2010 ELECTRICAL SYSTEM PROTECTIVE DEVICE STUDY.pdf

1、09-10 26 05 71 - 1 SECTION 26 05 71 ELECTRICAL SYSTEM PROTECTIVE DEVICE STUDY SPEC WRITER NOTE: Delete between / - / if not applicable to project. Also delete any other item or paragraph not applicable in the section and renumber the paragraphs. This section shall be included in all projects requiri

2、ng major primary replacement or modifications, large hospital construction, and those projects for which it is specifically requested by the Government. The inclusion of this section does not relieve the A/E of preparing short-circuit calculations and coordinating over-current devices. Its purpose i

3、s to ensure that the successful bidders equipment shall perform as intended. PART 1 - GENERAL 1.1 DESCRIPTION A. This section specifies the requirements of the Electrical System Protective Device Study (herein, “the study”). B. A short-circuit and selective coordination study shall be prepared for t

4、he electrical overcurrent devices to be installed under this project. SPEC WRITER NOTE: Insert the limits of the study in the blank space if a complete study is not required. C. The study shall present an organized time-current analysis of each protective device in series from the / individual devic

5、e / / _ / back to the utility/ and the on-site generator sources/. The study shall reflect the operation of each device during normal and abnormal current conditions. 1.2 RELATED WORK A. Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS: General electrical requirements that are common to m

6、ore than one section of Division 26. B. Section 26 13 00, MEDIUM-VOLTAGE SWITCHGEAR: Medium-voltage distribution switchgear. C. Section 26 18 41, MEDIUM-VOLTAGE SWITCHES: Medium-voltage switches. D. Section 26 23 00, LOW-VOLTAGE SWITCHGEAR: Low voltage switchgear. E. Section 26 24 11, DISTRIBUTION S

7、WITCHBOARDS: Low-voltage distribution switchboards. F. Section 26 24 16, PANEL BOARDS: Low-voltage panelboards. G. Section 26 24 19, MOTOR CONTROL CENTERS: Low-voltage motor control centers. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 05

8、 71 - 2 H. Section 26 24 21, MOTOR CONTROL PANELBOARDS: Low-voltage motor control panelboards. I. Section 26 32 13, ENGINE-GENERATORS: Engine-generators. J. Section 26 36 23, AUTOMATIC TRANSFER SWITCHES: Automatic transfer switches. 1.3 QUALITY ASSURANCE A. Refer to Paragraph, QUALIFICATIONS, in Sec

9、tion 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS. B. The protective device study shall be prepared by the equipment manufacturers qualified engineers or an approved consultant. The contractor is responsible for providing all pertinent information required by the preparers to complete the stu

10、dy. 1.4 SUBMITTALS A. In accordance with Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS, submit the following: B. Product data on the software program to be used for the study. Software shall be in mainstream use in the industry, shall provide device settings and ratings, and shall show

11、 selective coordination by time-current drawings. C. Complete short-circuit and coordination study as described in paragraph 1.6. D. Protective equipment shop drawings shall be submitted simultaneously with or after the protective device study. Protective equipment shop drawings will not be accepted

12、 prior to protective device study. E. Certification: Two weeks prior to final inspection, submit four copies of the following to the /Resident Engineer/ /COTR/: Certification by the contractor that the protective devices have been adjusted and set in accordance with the approved protective device st

13、udy. 1.5 APPLICABLE PUBLICATIONS A. Publications listed below (including amendments, addenda, revisions, supplements, and errata) form a part of this specification to the extent referenced. Publications are referenced in the text by designation only. B. Institute of Electrical and Electronics Engine

14、ers (IEEE): 242-01 . Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems 399-97 . Recommended Practice for Power Systems Analysis 1584a-04 . Guide for Performing Arc-Flash Hazard Calculations Provided by IHSNot for ResaleNo reproduction or networking permi

15、tted without license from IHS-,-,-09-10 26 05 71 - 3 SPEC WRITER NOTE: On small renovation projects, modify the scope to describe the proper extent of the study. 1.6 REQUIREMENTS A. The complete study shall include a system one line diagram, short-circuit and ground fault analysis, and protective co

16、ordination plots for all overcurrent protective devices. B. One Line Diagram: 1. On the one line diagram, show all electrical equipment and wiring to be protected by the overcurrent devices installed under this project. 2. On the one line diagram, also show the following specific information: a. Cal

17、culated fault impedance, X/R ratios, and short-circuit values at each feeder and branch circuit bus. b. Breaker and fuse ratings. c. Generator kW and Transformer kVA and voltage ratings, percent impedance, X/R ratios, and wiring connections. d. Voltage at each bus. e. Identification of each bus, mat

18、ching the identification on the construction drawings. f. Conduit, cable, and busway material and sizes, length, and X/R ratios. C. Short-Circuit Study: 1. Systematically calculate the fault impedance to determine the available short-circuit and ground fault currents at each bus. Incorporate the mot

19、or contribution in determining the momentary and interrupting ratings of the protective devices. 2. The study shall be calculated by means of a computer program. Pertinent data and the rationale employed in developing the calculations shall be incorporated in the introductory remarks of the study. 3

20、. Present the data conclusions of the short-circuit study in a table format. Include the following: a. Device identification. b. Operating voltage. c. Protective device. d. Device rating. e. Calculated short-circuit current. D. Coordination Curves: 1. Prepare the coordination curves to determine the

21、 required settings of protective devices to ensure selective coordination. Graphically Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 05 71 - 4 illustrate on log-log paper that adequate time separation exists between series devices, includi

22、ng the utility company upstream device. Plot the specific time-current characteristics of each protective device in such a manner that all upstream devices are clearly depicted on one sheet. 2. The following specific information shall also be shown on the coordination curves: a. Device identificatio

23、n. b. Voltage and current ratio for curves. c. 3-phase and 1-phase ANSI damage points for each transformer. d. No-damage, melting, and clearing curves for fuses. e. Cable damage curves. f. Transformer in-rush points. g. Maximum short-circuit cutoff point. 3. Develop a table to summarize the settings

24、 selected for the protective devices. Include the following in the table: a. Device identification. b. Relay CT ratios, tap, time dial, and instantaneous pickup. c. Circuit breaker sensor rating, long-time, short-time, and instantaneous settings, and time bands. d. Fuse rating and type. e. Ground fa

25、ult pickup and time delay. 1.7 ANALYSIS A. Analyze the short-circuit calculations, and highlight any equipment determined to be underrated as specified. Propose approaches to effectively protect the underrated equipment. Provide minor modifications to conform with the study (examples of minor modifi

26、cations are trip sizes within the same frame, the time-current curve characteristics of induction relays, CT ranges, etc.). B. After developing the coordination curves, highlight areas lacking coordination. Present a technical evaluation with a discussion of the logical compromises for best coordina

27、tion. 1.8 ADJUSTMENTS, SETTINGS AND MODIFICATIONS A. Necessary final field adjustments, settings, and minor modifications shall be made to conform with the study without additional cost to the Government. B. All final circuit breaker and relay settings and fuse sizes shall be made in accordance with the recommendations of the study. - - - E N D - - - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-