IEEE C37.121 1989

$31.42

American National Standard for Switchgear – Unit Substations – Requirements

Published By	Publication Date	Number of Pages
IEEE	1989	34

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Description

New IEEE Standard – Inactive – Superseded. This standard covers the requirements for three-phase unit substations for step-down operation in the range of 112.5 kVA through 10 000 kVA at primary voltages of 601 volts through 38 kilovolts. The standard is intended for use as the basis for the coordination of equipment by assisting in the selection of components. A variety of designs for unit substations are possible using various combinations of incoming sections, transformer sections, outgoing sections, and transition (throat) sections. Since the transformer section determines the kVA and voltage capabilities of a unit substation, the ratings of the various types of unit substations are described in terms of transformer capability.

PDF Catalog

PDF Pages	PDF Title
1	Title Page
3	Introduction Participants
5	CONTENTS
7	1. Scope
8	2. Referenced and Related Standards 2.1 Referenced American National Standards
10	2.2 Other Referenced Standards 2.3 Related Standards
11	3. Definitions
12	4. Service Conditions 4.1 General 4.2 Usual Service Conditions
13	4.3 Unusual Service Conditions 5. Transformer Section 5.1 Primary Unit Substation Transformers
14	5.2 Secondary Unit Substation Transformers 6. Incoming Section 6.1 High-Voltage (or Primary) Bushings on the Transformer Cover 6.2 Terminal Chamber 6.3 Metal-Clad Switchgear 6.4 Metal-Enclosed Interrupter Switchgear
15	6.5 Cutout, Fuse, or Fuse Link 7. Outgoing Section 7.1 Metal-Clad Switchgear 7.2 Metal-Enclosed Interrupter Switchgear 7.3 Metal-Enclosed, Low-Voltage, Power-Circuit-Breaker Switchgear 7.4 Molded-Case, Circuit-Breaker, Dead-Front Switchboards 7.5 Motor Control Centers 8. Ratings 8.1 Rated Frequency 8.2 Rated kVA
16	8.3 Rated High Voltage (or Primary Voltage) and Rated Low Voltage (or Secondary Voltage) 8.4 Rated Continuous Current 8.5 Rated Short-Circuit Current (Carrying) 8.6 Rated Short-Circuit Current Withstand (Momentary)
17	8.7 Rated Low-Frequency, One-Minute Withstand Voltage 8.8 Rated Impulse-Withstand Voltage (BIL) 9. Construction 9.1 Phase and Polarity Arrangements
18	9.2 Phase Sequence 9.3 Metal Barriers 9.4 Interlocks 9.5 Grounding 9.6 Nameplates 9.7 Drawings-Diagrams-Instructions
19	9.8 Coordination 10. Typical Arrangements
20	11. Guide for Selection, Application, Installation, and Maintenance of Unit Substations 11.1 Application Considerations 11.2 Unusual Service Conditions
21	11.3 System Conditions 11.4 Location—Transformer Selection
22	11.5 Load Requirements
23	11.6 Miscellaneous Design Considerations
25	11.7 Installation, Field-Testing, Operation, and Maintenance