IEEE Std C37.20.2-1999 IEEE Standard for Metal-Clad Switchgear -Description
Abstract: Metal-clad (MC) medium-voltage switchgear that contains drawout electrically operated circuit breakers is covered. MC switchgear is compartmentalized to isolate all components such as instrumentation, main bus, and both incoming and outgoing connections with grounded metal barriers. Rated maximum voltage levels for metal-clad switchgear range from 4.76 kV to 38 kV with main bus continuous current ratings of 1200 A, 2000 A, and 3000 A. MC switchgear also contains associated control, instruments, metering, relaying, protective, and regulating devices, as necessary. Service conditions, ratings, temperature limitations and classification of insulating materials, insulation (dielectric) withstand voltage requirements, test procedures, and applications are discussed.
Keywords: control, cumulative loading, current transformers, drawout, indoor, instrumentation, load current-carrying, metal-clad (MC) switchgear, metal-enclosed (ME) power switchgear, outdoor, protection, qualifying terms, switchgear assemblies, transformer accuracy, voltage transformers
Content
1. Scope
2. References
3. Definitions, qualifying terms,and common or related terms
3.1 General
3.2 Qualifying terms
3.3 Common or related terms
4. Service conditions
5. Ratings
5.1 General
5.2 Voltage and insulation levels
5.2.1 Rated maximum voltage
5.2.2 Rated insulation levels
5.2.3 Voltages and insulation levels
5.3 Rated power frequency
5.4 Rated current
5.4.1 Rated continuous current
5.4.2 Continuous current ratings
5.4.3 Rated momentary withstand current
5.4.4 Momentary withstand current rating
5.4.5 Rated short-time withstand current
5.4.6 Short-time withstand current rating
5.5 Temperature limitations
5.5.1 Limiting temperature
5.5.2 Temperature limits for insulating materials
5.5.3 Temperature limits for buses and connections
5.5.4 Temperature limitations for air surrounding devices within an enclosed assembly
5.5.5 Temperature limitations for air surrounding insulated power cables
5.5.6 Temperature limitations for external parts subject to contact by personnel
5.6 Current transformer ratings
5.6.1 Current transformer mechanical rating
5.6.2 Current transformer thermal ratings
5.6.3 Current transformer ambient temperature
5.7 Current transformer accuracies
6. Tests
6.1 General
6.2 Design tests
6.2.1 Dielectric tests
6.2.2 Rated continuous current tests
6.2.3 Momentary withstand current tests
6.2.4 Short-time withstand current tests
6.2.5 Auxiliary equipment primary disconnecting device momentary current withstand test
6.2.6 Mechanical endurance tests
6.2.7 Sheet, molded, or cast-insulating materials
6.2.8 Flame-resistance tests for applied insulation
6.2.9 Coating (paint) qualification test
6.2.10 Rain test for outdoor MC switchgear
6.3 Production tests
6.3.1 Dielectric tests
6.3.2 Mechanical operation tests
6.3.3 Grounding of instrument transformer case tests
6.3.4 Electrical operation and control wiring tests
6.4 Conformance tests
6.5 Field dielectric tests
7. Construction
7.1 Buses and primary connections
7.1.1 Phase or polarity arrangements
7.1.2 Phase sequence
7.1.3 Cable terminations
7.1.4 Bushings, potheads, or other terminators
7.1.5 Main bus splices
7.2 Grounding
7.3 Control and secondary circuits and devices
7.3.1 General
7.3.2 Voltage transformer fusing
7.3.3 Control, secondary, and logic-level wiring
7.3.4 Secondary-wiring terminals
7.3.5 Terminal blocks
7.3.6 Designation of auxiliary switches and contacts
7.3.7 Device function numbers
7.3.8 Voltage limits of instrument and control circuits
7.3.9 Polarity of dc connections to device coils
7.3.10 Isolation
7.3.11 Control voltage ranges
7.4 Miscellaneous
7.4.1 Nameplate marking
7.4.2 Wiring devices
7.4.3 Inspection windows
7.4.4 Covers
7.4.5 Ventilation openings and vent outlets
7.4.6 Service disconnecting means
7.5 Materials, finishes, and color
7.5.1 Materials
7.5.2 Finishes and color
7.6 Precautionary labels
7.7 Barriers
7.8 Shutters
7.9 Insulating materials for covering buses and connections
7.10 Interlocks
7.11 Interchangeability of removable switching and interrupting devices
7.12 Primary fuses and transformers
7.13 Secondary disconnect devices
7.14 Control wiring
7.15 Handling device
7.16 Test cabinet
7.17 Indoor MC switchgear, access, and ventilation
7.18 Outdoor MC switchgear, access, and ventilation
7.19 Circuit breaker open/close position indication
7.20 Enclosure categories
7.21 Ground and test devices
7.22 Load interrupter switches
8. Application guide for MC switchgear
8.1 Unusual service conditions
8.1.1 Ambient air temperature above 40°C
8.1.2 Ambient air temperature below -30°C
8.1.3 Application at unusual altitudes
8.1.4 Modification of equipment for unusual environments
8.2 System characteristics—voltage and frequency
8.3 Overvoltage considerations—insulation levels
8.4 Continuous current rating and overload capability
8.4.1 Load current-carrying capabilities under various conditions of ambient temperature and load
8.4.2 Load current-carrying capability of MC switchgear
8.4.3 Special continuous current ratings
8.4.4 Conductor temperature
8.4.5 Conductor terminations
8.4.6 Control supply terminations
8.5 Short-circuit considerations
8.6 Nuclear power plant application
8.7 Associated devices often used in MC switchgear
8.7.1 Current transformers
8.7.2 Surge protective devices
8.8 Protection and isolation of switchgear connected to other circuit protective equipment
9. Guide for handling, storage, and installation
9.1 General
9.2 Handling
9.2.1 Receiving
9.2.2 Rigging
9.2.3 Storage
9.2.4 Installation
9.2.5 Removal of shipping members
9.2.6 Connections
9.3 Preoperation check
9.4 Removable elements
9.5 Interlocks
9.6 Energizing
Annex A Guide for enclosure categories and related requirements
