IEEE Std C37.20.2-1993 IEEE Standard for Metal-Clad and Station-Type Cubicle Switchgear -Description
Abstract: Metal-enclosed medium voltage switchgear (ME), which can contain either drawout electrically operated circuit breakers or stationary electrically operated circuit breakers in individual three-pole grounded metal compartments, is covered. Further, metal-clad switchgear (MC) 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 (MC) range from 5 kV through 38 kV with main bus continuous current ratings of 1200 A, 2000 A, and 3000 A. Rated maximum voltage levels for station-type cubicle switchgear (SC) range from 15.5 kV through 72.5 kV with main bus continuous current ratings of 2000 A, 3000 A, 4000 A, and 5000 A. ME 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 application are discussed.
Keywords: common or related terms, control, cumulative loading, cubicle switchgear, current transformers, drawout, indoor, instrumentation, load current-carrying, metal-clad switchgear (MC), metal-enclosed power switchgear (ME), metering, outdoor, protection, qualifying terms, stationary, station-type cubicle switchgear, switchgear assemblies, transformer accuracy, voltage transformers
Content
1. Overview
1.1 Scope
1.2 References
2. Definitions
2.1 General
2.2 Qualifying terms
2.2.1 accessible
2.2.2 alive (live)
2.2.3 automatic (self-coupling)
2.2.4 enclosed
2.2.5 insulating
2.2.6 isolated
2.2.7 ventilated
2.2.8 electrical
2.2.9 enclosure
2.2.10 flame-resistant (retardant)
2.2.11 indoor
2.2.12 metal-enclosed
2.2.13 outdoor
2.2.14 resistant (suffix)
2.2.15 secondary
2.2.16 ventilated enclosure
2.3 Common or related terms
2.3.1 asymmetrical
2.3.2 auxiliary switch
2.3.3 barrier
2.3.4 bus
2.3.5 connected position
2.3.6 continuous current tests
2.3.7 current-limiting fuse
2.3.8 disconnected position
2.3.9 drawout-mounted device
2.3.10 ground bus
2.3.11 live parts
2.3.12 main (primary switchgear connections)
2.3.13 normal frequency
2.3.14 primary disconnecting devices
2.3.15 removable element
2.3.16 secondary and control wiring
2.3.17 secondary disconnecting contact
2.3.18 shutter
2.3.19 silver surfaced
2.3.20 stationary mounted device
2.3.21 symmetrical
2.3.22 terminal
2.3.23 terminal block
2.3.24 test position
3. Service conditions
4. Ratings
4.1 General
4.2 Voltage and insulation levels
4.2.1 Rated maximum voltage
4.2.2 Rated insulation levels
4.2.3 Voltages and insulation levels
4.3 Rated frequency
4.4 Rated current
4.4.1 Rated continuous current
4.4.2 Continuous current ratings
4.4.3 Rated momentary current
4.4.4 Momentary current rating
4.4.5 Rated short-time current
4.4.6 Short-time current rating
4.5 Temperature limitations
4.5.1 Limiting temperature
4.5.2 Temperature limits for insulating materials
4.5.3 Temperature limits for buses and connections
4.5.4 Temperature limitations for air surrounding devices within an enclosed assembly
4.5.5 Temperature limitations for air surrounding insulated power cables
4.5.6 Temperature limitations for external parts subject to contact by personnel
4.6 Current transformer ratings
4.6.1 Current transformer mechanical rating
4.6.2 Current transformer thermal ratings
4.6.3 Current transformer ambient temperature
4.7 Current transformer accuracies
4.7.1 Current transformer accuracies for MC switchgear
4.7.2 Current transformer accuracies for SC switchgear
5. Tests
5.1 General
5.2 Design tests
5.2.1 Dielectric tests
5.2.2 Rated continuous current tests
5.2.3 Short-time current withstand tests
5.2.4 Momentary current withstand tests
5.2.5 Mechanical endurance tests
5.2.6 Sheet, molded, or cast-insulating materials for support of primary buses and connections
5.2.7 Flame-resistance tests for applied insulation
5.2.8 Paint qualification test
5.2.9 Rain test for outdoor ME switchgear
5.3 Production tests
5.3.1 Dielectric tests
5.3.2 Mechanical operation tests
5.3.3 Grounding of instrument transformer case tests
5.3.4 Electrical operation and control wiring tests
5.4 Conformance tests
5.5 Field dielectric tests
6. Construction
6.1 General requirements
6.1.1 Buses and primary connections
6.1.2 Grounding
6.1.3 Control and secondary circuits and devices
6.1.4 Miscellaneous
6.1.5 Materials, finishes, and color
6.1.6 Precautionary labels
6.2 MC switchgear
6.2.1 Barriers
6.2.2 Shutters
6.2.3 Insulating materials for covering buses and connections
6.2.4 Interlocks
6.2.5 Interchangeability of removable switching and interrupting devices
6.2.6 Primary fuses and transformers
6.2.7 Secondary disconnect devices
6.2.8 Control wiring
6.2.9 Handling device
6.2.10 Test cabinet
6.2.11 Indoor MC switchgear, access, and ventilation
6.2.12 Outdoor MC switchgear, access, and ventilation
6.2.13 Position indication
6.2.14 Enclosure categories
6.3 SC switchgear
6.3.1 Barriers
6.3.2 Buses and connections
6.3.3 Interlocks
6.3.4 Control wiring
6.3.5 Indoor station-type cubicles, access, and ventilation
6.3.6 Outdoor station-type cubicles, access, and ventilation
6.3.7 Secondary and control devices
7. Application guide for ME switchgear
7.1 Unusual service conditions
7.1.1 Ambient air temperature above 40 °C
7.1.2 Ambient air temperature below -30 °C
7.1.3 Application at unusual altitudes
7.1.4 Modification of equipment for unusual environment
7.2 System characteristics—Voltage and frequency
7.3 Overvoltage considerations—insulation levels
7.4 Continuous current rating and overload capability
7.4.1 Load current-carrying capabilities under various conditions of ambient temperature and load
7.4.2 Load current-carrying capability of metal-clad switchgear
7.4.3 Special continuous current ratings
7.4.4 Conductor temperature
7.4.5 Conductor terminations
7.4.6 Control supply terminations
7.5 Short-circuit considerations
7.6 Nuclear power plant application
7.7 Associated devices often used in ME switchgear
7.7.1 Current transformers
7.7.2 Surge protective devices
7.8 Protection and isolation of switchgear connected to other circuit protective equipment
8. Guide for handling, storage, and installation
8.1 General
8.2 Handling
8.2.1 Receiving
8.2.2 Rigging
8.2.3 Storage
8.2.4 Installation
8.2.5 Removal of shipping members
8.2.6 Connections
8.3 Preoperation check
8.4 Removable elements
8.5 Interlocks
8.5.1 Metal-clad switchgear
8.5.2 Station-type cubicle switchgear
8.6 Energizing
Annex A Guide for enclosure categories and related requirements
