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The S&C Vista® SD Underground Distribution Switchgear is designed for outdoor distribution applications at 17.5 kV and 29 kV, incorporating Visi-Gap® Load-Interrupter Switches and Visi-Gap® Fault Interrupters. This instruction sheet provides comprehensive guidance for the installation, operation, and maintenance of the switchgear, emphasizing safety and proper handling.
The Vista SD Switchgear serves as a critical component in underground electrical distribution systems, enabling the safe and efficient management of power. Its primary function is to interrupt load currents and isolate faults within the distribution network, thereby protecting equipment and ensuring system reliability. The Visi-Gap® Load-Interrupter Switches facilitate controlled opening and closing of circuits under load, while the Visi-Gap® Fault Interrupters automatically clear fault currents, preventing widespread outages and equipment damage. The switchgear is available in both vault-mounted and pad-mounted styles, offering flexibility for various installation environments.
The switchgear is designed for use by qualified persons who are knowledgeable in the installation, operation, and maintenance of overhead and underground electric distribution equipment. Safety is paramount, with detailed instructions provided for understanding safety-alert messages (DANGER, WARNING, CAUTION, NOTICE) and following safety precautions.
For vault-mounted installations, the switchgear can be placed directly in a vault or installed through a 31½-inch manhole. Specific steps are outlined for securing the switchgear, removing and re-installing optional components like motor operators, continuous ground buses, and bushing/bushing-well adapters. Cable installation involves removing shipping covers from bushings and bushing wells, installing cable support brackets, and terminating cables with user-furnished separable insulated connectors. Proper cable installation practices, including strain relief and looping, are emphasized to prevent damage to bushings. Grounding procedures are detailed, requiring connection of ground pads to the system ground and, if applicable, the continuous ground bus. Fault indicators, furnished by the user, are to be mounted on provided brackets with sensors attached to the cables.
Pad-mounted style installations involve unbolting the switchgear from its skid and lifting it onto a mounting pad. The enclosure must be leveled using shims and secured to the pad with anchor brackets, ensuring all doors and the hinged roof open and close without binding. Access to the interior is gained by removing a shipping clamp and rotating a pentahead (or hexhead) socket wrench to unlatch the hinged roof. The hinged roof can be lifted to a 45° "hold-open" position, with a latching mechanism engaging automatically. For cable pulling, the hinged roof can be lifted to a second, more vertical position by releasing latches on the "hold-open" mechanisms. Cover panels are removed by unscrewing pins and disengaging tabs, allowing access to the termination compartment. Hinged-roof counterweights are attached by removing shipping materials, pivoting lever arms, and pressing captive pins through aligned holes.
The instruction sheet provides guidance for completing the installation, which includes aspects that contribute to long-term maintenance and reliability. Caulking around the bottom of the enclosure with a weather-proof, room-temperature vulcanizing (RTV) silicone-rubber compound is recommended to seal against rodents, insects, and moisture, and to discourage tampering. Any spaces between cables and conduits should be filled, and empty conduits capped. The exterior of the enclosure should be wiped clean, and any scratches or abrasions refinished with S&C red-oxide primer and touch-up finish to prevent rust and maintain the integrity of the enclosure.
Appendix A details routine switchgear testing, including dc cable testing and fault locating, very low frequency (VLF) cable testing, and fault-interrupter testing. These tests are performed by qualified personnel to assess the condition of the cables and switchgear. For dc cable testing, specific withstand voltage limits are provided, and precautions are outlined to prevent flashover, injury, and equipment damage. VLF cable testing, used for evaluating shielded power cable systems, also has specified sinusoidal waveform test voltages. The document emphasizes that the switchgear should be completely de-energized and disconnected from all power sources during these tests. Routine testing of vacuum fault interrupters is generally not recommended, but instructions are available from S&C Sales Offices for those who desire to perform such tests.
The manual stresses the importance of retaining the instruction sheet as a permanent part of the switchgear, designating a location for easy retrieval and reference. Replacement instructions and labels are available from S&C, and it is crucial to replace any missing, damaged, or faded labels immediately to ensure ongoing safety and proper operation.
General| Continuous Current | 600A |
|---|---|
| BIL Rating | 95 kV |
| Interrupting Capacity | 12.5 kA |
| Continuous Current Rating | 600 A |
| Interrupting Rating | 12.5 kA |
