Gas-insulated, arc-resistant switchgear for critical power applications (white paper)

Overview

The paper argues that GIS with vacuum interrupters and SF6 insulation reduces maintenance, removes environment-driven failure modes and improves operator safety through arc-resistant design. It is a manufacturer publication, so it is an advocacy piece listing the advantages of one product class rather than a neutral comparison, and its claims should be read that way.

The floor-space figures are the most concrete claim: compared with air-insulated switchgear, GIS saves on average more than 50% of footprint for systems up to 15 kV and more than 75% up to 38 kV. The other listed benefits are a 10-year inspection interval, an isolated-phase design that removes phase-to-phase faults, and arc-resistance tested to ANSI/IEEE C37.20.7.

The reliability argument rests on IEEE 493 (Gold Book) failure-cause data. For AIS, moisture accounts for 30% of failure causes, protective-device malfunction 10%, dust and contaminants 10% and ageing 10%. The paper estimates that about 50% of failure causes do not apply to sealed MV GIS. This is an inference from the cause distribution, not a measured failure rate.

The closing section says the highest-reliability data-centre substations should accept utility power from at least two sources, with automatic switching and interlocking. It adds that isolated-phase GIS lineups can be extended without interrupting supply to connected load.

Key points

1. GIS footprint savings average over 50% for systems up to 15 kV and over 75% up to 38 kV versus AIS.
2. Claimed benefits: 10-year inspection interval, isolated-phase design removing phase-to-phase faults, arc resistance tested to ANSI/IEEE C37.20.7.
3. IEEE 493 AIS failure causes: moisture 30%, protective-device malfunction 10%, dust/contaminants 10%, ageing 10%.
4. An estimated 50% of AIS failure causes do not apply to MV GIS.
5. Highest-reliability substations should take utility power from at least two sources with automatic switching and interlocking.
6. Isolated-phase GIS lineups can be extended without interrupting supply to connected load.

Using it in design

• In the MV switchgear catalogue store insulation {AIS, GIS}, arc-resistance standard and rating, inspection interval and footprint.
• Apply the paper's footprint factors in the space planner when GIS is selected.
• Let the reliability model use lower failure-rate assumptions for sealed GIS, citing the IEEE 493 cause categories.
• For Tier III/IV targets, require two utility incomers with automatic transfer at the MV substation.

Who should read it

Electrical designers and decision makers choosing between AIS and GIS for a data-centre substation.

Related standards

• IEEE C37.20.7
• IEEE 493
• IEEE C37.20.2

Publication details

Authors

Siemens

Publisher

Siemens

Year

2021

Document number

SIDS-T40117-00-4AUS

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation