MediumVoltage Switchgear Then and Now

1
Medium-Voltage Switchgear - Then and Now -

• Hans-Joachim Müller

2
Evolution of Medium-Voltage Switchgear
Source ABB
Local installation
Workshop manufacture
Factory-assembled, type-tested
Factory-assembled, compact
Factory-assembled, SF6-insulated
non type tested
type tested
Gas-insulated
Cast-resin insulated
Air-insulated
Air/solid-insulated
3
Situation in the Past

• Yesterday, switchgear were air, oil or
  cast-resin insulated with the following
  features
• Huge dimensions
• Dependent on pollution and climate
• Maintenance at regular intervals
• Human failure during maintenance
• High fire risk
• Not arc-fault tested
• This means
• High investment for buildings
• High costs for maintenance staff and system
  transfer in the network
• Breakdown of the network (longer downtimes)

4
Restricted Availability and Reliability of Supply
After short circuit at the rear side of an
epoxy-resin insulated switchgear
Burned-out 10 kV substation Fire after short
circuit in an epoxy-resin insulated ring-main unit
5
Objectives for the Development of New Switchgear

• Requirements for development
• Personal safety
• Reliability of supply
• Maintenance-free design
• Suitability for all switching duties
• Sufficient power reserves
• Low fire risk
• Small, light design
• Concept options for new switchgear due to
  availability of the following equipment
• Maintenance-free switching devices
• Shockproof cable plugs and bar connections
• Electronic measuring and protection devices

6
Implementation of the Development Tasks

• Constructional implementation
• Solid insulation is replaced by insulating gas
  with constant properties
• Sealed enclosure of primary part
• Installation of fixed-mounted, maintenance-free
  switching devices- Vacuum circuit-breaker-
  Three-position switch- SF6-switch-disconnector
• Shockproof cable plugs
• Use of current and voltage transformers with low
  susceptibility to faults
• Verification of safe isolation from supply with
  capacitive voltage dividers
• Maintenance-free and reliable operating elements
  with few parts inside the enclosure
• Easiest operation
• Pressure-resistant enclosure with defined
  pressure relief

7
Situation with Gas-Insulated Switchgear

• Todays state of the art is gas-insulated
  switchgear with the following main benefits
• Small, compact dimensions
• Independent of environmental effects and climate
• Widely maintenance-free
• Maximum safety for staff
• Low fire risk
• Arc-fault tested
• Advantages
• Low invest for buildings due to compact
  dimensions and climate-independent design
• Maximized power supply reliability
• Maximum personal safety
• Lowest life cycle costs
• Reduced operational costs - no additional
  maintenance costs

8
First SIEMENS Gas-Insulated Medium-Voltage
Switchgear (April 1982)
Kulmbach / Germany 8DA10 16 panels 24 kV / 16 kA
(3s) / 1250 A
9
Applications Today
Tibet / China 8DA10 205 panels 40.5 kV / 31.5 kA
(3s) / 1250 A
10
First SIEMENS Gas-Insulated Medium-Voltage
Ring-Main Unit (April 1982)
Stadtwerke Lambrecht / Pfalz, Germany Project Mun
icipal power supply Electrical data 24 kV, 16
kA, 630 A Typicals 8DJ10, scheme 10
11
Switchgear Type 8DJTypical Application Examples
12
Thank you very much for your attention!