Composite Power Group sells Solid Insulated bus bar systems (SIS) manufactured by Ritz at their facility in Germany.

Example of an SIS Bus Bar System rated at 3000A used to connect main breakers inside the basement of a substation. Picture shows system affixed to the substation ceiling and earthed in accordance with manufacturer recommendations.

Solid Insulated Bus Bars

Solid Insulation (SIS) Bus Bars are fully insulated segregated Iso Phase (ie. one fully insulated bus bar per phase) systems for transmitting high currents at voltages up to 36kV. They are used as an alternative to cable bus or metal enclosed bus ducts inside substations for the interconnection of electrical equipment.

Applicable for system voltages up to 36kV and currents up to 6500A
Ideal for areas with complex bends or tight space restrictions where multiple cables or large bus ducts just don’t fit
Can reduce the number of switchgear cells by eliminating parallel cable runs that may not fit into a single cell in high current applications
Fully designed and rated for Indoor and Outdoor applications
Solidly insulated for reliability and added safety
Easy to assemble and install (no welding) and come pre-terminated for the application (including options such as wall bushings and MV GIS terminations)

Bus Bar Design

At the heart of SIS technology is the use of a resin impregnated paper (RIP) insulation system applied directly to the main current carrying conductor, resulting in a maintenance free, fully insulated, touch safe, bus bar capable of operating up to 36kV. RIP technology has been in wide spread use in the electrical industry for medium to high voltage and EHV applications for over 50 years, mainly in the manufacture of high current RIP transformer bushings.

RIP works well for bus bars because of the design objectives of the bus bar system:

Fully isolate the high voltage conductor from the rest of the system.
Minimize voltage stresses in the insulation system through capacitive grading.
Ensure void free insulation to eliminate partial discharge and insulation degradation.
Carry the full current while maintaining acceptable temperature rise.
Ensure acceptable operating temperatures in the conductor and insulation as not to compromise material integrity and loss of life.

SIS bus bar can be thought of as a continuous RIP bushing that extends the reach from one piece of equipment to another. Instead of transitioning to another technology to accomplish the transmission and isolation of the current and voltage, i.e. insulated cable or metal enclosed bus duct, a continuous RIP system is employed to accomplish the connection.

Layout of a Transformer Yard that uses SIS Bus to connect the secondary of the main transformer to the switchgear

3D CAD Layout of a 3000A SIS Bus system detailing the interconnection of main breakers across three GIS switchgear lineups.

Specification Considerations

The specific operating requirements of the bus bar system will dictate the design parameters for the bus bar system. Basic information required to prepare a layout includes:

Maximum system voltage and current
Ambient temperature
Proposed routing of the bus bars and clearances to equipment
Equipment connection details/specs
Indoor vs Outdoor installations
Local seismic requirements

Standards and Testing

Once the bus bar segments are manufactured according the proven RIP processes for vacuum impregnation and resin curing, each and every bus bar segment and connection sleeve is individually tested according to IEC 60137, Insulated bushings for alternating voltages above 1 000 V (comparable to ANSI IEEE C57.19.00 and IEEE C57.19.01) to ensure acceptable test levels for power frequency, partial discharge, capacitance and loss factors. This test criterion is the essential element of verifying a void free insulation structure that will lead to partial discharge free operation.

All Ritz SIS Bus Bar voltage class designs and current capacity ratings have been verified through type testing procedures also covered under IEC 60137 according to the following test regimen:

Power frequency test and pd measurements.
Impulse voltage test.
Power frequency test and pd measurements repeated.
Temperature rise test
Temperature cycling.
Power frequency test and pd measurements repeated.

CSA Compliance

Presently there are no standards that specifically address SIS bus bar designs, manufacturing and testing, however, the CSA Standard C22.2 No. 273-11 for Cablebus Systems is considering incorporating the SIS concept into this standard and we expect to fully comply with this standard once a final draft is presented. In the interim, there are procedures for applying CSA or UL labeling on a project specific basis.