Data center is solidly grounded

Syska Hennessy Group designed a data center that required solidly grounded underground duct banks.


Recently, Syska Hennessy Group led the design of a large data center that required a 25 kV utility service, solidly grounded, in underground duct banks. The service was 25 kV, 100% insulation level, copper conductors with ethylene propylene rubber (EPR) insulation.

The facility has an on-site 25 kV/13.2 kV substation to supply a 13.2 kV distribution system in underground duct banks. The system is impedance grounded and can be operated with one phase grounded for an unlimited time. When design engineers couldn’t find a cataloged 15 kV class cable with 173% insulation level, Syska used a 25 kV-class cable with 100% insulation level, copper conductors, and EPR insulation. The data center’s electrical infrastructure 600 V class facility distribution system was designed solidly grounded in overhead conduits and includes the following:

  • 600 V class copper conductors with thermoplastic high heat nylon (THHN) insulation
  • 600 V class facility distribution system, solidly grounded, in underground duct banks
  • 600 V class copper conductors with rubber high heat waterproof (RHHW-2) insulation
  • 600 V class plug-in bus ducts with copper conductors for distribution to IT equipment cabinets
  • 600 V class feeder bus duct with copper conductors for maintenance bypass and load bank circuits that are only occasionally used
  • 600 V class cable bus with copper conductors for large capacity feeders in the critical distribution system.


Christopher M. Johnston is a senior vice president and the chief engineer for Syska Hennessy Group's critical facilities team. Johnston specializes in the planning, design, construction, testing, and commissioning of mission critical 7x24 facilities, and leads team research and development efforts to address current and impending technical issues in critical and hypercritical facilities. With more than 40 years of engineering experience, he has served as quality assurance officer and supervising engineer on many projects.

Anonymous , 06/11/13 08:36 PM:

If the 13.2kv system is ungrounded you need only a 133% cable insulation. When the system is high impedance grounded why use a 173% cable insulation? Should the 133% insulation suffice?
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Choosing controllers: PLCs, PACs, IPCs, DCS? What's best for your application?; Wireless trends; Design, integration; Manufacturing Day; Product Exclusive
Variable speed drives: Smooth, efficient, electrically quite motion control; Process control upgrades; Mobile intelligence; Product finalists: Vote now; Product Exclusives
Machine design tips: Pneumatic or electric; Software upgrades; Ethernet advantages; Additive manufacturing; Engineering Leaders; Product exclusives: PLC, HMI, IO
This article collection contains the 5 most referenced articles on improving the use of PID.
Learn how Industry 4.0 adds supply chain efficiency, optimizes pricing, improves quality, and more.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again
Pipeline vulnerabilities? Securing hydrocarbon transit; Predictive analytics hit the mainstream; Dirty pipelines decrease flow, production—pig your line; Ensuring pipeline physical and cyber security