Three Phase Protection For Confined Space Applications

Published 07 Jan 2021

Three Phase Protection For Confined Space Applications

Confined Space Applications By G&W Electric

The following Case Study by G&W Electric and presented by Thorne & Derrick describes three phase protection for confined space applications.

Thorne & Derrick are Specialist Distributors of Substation, Electrical Safety, Cable Jointing & Accessories to UK and international utilities and contractors providing electrical power at distribution and transmission voltage levels.

Padmount recloser (left), three phase stepdown transformer (center) and single phase transformer.

Challenge

The utility serves approximately 95,000 residential and 13,000 commercial/industrial customers. The distribution system is 70% overhead and 30% underground. Nominal system voltage is 12.47kV transformed from a 34.5kV sub-transmission system.

A new substation was required to provide additional power and increased reliability to a growing tourist area of the utility’s service territory. The utility decided to tap off an existing 34.5kV line however, space for constructing a new air insulated substation was just not available. This mandated system designers to consider a different approach.

Recloser front view with SEL 351-R control

Recloser rear view cable connections

Solution

Working with their G&W Electric representative, the decision was made to go underground using padmount equipment. A standard three phase, dead-front, 2.5MVA transformer was used to step down the voltage from 34.5 to 12kV. To provide three phase protection to the new critical loads fed from the transformer, the utility also required an automatic recloser. To maintain the smallest footprint possible, G&W Electric was able to provide a padmount, three phase, solid dielectric Viper® recloser with SEL 351-R control.

The use of solid dielectric technology permitted an ideal compact solution while offering reliable protection and superior user programmable control features. A single phase, deadfront padmount transformer was also installed to provide a 120 V source for the recloser control. A new, compact, deadfront substation using state-of-the-art recloser technology provides reliable power to the new loads.

G&W ELECTRIC

Overview of G&W Cable Accessories

In 1905 G&W introduced the first disconnectable cable terminating device.

Over 100 years later, G&W continues to create technical innovations that have improved performance and reliability. With over 100 years experience, G&W is the name you can trust for quality cable accessories. With sales representation worldwide, G&W has a proven track record for success.

G&W cable accessories are designed to accommodate cables from all manufacturers and can be created to accommodate any customer cable system. The optional mechanical shrink feature offers an easier and faster installation while reducing possible damage during installation. G&W also offers installation supervision and installation training, which can be customized to suit the audience.

G&W offers a variety of transmission cable accessories for extruded dielectric cable systems. Cable terminations are available for outdoor applications to 230kV and include porcelain or composite insulator options and premolded designs. Gas insulated substation designs are available to 230kV.

Transition cable splices and cable joints are available to 138kV and include premolded designs. All cable terminations and cable joints incorporate built-in stress control and dielectric fluid. Dry type designs are also available for maximum ease of installation.