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.
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.
Substation, Electrical Safety, Cable Jointing & Accessories | 11kV 33kV 66kV to 400kV
Oil Fuse Cutout Replacement By G&W Electric
The following Case Study by G&W Electric and presented by Thorne & Derrick describes the process of a major downtown city necessitated an upgrade of the electrical service by the utility company.
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.
Challenge
Continuous expansion of a major downtown city necessitated an upgrade of the electrical service by the utility company. The utility was faced with replacing the old substation equipment with new switchgear and associated apparatus.
This apparatus was located in a separate substation building fed by 50 year old, 138kV self-contained oil filled cable. To abide by their latest safety regulations and to simplify cable connection to the new equipment, the utility decided to eliminate all oil filled devices in the building including the cable.
This necessitated changeout of the old oil filled cable to a cable utilizing an extruded dielectric insulation. Furthermore, the apparatus building was located directly adjacent to a major downtown intersection. Because of this, the utility was concerned about the amount of space and downtime required for construction work to splice the cable.
Solution
The utility investigated cable accessory suppliers with reliable track records who offered a product for their application. G&W Electric was selected because their transition joint featured prefabricated components and perforated paper roll stress relief which minimized the installation time and required expertise of the installers.
Another feature was G&W Electric’s exclusive separable connection method which permitted deadending of each cable end. This offered the unique advantage of reusing the same joint for possible future changeout of the remaining oil filled cable. The compact construction of the joint also permitted separate joint enclosures to be installed for each leg of the three phase, oil filled cable.
This permitted the enclosures to be placed either stacked above each other on a rack or parallel to each other thereby minimizing the space required. The rugged construction of the joint design allowed the utility crew to direct bury the units in a shallow opening. This helped minimize the time and cost in constructing an accessible vault.
G&W Electric engineers worked with the utility to provide a custom solution for their specific requirements. The project installation was completed in record time with little disruption of the surrounding city streets resulting in considerable cost savings.
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.
Substation, Electrical Safety, Cable Jointing & Accessories | 11kV 33kV 66kV to 400kV
G&W Electric
The following Case Study by G&W Electric and presented by Thorne & Derrick describes how a southern utility was interested in improving service reliability by installing an underground fault detection, isolation, and restoration scheme for a circuit feeding several important residential/ commercial customers.
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.
Challenge
A southern utility was interested in improving service reliability by installing an underground fault detection, isolation, and restoration scheme for a circuit feeding several important residential/ commercial customers. They needed a solution that could be scalable from an individual switch to a full circuit of switches capable of performing an open loop restoration. A base loop would be installed first and new switches added as the funds became available.
Solution
G&W Electric worked with the utility to help design a system that was flexible enough to meet their current and future needs. The design concept was based around multi-way automated switches connected to each other in an open loop. Communication would be through fiber optic cable for the protection circuit and SCADA.
Four-way Trident®-SR solid dielectric switches were chosen for the load switching and fault interrupting. The Trident-SR was an ideal switching product for this solution due to the ease of automating it with any relay, innovative cycle speed operation, and multi-way mounting configurations. A front/back switch design was chosen due to its narrower footprint which would fit traditional air gear pads (see Images 1 and 2).
Image 1 Padmount switch with side control enclosure
Image 2 Front or back access padmount
The two source ways of the Trident-SR switches were controlled and protected by SEL-451 relays. The two load ways were controlled and protected by SEL-751A feeder protection relays. G&W Electric designed and built the two relay panels in a common enclosure on the side of the switch. Both panels had 120 V outlets which allowed operators to plug in laptops when working on or near the switches (see Image 3).
Image 3 SEL-751As and 451 were mounted in a common enclosure on the side of each switch.
The relay logic was designed to be extremely flexible so the same program could be used in multiple scenarios. This was accomplished using the extensive logic capability and multiple setting groups in the SEL-451 relay. The utility could choose whether to use the switch as a standard automatic transfer switch, as a through point automated loop switch where both
line ways are normally closed, or an open point automated loop switch where one line way is normally open.
When in the automated loop settings, each switch only communicated with the switches on either side of it. That meant there was no physical limit to the number of switches in the restoration circuit. This innovative control design allowed the utility to build their automation loops one switch at a time and add future switches as their budget permitted. It also provided a common switch design with single stock code which simplified future replacement requirements and training for their maintenance and installation crews.
The communication method for the protection circuit and SCADA system was single-mode fiber optic cable and SEL 2829 transceivers. This communication network was used to allow critical information to be passed between switches to automatically isolate faults and restore power in a minimal amount of time without having to dispatch crews.
This “smart switching” scheme is one of the most advanced technologies on the market and has been implemented by utilities worldwide who wish to provide the best service reliability to their customers.
When a fault is sensed, the relay trips the closest fault interrupter and disables the tripping of the other line way fault interrupter to maintain power to the loads. Next, a Mirrored Bits® signal is sent from the interrupting switch toward the open point. If the next switch in the line is closed, the signal will tell it to open to isolate the faulted line.
The signal is passed down the network from switch to switch until it encounters the open point. When the signal is received by the open point switch, it closes to restore power. This allows for an unlimited number of switches to be in the protective circuit and still maintain fast and effective isolation and restoration.
Conclusion
The scheme was tested and its operation witnessed by the customer at G&W Electric’s facility in Illinois. The initial phase has been installed and is up and running. It has inspired other utilities in the region to use a very similar scheme for their automated loops.
Figure 1 System Diagram
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.
Substation, Electrical Safety, Cable Jointing & Accessories | 11kV 33kV 66kV to 400kV
G&W Electric
The following Case Study by G&W Electric and presented by Thorne & Derrick describes how their wind farm fault protection saves upgrading equipment costs.
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.
Challenge
A new wind farm was being constructed in the Central Midwest.
The design was for 240 wind turbines with the goal of 400 MW of total capacity. The project was scheduled to be done in two phases with roughly half of the capacity in each phase. When fully operational, the wind farm would provide renewable energy to almost 120,000 homes. The wind farm was designed, the work was planned, and the equipment was ordered for the first 121 turbines of the project.
Coincidentally, during that time, the utility fault current levels at the wind farm substation increased unexpectedly after the above was completed. This meant that all of the equipment on order would now be under- rated.
The developer had two choices. The first was to change the current orders for new equipment, incur the costs associated with the higher rated gear, and delay the project by several months. The second option was to determine a way to reduce the fault current to an acceptable level without delaying the project.
38kV current limiting protectors mounted at the utility grid substation protects the utility from potential wind farm faults and the wind farm from potential utility faults.
Solution
The wind farm developer chose to put a G&W Electric CLiP® on the distribution voltage side of the substation transformer. The substation designer was familiar with the concept of a triggered current-limiting fuse. The 4000A continuous current requirement of the 38kV system however, was extremely high. At the time, G&W Electric had not produced a unit of that size at that voltage level. Working with the developer however, G&W Electric was able to build a CLiP that could meet the customer’s voltage, continuous current and interrupting duty requirements.
Wind Farm Fault Protection
Conclusion
The CLiP was incorporated into the design, manufactured, and installed without delaying the project or incurring the cost of upgrading all of the equipment. The customer was able use the existing equipment to protect the first 121 turbines on the project. A secondary benefit was that the utility transmission grid was also protected from any potential faults occurring in the wind farm. The developer is considering using lower rated gear on future installations with a CLiP to save money and protect equipment from changing fault currents.
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.
Thorne & Derrick are Specialist Distributors to the UK and international Offshore Wind & Renewable industry to provide safe and reliable LV HV Electrical Cable & Power Distribution Systems up to 66kV – we are highly customer responsive and absolutely committed to providing a world-class service.
Contact our UK Power Team for competitive quotations, fast delivery from stock and technical support or training on all LV-HV products.
Key Product Categories: Duct Seals | Cable Cleats | Cable Glands | Electrical Safety | Arc Flash Protection | Cable Jointing Tools | Cable Pulling | Earthing | Feeder Pillars | Cable Joints LV | Joints & Terminations MV HV
See how T&D support, supply and service the Renewable Energy industry.
MV HV Cables 11kV 33kV 66kV | Cable Joints, Terminations & Connections
Cable Socks & Grips By Slingco | Offshore Cable Support & Strain Relief
Slingco understands that choosing the right cable sock can be a challenge. There are key factors to consider when specifying cable socks, such as:
Typically, where longer term saltwater exposure is involved, the choice is Aramid – specialist non-metallic socks.
Press Release | Thorne & Derrick Appointed Approved Stockist for UK Leading Cable Pulling Equipment Manufacturer
Slingco have tested their cable socks by an independent leading, inspection, verification, testing and certification company. Here’s a sample from the test results of the effects of saltwater on steel socks.
Galvanised cable sock ZCS0307 after 40 days saltwater exposure
Galvanised cable sock ZCS0307
Extensive red rust corrosion covered the majority of the component. Red rust was observed from the first interval check, with white rust deposits on 2 sections.
Stainless steel cable sock ZCS1895 after 40 days exposure to saltwater
Stainless steel cable sock ZCS1895
Red rust corrosion was apparent on 60% of the sample. White rust deposits were observed on 5 sections, with the onset of degradation occurring after 1 week.
Aramid cable socks ZCS2816 after 40 days exposure to saltwater
Aramid cable sock ZCS2816
As you can see, there was no degradation or rusting throughout the test exposure, making these the most reliable cable socks for saltwater application.
Slingco have also undertaken extensive destruction tests on socks exposed to saltwater. To request a copy of the saltwater test report or the saltwater destruction report, please contact Thorne & Derrick.
➡ Thorne & Derrick distribute the complete range of Cable Pulling Products to support safe installation of LV, MV & HV cables into underground ducts, conduits and trenches by cable pulling, laying and jointing contractors.
Cable Socks | Pulling Underground Cables & Stringing Overhead Conductors LV MV HV
Complete range of LV, MV and HV cable pulling products for installation and enabling cable jointing in trench or ducts including LV, 11kV/33kV medium voltage (MV), 66kV/132kV high voltage (HV) and EHV transmission and distribution cables up to 400kV.
➡ See Also Cable Laying, Installation & Support Products | MV HV Windfarm
Cable Rollers | Duct Rods | Cable Socks | Cable Lubricant | Duct Seals | Cable Duct
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