CHANGING WHAT’S INSIDE
Encapsulated LV Frame puts safety first working close to live feeders. The As the demand for more connecdesign allows the incomer to remain tivity on the low voltage side of safely live and continuously feed the network company transformers inphases not being worked on. creases and the need for ever-safer Dickerson says if you are going work environments increases along to install a new vertical disconnect with it, the Encapsulated LV Frame you no longer have to remove a from TransNet is now meeting both panel to uncover the bus. The new challenges effectively. frame reduces the area of exposed Designed to be mounted either bus to a minimal 60 mm square proin a transformer cabinet or as a distected by a removable touch-safe tribution board on a wall in a kiosk, cover. the Encapsulated LV Frame is the The design innovations also infirst to have a fully-enclosed busbar crease safety during transformer system to prevent accidental conmaintenance. tact with live parts and to seriously Whether it is bolted to a pad in reduce the likelihood of an arc flash a transformer or installed freestandoccurring. ing on optional Unistrut legs, the TransNet’s utilities general manframe is designed to allow a transager, Jason Woodcock, says the former to be safely removed and new frame was developed three replaced when a fault occurs. years ago by TransNet engineers in To achieve this with minimal conjunction with a network compatime and effort, Dickerson has ny and its contracting team. allowed for generator ports on the “It had become clear at the time front of the board to allow generathat the lack of arc flash mitigation The Encapsulated LV Frame developed by TransNet tors to be plugged in once the bus and the level of safety risks in traprovides a safer installation and maintenance path for is isolated. The generator and the ditional LV frames were no longer transformer upgrades transformer are then synchronised acceptable. To come up with a safer and, once the generator is energised, solution we identified those risks, with inadequate clearances between phasthe transformer can be safely removed and then set about designing an LV frame that es and also between a phase and earth replaced while the generator is supplying would keep operators safe while working in increased the likelihood of a flash-over under power to consumers. Safety is assured toall the conditions they meet in the field.” fault conditions, so the first challenge was to day because the entire busbar system at the He says steel frames in steel cabinets design a busbar system that would elimiback of the frame is sealed in the black plasnate the likelihood of an arc flash as much tic enclosure to prevent any live contact. as possible by increasing the clearances and
Jason Woodcock
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by eliminating unnecessary exposure to bare conductors. Rather than trying to achieve this protection by heat-shrinking individual bars, TransNet opted for a complete plastic enclosure to prevent access to the busbars other than through designated access points on the front panel. TransNet’s designer of the encapsulated frame, Rob Dickerson, says this safety improvement minimises the risk of electric shock or arc flash when adding circuits or
March - April 2022
Modular design While TransNet was addressing the safety risks, the company also looked at making the Encapsulated LV Frame a lot more flexible in its design and sizing to suit different network companies and their requirements. This meant ensuring it was easier to install by making it modular and allowing more vertical disconnects to be added, depending on how many outgoing circuits and phases were required.
FROM ELECTROLINK MARCH/APRIL 2022 The flexibility designed into the Encapsulated LV Frame now allows it to be configured for any number of cables coming out of a transformer as well as their current ratings. Disconnectors can be mounted on the LV Frame to allow either top or bottom feed. Woodcock says each unit can be ordered from TransNet as a base frame for customers to build onto, or TransNet can wire the complete solution and bring it up to customer requirements for each job. “Our workshop is set up to for this. We have designated assembly areas for the frames and a test lab to verify the results meet the specification.” He says working with a network company was helpful in making design adjustments for the Encapsulated LV Frame which has now proven itself in the field and is ready for all network companies to consider as they upgrade the safety of their transformers. Key to both the flexibility of the design and the safety of workers and operators is the way a panel is provided on the right-hand side of the frame for easy customisation. This grey panel is for the optional mounting of equipment such as ripple relays, pilot fuses, ferro-resonance kits, demand metering fuses, CT test blocks, LV monitoring equipment, communication routers, and power points for tools. The accessory panel could also be used for generator ports if a customer wants the full use of the standard 6-way panel. Often additional fittings like these have to be added in the field while the busbars remain live. Woodcock says this work can now be done safely because TransNet has designed the frame so that there are no busbars behind the panel. This safety
Traditional bus protection still leaves exposed live parts (right). The rear of the new TransNet frame completely protects workers removing and replacing transformers measure eliminates the risk of hitting a live busbar when accessories are being installed. TransNet can also pre-install this equipment before the frame is shipped. Another key design improvement is the way TransNet has balanced the robustness of the frame and its weight to enable safe one-man installation. The new frame is now light enough for one man to install in the low voltage end of a 100 kVa to 300 kVa transformer and bolt it into place. Woodcock says this makes the Encapsulated LV Frame so much more versatile and the ideal solution to retrofit into an existing transformer during an emergency. “The whole frame can be set up and ready to install at any time and can be converted very quickly to a top or bottom feed on the job without disrupting access for tap changes.”
Higher safety standard
Installing disconnectors is a lot safer with removable touch-safe covers
Safety is further assured by the higher current rating designed into the busbar system. TransNet’s test and measurement specialist, Garry Tucker, says the Encapsulated LV Frame is rated for up to 800 amps while a typical 300 kVa transformer fully loaded draws about 430 amps. “We have built a significant safety margin into the frame design with its slightly thicker busbars. Even if a transformer is running at full load and under a high ambient tempera-
ture, the frame will never get close to its maximum thermal rating and overload capacity.” The new frame is the latest development in a range of LV pits and pillars designed, engineered and manufactured in New Zealand by TransNet. The company supplies 4, 6 and 8-way frames, and developed the new encapsulated frame concept as an extension of its successful EP7 3-way pillar. Rob Dickerson says in his technical support role and as a former cable jointer, he sees customers as workmates. This view is reflected by many in the company with similar real-world expertise and carries through into the range of products designed by TransNet to make electrical work safer and easier. “The Encapsulated LV Frame now offers an unprecedented level of safety as standard, while still enabling a high level of customisation to meet any specification,” says Dickerson. “As an ISO 14064-1 certified company, we have also factored in end-of-life environmental impacts and, where possible, we have chosen components that can be easily recycled.” For further information:
TransNet NZ Limited P: 09 274 3340 E: sales@transnet.co.nz W: www.transnet.co.nz
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March - April 2022
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TRANSNET NEW ZEALAND LTD 78 Cryers Road East Tamaki Auckland NEW ZEALAND Ph 0800 442 182 PO Box 39 383 Howick, Auckland sales@transnet.co.nz
www.transnet.co.nz