T&D World Magazine
Compact Ground-Mount Kiosk for Distribution Network Protection

Compact Ground-Mount Kiosk for Distribution Network Protection

The new ground-mount kiosk houses a NOJA Power OSM series ACR, together with an RC10 control and communication cubicle.

NOJA Power has released an enhanced ground-mount kiosk that takes advantage of the OSM 310 series 15- and 27-kV Automatic Circuit Reclosers’ direct-cable connection resulting in a more compact kiosk design.

The new ground-mount kiosk houses a NOJA Power OSM series ACR, together with an RC10 control and communication cubicle. The kiosk is equipped with a set of doors at each end allowing immediate access to the ACR or the RC10 cubicle.

In addition to the ACR and RC10 cubicle, the previous generation of ground mount kiosks housed an earth switch, copper busbars and cable-connection bulkhead. The busbars extended from the ACR’s bushings to the bulkhead where cable connections were made.

In the new kiosk design, the earth switch has been eliminated due to adaptations to safe working practices. Now internal earthing and improved live cable insulation allow linesmen to remove feeder cables directly from the ACR and mount them on a purpose-designed accessory during maintenance work without the need for an earth switch to isolate the ACR. The copper busbars and cable-connection bulkhead have also been eliminated because cables can now be directly connected (using dead break elbows) to the OSM 310 series 15- and 27-kV ACRs due to the units’ industry-standard DIN taper bushings.

Elimination of the earth switch, busbars and cable-connection bulkhead has enabled NOJA Power to reduce the size of the ground mount kiosk from 1800 by 1250 by 1600 mm (L x W x H) to 1000 x 1200 x 1300. The volume of the original kiosk measured 3.6m³ while the new product measures 1.55m³ for a volumetric reduction of 57 percent.

The vandal-proof ground mount kiosk is manufactured from 304 stainless steel and finished using a powder coat in APO Grey with a ripple finish. The result is a more compact, less obtrusive and lower cost ground mount kiosk with greater aesthetic appeal because it blends into its surroundings.

Ground mount kiosks are popular in regions such as Scandinavia where metropolitan electricity distribution networks are sited underground, but cables revert to overground grids in rural areas. The kiosks house the transition between the underground and overhead networks while providing auto-reclosing protection for both grids. Traditional underground switchgear lacks the functionality of pole-mounted ACRs; with NOJA Power’s introduction of the ground mount kiosk for its OSM 310 series ACRs, the extensive protection, control, data logging and communications functionality of pole-mounted equipment can be applied to underground grids.

The OSM 310 series products used in conjunction with the new cubicles benefit from all the key features that have made NOJA Power’s products popular with utilities around the world. Notable among these are the use of a vacuum interrupt and solid dielectric insulator instead of the environmentally unfriendly oil or sulphur hexafluoride (SF6) gas used in older products. Another key feature of the 310 series is its stainless steel enclosure that forms the only solid dielectric unit with controlled arc venting on the market. The controlled arc venting design meets the requirements of IEC62271-200 Clause 6.106 and Annex A, and the efficacy of this important safety feature has been verified as part of the type-testing procedure.

The RC10 cubicle is a SCADA-ready controller that provides a directional overcurrent, earth fault and sensitive earth fault relay, auto reclosing relay, instantaneous metering, event log, demand logger and remote terminal unit (RTU) for remote control in a single package.

“Ground mounting ACRs is currently a niche activity but is growing in importance in regions that use a mix of underground and overground distribution grids,” says Neil O’Sullivan, NOJA Power’s Managing Director. “The introduction of the OSM 310 series auto reclosers last year prompted a redesign of our first generation ground mount kiosk and the result is a less expensive––due to elimination of the earth switch, busbars and bulkhead––and much more compact installation. This is a great advantage for those utilities that need to site auto reclosers on the ground because it makes the final installation far less unsightly.”

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