Nexans OJC Offshore Medium Voltage Junction Cabinets For Wind Power Projects

Published 22 Oct 2019

Nexans Power Cable Accessories For Wind Energy Projects

by Chris Dodds T&D - estimated reading time 5 minutes

Nexans Offshore Junction Cabinet (OJC)

Offshore MV Junction Cabinets (Medium Voltage Up To 42kV)

T&D are UK Distributors for Nexans Power Accessories – this includes a range of medium and high voltage accessories including cable joints, terminations and connectors suitable for wind turbines on offshore and onshore energy projects.

Nexans Offshore Junction Cabinets (OJC) are designed to improve revenue streams for offshore wind power developments – the offshore junction cabinets are used as a disconnecting point for internal tower cable to external subsea array cables.

This can be used as a demarcation point between tower, transition piece and array cable related parties – Nexans OJC junction cable chambers are used as a connecting point for internal tower cable to external subsea arrays cables.

Nexans OJC can provide a convenient test point and can help with the earlier generation of power to help create revenue sooner.

The marine grade stainless steel cabinets is specifically suitable to be installed in severe offshore conditions.

The split cable gland plates allow to use pre-terminated and tested jumpers, reducing the installation time and increasing the quality of the cable installation.

Up to 42 kV
1250 A
Robust design with IP66 degree of protection (BS EN 60529:1992).
Short circuit tested acc. to DIN VDE 0278-626-1(HD 629.1 S2:2006 + A1:2008): 2009-07: Thermal short-circuit 25kA/1s, Dynamic short-circuit 62.5 kA.

➡ There are also 33kV onshore junction cabinets known as Nexans ONJC-S that are designed, tested and manufactured for onshore renewable projects that can be used as a disconnecting point for branching between grid and applications – for applications with MV-HV separable connectors up to 42kV (630A) according to CENELEC HD 629.1 S2.

Also: 33kV Cabinets Onshore

Nexans OJC Benefits

Medium/High Voltage MV HV Cable Cabinets

Suitable to be installed in the severe conditions of the transition piece prior to installation of the tower
Simplified interface management, clear division of responsibility
The chamber design is specifically suitable to be installed in the transition piece of the tower
High accessibility for ease of installation
Ideal test and demarcation point
Possible use of pre-terminated and tested jumpers to tower equipment
Time saving
Distance involved between hang off and switchgear mean time/cost offshore for cable preparation
Pre-terminated MV HV cable leads also saves space/complexity
Prepared and tested onshore, ready to plug and play
Project critical path activity, no delays for installer
Efficiency of operation which can be highly beneficial for planning the installation of the collector cables from the array, thus creating additional potential cost benefit
Accommodation offshore on the OSS maybe limited
REDUCTION OF INSTALLATION TIME (30%)

Nexans OJC Offshore Cabinets/Junctions

Nexans Power Accessories have studied the installation of subsea array cables in the offshore towers and have developed a system that gives the developer and installer certain advantages over other medium/high voltage cable connection methods.

By employing pre-terminated cable leads that utilise less expensive flexible cables, a developer may save money and an installer can save time on the preparation and testing of the medium voltage cable link between the MV transformer to MV switchgear and/or MV switchgear to the array cable.

By using a cable termination point near to the hang-off rather than taking the array cable directly to the equipment, an installer may also save time on the preparation of the array cable and spend less time in the tower dealing with the inconvenience of stripping longer lengths of arrays.

This results in less reliance on the weather giving a cost saving to the developer due to the implications of the waiting on weather charges as more work can be done onshore preparing and testing the equipment.

By saving time on the installation offshore, this would in our opinion, give an earlier completion date and thereby earning the developer revenue sooner.

Nexans Offshore Junction Cabinets OJC – Design Specification

Aluminium bushing support plate to feed through switchgear/transformer bushings
Access panel for 2 array cable connections
Split cable gland plate incorporating 9 feed through sealed glands
Access panel for turbine connection
Earth bar on insulated standoffs
Cabinet secured by 4 x M16 internal base fixings
Different cable connectors and surge arrester combinations are possible
Cable cleats arrangement for 9 single core high voltage cables
Channels for mounting external accessories
Lifting eyes

Nexans Junction Cabinets & Separable Connectors – Possible Arrangements

Extension to larger cable sizes and additional array cables possible.
Junction cabinet can be equipped with different connector combinations.
Spare room at turbine connection to add surge arresters to protect tower equipment from high voltage surges.
Pre-terminated and tested jumpers to connect junction cabinet with tower equipment.

Offshore Junction Chamber Type	Voltage Um (kV)	Outer dimensions of chamber (w x d x h)(mm)	Fixing points	Conductor sizes (sqmm)
				min	max
Nexans OJC1	42	600 x 800 x 1125	4 x M16	50	630

Thorne & Derrick

Thorne & Derrick are national distributors of LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment – servicing businesses involved in cabling, jointing, substation, earthing, overhead line and electrical construction at LV, 11kV, 33kV, 66kV and EHV. Supplying a complete range of power cable accessories to support the installation and maintenance of low/medium and high voltage voltage power systems: