nVent ERICO, manufacturers of the CADWELD^® range of exothermic welding equipment, recently carried out some fusing tests on their CADWELD connections at their HV laboratory in Solon, USA.

In the tests, 10kA is applied until either the conductor or the CADWELD connection fails. To pass the test, the conductor must fail (melt) before the CADWELD connection does, proving that connections made using the CADWELD system are not the weak point of a grounding system.

GRC-182Q Fusing Test (cable to ground rod connections)

Conductors Used: nVent ERICO Cadweld connecting 3/4″ (19mm) ground rod to 4/0 (107mm) copper conductor.

Test Parameters: 10100A RMS 60Hz applied until fusing

Pass/Fail Criteria: The grounding connector shall not crack, break, or melt when subject to the test current.

SSC-2Q Fusing Test (cable to cable connection)

Conductors Used: 4/0 copper conductor to 4/0 copper conductor with nVent ERICO Cadweld

Test Parameters: 10100A RMS 60Hz applied until fusing

Pass/Fail Criteria: The grounding connector shall not crack, break, or melt when subject to the test current.

nVent ERICO also carried out some short-circuit current tests on their tinned copper braid (MBJ) product, in accordance with standard UL467 (Ground and Bonding). In this test 5.9kA is applied for 6.1 seconds. To pass the test, the braid must not fuse (melt) and still be able to carry current afterwards.

MBJ-50-500-10 Fusing Test (50mm² tinned copper braid bond)

Conductors Used: 556980 (MBJ 50 – 500 – 10) tinned copper earth braid (MBJ) 50mm², 500mm length, 6mm hole.

Test Parameters: 5960A RMS 60Hz applied for 6.1 seconds

Pass/Fail Criteria:

7.5.1 – A grounding or bonding device shall not crack, break, or melt when subject to the current and time specified in the Test Perameters.

7.5.2 – After having carried the current specified in Clause 7.5.1, continuity shall be maintained on the test sample assembly.

ETS are the authorised UK stockist and reseller of nVent ERICO Cadweld exothermic welding equipment and can also provide a comprehensive on-site CADWELD PLUS training course, carried out by a fully qualified ETS operative on behalf of nVent ERICO.

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Screened separable connectors and elbows are used to terminate polymeric (XLPE & EPR) insulated cables onto switchgear and transformers fitted with ANSI/CENELEC-style bushing interfaces up to 42kV.

Layers of alternate insulating and semi-conductive EPDM rubber replicate the cable construction and provide a touch-safe interface between the cable and equipment.

Suitable for use on the five main bushing interfaces including: Interface A, Interface B, Interface C, Interface D, and Interface E, the new CENELEC Interface F is also available for high-current applications.

There are a number of advantages of using a separable screened connector system including:

– Rugged compact design – allows installation in modern compact substations
– Full screened cable-equipment interface – touch-safe
– Maintenance free
– Quick and simple to install
– Easy to disconnect de-energised cables
– Can connect more than one cable to a single bushing interface
– Fully moisture-resistant – can be used outdoor without a cable box
– IP67 protection – dust tight and protection against the effects of moisture
– Resistant to UV, Ozone, chemicals, mechanical abuse
– Temperate range from -60oC + 130oC
– Offers many test options: capacitive test points, cable tests
– Suitable for cables between 12kV–36kV, 250amp-1250amp (42kV and 2500amp for the Interface F)

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Ex d requirements insist that cable used in hazardous areas should be a considerably compact circular cable with extruded bedding and using fillers that are non-hygroscopic.

Further more, thought should be given to the volume of cable required and how it will be terminated. If numerous cables are to be terminated at the same point, the size of glanding panel may impact on the required control box enclosure size.

Using Flexicon conduit systems removes these issues as cables can be run through a protective conduit, allowing multi-cores to share the same space and so reduce the number of entry points required into the control box.

Calculating the cross-sectional area of the cables to be run through a single conduit will enable the correct specification and selection of conduit system required.

Key benefits of using a Flexicon conduit with a flameproof EXD barrier gland over cable:

For more information on our range of Flexicon flexible conduits, please contact our Sales Team.

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Nexans WINDLINK enclosures for offshore wind farms aim to reduce installation time on site as well as offering considerable cost savings. The available range of offshore junction cabinets (OJC) and frames for use in turbine towers, along with the ability to manufacture and supply pre-terminated leads offer considerable cost saving compared to traditional cable installation in the towers.

For offshore wind farms, the Nexans offshore junction cabinet/chamber can be used as a connection point for tower cables to subsea array cables. This can be used as a demarcation point between tower / transition piece and/or array cable responsible parties.

Fully commissioned and tested

Rated up to 42kV, the offshore cabinet is manufactured from marine grade 316L stainless steel, with a robust design with IP66 protection (BS EN 60529:1992), specifically suitable for use in offshore weather conditions.

The Nexans junction cabinet has been short circuit tested to DIN VDE 0278-626-1 (HD 629.1 S2:2006 + A1:2008). 2009:07. EN IEC 61442, IEC62271-201: High Voltage switchgear and control gear.

Accessories and reliability

These Nexans offshore enclosures can be equipped with different connector combinations and surge arresters to protect tower equipment from HV surges. These, together with pre-terminated and tested leads to connect the junction cabinet with turbine tower equipment, we believe reduces the installation time and increases the quality of the installation.

All Medium Voltage connection cabinets are reliable, safe and can be tailored to meet customer specific requirements. It can provide a convenient test point and can help with earlier generation of power.

Benefits of the Nexans OJC

– Chamber design is specifically suitable to be installed in the severe conditions of the transition piece of the tower.
– Easy to install due to high accessibility.
– Ideal test and demarcation point.
– Time saving.
– Reducing overal cost of installation.
– Possibility to use pre-terminated and tested jumpers to tower equipment.

For more information on Nexans products and off-shore wind farm cable accessories please contact our Sales Team.

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To allow compliance with the LUL fire regulation standards, all joints for use within Section 12 of the London Underground Network must comply with the LUL 1-085 standard.

To enable compliance for joints required in Section 12 areas, 3M developed a universal joint protection system to manage this. It is known as the Smoke, Toxicity, Fire and Fume joint sleeve or STFF for short.

Installation of the STFF sleeve

The sleeve is slipped onto one of the cables ready to be joined and parked back along the cable. The joint is made off in the normal way and the STFF sleeve is now slid over the joint and held in place by two stainless steel cable ties, one at each end.

There are a number of variants of the STFF shield, including a sleeve design for joints or with a closed end, suitable for cable abandonment applications. A retrofit wrap around version can also be supplied if the joint has already been installed.

Suitable LUL Section 12 and Hazardous Area applications

Designed for use with all single or multi core HV and LV cable joints as well as cable abandonment applications, the STFF joint sleeve is approved on the LUL register (Register Number 1106) for use with 3M Cold Shrink jointing systems.

The joint protection sleeve has applications for jointing on LUL projects as well as other hazardous and petrochemical applications, both on and off-shore.

The 3M joint sleeve can only be purchased with the appropriate joint and is not available as a separate item.

For more information on the 3M STFF sleeves applications, prices and availability, please contact our Sales Team.

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Bentonite and Marconite have certain similarities, they are both ground enhancement materials used to lower the resistance to earth. However, there are a number of differences between the products and the applications they should be used for.

Bentonite Moisture Retaining Clay

Bentonite is often used to reduce the resistance between the soil and earth-electrode (earth rod or earth mat) by retaining moisture. The naturally occurring Bentonite compound consists mostly of montmorillonite, the sodium based clay swells to many times its size when mixed with water.

Available in both powder and granular form, preference usually lies with granular form as it is often considered easier to handle and prepare.

Marconite Conductive Aggregate

Marconite is a synthetic material manufactured specifically for earthing purposes. Utilising specific raw materials and minerals, mixed in carefully controlled ratios. The Marconite compound then goes through a range of manufacturing processes and thermal treatments, designed to create a consistent, fit-for-purpose earthing compound.

The resulting precisely measured, granular mixture is virtually dust free and has exceptional electrical properties.

Bentonite vs Marconite

Resistivity

All earthing aggregates can be called conductive with a resistivity of 5 ohms metres or less. Bentonite has a typical resistivity level of around 3 ohms.m. Marconite with a resistance level of .001 ohm.m, has a far low resistance than its competitors, even when mixed with cement, the resulting resistance level is still only 0.19 ohms.m.

Chemical balance

As Bentonite is a naturally occurring material, there can be anything from 15-20% impurities which can be corrosive and will corrode any earth-electrode connections, resulting in earthing system failure, which can cause costly damage and lengthy repairs.

Marconite is a chemically inert compound and as such is non-corrosive to steel or copper, it does not attack cement structures and has a pH level within the neutral range. Allowing Marconite to be used with all conventional types of cement, as well as most proprietary resin-based cements, adhesives and gypsum plasters.

Versatility

One of Bentonite’s key features is also one of its weaknesses. The ability to absorb rain water once installed, helps increase the conductivity but also makes the material liable to drying out and therefore shrinking or even being washed away entirely. Therefore requiring maintenance every few years, such as adding additional water or salts to continue to achieve the desired earth values.

Suitable for most ground conditions, Marconite becomes a permanent solid structure, especially when mixed with concrete and is not prone to these problems.

High strength

Due to its clay-like nature, Bentonite has limited strength levels, this added to the materials expansion when mixed with water, makes it unsuitable to be included within building structures themselves. Whereas Marconite can achieve strengths higher than Grade 25 concrete and therefore is suitable to be used as part of the building structure.

Cost effectiveness 

When it comes to cost, there is a clear difference between Bentonite and Marconite. Being considerably cheaper, Bentonite offers an earthing solution for cost conscious buyers, although the cost of maintenance every few years should be considered, it can still work out as an effective solution.

Marconite on the other hand is a more expensive product, however once installed, the permanent earthing solution requires no ongoing maintenance so this should be factored in when considering the more costly material.

Ease of use

Both earthing compounds are simple to instal as a backfill for earth-electrodes. However as Marconite can be used to replace sand and aggregates within conventional concrete mixes, it should be carefully mixed in ratios of 3 parts Marconite and 1 part cement by weight, with the addition of 1 litre of water per 4kg total mix.

Due to the slightly more complicated nature of using Marconite within a permanent concrete structure, it is available in a premixed bag. The 25kg premix sack contains pre-measured and pre-mixed ratios of Marconite and Portland Cement powder, requiring only 5 litres of water. Reducing on-site confusion and ratio errors. However the hydroscopic Portland cement used within the premix means it must be used within 6 weeks of purchase.

Marconite and Bentonite each have their own advantages and disadvantages for different applications, with cost and longevity of installation often being the deciding choosing factors. For more information on which earthing compound is best for your needs, please contact our Sales Team for advice.

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