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Bonding and grounding

Roxtec seals for bonding and grounding

Protect your electrical and electronic equipment.

Use the Roxtec BG™ sealing system for armored cables or metallic pipes to ensure maintained safety in the event of short circuits and the effects of lightning strikes. The system is approved by all major classification societies and covers the needs of many demanding industries and applications. Roxtec BG™ seals provide electrical bonding and grounding as well as certified protection against fire, gas and water.

Consult a sealing expert

Bonding and grounding are methods to ensure personal safety as well as to protect sensitive equipment. Bonding of metallic objects prevents the build-up of electric energy and minimizes the risk of personal danger when a person gets in touch with several objects with different potential at the same time. Grounding is the means of draining transient voltages that can be caused by short circuits or lightning strikes.

If the application has electromagnetic shielding requirements, we recommend the Roxtec ES system.

What is bonding and grounding?

Click for explanations of important words within electrical safety.

Bonding

Bonding jumper

Grounding

Personal safety

All electric applications with voltages above 50V are to be treated as risk objects for personal safety. If the objects are not electrically protected they can form a circuit via a human body creating an electrical shock that in worst case can lead to life-threatening injuries or death. To achieve personal safety, the joining of electrically conductive objects to a common reference point can be utilized.

Standards and terminology

Here is a list of selected applicable standards and examples of their terminology regarding bonding and grounding.

IEC 60364

IEC 60364 is an international standard for electrical installations for buildings.

Equipotential bonding

The IEC term for bonding, the act of electrically joining two or more electrically conductive objects together in order to equalize the voltage level in the electrical system.

The color of the equipotential bonding conductor can be green or yellow/green.

Protective earthing, PE

Protective earth refers to connections and conductors that run back to the earthing point of the power source, known as “system earth” or “supply earth”.

It has code-driven requirements for voltages above 50V.

It is intended as a return path for fault currents until a fuse breaks the circuit.

Protective earth is always connected to touchable conductive equipment parts. This is called an “electrical supply closed loop”.

The color of the PE conductor must be green or yellow/green.

Functional earthing

A functional earth connection serves other purposes than electrical safety and may carry current as a part of its normal operation.

NEC/CEC

NEC is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States.

Bonding

Bonding is according to the NEC definition “connected to establish electrical continuity and conductivity”. It is the joining of metal objects together to form an electrically conductive path that has the capacity to conduct safely any fault current likely to be imposed on it. These objects are normally non-current carrying and the bonding jumper establishes an effective ground-fault current path. This means that all conductive objects should have the same potential for personal safety, eliminating the risk of shock hazard. The bonding jumper should be a reliable conductor, sized according to NEC article 250 to ensure electrical continuity between electrical parts of the electric installation.

Grounded/grounding

Grounded/grounding is per the NEC definition “connected (connecting) to ground or to a conductive body that extends the ground connection”. Grounding provides a path for conducting electrical energy to earth to prevent arcing, heating or explosion during a lightning strike. It also ensures, in conjunction with bonding, that normally non-current carrying conductive bodies remain at ground potential.

BS7671

This British standard sets the standards for electrical installations in the UK and many other countries and is the authority on electrical installation.

Bonding conductor

A protective conductor providing equipotential bonding.

Equipotential bonding

Electrical connection maintaining various exposed-conductive-parts and extraneous-conductive-parts at substantially the same potential.

Earthing

Connection of the exposed-conductive-parts of an installation to the main earthing terminal of that installation.

Earthing conductor

A protective conductor connecting the main earthing terminal of an installation to an earth electrode or to other means of earthing.

Earthed concentric wiring

A wiring system in which one or more insulated conductors are completely surrounded throughout their length by a conductor, for example a metallic sheath, which can act as a PE conductor.

Disclaimer

Roxtec is always striving to refer to the valid revision of the official standard applying to the application when explaining the functionality of our products. The details are, however, subject to change over time, so the information presented is neither to be seen as the full nor valid regulation text. The Roxtec BG™ sealing system as well as all the Roxtec products are sold in accordance with the Roxtec General Terms and Conditions of Sales and Services (the “T&Cs”). You can find the last version of the T&Cs here.

The act of bonding and grounding is essential to ensure personal safety and protect critical electronics.

Mikael Grudd, EMC Technical Product Specialist, Roxtec

Eliminate the risks

By bonding and grounding your cables and pipes you assure personal safety and protect your electrical equipment at the same time. Roxtec BG™ is designed to supply a cost-effective and space efficient solution for all your applications.

Installation of a Roxtec BG™ cable entry seal for cabinets.

The Roxtec BG™ system

The purpose of Roxtec BG™ transits is to ensure personal safety and protect your electronic equipment. The system is a modular-based cable and pipe transit for bonding and grounding applications as well as a mechanical penetration seal. At the same time, it is providing environmental protection against risks such as fire, water, dust, dirt and rodents.

System components

The system consists of an electrically conductive steel or aluminum frame, Roxtec BG™ sealing modules, stayplates and a compression unit plus lubricant for use during installation. The frames come in different shapes and sizes. You can incorporate them into the construction, either during the building process or after, to make openings for cables and pipes passing through walls and partitions.

An electrical connection between the frame and the potential equalization system is vital. You insert Roxtec BG™ sealing modules into the frame to seal around the cables and pipes. The built-in braid connected to the cable armor/metallic pipe ensures electrical continuity to the frame. Then you insert the compression unit, the Roxtec Wedge, and tighten it to complete the seal.

Roxtec RM BG™ B system installation.

Components in the Roxtec BG™ system.

The success of the system is due to the fact that one sealing module can handle many different cable and pipe dimensions. Thanks to the Roxtec invention Multidiameter™, you can adapt the modules to the right size by removing rubber layers. Modifying a Roxtec BG™ module in such a way is straightforward and ensures a tight seal. Multidiameter™ makes the Roxtec BG™ system perfectly adapted to the frequent request for simple cable and pipe transit modifications.

Tested and certified for bonding and grounding

Once complete, the Roxtec BG™ seal protects the penetration and any attached equipment from effects of transient voltages and fault currents. The system has undergone numerous types of tests performed by different authorities, for example earth continuity, IEC 60079-0, short circuit and current withstand capabilities, EN 50262/IEC 62444, and current surge, IEC 62305. The Roxtec BG system is certified by CSA according to UL 514B and CSA C22.2 No. 18.3-04 requirements for fittings for use with cable and conduit and UL 467 and CSA C22.2 No. 47-07 bonding and grounding equipment.

Roxtec BG™ system.

Roxtec BG™ and BG™ B solutions

The Roxtec BG™ and BG™ B product family is designed to safely and efficiently bond or ground armored or shielded cables and metallic pipes through a single cut-out. Each module in the Roxtec BG™ or BG™ B system has an individual conductive bonding braid which directly or through adjacent modules is in contact with the metallic frame. Each cable or pipe passing through the system can be individually bonded via the module. The frame is then acting as an intermediate earth bar when connected to the ordinary earthing system.

The Roxtec BG™ B solutions are up to 70% more area efficient than cable glands, and a direct replacement for cable glands terminating metal-clad and armored cable types. With a single cable entry, you can seal varying diameters of single or multiple cables while ensuring a certified bonding or grounding termination. The solutions are efficient and flexible, and thanks to the simplicity of the system, they are easy to install.

The Roxtec BG™ module consists of two identical halves, which form a single unit when installed. Cylindrical, concentric layers of rubber make up the center of it, and they are removable to ensure a tight fit to the cable. The rubber layers enable you to adapt it to both the diameter of the cable jacket for environmental protection and to the cable armor for electrical protection.

The Roxtec BG™ B modules has the part providing electrical safety on one side and environmental protection on the other, and is the perfect solution for cabinets and electrical enclosures.

BG modules_innovative technologies_BGB.jpg

The Roxtec BG™ modules has the part providing electrical safety in the center and provides environmental protection at both ends. The Roxtec BG™ solution works in floor or wall entries where a pass-through functionality is required.

BG modules_innovative technologies_BG.jpg

The Roxtec BG™ and BG™ B solutions are certified for:

Electrical safety
Hazardous (Ex) locations
Bonding and grounding
Fire protection, gas and water tightness

Test of Roxtec BG™ system

Roxtec BG™ solutions are designed for applications where high levels of currents can occur. A current, that corresponds to the specified withstand level, is routed through a module to the frame and its termination connector. The current level is determined by applicable electrical standards and depends on the size of the routed service. The Roxtec BG™ system handles this as the braid’s cross-sectional area increases with the module size.

The table shows the copper cross-sectional area per module size and to which current level it has been tested. This is an example of information that can be found in the technical specifications.

Braid data per module size

BG module size	Cable range (outer Ø mm)	Total braid cross-section (mm²)	Approximately equivalent AWG
20w40	3.5 - 16.5	4	11
20	4 - 14.5	8	8
30/30w40	10 - 25	13	6
40 10-32	9.5 - 32.5	21	4
40	21.5 - 34.5	21	4
60 24-25	24 - 54	42	1
60	28 - 54	42	1
80/90	48 - 71	42	1
120	67.5 - 99	42	1

Current and surge withstand capabilities per module size

BG module size	AC SHORT CIRCUIT TEST
	UL 514B/UL 467, CSA 22.2 No 18.3-04/No 41.07 requirements		Tested to:		EN 50262,/A1,/A2 Armored cables Category B current req. A, 1 sec	Tested to A, 1sec
	Current (A)	Sec	Current (A)	Sec		Tested to A, 1sec
20w40	1180	4	1530	6	Cat A, 500	500
20	1180	4	1530	6	3060	3480
30/30w40	1530	6	1530	6	4000	4101
40/40 10-32	2450	6	2450	6	5400	5409
60/60 24-54	4900	6	5050	9	7200	7495
80/90	5050	9	5050	9	10400	15274
120	5050	9	8030	9	10400	15274

Testing at Roxtec - Short circuit grounding

How to verify bonding and grounding functionality

In all electrical installations, you have to verify the functionality. To verify the electrical functionality of Roxtec BG™ solutions, we recommend you to verify the contact resistance with the 4-pole method with minimum 10 ADC following national legislation.

Installation verification of Roxtec BG™ systems

Roxtec BG™ solutions as lightning protection

A lightning protection system, LPS, is intended to divert transient currents caused by lightning strikes to earth. The Roxtec BG™ system is not designed to act as a primary lightning protection system. Instead, it protects from the effects of indirect lightning strikes. Even indirect lightning strikes can induce high voltages into metallic objects, cables or pipes in proximity. By using Roxtec BG™ seals, you can minimize the effects of indirect lighting strikes. The surge and transients from a lightning strike have a broadband spectrum, which requires EMI designed grounding methods to avoid equipment damages.

The Roxtec BG™ system is tested according to IEC 62305-1, which is a standard for protection against lightning. This standard is a tougher standard than the IEC 60060-1 with strikes containing approximately 20 times more energy.

Comparison between IEC 62305-1 and 60060-1

To simulate a wind turbine lifecycle, a test cycle of totally 33 surges was tested with current levels from 50kA up to 200kA. The test showed that the contact impedance of the tested cable was unchanged during the whole test period.

Different types of strikes

There are different types of strikes:

Direct strike
Strike to earth close to the application
Direct strike to power supply line
Strike to earth close to power supply line

These strikes can cause different types of damages such as electric shock, fire, explosion or failure to an electrical system.

Lightning strike animation

Example of a lightning strike. The lightning strike hits the top of a tower. The tower itself is protected by a lightning protection system, LPS, not a Roxtec product. When the energy travels along the primary protection towards ground, strong surges and transients are induced into cables routed along the tower. These secondary effects of the lightning strike can easily damage connected equipment inside buildings, etc. In the case where the cables are shielded, the surges and transients are induced into the cable shields instead. So by using Roxtec BG™ sealing solutions, you can limit the effects and protect the connected equipment.

Roxtec BG™ – features for free

A bonding conductor requires a certain cross-sectional area to withstand a certain current if there is a fault. Electrical codes give guidance regarding sizing. However, the shape of the conductor plays a big role in making it work efficiently also as a conductor for frequencies much higher than those of the supply power, which are usually 50/60Hz.

As a feature for free, the beneficial geometry of the integrated bonding braid in combination with minimized length gives very low impedance. The rule is that the wider the conductor, the better, because the higher frequency, the more the signals tend to propagate only on the surface of a material. A shorter route is also better for achieving low impedance, which is important when it comes to protecting against high-frequency interference conducted on cable armor and shields. This gives an efficient high-frequency functional grounding, which is crucial for electromagnetic compatibility and EMI, electromagnetic Interference, protection. Electromagnetic disturbances conducted via the cable armor/shield or metallic pipe are efficiently diverted to ground and the electrical safety aspect is not compromised. The Roxtec BG™ system offers a highly efficient solution for electromagnetic shielding applications up to 100MHz.

Contact impedance of a Roxtec BG™ system.

Typical electromagnetic shielding characteristics of Roxtec RM BG™ systems.

Roxtec seals are tested according to standards for shielded enclosures, such as IEEE 299. They are fitted into the wall structure before measuring the shielding effectiveness of the complete enclosure.