TGB, TBB, MGB and Substation Ground Bars

Grounding systems in telecom facilities, data centers, substations, industrial plants, and low-voltage distribution equipment often use several different grounding bars and bonding conductors. Terms such as TGB, TBB, MGB, EGB, LV ground bar, and substation ground bar may appear similar, but they describe different parts of the grounding network.

Understanding the function of each component is important when designing a grounding system or specifying a custom copper ground bar. The bar dimensions, conductor terminals, hole pattern, mounting method, surface treatment, and installation location should all match the equipment and grounding design.

For telecom equipment manufacturers, electrical enclosure builders, data center contractors, switchgear manufacturers, and substation projects, custom copper grounding bars provide a centralized and reliable connection point for grounding and bonding conductors.

What Is a Ground Bar?

A ground bar is a conductive metal bar used to terminate and connect grounding or bonding conductors. It is usually made from bare copper or tin-plated copper because copper provides high conductivity, good mechanical strength, and reliable long-term electrical connections.

Depending on the application, a ground bar may connect:

• equipment grounding conductors
• telecom bonding conductors
• cabinet and rack bonding conductors
• cable tray grounding conductors
• building grounding conductors
• surge protection devices
• switchgear enclosures
• transformer housings
• substation equipment
• main grounding electrode conductors

The ground bar creates an organized common connection point rather than allowing grounding conductors to terminate at unrelated locations.

A ground bar normally does not carry continuous operating current. Its main purpose is to provide a low-impedance path for fault current, surge current, static discharge, and bonding between exposed conductive parts.

For a broader explanation of copper grounding bar materials, configurations, mounting methods, and industrial applications, see our main guide to custom electrical ground bars and grounding busbars.
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What Is a TGB Ground Bar?

TGB commonly means Telecommunications Grounding Busbar.

A TGB ground bar is installed in a telecommunications room, equipment room, data room, or other telecom space. It provides a local grounding and bonding point for the equipment located in that room.

A typical TGB may connect:

• telecom racks
• network cabinets
• patch panels
• cable trays
• ladder racks
• equipment frames
• metallic conduits
• surge protection devices
• telecom equipment chassis
• bonding conductors from nearby rooms

The TGB is generally connected to the wider telecommunications bonding network through a bonding conductor.

In a building with several telecommunications rooms, each room may have its own TGB. These local grounding bars help reduce long grounding conductor runs and provide clearly organized termination points near the equipment.

Common TGB construction

A TGB is commonly manufactured from:

• bare copper
• tin-plated copper
• C11000 copper
• Cu-ETP copper
• T2 copper

The bar may include:

• multiple drilled terminal holes
• threaded holes
• studs
• compression-lug connection points
• insulated standoffs
• wall-mounting brackets
• grounding labels
• mounting hardware

Custom TGB ground bars may be produced according to the number and size of grounding conductors required in the telecom room.

What Is a TBB?

TBB normally means Telecommunications Bonding Backbone.

Unlike a TGB, the TBB is generally not a grounding bar. It is the main bonding conductor that connects telecommunications grounding components between different rooms or floors.

A typical telecom grounding arrangement may be represented as:

Telecom equipment → TGB → TBB → main telecommunications grounding point

The TBB creates a continuous bonding path through the building. It may connect several TGBs to a main grounding busbar or telecommunications main grounding busbar.

Therefore, the phrase TBB ground bar is often used informally in searches, but technically the TBB usually refers to the backbone conductor rather than the copper bar itself.

Ground bars associated with the TBB may include:

• local TGBs in telecom rooms
• a main grounding busbar
• a telecommunications main grounding busbar
• grounding bars in entrance facilities
• grounding bars in equipment rooms

When manufacturing grounding components for a telecom system, it is important to confirm whether the customer requires the actual TGB or MGB copper bar, or only the connecting bonding conductor and terminals.

What Is an MGB Ground Bar?

MGB usually means Main Grounding Busbar.

An MGB ground bar acts as a primary grounding and bonding point for a building, electrical room, data center, telecom facility, industrial plant, or equipment system.

Compared with a local TGB, an MGB normally serves a larger part of the grounding network and may receive larger grounding conductors.

An MGB may connect:

• local telecommunications ground bars
• building steel
• electrical grounding systems
• cable trays
• data center equipment
• grounding electrode conductors
• incoming service grounding conductors
• surge protection devices
• generator enclosures
• UPS systems
• electrical switchboards
• multiple equipment grounding networks

The exact meaning of MGB can vary between projects, so drawings and electrical specifications should always be checked before production.

MGB ground bar design

An MGB usually has:

• a larger copper cross-section
• more terminal positions
• larger main conductor holes
• a combination of small and large terminals
• strong wall-mounting brackets
• optional insulated supports
• optional transparent protective cover

A custom MGB ground bar may include small terminals for branch grounding conductors and larger terminals for the main grounding electrode or bonding conductors.

What Is an EGB Ground Bar?

EGB commonly means Equipment Grounding Busbar.

An EGB ground bar provides a connection point for the protective grounding conductors of electrical or electronic equipment.

It may be installed inside:

• switchboards
• switchgear cabinets
• control panels
• power distribution units
• data center cabinets
• telecom enclosures
• UPS cabinets
• inverter cabinets
• battery cabinets
• industrial machines

The EGB bonds equipment housings and exposed metal parts to the protective grounding system.

Depending on the design, an EGB may be mounted directly to a metal enclosure or installed on insulating supports.

Direct-mounted EGB

A direct-mounted equipment ground bar may be electrically bonded to the enclosure through its mounting hardware.

For this arrangement, paint, powder coating, oxidation, and other surface layers should not prevent electrical continuity.

Isolated EGB

An isolated EGB is mounted on insulating standoffs and remains separated from the enclosure except through a designated conductor.

This arrangement may be selected when the grounding design requires controlled bonding points or separation between different grounding networks.

The correct installation method should be determined by the equipment designer or electrical engineer.

TGB vs MGB vs EGB

Although all three components may be made from similar copper bar material, their functions are different.

The same project may use several of these components together.

For example, a data center may use local TGBs in individual telecom rooms, an MGB in the main electrical or grounding room, EGBs inside equipment cabinets, and TBB conductors connecting the telecom grounding network.

LV Ground Bars for Low-Voltage Systems

An LV ground bar is used in low-voltage electrical equipment and power distribution systems.

Typical applications include:

• low-voltage switchboards
• distribution panels
• motor control centers
• electrical cabinets
• control panels
• generator panels
• UPS systems
• inverter cabinets
• industrial machinery
• power distribution units

The LV ground bar provides terminal positions for protective earth conductors from outgoing circuits, enclosures, doors, mounting plates, and internal devices.

It may also be called:

• low-voltage grounding bar
• PE ground bar
• protective earth bar
• panel ground bar
• equipment ground busbar
• electrical grounding busbar

An LV ground bar is normally separated from positive, phase, neutral, and DC negative busbars unless the system design specifies a particular bonding arrangement.

Typical LV ground bar configurations

An LV ground bar may be manufactured as:

• a flat copper strip
• a drilled copper bar
• a bar with threaded holes
• a bar with brass or steel terminal screws
• a DIN-rail-mounted grounding bar
• an L-shaped copper grounding bar
• a covered grounding bar
• an isolated ground bar assembly

The required dimensions depend on conductor size, terminal quantity, fault-current requirements, and available panel space.

Substation Ground Bars

A substation ground bar is used to connect grounding and bonding conductors within a power substation.

Substation grounding systems may contain an underground grounding grid together with grounding conductors connected to equipment, structures, control panels, transformers, switchgear, and protection systems.

Copper grounding bars may be installed in:

• substation control rooms
• relay panels
• switchgear rooms
• communication rooms
• transformer control cabinets
• protection and metering panels
• SCADA cabinets
• battery rooms
• DC control panels
• cable termination areas

The substation ground bar provides an accessible termination point between internal equipment grounding conductors and the wider substation grounding network.

Equipment connected to a substation ground bar

Depending on the project, the ground bar may connect:

• switchgear enclosures
• control cabinets
• relay panels
• transformer housings
• cable shields
• cable trays
• communication equipment
• battery chargers
• DC systems
• surge protection devices
• metallic structures
• external grounding grid conductors

Substation grounding bars often require larger copper cross-sections and heavy-duty terminals because they may be part of a grounding network designed for substantial fault currents.

The dimensions should always be based on the project’s electrical calculations and drawings.

Ground Bars in Substation Control and Communication Rooms

Modern substations contain not only high-voltage electrical equipment but also sensitive control, protection, automation, and communication devices.

A grounding bar inside the control room may provide a common connection point for:

• relay cabinet grounding
• SCADA equipment
• communication racks
• control cable shields
• protection panels
• DC distribution panels
• monitoring equipment
• telecom devices

In some projects, separate grounding arrangements may be used for power equipment, control systems, communications, or sensitive electronics. These grounding networks may then be bonded at designated points.

Ground bar manufacturers should not assume that every copper bar in a substation has the same function. The drawing should clearly identify the required material, dimensions, terminals, and isolation method.

Selecting Copper Ground Bar Dimensions

There is no universal size for every TGB, MGB, EGB, LV, or substation ground bar. The correct dimensions depend on the grounding design.

Important factors include:

Copper bar length

The bar must be long enough for all cable lugs and grounding conductors. Extra terminal positions may be added for future expansion.

Width and thickness

The bar cross-section should provide sufficient fault-current capacity and mechanical strength.

A larger MGB or substation bar will usually be thicker or wider than a small equipment grounding bar.

Hole quantity

The number of holes should match the number of incoming and outgoing grounding conductors.

Hole diameter

Terminal holes should match the intended bolts, studs, cable lugs, and conductor sizes.

Common hardware sizes may include:

• M4
• M5
• M6
• M8
• M10
• M12

Custom bars may combine several terminal sizes.

Hole spacing

Sufficient spacing is necessary to prevent cable lugs from overlapping and to allow access for installation tools.

Main conductor connection

A TGB or MGB may require one or more larger terminals for the backbone or main grounding conductor.

Bare Copper or Tin-Plated Copper

Both bare and tin-plated copper are commonly used for grounding bars.

Bare copper

Bare copper provides excellent conductivity and is widely used in indoor telecom rooms, data centers, electrical rooms, and clean industrial environments.

Tin-plated copper

Tin-plated copper helps reduce surface oxidation and may be selected for:

• humid environments
• outdoor installations
• industrial plants
• substations
• coastal locations
• battery rooms
• locations with condensation
• environments containing corrosive contaminants

Tin plating may also provide a consistent contact surface for cable lugs and terminals.

The plating thickness should be specified according to the environmental requirements and customer drawing.

Custom TGB, MGB and Substation Ground Bar Manufacturing

Standard ground bars may not fit every room, cabinet, rack, or electrical panel. Custom manufacturing allows the bar dimensions and terminal layout to match the actual project.

Common production processes include:

• copper bar cutting
• CNC punching
• drilling
• tapping
• milling
• bending
• deburring
• surface cleaning
• tin plating
• nickel plating
• stud installation
• insulator assembly
• bracket assembly
• cover installation

Custom grounding bars can be supplied as:

• individual copper bars
• bars with mounting brackets
• isolated ground bar assemblies
• bars with threaded studs
• bars with bolts and washers
• bars with cable lugs
• wall-mounted grounding kits
• covered grounding bar assemblies

Before production, the following information should be confirmed:

• application
• copper grade
• bar length, width, and thickness
• hole diameter
• thread size
• terminal spacing
• mounting-hole dimensions
• surface treatment
• insulated or direct mounting
• hardware material
• cover requirements
• order quantity

A detailed 2D drawing is usually the most reliable basis for manufacturing.

Applications

TGB, MGB, EGB, LV, and substation grounding bars are commonly used in:

• telecom rooms
• data centers
• server rooms
• network equipment rooms
• telecommunications facilities
• substations
• switchgear buildings
• low-voltage switchboards
• control panels
• relay panels
• UPS systems
• battery rooms
• industrial plants
• power distribution cabinets
• communication shelters

Although the copper bar may look simple, the terminal arrangement and mounting design should match its exact role in the grounding network.

Conclusion

TGB ground bars, MGB ground bars, EGB ground bars, LV ground bars, and substation ground bars all provide grounding and bonding connection points, but they serve different parts of an electrical or telecommunications system.

A TGB is normally a local grounding busbar in a telecom room. The TBB is generally the backbone conductor connecting telecom grounding points. An MGB acts as a main grounding busbar, while an EGB provides grounding connections for equipment and enclosures.

In substations and low-voltage distribution systems, copper ground bars connect switchgear, control cabinets, cable shields, equipment frames, protective earth conductors, and the wider grounding network.

Custom bare copper or tin-plated copper ground bars can be manufactured with specific dimensions, mixed hole sizes, threaded terminals, studs, insulated standoffs, mounting brackets, and protective covers to suit telecom, data center, industrial, low-voltage, and substation grounding applications.