Electrical Engineering

In Article " Verifying Ground Rod Installation ", I explained the following points:

Resistance to Earth,

Design Guidelines and Requirements,

Measuring Rod Resistance.

Today, I will explain the following points:

Verifying Ground Connection/Interconnection Installation,

Verifying Fence Ground Installation.

You can review the following Articles For more information:

Introduction to Earthing System

Ground Resistance Calculations

Ground Resistance Measurements

5- Verifying Ground Connection/Interconnection Installation

Important!!!

As an Electrical Inspector, you must know that a well-made connection is another critical component in the grounding system. When you make a low-resistance connection, the grounding system operates properly and safely. When you make a high-resistance connection, or if a connection becomes defective, it destroys the effectiveness of the grounding system. The system at that point or any part related to it becomes a potential danger.

5.1 Design Guidelines and Requirements for Ground Connection/Interconnection Installation

1- Ground Connections/ Interconnection Types

Make buried connections and connections elsewhere, where practical, by thermite welding, brazing or approved compression ground connectors. Figure (1) is a typical grid that is thermite welded. Figure (2) is a typical grid that is compression connected.

Figure 1. Typical thermite welded ground grid

Figure 2. Typical compression connected ground grid

2- Compression connectors Requirements

Compression connectors must be Burndy Hyground System or equivalent and should have the following characteristics:

The tensile strength and torque strength of the connection joint is greater than that of the conductor.
The connector is marked with cable size and die index number.
The compression tool used on the connector is designed to lock in during compression and only release after the compression stroke is completed or when a safety release trigger is activated.
The die will leave a mark on the connector after compression that matches the original die index number on the compression tool.

3- Other Requirements

3- Bury no mechanical connections below grade.

4- Connect equipment and system grounds to the ground bus or the ground grid by separate conductors.

5- Avoid looping of grounding conductors from one equipment to another. Provide a separate conductor from the ground bus or ground grid to each item of equipment.

6- All grounding conductors must be as continuous as possible. The "through" conductors at cross and tee connections must be uncut. Avoid unnecessary connections elsewhere.

7- Bolted links or similar means of ready disconnection for test purposes is provided in grounding connections to the:

Generator neutrals
Transformer neutrals
Grounding electrodes such as groundwells or groups of ground rods
Switchgear equipment ground bus
Switchgear neutral buses

Note: Do not install any other ground disconnecting devices.

8- Verify that all grounding devices and conductors are installed so that they are protected as much as possible against mechanical injury. In frequented areas, buried conductors, 120 mm2 (4/0 AWG) or less, emerging from the ground must be protected by a non-metallic conduit for 6 to 12 inches (150 mm to 300 mm) above and below grade. Run conductors in a duct below concrete or where similarly inaccessible, preferably using non-metallic pipe. Metallic conduit and cable tray shall be grounded at each end. These systems shall also be electrically continuous.

9- A grounding bus should form a closed loop so that equipment grounds and system neutrals tee-connected to it have two current paths.

10- Where a site includes ground buses and ground grids in combination, and their ground resistance area overlaps, they must be interconnected by at least two conductors per bus or grid.

6- Verifying Fence Ground Installation

Where fences surround electrical facilities or areas where a fence could be energized from a fault, either from within the facility or one transferred in from attached fences or other metallic connections, they must be grounded to protect both the worker in the facility and the general public who may touch it from the outside.

6-1 Design Guidelines and Requirements for Power Distribution Substation Fences

These fences must be designed to meet the following requirements:

Metal posts must be used for the substation fence.
A metal chain link fence must be used that is non-PVC coated.
The peripheral grounding conductor of the substation grounding grid must be buried to a depth of 2 to 3 feet (0.6 to 1 m) and 3 feet (1 m) outside, and parallel to the fence.
the fence must be bonded to the peripheral grounding conductor at intervals of 50 feet (15 m) maximum with a minimum size of 70 mm2 (2/0 AWG) conductors.
Corner and gate posts must be connected to the grounding conductor. Gates must be bonded to gate posts with flexible connectors.
The grounding conductor run outside the fence must have a minimum of two connections to the ground grid.