Articles

Grounding Surveys

email_Icon_24X24Contact us to find out which products and services are right for your needs.

Alltec Protection Pyramid™ surveys

A three part series

Introduction & Part I- Grounding / Bonding

Introduction

Alltec calls the methodology used for visualizing, designing, and implementing its unique and industry leading three-tier comprehensive facility protection approach for grounding, surge suppression and lightning protection, the Protection Pyramid™.

It is important to realize the interrelationship and interdependence of the three tiers in protecting any facility. Without proper grounding, neither the surge suppression nor lightning protection will function correctly. Without surge suppression, equipment is exposed to the secondary effects of lightning as well as internally generated transient voltages. Direct strike lightning protection protects the physical structure and its contents. These three subsystems interlock into a very robust and stable whole.

Alltec proposes that its engineering team work with your designated site representative(s) to inspect your facility and investigate all problems and concerns related to lightning protection, surge suppression and grounding. Alltec personnel have the skills, experience and tools to accomplish the requirements of this project in a timely and professional manner. We look forward to working with you.

This first of a three part series begins with the base of the Protection Pyramid™- Grounding and Bonding, which is the foundation required to:

  • Protect critical facilities, equipment, records, and assets.
  • Provide a safe working environment for personnel.
  • Reduce the risk of downtime and lost revenue.
  • Reduce vulnerability of interdependent critical infrastructures, and build a disaster resilient enterprise.
  • Minimize liability and maintain a competitive posture.

A number of standards and references are used when conducting a grounding survey, including:,/p>

  • NFPA 70 – National Electrical Code (NEC)-2014
  • NEC Article 250 – Primarily for Safety from the use of Electricity
  • NFPA 780 / UL 96A – For Lightning Protection System Grounding
  • IEC 62305/NFC Standard – International Standard for Lightning Protection Systems
  • IEEE Standards
  • IEEE 80 – For Ground System Design of High Voltage Substation
  • IEEE 81 – IEEE Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System
  • IEEE 65 – For Ground System Design of Generating Stations
  • IEEE 142-2007 (Green Book) – Grounding of Industrial and Commercial Power Systems
  • IEEE 1100 (Emerald Book) – Powering and Grounding Electronic Equipment
  • Motorola R56 – For Telecom Tower applications
  • FAA and Military Handbooks on Grounding & Bonding – For Commercial installation including Telecom Towers
  • Company and Equipment Manufacturer’s Standards

Electrical systems that are grounded should be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operations.

The National Electrical Code (NEC) has become the most widely adopted code in the United States, although the ground system resistance requirements should be interpreted for different facilities by different standards. For example, NEC article 250.56 requires a 25 ohm ground system resistance with installation of a single ground electrode for any service entrance electrical system in order to safeguard persons and property from the hazards arising from the use of electricity. It also states that, if the required resistance goal is not achieved by a single electrode, a single additional electrode is to be installed. Thus, this NEC safety requirement might possibly be satisfied by the installation of two (2) electrodes which result a much higher resistance than 25 ohms, and which in some situations certainly may not be sufficient from a power quality performance standpoint for critical micro-processor based instrumentation within the facility.

Additionally, grounding for lightning protection systems or bonding requirements for flammable operations may differ from standard electrical codes, and grounding system resistance for high voltage applications should be low enough to meet safety step and touch voltage criteria as per the IEEE-80 standard.

As the preceding paragraphs infer, ground system surveys can be convoluted, possibly confusing, and may not result in optimal solution recommendations unless the survey team has a good understanding of the referenced codes, as well as experience with different types of grounding applications and can relate this information to the needs of the facility under study. Furthermore, testing must be planned to harmonize with expectations of what will actually yield desired results and be possible with available funds. Therefore, the best way to start is with a site evaluation:

  • Collect information on types of damages experienced or anticipated by the facility, and create a prioritized outline of survey requirements.
  • Study existing site plan drawings, site grounding system layouts, one-line electrical riser diagrams and one-line data riser diagrams.
  • Review the physical site to identify zones of activities, main electrical panels, grounding system test locations, and bond points.

After developing an understanding of the facility and its needs, and creating a site specific test plan, typical actions include:

Execution of a visual inspection of external grounding systems and internal bonding systems and visual inspection of corrosion/maintenance issues.

Execution of a visual inspection of external grounding systems and internal bonding systems
Inspection of corrosion maintenance issues

Execution of Fall-of-Potential Tests as per IEEE-81 Std.

Execution of Fall of Potential Tests as per IEEE-81 Std

Clamp-on Resistance and Leakage Current testing

Clamp on Resistance and Leakage Current testing 1
Clamp on Resistance and Leakage Current testing 2

Performance of Point-to-Point Testing as required, to evaluate the resistance of existing grounding and bonding systems.

Evaluate sampling of local/equipment bonding in flammable areas with Intrinsically Safe point-to-point test equipment, as identified in initial site evaluation

Point to Point Testing

Execution of 4-Point Testing (Wenner Method) as per IEEE-81 Std. to evaluate earth resistivity for ground system modeling

Executing 4 Point Testing

Soil Resistivity Data, Parameters and Study

Soil Resistivity Field Report
Grounding System Parameter Model
Wenner Method Soil Parameter

Create two-layer soil model in grounding system modeling software and analyze, in order to determine necessity and/or viability of additional grounding, if required

Analyzed Ground System Model – Plan View
3-D Ground System Model

Special studies for high voltage scenarios may include:

  • Grounding Study for the High Voltage Substation and the Power Utilities facilities: Evaluate site design, and conduct Ground Potential Rise Studies.
  • 3D Ground Potential Rise (GPR) Analysis using the computer modeling, to determine IEEE 80 step & touch voltage hazards. Provide site design with recommended safety improvements if needed.
Step Analysis 1
Touch Analysis
Step Analysis 2
Touch Analysis

On-Site Survey & Testing, Data Analysis and Computer Modeling should yield a Survey Report and supporting documentation containing observations, testing and data analysis, and site photographs      as needed. Reports should include:,/p>

  • Listing of compliance of grounding and bonding systems and upgrades required to cover noncompliance.

One of the most important investments a company makes is in sensitive electronic equipment. As this equipment becomes more sophisticated and electrically susceptible, the need for a low-resistance grounding system becomes more crucial. Examples, such as cellular, radio and television broadcasting sites, computer facilities, power substations, communication centers, medical facilities and industrial plants all share the common need for the design, implementation and inspection/maintenance of high quality ground systems.

ALLTEC offers a strategic approach to meeting our client’s needs, the ALLTEC Protection Pyramid™. This approach looks at all aspects of a facility and works in a holistic fashion to make sure all areas are protected with an effectively interlocking defense. If you have an existing or planned facility, be sure to give ALLTEC a call or email. We can make sure your operation is the safest possible facility, backed by our team of dedicated risk-mitigation experts. If you have a current or future project that needs grounding/bonding solutions, surge suppression or lightning protection please contact ALLTEC at either 1-828-646-9290 or online-info@alltecglobal.com

Rev. 20160720

Share this post with your friends!