Lightning protection grounding resistance standards

Wednesday, 26/06/2024, 23:10

Ensuring the safety and efficiency of lightning protection systems is a top concern for many customers. One of the key factors to achieve this is determining the proper grounding resistance. TAEC introduces a set of standards from Vietnam and around the world regarding grounding and grounding resistance.


Grounding Resistance Standards of Vietnam and the World


For lightning protection systems (LPS), grounding resistance or earthing resistance according to standards is a critical factor in the effectiveness and safety of the system. Compliance with grounding resistance standards not only protects people but also safeguards electrical equipment from potential risks.

What is Grounding Resistance?

Grounding resistance measures the electrical conductivity of a grounding system. The lower the resistance, the higher the conductivity, ensuring safety for electrical equipment and people during lightning strikes or electrical leakage. Grounding resistance is measured in Ohms (Ω), and grounding systems must comply with standard resistance values to ensure effectiveness and safety.

Below are some common standards that specify grounding resistance values:

Grounding Resistance Standards of Vietnam

TCVN 4756:1989 - Code of Practice for Grounding and Bonding of Electrical Equipment

This standard specifies technical requirements and measurement methods for establishing grounding and bonding systems for electrical equipment.

  • Article 4.1.6: "Grounding Resistance Testing"
    • Procedures and methods for testing grounding resistance, including equipment and testing frequency.
  • Article 4.2.1: "Grounding Resistance Requirements"
    • Grounding resistance for lightning protection systems should not exceed 10 Ohms.
    • Grounding resistance for power systems should not exceed 4 Ohms.

TCN 68-174:2006 - Telecommunication Industry Standard for Protective Grounding and Lightning Protection for Telecommunication Facilities

This standard applies to telecommunication facilities, specifying requirements for protective grounding and lightning protection.

  • Article 5.1: "Protective Grounding Resistance"
    • Specifies that grounding resistance for telecommunication systems should not exceed 10 Ohms to ensure safety.

International Grounding Resistance Standards

IEC 62305-3 - Lightning Protection - Part 3: Physical Damage to Structures and Life Hazard

IEC 62305 provides detailed requirements and guidelines for protecting structures and electronic equipment from lightning strikes.

  • Article 5.3.6: "Reduction of Earth Resistance"
    • Describes methods to reduce grounding resistance such as using multiple grounding rods, adding chemicals, or expanding the grounding system.
  • Article 6.2.2: "Earthing and Bonding"
    • Specifies that grounding resistance for lightning protection systems should not exceed 10 Ohms.

IEEE 80 - Guide for Safety in AC Substation Grounding

IEEE 80 provides detailed guidelines for designing, installing, and testing grounding systems at AC substations.

  • Chapter 14: "Grounding System Design"
    • Designing grounding systems, including methods and techniques to achieve low grounding resistance.
  • Chapter 16: "Testing and Maintenance"
    • Guidelines for testing and maintaining grounding systems, including methods for measuring resistance and testing frequency.

Other Grounding Standards

NFPA 780 - Standard for the Installation of Lightning Protection Systems

NFPA 780 specifies requirements for designing, installing, and maintaining lightning protection systems for structures.

  • Chapter 4.12: "Grounding"
    • Grounding resistance for LPS must be below 10 Ohms and describes methods to achieve this.

BS 7430 - Code of Practice for Protective Earthing of Electrical Installations

Provides guidelines for designing and installing grounding systems.

  • Section 9.2: "Resistance of Earth Electrode"
    • Grounding resistance for LPS should not exceed 10 Ohms and below 1 Ohm for critical power systems.

Industry-Specific Standards

ITU-T K.27 - Protection of Telecommunication Lines Against Lightning Discharges

The International Telecommunication Union (ITU) provides guidelines for protecting telecommunication equipment from lightning strikes.

  • Article 8.2: "Earthing Requirements"
    • Grounding resistance for telecommunication protection systems should not exceed 10 Ohms.

EN 50522 - Earthing of Power Installations Exceeding 1 kV a.c.

European standard providing regulations for grounding power systems with voltages above 1 kV.

  • Article 5.1.1: "Resistance to Earth"
    • Grounding resistance must be designed to ensure safety and efficiency, typically below 1 Ohm for critical systems.


At TAEC, we understand the importance of complying with grounding resistance standards to ensure the safety and efficiency of lightning protection systems. These standards provide specific guidelines for design, installation, and testing, helping to mitigate risks and protect people and electrical equipment. ThyAn Lightning Protection Company is committed to providing optimal grounding solutions that fully comply with national and international standards, ensuring comprehensive protection for your projects.

Note: The grounding resistance values specified by the standards are the maximum allowable values; the lower the value, the better. Lower resistance allows for faster and safer dissipation of electrical currents. This also helps to prevent changes due to seasonal and geological fluctuations.

Further Reading:

Other news

Lightning rod is a common name used to refer to a system installed on the top of a building or on a high pole, consisting of one or more metal rods with pointed ends connected to ground conductors for protection. for structures, buildings and objects below from being struck by lightning.
The surge protection selection must be done following the local electrical code requirements (e.g. : minimum rating for In) and specific conditions (e.g. : high lightning density).
This article will guide you through international, continental, national, and Vietnamese lightning protection standards, highlighting their significance and practical applications in various sectors.
Alongside lightning rods that protect structures, transient surge protection plays a crucial role in protecting internal electrical and electronic devices.
Learn about the lightning protection system (LPS): definition, purpose, types, and detailed installation guide to protect buildings and equipment from lightning damage.
Lightning protection involves using technical measures and systems to protect people, property, and infrastructure from the harmful effects of lightning. This system helps minimize the risk of damage caused by direct lightning strikes or induced surges.
Surge surge protection devices (SPDs), also known as surge suppressors, are specific products in the electrical industry, the specifications of lightning protection devices on documents or products displayed Displays symbols and parameters to describe their own properties. Based on these parameters we can understand and compare the technical features of the devices, in order to use them most effectively.
Different electrical networks have different specifications and connections, so manufacturers have designed products for their respective protection installations. If selected incorrectly and installed improperly, not only will it lose its effectiveness, but it can also cause damage, fire, loss of electrical safety and affect the entire system.
Brazilian researchers captured on camera the moment when lightning rods on buildings released an upward discharge to attract incoming lightning.
Some standards on Lightning Protection, Earthing of International (IEC, IEEC), Vietnam and other countries (France, Spain, US, British ..)