Earthing & Lightning Protection Audit
Safety and reliability is our primary objective
Earthing System Testing
The earthing system is designed and engineered to perform safely during earth fault conditions. However, it is also critical that commissioning and routine testing is undertaken to validate and ensure that the earthing system performs safely.
The following activities are conducted as part of WAPP’s earthing and lightning protection review:
✓ Touch, step and transferred voltage hazard measurements
✓ Determination of individual and overall earthing system impedance
✓ Determination of lightning protection earthing impedance and physical integrity
✓ Determination of earth potential rise (EPR) contours
✓ Soil resistivity testing
✓ Continuity of equipment earth connections
✓ Visual inspections
✓ Current distribution measurements
✓ Determination of earth grid conductor sizing suitability
✓ Assessment of switch-yard surfacing
Testing Methods Injection Testing
The concept of injection testing is to simulate a system earth fault at a much smaller scale. This is performed by injecting an off-frequency current into the earth grid which in turn causes the earthing system to rise in voltage. The purpose of injecting an off-frequency current (typically 58 Hz), is to ensure that the earthing system is isolated from any interference, including the 50 Hz system frequency and harmonics.
Correct set up of the injection test does not interfere with the operation of the asset or the site. Therefore, the test can be conducted while the site is still live. The following parameters are able to be measured during an injection test:
- Earthing system impedance
- Touch, step and transferred voltages
- Location of Earth Potential Rise (EPR) contours
- Earth Grid Voltage Rise (EGVR)
Soil Resistivity Testing
The soil resistivity structure is the biggest contributing factor in the performance of the earth grid. The soil structure governs the way the voltage dissipates from the earthing system during an earth fault event and the susceptibility of the change in earth resistance in relation to the amount of earth grid conductor added.
The most accepted and accurate method in measuring the average resistivity of large volumes of undisturbed earth is the Wenner Array method. The Wenner Array method uses four electrodes spaced at equal distances apart to create the test circuit. The two outer electrodes create the current circuit and the two inner electrodes measure the voltage on the earth’s surface in relation to the current electrodes.
Fall of Potential (FOP) Testing
The fall of potential (FOP) method is used to determine the resistance of a small earthing system.This test is typically used to measure the earthing resistance of lightning protection systems and small kiosk/pole mounted substations. This test only gives a resistance value and does not confirm safety with respect to touch and step voltages.
Continuity tests are conducted to check the connections of primary pieces of plant are adequately bonded to the earth grid. The resistance between a primary piece of plant and reference point is measured using a micro-ohmmeter.This method allows the user to determine the resistance between a path and to identify defects which otherwise cannot be visually inspected.
Design and Management
Electrical systems comprise of various individual components that need to work effectively and efficiently with each other in order to achieve the system objective. A design process involves selecting such components according to technical, regulatory and safety requirements. A proper design methodology ensures that the design outcome achieves the desired technical objectives as well as regulatory and safety compliance.
It is also crucial to correctly configure the individual components such as protection relays according to the design outcome as well as assess and manage the system to ensure that objectives are met. Our design solutions include:
- Earthing System Design
- System Configuration and Assessment
- Lightning Protection Design
- Commissioning Management
- Protection, Control and Metering
Testing and Commissioning
Electrical systems are designed to fulfil specified functions as well as comply with technical and regulatory standards. Before any electrical installation is put into service, it is vital to verify that the specified functions are being fulfilled, that the installation complies with relevant technical & regulatory standards and that the installation is safe for use. Effective verification can only be achieved through a well planned and executed testing and commissioning regime.
- Earthing Systems
- Instrument Transformers (VTs and CTs)
- Protection Relays
- Power Transformers
- Energy Meters
- Circuit Breakers
- A Rotating Machines
- Power Cables
- Hydro Power Plants