Earthing System AuditThe most effective way to ensure that protection systems on high voltage installations

will operate appropriately during a fault.

Benefits Identify installations where remedial action is required

Comply with safety regulations, including BS 7430

Prevent damage to network assets and personnel

Reduce risk of liability and claims

Fast and excellent value

Bespoke design service for earthing system upgrades

Ensure that protection systems will operate safely in the event of a fault

3 steps to cost-effective earthing protectionElectricity Supply Regulations specify that electricity network assets should be bonded to earth, to ensure that any fault can return to its source in a controlled manner. This allows protective equipment to operate efficiently, avoiding damage to plant and equipment, and the risk of electric shock to personnel

Typical applications Although effective earthing systems are part of the design of modern high voltage installations, earthing system audits are recommended in a range of situations including:

Checking the integrity of older and upgraded substations

New operating conditions

Damage or theft of earthing system components

1. Site survey and measurement Earthing System Audits begin with a visual inspection of all electrical bonds to equipment, followed by an array of measurements:

Soil resistivity One of the most important influences on the performance of an earthing system is the impedance of the soil surrounding the electrodes. This is called soil resistivity and is expressed in Ohm metres (Ω/m). Surveys may be carried out across large areas covering multiple assets or on specific sites, for example individual substations.

The most widespread technique for measuring soil resistivity employs the Wenner method of interpretation. This test uses a four terminal instrument and involves four short probes being driven into the ground, spaced an equal distance apart. To gain a typical soil structure for the area, measurements are normally taken to represent a vertical depth of 54m.

Resistance To verify the resistance of an earthing system, measurements are taken using a four terminal instrument, which employs the ‘fall of potential’ method of interpretation. Test routes and distances are chosen to account for the size of the installation and any interference by buried cables or third party services.

ContinuityIt is important that all equipment is bonded together and to earth. We therefore undertake continuity measurements to ensure that adequate bonding is present. This also includes the use of specialist tracing equipment to confirm the location of electrodes.

2. Computer modelling and design We use the latest CDEGS computer modelling software to simulate the earthing system under review. This includes creating a register of hot zones where there are earthing issues, examining the effects of changes to the system and producing the most cost-effective options for upgrades and replacements:

Using information gained during the site survey, our software creates an electrical equivalent soil model of the earthing system, so we can review its performance under fault conditions.

Earthing designs are inserted in the model via an X, Y and Z co-ordinate system, including information on the soil structure and the electrode radius. Values of fault current can be stipulated, so the calculation of the actual potentials that will be experienced during an earth fault can be undertaken.

Once a simulation has taken place, graphical plots of touch and step potential are produced and evaluated. These simulations allow direct comparison of the actual potentials with those stated in current standards.

We make changes to the earthing system design, so that potentials occurring in fault situations are reduced to within the stipulated limits.

The end results are bespoke designs, which are based on EA Technology’s extensive experience of earthing systems. 3. Installation and

performance measurement Our service includes providing detailed specifications for new and enhanced earthing systems.

When the installation of a system is complete, we revisit the site to carry out further measurements. This ensures that the new system’s performance meets values predicted during the modelling and design

Protection system audit and design Earthing system audits are ideally conducted in conjunction with an audit of a site’s protection systems.

Protection system audits are carried out by EA Technology Consulting’s Network Asset Management specialists to ensure that:

Existing protection systems are working correctly

All relevant assets are adequately protected

Each protection system audit includes recommendations to address any protection issues. The Network Asset Management Team also has the facilities to:

Review and enhance the design of current protection systems

Produce cost-effective designs for new protection systems

Global supportCondition Assessment of HV assets can be supplied anywhere in the world, through our network of international

sales offices and distribution partners. We provide excellent lifetime support for this system, including:

Installation and commissioning Lifetime technical support

Training Online data analysis and reports

Our expertiseWe provide world-leading asset management solutions for power plant and networks.

Our customers include electricity generation, transmission and distribution companies,

together with major power plant operators in the private and public sectors.

Our products, services, management systems and knowledge enable customers to:

Prevent outages Make smarter investment decisions

Assess the condition of assets Build smarter grids

Understand why assets fail Achieve the latest standards

Optimise network operations Develop their power skills