Richard Evert, National Director of the Earthing and Lightning Protection Association (ELPA) has provided Sparks Electrical News with a comprehensive series on lightning. The series will cover Risk Management; Lightning Protection Design; Lightning Protection System (LPS) Installations; Surge Protection Measures; Earthing and Resistance; and more. Be sure to catch all the articles over the next few months.
Effective lightning protection system (LPS) installation requires a suitable design plan, the materials to fulfil the design expectation and competent personnel to do the work.
Materials
The bill of materials may be dictated by the content of the design but the responsibility to install the correct materials rests with the company doing the installation work.
SANS 62561 gives direction on what materials are required for the different components of a lightning protection system starting at the top where lightning is expected to strike right down to the earth electrodes where the lightning current is expected to dissipate into the ground.
ELPA will be moving forward with training programmes and national supporting workshops to help facilitate a better understanding of what this actually means and why compliance is in the best interests of both the service provider and the vested property stakeholders.
Bonding continuity
The responsibility to achieve the correct measures of continuity between bonding points rests with the company doing the installation work.
The best practice in the management of electrical continuity of electrical conductors is to ensure good bonding at the time of construction.
* A suitable construction strategy must be in place to confirm that bonding of all conductors in the installation will not hamper the flow of lightning current when this lightning protection system is called upon to protect people and property from the lightning descending upon them
* An absolute guaranteed measure of assurance can be given by simply measuring that continuity as an ohmic value – measure the resistance.
A critical part of the lightning protection system that involves continuity is the conductive path that the lightning current will flow through from the top of the LPS at the Air-Termination System (ATS), through the Down-Conductor System (DCS) to the bottom into the Earth-Termination System (ETS).
* This path is so critical that the South African National Standard (SANS) SANS 62305-3 specifically mentions it and stipulates a maximum overall resistance of 0.2 Ohms.
* If a service provider deems it not practical to do continuity measurements, how can you trust them to adhere to an industry standard?
Earth resistance
Similarly, while the earth electrode resistance is a function of the soil resistivity and the earth electrode design, the company doing the installation work must provide numerical evidence of the final earth resistance value obtained.
If soil resistivity was not measured and the prevailing soil resistivity conditions were not integrated into the design, the probability that the earth electrode will exceed maximum design limits increases tremendously.
But who is responsible for amending the desired earth electrode design to achieve the target maximum resistance when this happens?
Why measure?
Thus, such a discussion will re-open the debate about doing measurements.
* The effectiveness of an earth electrode is determined when the electrode materials are installed in the ground.
* High soil resistivity will increase the resistance obtained from the same earth electrode used in soils with lower soil resistivity.
Who is going to pay?
If the design upon which the installer is constructing the LPS has not taken the soil conditions into account, the installer may be faced with some difficulties:
* Who is responsible for addressing higher electrode earth resistance values?
* Who understands why a high earth electrode resistance is very, very bad?
* Is the installer legally allowed to amend the design without approval from the designer?
* If the installer can make such changes, why is the designer required at all for earth electrode designs?
Obviously, some of these questions are asked with 'tongue-in-cheek':
* The designer remains responsible and liable.
* If the vested property stakeholder authorises an amendment by the installer, then the agreements with the designer are voided along with any liabilities of the designer for the design submitted by that designer.
A conundrum
Conundrum means "a confusing and difficult problem or question" and is often used when experts are scratching their heads. The conundrum here is that good earthing starts by understanding what soil exists at the location where the earth electrode will be required.
There is only one guaranteed method to ensure the design starts off on the best footing (excuse the pun) and that is with a soil resistivity measurement. In most building projects and/or civil works, lightning protection is only considered at an advanced stage of the project and usually at a time where most contracted designers will not be afforded the opportunity (allocated time) to do soil resistivity measurements. There is a cost involved in securing reliable soil resistivity measurements:
* The equipment is exclusive.
* The number of service providers available to produce an accurate report are limited.
* The impact of measurements has historically not translated into any verifiable consequences to the project teams.
* Lower demand increase cost of services.
* Without soil resistivity measurements the designer will resort to soil type classifications.
* Since the soil resistivity is generally a misunderstood and abstract concept, designers are hesitant to jeopardise a potential source of revenue by demanding that the value of this parameter by determined as an essential part of the scope of work and thereby risk delays in the project plans.
Higher soil resistivity conditions will require more elaborate earth electrode designs to achieve the same maximum earth electrode resistance values and therefore will require more materials per electrode.
The final cost considerations are impacted by the amount of material required to construct an earth electrode. The larger the site, the more such design considerations will ramp up the volume of material and therefore the cost of the installation.
Therefore, this seemingly abstract concept of soil resistivity has a greater financial impact on projects than the project leaders can stomach. Inevitably, the soil resistivity reports will be ignored in too many cases. So, what happens?
Solution A to conundrum
Ignore the lack of information and make a conservative estimate to keep the consequential cost down. On site, the following are the reality:
* The bill of materials – sourced from the design.
* The delivered materials as per the bill of materials, and;
* The installed earth electrode as per the delivered materials.
* Soil resistivity – no, it has not gone on holiday, it is still there, exactly where it should be.
* The omission on the part of the project team and endorsed by the LP designer, is exposed when the earth resistance is proof that the electrode design was inadequate.
So here is the conundrum with solution A:
* The earth electrode is installed because of soil resistivity.
* Soil resistivity is the proof that soil is not a good conductor.
* Because of soil resistivity, an earth electrode is required - I know, repeated yes, but have you understood yet?
* If there is a discrepancy between the estimates used to compile the design, and the soil that is now around the earth electrode, the earth resistance test will reveal that the project team have failed.
The conundrum poses the following questions:
* Why take the chance and do the test?
* Should we do the test?
* If the test is done, should we take it seriously?
* Do we really want the test to be done accurately?
* Do we really expect the test to confirm that the project team succeeded?
* What is the probability that the project team will find that they failed if an accurate test is done?
* What is the probability that the earth electrode resistance value will exceed the recommended maximum value stipulated in the standards?
* Who really decided what that maximum ohmic value was anyway?
* What will happen if we just ignore the resistance value?
* Who can we hold responsible for any future problems that may be experienced once all the service providers have left the scene?
There is a term for such behaviour, and it is known as ‘pot luck’.
In general, the conundrum is resolved by delegating the task to the electrical contractor who in turn delegates the task to either another service provider or an employee.
At this point, without consideration of soil resistivity, the earth resistance test result is of academic interest to the project teams responsible for the site construction since no design tolerances were issued with the design. A designer should be able to report the anticipated range of resistances given the electrode design and the soil resistivity on site.
Conundrum solved:
* Ignore the problem.
* Throw someone else under the bus if and when it becomes necessary.
* In the long term, problem not solved.
* And that is why this is a conundrum.
Solution B to the conundrum
The designer will knowingly over-compensate to avoid risk of failure in any shape or form. The designer places his/her reputation above the potential loss of revenue and company branding dictates that clients know they must anticipate a higher budget when dealing with this designer.
Conundrum solved:
* Ignore the problem.
* Cost unjustifiably higher than including soil resistivity measurements into project.
* Earth electrode resistance will be within the desired limits.
* Next project - designer will be competing with 'those other designers'.
* The industry problem not solved.
* And that is why this is a conundrum.
High earth resistance needs surge protection
The maximum value of earth electrode resistance is not compulsory, and neither is it always possible to achieve the typical earth resistance values described in the standards. The standard does not stipulate a maximum value as a critical limit but rather as a preferred value in the context of the typical design solutions proposed.
Nothing is for free.
Where the recommended earth electrode resistance limits cannot be achieved, over-voltages are more prevalent and have to be contained. In the design stages and within the risk management task, over-voltages have been covered and carry their own cost and required measures.
Surge protection devices should already have been included in the design where necessary, as part of the surge protection measures (SPM). Useful information on that process is carefully laid out in SANS 62305-4.
Consequences
Avoiding the cost of addressing earthing diligently leads to high earth electrode resistance:
* This will lead to higher voltage rise than was allowed for in the designs.
* This will lead to LPS failure.
* This will lead to damage to electrical and electronic equipment within the structures (if there are any).
The failure to constrain the earth electrode resistance gives rise to excessive voltage rise or more aptly described as ‘ground potential rise’. Now the vested property stakeholder must contest with over-voltages.
An exploding toaster is electrical equipment demonstrating to the vested property stakeholder that the earthing of the LPS was probably not adequate. The destruction of production equipment in a factory from one lightning storm will be electrical and electronic equipment demonstrating to the vested property stakeholder that the earthing of the LPS was probably not adequate.
The exploding toaster will be more affordable than the loss of production on a factory floor. Therefore, sound risk management would dictate that earth electrode resistance should be treated with the importance it carries when the bottom line is at risk - unplanned financial losses.
Knee jerk solutions
Since the damage of omission was done during construction, remedial work years later, to correct the earthing in many instances is simply not viable or even physically possible without some form of demolition work.
The marketing and sales force of various surge protection commercial products thrive in these conditions since the stakeholders are in reaction mode after suffering tremendous losses and are vulnerable.
* In particular, large organisations and the insurance industry.
* The evidence showing that lightning was the cause of damage is now readily available.
* The delegated responsible persons who must answer to the shareholders has no recall to the designers or project team involved in the construction of the buildings (at least not yet).
* The root cause of the problem is no longer the priority.
* The solution to prevent a repeat failure has become the priority.
* The symptomatic cause of failure is now over-voltages.
* These over-voltages are higher and more frequent than anticipated and therefore existing surge protection devices included in the original design would be inadequate.
* Solution to over-voltages where we cannot bond conductors together is the installation of more surge protection devices.
Industry response
The matter pertaining to soil resistivity is underplayed by many so-called subject matter experts who find themselves in one of two camps of thought:
In camp 1:
* The privileged expert, protected by organisational structures:
* As an expert directly involved in the day-to-day operations, they have experienced very few instances of significant damage.
* They point to the seasonal variance of soil conditions to justify ignoring soil resistivity as an influencing parameter.
* These experts also find themselves in the fortunate circumstance where over designing is an inherent part of their business practices.
* The downside here is when the budgets do not support those practices.
* It becomes difficult for these experts to now advocate measurements that they denied had significant relevance in the past.
In camp 2:
* The reliant expert with a vested interest in one or other product or in one or other scientific or engineering procedure.
* These vested interests are fed by the positive exposure for more product, due to the outputs of the conundrum.
* Thus, they benefit from sales in products or,
* They receive (or think they do) increased academic and scientific exposure to enhance their hypothesis.
* They justify their vested career long dedication to whatever their flavour may be that benefits from this conundrum.
Lone voices are getting louder and questioning the foundation upon which we have built this seemingly unrelated circumstance that does not pinpoint the source of the problems. The same message is being raised in the halls of the SABS and in SAIEE forums.
Are we able to review lightning protection designs, the as-built solutions and then the effectiveness of those designs through a curtailment of lightning damage, organisational losses, fatalities and permanent injuries?
SELPA response
ELPA do not see any way in which interventions can be avoided that will leave a considerable number of players in the industry questioning the very foundation of their business ethical practices. As such the message from ELPA is both conciliatory and non-negotiable. Nothing is for free. Let's assign the cost to the experts, people and companies in accordance with the facts before us.
Having reliable soil resistivity values at the outset may lead to a higher short term capital investment but let the vested property stakeholders make that decision based on factual reported knowledge.
Where those decisions are documented, shareholders are afforded the opportunity to make wise decisions on the back of lessons learnt. Where the facts are hidden, mistakes will be repeated. ELPA will persist with bringing the facts to the table, preferably with a growing support from all industries in South Africa.
Enquiries: www.elpasa.org.za
Read part 1 here: https://www.crown.co.za/sparks-electrical-news/contractors-corner/24412-lightning-series-part-1-risk-management
Read part 2 here: https://www.crown.co.za/sparks-electrical-news/contractors-corner/24834-lightning-series-2-lightning-protection-design
