Nederlandse Aardolie Maatschappij (NAM)
Work safely…
“Thanks to Eaton’s arc flash hazard analysis we are now able to calculate the effects of an arc fl ash, that provides us to make well-considered decisions.”
Gerrit Guichelaar
Electrical Engineer, NAM
Background
For many people “arc flash hazard analysis” sounds like a rather Amercian concept. In Europe there is usually scant attention paid to explicit arc flash harzards, for the most part, people have faith in the intrinsic safety of electrical installations. The Dutch gas producer Nederlandse Aardolie Maatschappij recently had an arc flash hazard analysis performed by Eaton.
NAM is the largest gas producer in the Netherlands, producing some 67 billion m³ of gas each year. Over three quarters of this gas comes from the Groningen gas field, and the remainder comes from a variety of smaller fields on land and from the North Sea. NAM is responsible for around 75% of the total gas production in the Netherlands. The company also continues to extract oil, and in 2011 the oilfield at Schoonebeek was brought back into use.
At NAM, safety is of paramount importance, just as it is throughout the gas and oil industry. This is evident from, for example, the fact that staff are not allowed to work on live electrical installations under any circumstances. “Safety is more important than availability”, says Rien Luchtenberg, Electrical Team Leader, Shell. The question of why NAM had an arc flash hazard analysis carried out is an easy one to answer for Luchtenberg: “Because the calculation methods became available”. Luchtenberg explains further: “At a company where the safety of staff, contractors and the environment is so important, the use of new technological developments and insights for the purposes of safety and working methods is self-evident”. The risks that accompany maintenance of electrical installations can be limited by using modern equipment and proper work instructions. However, this does not always rule out the chances of a personal accident completely. Work such as disconnecting the installation, removing fuses on the power supply side of a switch or failure finding is always potentially risky - even in the case of switchgear that has been tested on the basis of the latest IEC standards. It is not without reason that this type of hazard is cited explicitly in the new NEN 3140 standard.
Challenges
Arc flash is the result of an electric current that is passed through air when insulation or solation between electrified conductors is no longer sufficient to withstand the applied voltage. The majority of arc flashes arise during or immediately following work on an electrical installation. An arc flash is usually the result of human error, such as (for example) dropping tools onto live parts of the installation. The current involved in an arc flash results in a huge amount of heat energy being released, as a result of which copper and steel in the installation melt and evaporate. This causes the volume of these materials to increase exponentially. The result is a fiery explosion that has the capacity to produce extremely serious and fatal injuries. Professional analysis is required in order to properly protect staff from this risk.
Before work can be carried out on an electrical installation at NAM, be this by contractors or its own staff, a work permit must first be applied for, irrespective of whether the work is changing a bulb in the operating area or carrying out maintenance on a circuit breaker. The permit will only be issued once a Work Risk Assesment, which entails assessment of both the chances and effect of potential hazards, has been performed. An estimate of the risk of an arc flash occurring is made on the basis of static data and experience.
Predicting the effects of an arc flash always used to be a tricky task - after all, the arc current in an arc flash behaves very differently to the short-circuit current upon which the system has been calculated. An arc flash hazard analysis involves calculating the energy released in an arc flash, and the method for performing arc flash calculations has been set out and published in IEEE Standard 1584-2002. This standard takes a great deal of design factors into consideration and is based on many years of research and empirical testing of the arc flash phenomenon.
The major benefit of an arc flash hazard analysis is that decisions in an exceedingly important area – the personal safety of maintenance staff- are now being made on the basis of facts rather than estimates. The results of an arc flash hazard analysis are used to detect potentially hazardous situations and subsequently to minimize the danger. The arc flash hazard analysis also provides the appropriate criteria for selecting the most suitable personal protective equipment (PPE) for the working environment being analyzed.
Solution
Following a brief inspection by the experts from Shell, it was clear to NAM that an arc flash hazard analysis produces genuine insight, as a result of which risks related to the electrical installation can be reduced. The search then commenced for a partner who would be able to swiftly assess the 140 sites. Eaton was selected on the grounds of its demonstrable expertise, and because their way of working extends far beyond making calculations and drawing up a report.
An important point for NAM was that Eaton also advises on the way in which arc flash safety can be included in the safety plan. This is rendered possible by pointedly taking into consideration in the analysis not only IEEE 1584-2002 but also the relevant European standards (EN 50110; IEC 61482; IEC 61641 (low voltage) / IEC 62271-200 (medium voltage); IEC 60909)
The starting point for NAM was a substantial report containing a thorough analysis and recommendations. The objectives were to prevent hazardous situations and to categorize unavoidable hazards.
Eaton charted the arc flash energy levels and recommended improvements. Sometimes it emerged that only a minor modification would be required to solve the issue - for example, in some cases energy levels can be reduced without making any investment by adjusting protective device settings. Naturally this should not be to the prejudice of selectivity. Growing awareness of arc flash risks can prompt modifications - in theory it can even impact on the replacement schedule. But usually it is precisely the minor adjustments that give rise to a safe situation. The ultimate assessment as to whether a risk is acceptable, and whether a solution should be sought to combat the risk itself and/or its effect, remains a decision for NAM’s electrical experts. Reliable information is essential to make this decision. The crucial question for NAM’s experts is always: will you be able to justify your decision after the fact if something does go wrong? The inspection also brought to light some arc flash risks that cannot be reduced to an acceptable level of energy by means of modifying the electrical installation. Here, the best possible response to these risks was to opt for the use of personal protective equipment (PPE). Well-chosen PPE protects people from burns and eye injuries.
It is not always practical because, due to the lack of ventilation options, wearing PPE can be excessively warm. This is not particularly enjoyable, but for brief tasks such as securing a system its use is imperative. For more protracted work and for arc flash hazards in the most serious category, PPE is not a real option. In such cases, the entire electrical installation and overhead power supply have to be switched off.
Result
Although the risk analysis is not yet fully complete, Rien Luchtenberg and Gerrit Guichelaar are unanimous in their response to the question: “What does the arc flash hazard analysis provide for NAM in concrete terms?”
First and foremost, it appears that awareness of arc flash hazards has increased. When it comes to protecting the person next to the one carrying out the work on the electrical installation, for instance - measures based on facts are easier to explain than measures based on intuition. Arc flash calculations also occasionally show that intuition is misleading.
As is the case with many maintenance and safety topics, the financial returns of an arc flash hazard analysis are part of a tricky calculation. “The fact that we are doing it shows that we deem it important”, says Luchtenberg. “At NAM we always try to work as safely as possible, but since there’s a method available to assess risks even better, we want to use it. The chances of an arc flash are slim, but the consequences could be dire. Thanks to the hazard analysis we are now able to calculate the effects with precision. In itself, performing a hazard analysis does not offer any guarantee that fewer accidents will occur, but it does provide the right pointers for making well-considered decisions”.
Up to now, the arc flash hazard analysis has not brought to light any situations in which safe working in relation to the danger of arc flash leads to real problems. In a number of cases it has even been possible to reduce the potential danger of arc flash in a straightforward manner without investing in equipment or further studies, and it is anticipated that there will be increased usage of more carefully selected PPE.
The arc flash hazard analysis performed also has consequences for NAM’s new projects. Arc flash calculations are now being made in advance, alongside load calculations and system studies, for extensions and new construction work. This assures NAM of the fact that new installations will provide sufficient scope to limit the arc flash energy released as a result of any errors to an acceptable level.
