Engineering Failure Analysis 35 (2013) 360–369

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Engineering Failure Analysis

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Taxonomic analysis of Chinese power transmissionand distribution industry accidents based on hazardcomponents

1350-6307/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.engfailanal.2013.02.032

⇑ Corresponding author. Tel.: +86 13521512288.E-mail address: fanyxiao@cugb.edu.cn (Y. Fan).

Yunxiao Fan ⇑, Jingjing Pei, Yun LuoSchool of Engineering & Technology, China University of Geosciences (Beijing), Beijing 100083, China

a r t i c l e i n f o a b s t r a c t

Article history:Available online 15 March 2013

Keywords:Power transmission and distributionindustryAccident/mishapHazard componentsHazard typeTaxonomic analysis

Power transmission and distribution were critical components for the development of Chi-nese economy. As in all sectors of the economy it was important to reduce the accidentsrate as low as possible. This research adapted accident taxonomic analysis to identifythe main factors associated with accidents and then provided accident prevention counter-measures in the industry in China. Because of lack of systematic power transmission anddistribution accident information in China, 324 power grid accidents from 1961 to 2008were collected through a wide range of sources and classified according to hazard elementswhich were target and threat, hazard element and initiating mechanism respectively andthen the initiating mechanisms were further classified by hazard types. Through taxonstructures the direct and indirect factors were identified in the industry accidents andstrategies of accident prevention were recommended based on them. The taxon structuresalso can be further developed to form tailored safety checklist for the front workers.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Electricity in China is transmitted through a series of electrical transmission and distribution (T&D) lines. The electricalT&D industry is one of the main contributors to the growth of national and regional economies. There is plan to increasepower T&D from the west to the east to 66,700 MW, 52,800 MW and 29,700 MW for the north, middle and south pas-sage-ways respectively in 2020. Studies have shown that it is necessary to build long distance, great capacity and low lossUHV power transmission system [5,32]. Rapid development of power plant projects increases the likelihood of minor humanerrors and productivity loss. Workers involved in the construction and maintenance of these electrical T&D lines are exposedto high risk of electrocution [1]. The nominal voltage in bulk transmission lines can reach 750 kV, which can cause instantdeath on contact [27]. According to the Electrical Safety Foundation International [7], contact with overhead power lines ac-counted for an average of 43% of all electrocutions between 1992 and 2009. Other major causes of occupational electrocu-tions included contact with wiring, transformers, or other electrical components (27%) and contact with the electricalcurrent of machines, tools, appliances, or light fixtures (17%) [1]. Also, workers face other types of hazard such as falling fromheight and hit by falling objects during operation or maintenance of the electrical T&D. Additionally, non-compliance tooperating procedures or unsafe acts may also cause power outage, disruption to the whole system or damage to the equip-ment [8,10]. Therefore, in tandem with the rapid development, accident prevention should be part of the key strategy in thegrowth of Chinese Power Transmission and Distribution (PTAD) industry [16,33].

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Accident is hazard that has resulted in harm, injury or ill-health [30]. American Standard of MIL-STD-882D distinguishedthe definitions between hazard and mishap/accident [4]. Ericson depicted the relationship between accident/mishap andhazard in Fig. 1. A hazard is a potential event while a mishap is an occurred event. The presence of hazard is the root causeof accident that can lead to human, economic, societal, and environmental losses [6]. Identifying errors that frequently resultin the occurrence of incidents and accidents may allowed appropriate prevention and/or mitigation strategies to be devel-oped [15]. The strategy of accident prevention based on hazard identification and risk control needs to be proactive. Themain aim of this research is to provide accident prevention measures with better understanding of hazards and how theycan cause accidents.

Hazards are specific to a work system under consideration and professional experience is required to accurately identifythem [23]. Identification of hazards is the first step in assessing the risk of injury [18], but debate on the definition of hazard[34,35] has prevented its effective application in China. Generally, it was difficult for the front line workers to identify thehazards in their work and they merely obeyed the instructions of their supervisors. Furthermore, they seldom identify haz-ard on their own actively. It was only after the occurrence of an accident that the workers would pay attention to workplacehazards, but such emphasis would disappear with time or change of supervisors [9,11]. In order to improve the safety atti-tude of the front line workers, it is important for them to recognize the importance of safety and to increase their awarenessof how accidents can occur. This research was a response to a request from Shanxi Electric Power Company to improve itssafety performance. Through this research, they hope (i) to identify common accidents that may occur in the industry; (ii) togain some insights into the factors causing these accidents; and (iii) to develop a hazard checklist for the front line workers.Accidents/mishaps are results of actualized hazards. The state of transition from a hazard to a mishap was based on a uniqueset of hazard components involved and the mishap risk presented by the hazard components [18]. Therefore, the taxonomicanalysis of the Chinese PTAD industry based on hazard components would form the basis of this research in accidentprevention.

2. Methods

2.1. Accident data collection

Little information on accidents has been systematically collected in the PTAD industry, which presents a major challengein any analysis of the records. Thus, the research team obtained information on accidents in this sector from a range ofsources. Besides sources from accident notification in the web of State Electricity Regulatory Commission (SERC) and itsbranches, the sources also included journals, magazines and other publicly and privately available sources, ranging the yearsbetween 1961 and 2008. From the data, 324 accidents scenarios were created through discussion with related work teams.

2.2. Analytical method

The original information was usually documented in simple accident narrative. The data collection should be carried outusing a harmonized data-collection format in order to analyze the data in a structured way [3]. The 324 accident recordswere first collected with the aim to improve the front line workers’ attitude. To encourage the front line workers’ involve-ment and to enhance their understanding of how these accidents could have occurred, accident scenarios were discussed bythe related work teams. Through such discussion, the probable direct and indirect factors associated with each accident wereidentified. According to popular view in Chinese companies, direct causes refer to unsafe act or unsafe work condition, andindirect causes refer to fault in management [2,19,29,31]. Usually these discussions were organized by their team leaderswho were responsible for their production and safety. After these discussions, final reports about the accidents were created,which included information on the area of work, accident type, accident narrative, the main factors and exposure faults andrelated countermeasures as shown in Table 1.

2.3. Taxonomic analysis

Taxonomy is one of the oldest and most time honored scientific methods, but it has been neglected by many professionsand has been forgotten by others. It is based on recognizing common patterns and the differences between incidents. It is

Fig. 1. Hazard–mishap relationship (adapted from Ericson [6]).

Table 1Accident scenarios report form.

Area of work No. Accident type Accident code

KeywordsBrief introductionAccident narrativeMain factors and exposure faultsCountermeasures from the accident

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useful to explore the nature and rules about issues using logical classification [17]. Examples of taxonomic analysis includedUS cranes fatalities and drive error [26,28]. Fan has studied PTAD industry accident taxonomy based on token parameter [8],accident causation model [10] and proposed related countermeasures of accident prevention in the industry. A taxonomyanalysis was dependent on the underlying theoretical model, the experience and perception of the taxonomist, and onthe available quantitative and qualitative data. Applying taxonomic analysis on occurred accidents has been an effectivemethod for accident prevention.

Hazard and mishap are two separate states of the same phenomenon linked by the occurrence of a state transition. Thestate transition from a hazard to a mishap is based on two factors: (1) the unique set of hazard components involved and (2)the mishap risk presented by the hazard components [18]. Ericson suggested that hazard was composed by Hazardous Ele-ment (HE), Target and Threat (T/T) and Initiating Mechanism (IM) and depicted a hazard using the analogy of a molecule asshown in Fig. 2, which is comprised of one or more atoms representing the three types of components that make up the mol-ecule [6]. The model indicated that when components within the hazard were in a specific alignment, the hazard transitionfrom a conditional state to a mishap state would fulfill (see Fig. 3). This viewpoint showed that the entire randomly orientedhazard components must line up (or occur) in the correct sequence before the mishap actually occurred.

Taxonomy is based on recognizing common patterns and the individual differences between incidents. Taxonomists di-vide into ‘‘lumpers’’ and ‘‘splitters’’. This research tries to identify contributory factors for the PTAD accident scenariosaccording to the hazard components of T/T, HE and IM.

2.3.1. Based on Target and Threat (T/T)Target and Threat (T/T) referred to the person or thing that was vulnerable to injury and/or damage, and it described the

severity of the mishap event [6]. Based on the definition of T/T, consequences for PTAD accidents could be classified intodeath/injury accident and damage to grid/equipment accident. Death/injury accident referred to employee in PTAD industryaffected by hazard/hazards during work time and at last some person(s) was caused illness, injury or death, so the target andthreat of hazard in this category was a person. Damage to grid/equipment accident referred to damage of the power grid andrelated equipment caused by human error, and that no person was hurt nor died. The target and threat of hazard in the dam-age to grid/equipment accident was power system, equipment or downtime.

2.3.2. Based on Hazardous Element (HE)Hazardous Element (HE) was the basic hazardous resource creating the impetus for the hazard. And it referred to a haz-

ardous energy source such as explosives being used in the system [6]. Until now there hasn’t been a detailed classification ofhazardous energy sources in China. Hazard identification in a project or a system is usually based on the Chinese NationalStandard GB6441-1986 [24]. It classified Chinese casualty accident into 20 types, which included struck by objects, vehicle

Fig. 2. Hazard–mishap actuation (adapted from Ericson [6]).

Fig. 3. Revised hazard–mishap actuation.

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injury, machine injury, crane injury, electric shock, drown, burn, fire, fall from height, collapse, cave-in, mine flood, fire a gun,powder explosive, fire damp explosive, boiler explosive, vessel explosive, other explosive, poisoning and asphyxia and otherinjuries. In this research, HEs was classified by working through the injury types for death/injury accidents. For damage togrid/equipment accident, HEs was classified according to the area of work.

2.3.3. Based on Initiating Mechanism (IM)Initiating Mechanism (IM) referred to the trigger or initiator event(s) causing the hazard to occur. The IM caused actual-

ization or transformation of the hazard from a dormant state to an active mishap state [6]. There was no standard associatedwith the types of IMs, which showed differences based on the affiliated industries. In this research the IMs would be iden-tified and classified according to the accident narratives.

2.3.4. Hazard type analysis based on IMBased on general accident model known as the energy model [13,14] and Reason’s Swiss cheese model of organizational

accidents [20,21], they showed how the performance of defenses was influenced by upstream human and organizational fac-tors, as illustrated in Fig. 4. The upper part represented the main elements of accident causation: hazards, defenses (safetybarriers), and losses. The lower part showed the development of an organizational accident: organizational factors influ-enced local workplace conditions, which combined with natural human tendencies to produce unsafe acts [25]. Accordingto Reason [21], unsafe acts may initiate holes in the defenses, only workplace conditions (time pressure, in sufficient training,ambiguous procedures, etc.) and organizational factors (strategic decisions and generic organizational processes, shaped bythe organizational culture) may also initiate failed defenses, as indicated by the latent condition pathways.

Mishaps were the immediate result of actualized hazards. In fact, sometimes T/T always existed and HEs could not beprevented for production, so it was only the IMs which drove the transition from hazard to mishap. In PTAD industry, theT/Ts were persons, power grid and related equipment and HEs such as electrical energy, and gravity energy were un-prevent-able. Therefore, only one or more MIs would initiate the ‘‘holes’’ in the defenses, and make HE(s) trajectory passing throughthe holes in successive defenses or ‘‘slices’’, hit on T/Ts, and cause accident/loss. The revised accident model was shown inFig. 5.

Fig. 4. Model of organizational accidents, adapted from Reason [21].

Fig. 5. Revised model of organizational accident based on hazard components.

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While visualizing the influence of human and organizational factors on the performance of safety barriers (in this case,safety instrumented systems, accident investigation model can propose a number of general failure types, which give anindication of the current state of ‘‘safety health’’ [12,22]. This research went further to analysis the general failure types,which showed the latent condition path ways based on IMs of PTAD accidents (see Fig. 5). The result was also shown inthe column of ‘‘Failure types’’ (see Figs. 9 and 10).

3. Results

The 324 PTAD accidents from 1961 to 2008 were separated into two parts according to T/Ts as depicted in Fig. 6. Therewere 173 death/injury accidents and 151 damages to grid/equipment ones which stood almost the similar number in theindustry.

3.1. Death/injury accidents

Although [24] divided accidents into 20 types which were regarded as death/injury accidents’ hazardous elements, onlynine types were observed in sufficient numbers to be reliably analyzed in the Chinese PTAD industry. They were electricshock, fall from height, vehicle injury, struck by object, explosive injury, crane injury, mechanical injury, burn and others.Fig. 7 depicted a breakdown of death/injury accidents by HEs according to accident numbers. Among them, there were

Fig. 6. Accident classification according to T/Ts.

Fig. 7. Death/injury accident numbers of different HEs.

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109 electric shock accidents with 63% of the all the cases, fall from height, vehicle injury, struck by object with 23%, 5%, 4% ofall respectively. Further breakdown of death/injury accidents by IMs was depicted in Fig. 9.

3.2. Grid/equipment accidents

In this research, the 324PTAD accidents included seven areas of work which were power transmission (PT), relay protec-tion (RP), substation equipment reparation (SER), dispatch automation (DA), transforming operation (TO), distribution net-work (DN) and rural power grid (RPG). This research used their abbreviation in parentheses. A damage to grid/equipmentaccident in PTAD industry referred to those threats against equipment or power system rather than person. It was difficultto use GB6441-1986 to break them down by HEs. Because different areas of word were affected by the different hazardouselements; therefore, the grid/equipment accidents would be broken down further by IMs. Fig. 8 depicted the numbers ofdamage to grid/equipment accidents in different areas of work and Fig. 10 depicted the taxonomy analysis of grid/equipmentaccidents into three hazard components and hazard types.

4. Discussion and recommendations

A hazard is the precursor to a mishap and each hazard consists of three components. Based on the taxonomy theory, thisresearch classified PTAD accidents and identified the associated factors based on three components and hazard types.

1. According to T/Ts, there were two types of accident which were death/injury and damage to grid/equipment accidents inPTAD industry. They both were of similar accident numbers. In past, not only government but also the companies paidattention to preventing death or injury in their work, but now more and more accident occurred without causingdeath/injury, but they would destroy the grid or equipment. These accidents should be recorded and analyzed by com-panies which could also provide basic information for accident prevention.

2. For death/injury accidents, the main HEs were electrical shock, fall from height, vehicle injury and struck by objects andso on. For each HE, the failure type was also analyzed in Fig. 11. Electrical energy was an inevitable main hazardous ele-ment in PTAD industry, this type of accidents was caused by 13 IMs which is much more than other energies. The IMs ofthis electrical energy included mal-touch live equipment, mal-climb live equipment, act against regulation, un-efficientsafety distance, etc. Among them, 84.4% of electrical energy cases were associated with unsafe acts.

Fig. 8. Damage to grid/equipment accident numbers in different areas of work.

Fig. 9. Breakdown of death/injury accidents in PTAD industry.

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3. Fall from height was also of high proportion among all death/injury accidents. The main IMs of this type of accidents wereloss of safe guard, fall down of pole or towers, poor equipment quality and so on. As show in Fig. 10, the main factor of thiskind of accidents were caused by poor workplace condition. Many accidents narrative described worker using safety beltsas their only source of protection when working at heights. Proper equipment should be provided for workers. For dam-age to grid/equipment accidents in each area of work, there were some accidents caused by faults of equipment. Althoughpeople in Chinese companies have improved their safety recognition, this study showed that managers still should paymore attention on safety. For instance, when equipment is purchased in future, safety issue should be an important con-sideration and not be neglected due to cost savings or other reasons.

4. Hazard types of damage to grid/equipments accidents were analyzed as Fig. 12. Unsafe acts, workplace factors and orga-nizational factors were associated with 80.8%, 16.6%and 2.6% of all cases. It showed unsafe acts were still the main factorsof damage to grid/equipments accidents. In Chinese PTAD industry, safety officers always complained there had been

Fig. 10. Breakdown of damage to grid/equipment accidents in PTAD industry.

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enough detailed safety procedures and safety requirements for the front line workers, but all these detailed proceduresand requirement still could not prevent common human errors. High proportion of unsafe acts from management levelcould not thoroughly accepted by the front line workers. Too often, safety at work was addressed in an ad hoc manner

Fig. 11. Column diagram of failure types in PTAD death/injury accidents.

Fig. 12. Column diagram of failure types in PTAD damage to grid/equipment accidents.

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rather than taking the everyday steps to prevent incident in the first place. Because of the diversity of PTAD job, tailoredprocedures for each job, even for each task should be developed. At the same time, common unsafe acts also showed thefront line workers had poor universal standards, so specific training should be stressed to improve their skills and knowl-edge. The regulations were essential, but the most important thing was to ensure that each employee has been aware ofthe regulation and operation procedures associated with his own job. Detailed job hazard analysis should be taken inPTAD industry to ensure that front line workers could recognize the hazards around them, and could recognize what theyshould do to prevent incidents or harm.

5. Based on the result, we can draw a conclusion that it is difficult to delete T/T and HE in PTAD industry accidents, The keyto accident prevention was focus on IMs and the main latent condition that cause ‘‘holes’’ of the ‘‘slices’’. Thus, for thefront line workers and their supervisors, it was important to get them to make safety a priority and proactively integratesafety into their everyday routines.

5. Conclusion

In power transmission and distribution industry accident prevention is of great importance for the national economy. Ahazard is comprised of three basic components which are target and threat, hazardous element and Initiating Mechanism,and it is also precursor of a mishap. To prevent accident in future, 324PTAD accidents had been collected and analyzedaccording to the three components of a hazard and failure types. According to T/T, the accidents were divided into two cat-egories which were death/injury and damage to grid/equipment types. For HEs, death/injury type was further dividedaccording to hazardous energies listed in GB6441-1986. The damage to grid/equipment accident was divided according tothe areas of work. Taxon structures have been built as shown in Figs. 9 and 10, which depicted the direct and indirect factorsof power grid accidents. Based on Reason’s accident causation model, IMs were further analyzed according to failure types.The structures depicted the contributor factors of PTAD accidents and could be developed as hazard checklist for the frontline workers. Related recommendations based on them were provided for accident-prevention in future.

Acknowledgments

Thanks are due to the members of the project Hazard Identification and Risk Control in Power Transmission and Distri-bution industry which was funded by Taiyuan Branch of Shanxi Electric Power Company. Thanks are due to Mrs. Yu Hongmei

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and Mrs. Wang Xiaohong who collected the 324 accidents and provided lots of advices. At last thanks are due to Mr. GeChangcheng. His care and comments have helped to clarify the work that is presented here.

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