Short communicationWhite stork risk mitigation in high voltage electric distribution networks
Introduction
The number of white stork nests in Portugal increased dramatically in the last decade, according to preliminary results of the 2014 national census of the species. Recent estimations shown an increase in the number of white stork nests, which currently account 11,694 occupied nests, more 4000 since the previous census, carried out in 2004, corresponding to an increase of 254% between 1994 and 2014 (Fig. 1) (Institute for Nature Conservation and Forests, 2014). White stork is becoming a resident non-migratory bird due to an easy access to dump sites and abundant red crayfish (Procambarus clarkii) in rice fields (Gilbert et al., 2014). Since 2000, the white stork population increased dramatically in the Mondego river basin, located between the cities of Coimbra and Figueira da Foz in Portugal (Iberia, 2014, Leo et al., 2002, Rosa et al., 2005, Rosa and Quintela, 2011) and is the predominant species using the electrical distribution support structures as a nesting place, both in Portugal and in some parts of Spain (Infante and Peris, 2003).
The increasingly demand for nesting and roosting in medium and in high voltage electrical distribution equipment (15–60 kV networks) has also contributed to an increase in white stork fatalities due to electrocution and recurrent outages due to the activation of the automatic safety protection devices (Santos, 2004, Janss, 2000) (Fig. 2).
The white stork is among the species of birds more seriously affected in Portugal due to electrocution, and causes a significant financial burden to electric companies and industrial clients as consequence of using the support structures for nesting (Araújo et al., 2013, Bochenski et al., 2006, Tryjanowski et al., 2006, Göcek et al., 2010, Manville et al., 2005). Electrocutions occur in areas of perching activity on poles without sufficient spacing to accommodate their wingspan and height (Avian Power Line Interaction Committee, 2006, Bevanger, 1998).
Deterrent devices may reduce considerably the impact of birds, although elimination of damage is almost impossible (Booth, 1994, Godin, 1994, Gorenzel et al., 1994). The main purpose of deterrent devices is to repel birds from breeding, roosting or feeding in areas and on structures important for economic activities, e.g. the electrical network (Avian Power Line Interaction Committee, 2006). Over the past, several techniques and types of equipment have been used or proposed to deter birds from critical locations, such as airports, aquaculture ponds and electric power lines, among others. In the early nineties, in Portugal, a program was initiated to manage the white storks on transmission towers by preventing nesting in dangerous areas and encouraging the use of dedicated pole platforms located close to the support towers (Avian Power Line Interaction Committee, 2006, Carreira et al., 2011, Santos, 2004).
EDP-D operates approximately 83,000 km of high voltage (60 kV network) and medium voltage (10–30 kV networks) lines and cables supplying about 6.1 million customers and is the main energy DSO in Portugal, is seriously committed in management of environmental aspects and to increase the quality of energy distribution, minimizing outages and associated economic losses. To provide a careful control of the main parameters of power quality (voltage level, continuity of service), EDP-D in collaboration with ICNF developed a program to clean nests and residues from network support structures and installed anti-nesting and anti-roosting devices in areas frequented by storks (Carreira et al., 2011, Santos, 2004). In addition, dedicated nesting platforms were built to replace the loss of potential nesting places. Currently, the standard dissuasion devices to prevent nesting and roosting are: passive wind turbines, metallic umbrellas, slanting (45°) metallic plates and triple chevrons (Fig. 3), as described in (Carreira et al., 2011).
Despite the implemented efforts (standard dissuasion devices) to minimize power outages and bird fatalities, nesting was still possible as shown in Fig. 4a and c.
Additionally, bird related incidents with outages exceeding 3 min increased by 47% between 2009 and 2010, and increased again by 83% between 2012 and 2013 (Fig. 5, Fig. 6). Furthermore, bird related incidents represent 6% of the total in the aerial network, and have a large impact on the main Technical Service Quality (TSQ) indicators (Fig. 7) (Araújo et al., 2013, Avian Power Line Interaction Committee, 2006, Carreira et al., 2011, Entidade, 2014).
Power outages have a large negative impact on the electricity users in all sectors of the economy. Some types of equipments are particularly sensitive to power disturbances (reduction of the voltage level or supply interruption). In particular, even short duration disturbances can affect computers, servers, industrial automation systems and other electronic controls, resulting into significant economic losses (Avian Power Line Interaction Committee, 2006, Carreira et al., 2011). As an example, one recorded voltage dip with an amplitude of 40% and duration of 178 ms, caused a 120 min interruption in an industrial production line (Carreira et al., 2011).
Fig. 8 highlights the main causes of power quality issues, being voltage dips the main reported disturbance. Voltage dips over 20% amplitude can affect production lines since the equipments are very sensitive to voltage fluctuations (Fig. 9). From the drawbacks reported by the customers, 59% are originated from voltage dips of amplitude larger than 50% and most of these recorded incidents are directly related to white stork activities.
There is a growing environmental awareness which encourages the electric companies to implement innovative solutions that meet the global challenges of competitiveness, quality of life and environmental sustainability, with the white stork risk mitigation activities being a high visibility case study (Rosa and Quintela, 2011). The increasing number of stork fatalities and economical losses, both in the industrial and electricity transmission and distribution equipment, motivated this stork risk mitigation project, involving the collaboration between EDP-D, Institute of Systems and Robotics (ISR) and the Life Sciences Department (DCV) of the University of Coimbra to develop and implement sustainable harmless technologies. The aim is to prevent nesting and roosting, namely: emission of irritant sound for storks, vibrating structures and powered turbines (Araújo et al., 2013), in order to supply the DSO with data and the effectiveness of each technology in terms of roosting and nesting mitigation on electrical infrastructures.
Several species of birds, when in danger (for instance in the presence of predators), use distress calls to communicate between them, therefore, these calls can be useful to disperse birds of the same species or other related species (Araújo et al., 2013). Several commercial sound systems are available, but published data on effectiveness of these systems is scarce. Another commercially available technique is the broadcast of ultrasounds. However, this is not particularly effective since most bird species do not perceive ultrasounds (Araújo et al., 2013). Sound systems emitting distress calls (Fig. 10a) are effective on storks, however have a negative impact on residential areas, where people complain of the grinding noise. This also lead to vandalism acts directed to the systems and theft of equipment was frequent. In rural areas, sound systems also repel other species from their habitat and on hunting areas these sound systems have been disabled by the hunters with rifle shots (Araújo et al., 2013). Powered turbines (Fig. 10b) and vibrating platforms (Fig. 10c) are very effective for roosting prevention, but their power sources are expensive (Araújo et al., 2013). These systems require quite a powerful battery (12–24 V and 40 Ah) to operate and as mechanical systems, periodic maintenance is required, leading to additional costs.
In this work it is proposed the use of a micro electroshock system to control the activity of storks. The objective is to minimize the damage caused by the stork activity, while protecting them from electrocution on the power lines.
The developed system applies controlled low energy (1 or 2 J) electric discharges on the birds trying to land on the power lines support structures. This is similar to the systems frequently used to control small birds (pigeons and other) on monuments, cathedrals and other qualified buildings to prevent the damage from the droppings, nesting and perching (Booth, 1994). Basically, similar technology is the electric fencing used in the control of cattle in pastures (International Electrotechnical Commission, 2005, International Electrotechnical Commission International Standard, 2013). The discharge will cause an unpleasant experience without endangering the bird's life. The working principle of this method is to present to the bird a negative experience associated with the landing on those type of structures, which will discouraged future landing episodes (Nahvi and Edminister, 2003). Commercially available electroshock units have been used to supply energy to the devices implemented and developed in this work.
Section snippets
Preliminary experiments with poultry
In the absence of data in literature regarding the reaction of storks to low energy electric discharge systems, tests were carried out in birds with a similar gait, in order to estimate the energy required to induce a feeling of discomfort, but harmless to the bird. These tests were carried out on a platform with comb type electrodes connected to an energizer shock equipment that could provide discharges of 1 or 2 J (Fig. 11).
The methodology has been proposed by the DCV, who accompanied all
Micro electroshock system
The program involves the implementation of a developed or modified non-harmful repelling technologies, which comprise:
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An electrifier equipment and power supply (Fig. 12);
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A set of electrified structures developed according to the architecture of each pole and the support plates (Fig. 13).
The energizer is a certified market model that supports our needs and all the protection standards and the low power consumption (3.2 W) is designed to be supplied by a low capacity 12 V battery. The amount of
Preliminary results with poultry
Turkeys (with a weight of 4–6 Kg), hens and cocks (2–4 Kg) have been selected. A path was designed with the electrode grid placed at the end. The birds were driven through the pathway up to the grid, then an immediate reaction was observed, the bird tries to fly to escape the energized platform. In a second trial, it was difficult to drive the birds through the pathway, since they turn back as soon as they could, particularly hens and cocks. The conclusion was that the birds remembered the
Conclusions
The white stork population has been growing very fast in Southern Europe. Since these birds often choose to nest in high voltage power line poles and towers, two worrying problems are becoming more and more relevant: the large number of bird fatalities from electrocution and the decreased reliability of the power system supplying millions of customers who expect uninterrupted supply. The implemented micro electroshock discharge technologies successfully addressed both of these concerns and
Acknowledgments
The project was financially supported under the scope of (Plan for the Promotion of Environmental Sustainability (PPDA)) supported by the energy regulator ERSE through the project Stork – Protection Strategy for Birds, and by EDP-D. We are also indebted to ICNF, the government institution responsible for nature conservation and biodiversity policies as well as the management of protected areas, for their valuable contribution. We are specially grateful to Manuel Pimenta who provided the
Glossary
- DCV
- Life Sciences Department
- DSO
- Distribution System Operator
- EDP-D
- Energias de Portugal – Distribuição
- EITIP
- Equivalent Interruption Time of the Installed Power
- ERSE
- Energy Service Regulatory Authority
- ICNF
- Institute for Nature Conservation and Forests
- ISR
- Institute of Systems and Robotics
- NDE
- Not Distributed Energy
- PPDA
- Plan for the Promotion of Environmental Sustainability
- SAIDI
- System Average Interruption Duration Index
- SAIFI
- System Average Interruption Frequency Index
- TSQ
- Technical Service Quality
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