Power plants are infamous for some of the worst industrial accidents in history. Perhaps nuclear power plants come first to our mind in this context. While nuclear power accidents such as the Chernobyl disaster in Russia (1986) or the Fukushima disaster in Japan (2011) top the list, other power generation facilities such as coal, gas and hydro have also witnessed industrial disasters in the past. Recently, in China, a flash explosion at a thermal power plant (TPP) in Chuzhou killed six workers.
In India, in November 2017, around 30 people were killed and several others injured due to an explosion at the 500 MW unit of NTPC Limited’s Unchahar TPP (in Uttar Pradesh) in one of the worst industrial accidents in years. The trigger for the accident was the build-up of coal ash and leakage in boiler tubes, which led to the abnormal functioning of the boiler and furnace, resulting in escape of super-hot gases and ash from the economiser. In July 2020, the Neyveli TPP in Tamil Nadu suffered a boiler blast, resulting in the death of 14 workers who were engaged in a routine maintenance operation. The plant’s thermal power station II was under shutdown and maintenance activities were being carried out, but a fire broke out in the boiler area following an explosion, resulting in injuries to NLC India Limited’s maintenance team. In August 2020, a major fire accident at the Srisailam Left Bank hydroelectric power station resulted in the loss of lives in Telangana. More recently, in April 2021, 13 people were injured at the Lanco Anpara TPP in Uttar Pradesh due to the collapse of a scaffolding during maintenance activities. These incidents have brought the spotlight back on industrial and power plant safety.
Moreover, occupational health and safety has assumed greater significance in light of the Covid-19 pandemic, as ensuring uninterrupted power supply is a daunting task. In addition, power infrastructure is especially vulnerable to natural disasters such as floods, cyclones and earthquakes, and the occurrence of extreme weather events is expected to increase as climate change exacerbates. Therefore, it is essential for utilities to have a firm disaster management plan in place.
Policy and regulations
The Central Electricity Authority (CEA) has issued Measures Relating to Safety and Electricity Supply Regulations, 2010. The regulations have been amended thrice, with the latest amendment, issued in 2019, detailing the Safety Provisions for Electric Vehicle Charging Stations. The CEA has also issued the Safety Requirement for Construction, Operation and Maintenance of Electrical Plants and Electric Lines Regulations, 2011 to avert or minimise damages that may be caused by any disaster at power plants.
As per the 2011 regulations, an on-site emergency management plan should be formulated for thermal and hydro power plants as well as substations and transmission lines to quickly and effectively deal with probable emergencies such as fire, explosion, gas leakages, landslides, floods, earthquakes, storms, cyclones, hurricanes, and crisis situations arising in the event of strikes, terrorist threats, attacks and sabotages, bomb threats, and explosions. The plant owner should ensure that a mock drill of the on-site emergency management plan is conducted at least once every six months. The plant owner is also required to furnish information pertaining to industrial activities under his control, including the nature, extent and likely effects of possible major off-site accidents, to the district collector. The details of the key employees of the emergency team and their responsibilities, information regarding the types of hazardous chemicals and fuels at plant site, and the internal and external communication plan in case of an emergency also needs to be furnished to the collector.
In January 2019, the CEA issued an advisory on the safety aspects of thermal power stations following the boiler accident at the Unchahar TPP (Unit 6). As per the advisory, all systems and facilities, including control and instrumentation, control loops, wall soot blowers and long retraceable soot blowers, should be completed before the commissioning of a unit/plant; the ash handling capacity of the bottom ash handling system, the economiser ash handling system, the air preheater ash handling system, and the electrostatic precipitator for the fly ash handling system should be designed keeping in view the likely maximum ash content of coal; water injection for dislodging ash build-up over the furnace bottom should be avoided; standard operating procedures/local management instructions of the plant should be periodically reviewed; the plant’s operating guidelines should be in line with the original equipment manufacturers’ recommendations; the permit system for undertaking operations and maintenance (O&M) activities should be endorsed by the safety department, in addition to the O&M department; and no maintenance work should be undertaken when the boiler is in operation. Besides, proper communication regarding maintenance work should be carried out to avoid risky operations; persons working in the ash handling area should be provided with thermal wear that can withstand high temperatures; plant engineers deployed at different levels should have adequate and relevant experience; and control room logbooks should be filled in a proper manner, indicating the prevailing status of key unit parameters, operating parameters of major equipment/systems and shift activities in a chronological order.
In January 2021, the CEA released the disaster management plan (DMP) for the power sector, which aims at evolving a more proactive, holistic and integrated approach to strengthening disaster mitigation and preparedness, and emergency response and recovery in the event of a disaster. It provides a framework and direction to utilities in the power sector for all phases of the disaster management cycle – mitigation, preparedness, response and recovery. It is intended to guide all agencies within the sector with a general concept of potential emergencies and roles and assignments before, during and following emergency situations. The DMP is in accordance with the provisions of the Disaster Management Act, 2005, the guidelines of the National Disaster Management Authority, issued occasionally, as well as with the National Disaster Management Plan, 2019. It is also consistent with the three landmark global agreements reached in 2015 – the Sendai Framework for Disaster Risk Reduction, the Sustainable Development Goals of the United Nations, and the Paris Climate Change Agreement (COP21), which together represent a nearly complete agenda for building disaster resilience.
Mitigation measures
Fire safety: Since fires at power plants can lead to fatal consequences, a proper well-equipped firefighting system is a key requirement in any thermal power station. The most common fires are usually caused by human activities such as human errors, faulty designs or mechanical failures. Fires are also caused as a secondary effect of disasters such as earthquakes. However, several fire incidents can be prevented and damage minimised by improving the reliability of firefighting equipment. An effective, documented inspection, testing and maintenance programme can help make sure that the system does not fail when needed in an emergency. Firefighting systems include a combination of mechanical and electrical components, and they must be adopted right at the design stage. The fire safety aspects of nuclear power plants are regulated by the Atomic Energy Regulatory Board (AERB). AERB has notified a standard titled Fire Protection Systems for Nuclear Facilities, Standard No. AERB/NF/SS/FPS (Rev. 1). It aims to minimise the probability and consequences of postulated fires. Nuclear facilities use the concept of defence-in-depth to achieve the required high degree of safety.
Cyclones, floods, and other natural hazards: As per the CEA’s DMP, power plant structures should be designed taking into account the wind loads and their effect on the structures as per the IS 875 Part-III Code to minimise the damage from cyclones. Also, there have been a number of incidents of flooding of hydropower stations during operation and construction. It has been seen that inadequate capacity of drainage and dewatering pumps and improper sealing of draft tube gates were major obstacles in preventing such incidents. The damage and rehabilitation period can be minimised with adequate measures at the design and construction stages. For prevention of damage due to earthquakes, utilities must adopt IS 1893 (Part 4): 2005 for industrial structures (plant and auxiliary structures) including stack-like structures.
Pandemics/Epidemics: The DMP suggests that power infrastructure should be classified based on the length of time for which it may operate without human intervention. Automation of power system operation should be carried out so that manual intervention is minimised. Modern technology such as drones may be used for various operational purposes such as surveillance, transportation of smaller parts and inspection of generation, transmission and distribution infrastructure. Further, local manufacturing and local supply chains must be encouraged. In addition, the pandemic response plans of power utilities should be prepared in consultation with other critical infrastructure providers such as fuel suppliers, transportation and emergency services.
Climate change: Currently, power infrastructure such as substations and electrical lines are designed to operate under various climatic conditions throughout the year. However, climate change could pose additional challenges yet to be accounted for in current planning and design. Therefore, lines, substations and structural aspects of the design should now incorporate additional safety factors than those prescribed in existing standards and codes. Further, technology needs to be deployed on a wider scale. For instance, gas-insulated lines can be explored to mitigate the effect of high wind speeds due to climate change, and anti-icing systems can be used in transmission lines in hilly areas.
Conclusion
It is imperative for power plant operators to have procedures in place that provide guidelines for employees to perform various tasks safely. Proper upkeep of safety and firefighting systems, safety audits, mock drills, and employee training and awareness are key to preventing accidents and ensuring safety at the power plant premises. Lastly, with the world facing multiple waves of the pandemic and the emerging threat of climate change, power generation utilities need to evolve their disaster mitigation strategies and plan continuously.