Safety engineering

The arc of survival

A laboratory set up at the University of São Paulo (USP) will test personal protective equipment and collaborate on electrical accident research

Eduardo Cesar Test conducted on material used in anti-short-circuit PPE clothing: the white flash is the electrical arc that generates a great amount of heatEduardo Cesar

Electrical accidents—including some fatal ones—are common at Brazil’s electric power plants. According to the Union of Engineers of the State of São Paulo (SEESP), approximately 70 workers die each year in the electrical industry, but this number would be greater if the data took into account workers from other industries. Although safety engineering solutions provide a means to reduce such incidents, workers remain exposed to risks once all technical resources have been exhausted.   Personal Protective Equipment (PPE) specific to the electrical industry is necessary in such situations, but the problem is knowing for sure whether clothing made of flame-resistant material, and heat-resistant gloves and face protection, are indeed capable of protecting workers, especially those in close proximity to high-voltage electrical equipment.     Brazil recently introduced specific laws to deal with these issues, and the shortcoming was addressed when an independent laboratory for testing PPE was set up at the end of 2016. As of that year, tests could be conducted at the Clothing Testing Laboratory (LEVe) of the Institute of Energy and Environment (IEE) at the University of São Paulo (USP).

To comply with the law, PPE against electrical accidents was sent abroad to be tested at foreign institutions. LEVe was accredited by the Ministry of Labor in August of 2016, and will be audited in April 2017 for admission to the Brazilian Network of Testing Laboratories (RBLE) by the National Institute of Metrology, Quality, and Technology (Inmetro). Only institutions in Canada, Spain and Switzerland have laboratories like LEVe. “There’s a similar laboratory in China, but we still have no information available about it,” says Márcio Bottaro, IEE technologist and technical coordinator of the LEVe project.

An electrical arc occurs when, for example, two fixed electrified conductors (such as metal plates or electrodes) are gradually separated as electrical current measuring thousands of amperes travels through them.  A flash of vaporized plasma is discharged and travels through the air between them when the conductors separate. “The phenomenon happens when, even though separated, these conductors transmit an electrical current through the plasma. The electrical current will stop only when there is a significant distance between the plates, or when the current is weakened or extinguished,” Bottaro explains. Conversely, when two electrified conductors come into contact, an uncontrolled and unexpected electrical arc—usually referred to as a short circuit—can occur. Plasma is one of the physical states of matter, and the plasma produced by a controlled high-energy arc can be used for tasks such as welding, plasma cutting, or in ovens for steel production. Low-energy arcs are found, for example, in fluorescent bulbs, photographic flash bulbs, and plasma monitors. However, when an electrical arc short-circuits, plasma will sustain the current, generating enormous heat capable of melting surrounding materials.

Fault simulation
Laboratories such as LEVe create controlled arcs. “These are simulations of faults in an electrical system, such as those that can occur, for example, in Petrobras’ oil platforms and stations,” explains Bottaro. “They lead to accidents, generating extremely high levels of radiative heat. What we do is test the capacity of materials and clothing to protect against these high temperatures.” The LEVe device has an 8 kiloampre (kA) current and approximately 3.6 megawatts (MW) of power. The arc is controlled for a very short time, which varies from tens of milliseconds to 2.2 seconds. Clothing, gloves, masks, face protectors and other PPE items are tested at a distance of 30 centimeters from the arc, where the heat can attain levels of 500°C.

“Petrobras, SEESP, the Ministry of Labor and PPE manufacturers for the electrical industry approached IEE in 2011 showing the need for a specialized laboratory,” says Bottaro. “After a number of technical visits and meetings, the project was presented to Petrobras, which approved it in December 2013 through a R$1.44 million investment.” IEE Assistant Director Ildo Luis Sauer was the project’s academic coordinator.

Petrobras, through its press office, explained that one of its reasons for investing in the LEVe project was the need to strengthen the supply chain for clothing and accessories used to protect against electrical accidents. Petrobras also explained that it routinely “collects some clothing already in use by company employees, to be tested in order to evaluate whether they maintain, over their service life, the protective features guaranteed by the manufacturers.” SEESP director and electrical and work safety engineer José Teixeira explains that the union decided to participate because one of the project’s objectives is to increase workplace protection for electricians.

Besides providing the market with more than 1,500 individual PPE items registered with the Ministry of Labor for protection against electrical accidents, the laboratory will serve to conduct studies of accidents that occur in the electrical industry. “This is important and was limited by the cost of travelling abroad to deal with very specific cases,” explains Teixeira. “Furthermore, LEVe will develop new protection technologies and encourage Brazilian researchers to participate in international committees, to not only keep up with what’s being done in the testing, but to contribute with their own studies.”

Anchoring system
Another important Petrobras investment, carried out jointly with the São Paulo state government through the National Petroleum Agency (ANP), involved implementing the Testing System for Anchoring Components (Seea) at the Institute for Technological Research (IPT). The equipment was developed to carry out static and dynamic testing of polymeric anchoring cables used to connect oil and gas platforms to mooring lines and anchors positioned on the sea floor. The platforms are generally equipped with 24 anchoring cables and operate at depths of up to 2,400 meters or more.

Seea equipment measures 28 meters in length, with large actuators, or hydraulic pistons, that are capable of simulating on the anchoring cables the incidental stresses from the sea around the platforms. The anchoring cables must resist specific stress levels according to technical compliance requirements for each application. “Petrobras acquires these cables from specialized manufacturers and conducts a number of safety evaluations and tests to demonstrate compliance with technical and safety specifications,” says James Weiss, Director of the Naval and Electrical Mechanical Technology Center at IPT. Only two laboratories—one in the United States and the other in Norway—have equipment like IPT’s. Seea received an investment of R$15.7 million, of which R$10.7 million came from Petrobras and R$5 million from the state government.