No abstract

The POD signals implemented in the existing Thyristor Controlled Series Compensators (TCSCs) of the Brazilian North-South (NS) interconnection are solely intended to damp the low-frequency NS oscillation mode. These signals are derived from the modulus of the active power flow in the NS line that is phase-lagged at the frequency of the NS mode and experience relatively large excursions following exogenous disturbances. This paper attempts deriving the POD signal from the same variable but with a different polarity and employing phase-lead compensation. A notch filter is also used to further reduce the adverse transients in the POD control loop, lowering the risk of TCSC saturation. The described results relate to a large-scale model for the year 1999, considering seventeen power flow scenarios and used by a multi-utility task force involved, at the time, in the planning studies of this interconnection.

As part of efforts to identify sources of noise pollution from construction, a methodology is developed here for the standardized assessment of noise from masonry saws, which are electric cutters that are commonly used in the industry. Such standardized assessments could aid the development of quieter machines and also of less disruptive and safer industrial practices. The proposed methodology compares the noise generated during cutting with that of free-running non-cutting equipment in accordance with ISO 3744:2010, which specifies methods of determining sound power levels of noise sources via measurement of sound pressure for an essentially free field over a reflecting plane. The cutting of the proposed standard load (concrete slabs) and different building materials was louder than the disengaged saw. The highest observed sound power level was 110.1 dB. The smallest difference observed between the cutting and disengaged saw was 5.5 dB. Noise generated by the saw was quantitatively assessed. The results allowed a standard material to be proposed for use in tests determining the sound power levels of masonry saws. This study also contributes to the analysis of occupational noise generation, considering the difficulties in obtaining previously reported values of the sound spectrum of masonry saws.

Despite a widespread recognition of the impacts of noise on hearing and other aspects of health, noise exposure in industry remains a significant problem, especially in the construction industry where noise exposure levels of workers are high, especially due to the use of manual equipment and machines used in constructions sites. The masonry saw is a portable power tool widely used in construction in small cuts and finishes for floors, tiles, bricks and woods. It stands out for versatility, lightness and its ergonomics. As part of efforts to identify sources of noise pollution from construction, a noise exposure is developed here for the occupational assessment from masonry saws, which are electric cutters that are commonly used in the industry. Different building materials commonly used in Brazil are used with the masonry saw in their conditions of loading and operation. The proposed methodology evaluates the noise generated during cutting with equipment in accordance with ISO 3744:2010 which specifies methods of measuring sound pressure levels on a surface enveloping the noise source in an environment that approximates an acoustic free field over a reflecting plane and the standard ISO 9612:2009 which specifies an engineering method for measuring workers' exposure to noise in a working environment and calculating the noise exposure level. The cutting of different building materials was louder than the disengaged saw. The highest observed sound pressure level was 106.9 dB(A) at operator ear and 99.1 dB(A) at 2 meters from the source. The smallest difference observed between the cutting and disengaged saw was 7.8 dB(A). Noise generated by the saw was quantitatively assessed. An occupational analysis illustrates that the sound levels generated in operations exceeded the tolerances permitted without protection. The subject is relevant to anticipating risks in the workplace in activities with the masonry saw cutting various building materials. Noise excess removal in the workplace is not just a legal responsibility of the companies, as it is also involved with the market interests of an organization. The safer and healthier a workplace is, the fewer probabilities of absenteeism, accidents and low performance, and consequently, cost savings will be achieved. This study also contributes to the analysis of occupational noise generation, considering the difficulties in obtaining previously reported values of the sound spectrum of masonry saws.

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