Chromatic Comparison of Environmental Factors of High-Voltage Circuit Breaker Gases

C. R. Jones and J. W. Spencer

Introduction

Although SF6 is a powerful high-voltage insulating gas, it is also recognised as one of the most serious greenhouse warming gases (Stocker et al., 2013; Seeger et al„ 2017). Alternatives have been considered from an environmental aspect as well as current interruption capabilities (Kieffel et ah, 2016; Seeger et ah, 2017). Three gas properties with environmental implications have been suggested as boiling point (BP) (°C), greenhouse warming potential (GWP) and toxicity (TOX) (Uchii et ah, 2002; Preve et ah, 2015; Gentils et ah, 2016; Preve et ah, 2016; Kieffel et ah, 2016; Seeger et ah, 2017). Some preferred pure gases with SF6 replacement potential are

Fluoroketones (C,F|0O)

Fluoronitrile (C4F7N)

Carbon Dioxide (C02)

Mixtures of some of these gases with air and CO, have also been considered.

Values of BP. GWP and TOX have been reported by several investigators for these gases (Seeger et ah, 2017).

To illustrate the potential of chromatic processing for comparing the environmental implications of these gases (CO,, SF6, C5Fl0O, C4F7N), data for these gases have been processed chromatically and represented on an effective magnitude (L) graph and an X, Y. Z chromatic map.

Data Normalisation

Numerical values for each of the three environmental parameters (BP. GWP, TOX) reported by investigators (Uchii et ah, 2002; Preve et ah, 2015; Gentils et ah, 2016; Kieffel et ah, 2016; Preve et ah, 2016; Seeger, 2017) are shown in Table 12.1 for C02, SF6, C5F1()0, C4F7N.

TABLE 12.1

Values of Normalised BP, GWP and TOX for C02, SF6, C5F,0O, C4F7N and Nominal Values for Air (Seeger et al., 2017)

GAS

BP (°C)

GWP

TOX (ppmv)

CO,

-7S.5

1

5000

SF6

-64

23.500

1000

c5Fl0o

26.5

<1

225

c4f7n

-4.7

2100

65

Air

-90 (nominal)

0

0

TABLE 12.2

Values of Normalised BP, GWP and TOX for C02, SF6, C5F10O, C4F7N and Nominal Values for Air

GAS

(BP)n

(GWP)n

(TOX)n

CO,

0.215

0

1

SF6

0.36

1

0.2

CsF ,0O

1

0

0.045

c4f7n

0.95

0.09

0.01

Air

0.1 (nominal)

0

0

These values have been normalised so that they lie within the range 0-1 using the following equations

The normalised values for the four pure gases and air using these normalising equations are given in Table 12.2.

Chromatic Analysis

The normalised parameters are treated as chromatic outputs R. G, В (Chapter 1) with chromatic responses R = BP, G = GWP, В = TOX. The R, G. В normalised values have been chromatically transformed (Chapter 1) to produce relative chromatic parameter values for BP. GWP and TOX, which are transformed to X. Y. Z and the effective magnitude L. The results have been compared in two graphs - an effective magnitude (L) versus gas type graph (Figure 12.1) and a relative magnitude X, Y, Z chromatic map (Figure 12.2).

The L versus test gas graph indicates the overall deviation of a gas from the sought-after norm. The X, Y, Z map indicates the relative deviation of each environmental parameter (BP, GWP, TOX) from the ideal and identifying the dominant deviation determining factor.

Effective magnitude of environmental impact (L) versus test gas. (L = [(BP)n + (GWP)n + (TOX)n]/3

FIGURE 12.1 Effective magnitude of environmental impact (L) versus test gas. (L = [(BP)n + (GWP)n + (TOX)n]/3.

X: Y: Z chromatic map of the relative magnitude of the three environmental effects for test gases SF, CO,

FIGURE 12.2 X: Y: Z chromatic map of the relative magnitude of the three environmental effects for test gases SF6, CO,. C5Fl0O, C4F7N. (X = [100 - (BP)n]/300L; Y = [GWP]n/3L; Z = [TOX]n/3L [Z = Diagonal through origin with Z = 1 at X = Y = 0]).

Interpretation

The effective magnitude (L) versus gas type (Figure 12.1) enables the overall deviation of environmental effects of the different gases to be compared. The most well-behaved gas (air) is taken to have the lowest value L value (~0.03), whilst SF6 is the worst-behaved gas, having a value of 0.52. CO, has an L value of 0.405, whilst C5F10O and C4F7N both have lower values of L (0.35) than CO, and SF6 but higher than air.

The X. Y, Z chromatic map (Figure 12.2) is shown as Y (GWP) versus Z (TOX), with X (BP) being indicated as X = 1 - (Y + Z) (Chapter 1). This map shows that an overall well-behaved environmental gas (air) is located at Y (GWP) = Z (Toxicity) ~ 0. and the boiling point temperature (X = 1) is also low. The worst relative global warming potential is that of SF6 (Y = 0.64), whilst the worst relative toxicity is that of CO, (Z = 0.82). Both C5Fl0O and C4F7N appear to have relatively high X(BP) values compared with their toxicity and GWP.

Summary

The chromatic results illustrate how compromises are needed between the three environmental factors. As a consequence, investigations are in place for exploring the possible compensating effects of mixing various gas components with these gas candidates (e.g., Seegeret al„ 2017). The chromatic approach has the potential for quantifying the relative advantages of such mixtures in addressing the environmental limitations.

References

Gentils. F.. Maladen. R.. Piccoz, D., and Preve, C. (2016). Load break switching in SF(, alternative gases for MV applications, Schneider Electric

Kieffel. Y., Irwin, T, Ponchon, P., and Owens, J. (2016) Green gas to replace SF(, in electrical grids. IEEE Power and Energy Magazine, Vol 14. Issue 2, pp. 32-39

Preve, C., Maladen. R.. Piccoz, D., and Biasse, J. (2016). Validation method and comparison of SF(, alternative

gases, CIGRE

Preve, C„ Piccoz, D.. and Maladen, R. (2015). Validation methods of SF(> alternative gas 23 Int. Conf. On Electricity Distribution paper 0493

Seeger, M. et al. (2017). Recent trends in development of high voltage circuit breakers with SF(, alternative gases. Plasma Physics and Technology Journal, Vol. 4(1), http://doi.org/10.1431 l/ppt.2017.1.8 Stocker et al. (2013). Climate Change 2013: The Physical Science Basis. Contribution of Working Group 1 to the Fifth Assessment Report of Intergovernmental Panel on Climate Change, https://www.ipcc.ch/ report/ar5/wgl/.

Uchii, T, Shinkai, T, and Suzuki. K. (2002). Thermal interruption capability of carbon dioxide in a puffer circuit breaker utilizing polymer ablation. IEEE PES T&D Conf

13 Chromatic Line of Sight

Chromatic Line of Sight Particle Monitoring

A. T. Sufian and J. W. Spencer

Introduction

There has been increasing concern over airborne microparticles in the environment and the potential health risks they produce (Nobel and Prather, 1998; Holgate et al„ 1999). Detection of such particles in real-world conditions has traditionally been done with laser light scattering using optical particle counters (OPCs) (Welker, 2012). However, the use of free space laser beams can be restrictive with regard to the location of such systems. A technique which avoids the need for using laser light has been successfully used and was based on the use of a polychromatic light source to address particles captured on part of a particle filter which was chromatically analysed. Part of the filter was used as a reference area (Reichelt et ah, 2006; Jones et ah. 2008). The system was further developed to monitor airborne particle pollution using urban closed-circuit television camera (CCTV) networks for monitoring the particle capturing unit remotely (Kolupa et ah, 2010). The chromatic technique has more recently been used as a line-of-sight approach based on combining a narrow-band chromatic source with a polychromatic source and an optical path several meters long in free air (Sufian and Spencer, 2018).

Chromatic Monitoring System

The monitoring system consisted of a white-light light emitting diode (LED) source, chromatic filters positioned in front of it and a red LED source placed near a camera emitting across the optical path between the camera and white LED source (Figure 13.1) (Sufian and Spencer, 2018). Particles near the camera passing through the red LED beam side scatter light into the camera. Particles in the optical path between the white light source and the camera backscatter the light. The chromaticity of the source could be varied by chromatic filters placed in front of the source for changing the sensitivity of the camera to the light affected by the particles.

Optical filters in the form of white paper placed in front of the source were used to diffuse the light intensity, along with various forms of transparent chromatic filters. Furthermore, a semicircular black paper shutter carrying various aperture geometries was used in front of the camera to govern the shape of the light image captured by the camera (Figure 13.2). A semicircular arrangement of a black paper filter covering the lower part of the source (Figure 13.2a) was used. Alternatively, the same arrangement with an orange translucent plastic filter covering the upper and lower parts of the optical source was used (Figure 13.2b). A rectangular aperture produced by a combination of two black filters covering the upper and lower parts of the source and an orange translucent filter in

Schematic diagram of the particle monitoring system (Sufian and Spencer, 2018)

FIGURE 13.1 Schematic diagram of the particle monitoring system (Sufian and Spencer, 2018).

Example of images obtained with different arrangement of chromatic filters

FIGURE 13.2 Example of images obtained with different arrangement of chromatic filters (Sufian and Spencer, 2018). (a) Images with white and black paper filters to form a semicircular aperture, (b) Images with white, orange and black paper filters to form a semicircular aperture, (c) Images with white, black and orange filters arranged to form a rectangular aperture, (d) Images with white, black and neutral-density filters arranged to form a rectangular aperture superimposed upon a semicircular aperture.

Different monitoring locations (Sufian and Spencer, 2018)

FIGURE 13.3 Different monitoring locations (Sufian and Spencer, 2018).

between has been used (Figure 13.2c), as well as a combination of a black filter covering the low'er part of the source and a neutral-density filter over the upper part with white light transmitted in between (Figure 13.2d).

Smoke particles produced by incense sticks (particle size 1-2.5 microns) affected the images. As the particle density increased, cloudy w'hite and red areas in parts of the image also increased. When the images were chromatically analysed, each showed a change in chromaticity, with the arrangement of Figure 13.2d showing the greatest change. Further tests were performed with various monitoring points on the image (Figure 13.3) addressing the side-scatter of the red LED beam from particles and the backscatter from the white-light LED. As the particle concentration increased, the back- and side-scattered light also changed.

Chromatic Test Results

Changes in the optical signals produced by different levels of particles were analysed chromatically from the camera R. G, В outputs at various locations on the images (Figure 13.3). Chromatic parameters L (lightness) and S (saturation) (Chapter 1) were calculated for the various particle conditions. Further chromatic parameters (Lr and L', S') were also derived from the information in the more restricted long- and medium-short-wavelength range of the visible spectrum, respectively, where Lr = R (intensity strength of the side-scattered red light) and L' = G + B/2, S' = (G - В)/ (G + B) (intensity and spread of the backscattered midrange light).

The variation of the chromatic parameters L and S wfith airborne particle concentrations is show'n in Figure 13.4. Figure 13.4a shows the variation of L and S for the reference area (Figure 13.3) to be independent of the particle concentration. Figure 13.4b corresponding to the side-scattered red light (Figure 13.3) shows that both the red channel intensity (Lr) and saturation (S) increase monotonically with particle concentration but with S changing more than Lr. Figure 13.4c (corresponding to the backscattered light) shows that both the lightness (L') and saturation (S') increase monotonically with particle concentration, albeit at a relatively low level and similarly to each other.

The implication of these results is that the saturation of the side-scattered light (S') provides a reliable parameter for tracking airborne microparticles without the need to use a particle filter to capture the particles. The constancy of the reference area under controlled experimental conditions also confirms the reliability of the approach.

Further chromatic analysis of the captured data is also possible. For example, chromatic information (L', S') may be extracted from the medium-short-wavelength range of the backscattered light and normalised for comparison. The result of such a procedure is show'n in Figure 13.5 for

Calibration graphs for various chromatic parameters (Sufian and Spencer, 2018). (a) Reference area; (b) side-scattered light; (c) backscattered light (Sufian and Spencer, 2018)

FIGURE 13.4 Calibration graphs for various chromatic parameters (Sufian and Spencer, 2018). (a) Reference area; (b) side-scattered light; (c) backscattered light (Sufian and Spencer, 2018).

Comparison of normalised trends for different parameters (side-scattering chromatic [S], backscattering chromatic [L'|, side-scattering [R output]) (Sufian and Spencer. 2018)

FIGURE 13.5 Comparison of normalised trends for different parameters (side-scattering chromatic [S], backscattering chromatic [L'|, side-scattering [R output]) (Sufian and Spencer. 2018).

medium-short-wavelength backscattered light (L'), the saturation (S) and the value of the intensity of the long-wavelength output (red-channel Lr as a function of particle concentration). The latter represents conventional methods of optically monitoring monochromic light scattering of particle and dust concentration (Renlsang, 2015) in air. These results show that each parameter increases in value w ith particle concentration and that the normalised sensitivity of the side-scattered saturation (S) and backscatter (L') is higher than that of the conventional approach.

Summary

Tests have shown that a camera-based chromatic line-of-sight monitoring approach has the capability of tracking variations of airborne microparticles. This is a further evolution of the chromatic monitoring of particulates which does not require their capture on a particle filter through w'hich air is mechanically draw n (Reichelt et al., 2006). As such, it has the potential for being a cost-effective and efficient system for operation at industrial mine sites and so on.

References

Holgate. S.. Samet. J.. Koren. H. and Maynard. R. (1999) Air Pollution and Health. London: Academic Press. Jones. G. R., Deakin, A. G. and Spencer. J. W. (2008) Chromatic Monitoring of Complex Conditions.

Kolupa, Y. E.. Aceves-Fernandez, M. A., Jones, G. R. and Spencer. J. W. (2010) Airborne particle monitoring with urban closed - Circuit television camera networks and a chromatic technique. Meas. Sci Tecltol. 21. 115204.

Nobel. C. and Prather. K. (1998) Air pollution: The role of particle. Phys. World 11. 39-43.

Reichelt. T. E., Aceves-Fernandez, M. A.. Kolupa. Y. E.. Pate, A.. Jones. G. R. and Spencer. J. W. (2006) Chromatic modulation monitoring of airborne particles. Meas. Sci. Techol. 17. 675-683.

Renlsang, X. (2015) Light scattering: A review of particle characterization applications. Particuology (Elsevier), 18.11-21.

Sufian. A. T. and Spencer. J. W. (2018) Chromatic Particulate Monitoring at Line of Sight. Internal Technical Feasibility Report. The Center of Intelligent Monitoring Systems, The University of Liverpool.

Welker, R. W. (2012) Chapter 4—Size Analysis and Identification of Particles, in Developments in Surface Contamination and Cleaning. R. Kohli and K. L. Mittal, Eds. Oxford: William Andrew Publishing, pp. 179-213.

 
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