!

"

#$

%

&'(

"( " )*

-.

,

! ! 23

+

/

" )*

-

,

' 0 1 -

/

+ -

"4'2 0

1 ,

/

" )*

-

,

-

+

/

6=8- "

> % ,) + ) +




9

%

7$E

40

,

30

6#8-

20

6E8

10 0

0

1

2

3

4

5

6

7

8

time (hours)

Fig.1. ageing cycles

-

" (4

"- * >

5

25 4'5'0'@

4 -

>

% >

) +=

5 -

7

2

)

, 7 =7

)7+

)+

%

-

+ ;

=

)

-

+

%

4

9

%

6E8- 5

C - 5

%

%

-

% -* %

100

20

80

15

60

10

40

5

relative humidity (%)

% -

20

0h

50 h

100 h

200 h

300 h

400 h

500 h

RMS value

*

0

ageing

Fig.3. Shrinking in time of the evolution of the RMS

5

% , %

9 )*

4 ;+- B

2 Fig.2. First experiment

F- 4

>

)=

, = )

+ %

% -

% 4

% 9

# G+

)7# 7H0+

!- 4

20 18

"

5

>

9

3

2

4

14

4 -5 >

%

12

)* -=+-

*

4 -

9

10 8 6

>

4

)

% D7

2

+- * %

1

16

RMS value

"- 0

(@5

50 0 0 200 0 hour 100

)* - +-

200 400

400 550 676 734 950 1008 1106 600 800 1000 1200 1400 1600 ageing 1800 300 500 630 800 960 1059 728

Fig.6. Distinction of four steps

,

-

%

4 4

> F )

Fig.4. Curve analysis method

% 4 % 9

AE G )* -#-+-

+ -* )* - #+-

4

%

20 18 16 14

RMS value

12 10 8 6 4 2 50 0 0 200 0 hour 100

200 400

400 550 676 734 950 1008 1106 600 800 1000 1200 1400 1600 ageing 1800 300 500 630 960 1059 728 800

Fig.5. High and low envelops of the RMS evolution

F-

*

Fig.7. Chosen model for the acoustic RMS value evolution vs. relative humidity

"

% % )

-

4 * - #+

%

)* -E+5% 7

α

0 * -A

)α +

* -E

* - $4 Table 1. Slope values from 0 to 500 hour ageing

%

*

% -

,

F 4

%

?7

-

*

% 7

G

%

-2 4

% 9

"

%

-

7 -7

=-7A

* -$ α= - 7 × 9

;

7 -$

% + - =$

-

$-7

=E-$

= -

, ) +

A -E

9

12

* : 0 hour o : 100 hours + : 300 hours

+ : 100 hours 8

o : 500 hours

10 7

6

RMS value

RMS value

8

6

5

4

3

4

2

2

1

0

40

50

60

70

80

relative humidity (%)

90

0 0

100

Fig.8. Acoustic RMS value vs. relative humidity with increasing ageing durations

100 150 electric charge in pC

200

250

Fig.10. Evolution of the RMS value versus electric charge in the first part of the ageing.

5

0.7

50

,

E

-

0.6

5

> %

0.5

α

slope value

0.4

0.3

>

+

4

)

- 5 )5 % +-

) +

Table2. Slope values from 550 to 800 hour ageing.

0.2

"

A;

A#A

#E

#;=

;

#

A-E

=-7

E

0.1

;A-E

?7

0

-0.1 0

50

100

150

200

250 age (hours)

300

350

400

450

500

7 -;

0.7

Fig.9. Slope evolution from 0 to 500 hours

0.6

0.5

4 -

>

)- -

+

0.4 slope value

>

0.3

0.2

% )

+

- 5

0.1

0

-* % ,

-0.1 0

200

300

400 age (hours)

500

600

700

800

Fig.11. Slopes evolution from 0 hour to 800 hours

5 )

100

% >

%

%

+

5

% - 5

>

>

) 0+ ) * +) % 0+ -5

BC+ F

5 ) +- 5

+-

<

%

% %

%

6E8- 5

%

4

) +

) >

%

%

-

< -

% -

5

% 4

-

J

0

% 9

* -A

%

J-

4 * 4 20

,% 5

$

-

4

% -5 -" 4 +-

% )

% 9 >

678

- -

68

" >

6;8

!

9

- 3

K- *

3

%

0

K

4

" #

5

%

- *

6=8

L F K

68

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M 2 &'''(

5

6A8 6#8

M- 2 - *

6E8

024 3

)

& *

+

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) - )7$E=+- ' -

)

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+ 0 % - F1< 0- K

!- 0'20@( '2 5 4 %

" % :' % =B M " $% $ %"

C & ?

-

> -5

#

I -

%

%

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*

> %

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2

- B C $

L 9 7$$ + ,) < D5 7 - 3

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