A Proposal for the Evaluation of HTV Silicone Rubber Composite Insulators
Abstract
:1. Introduction
2. Tested Composite Insulators
3. Specimens Preparation and Experimental Setups/Procedures for Testing Composite Insulators as Finished Products
3.1. Shore A Hardness Measurement
- A.
- Measurement on the Top Shed
- B.
- Measurement on a Half Shed
- C.
- Measurement on Two Layered Half Sheds
- D.
- Measurement on the Sheath between Two Sheds
- E.
- Hand-Held
- F.
- Mounted on a Stand
3.2. Tensile Strength and Elongation at Break Test
3.3. Tear Strength Test
3.4. Density Measurement
3.5. Inclined Plane Test
4. Results
4.1. Shore A Hardness Measurement
- SHA2:
- is the average shore A hardness measurement on the top of two half sheds, layered in opposite direction.
- SHA1:
- is the average shore A hardness measurement on one half shed.
- M2:
- is the shore A hardness on two half sheds (shore A hardness units).
- M1:
- is the shore A hardness measurement on one half shed (shore A hardness units).
- k:
- is the correction factor (k = 0.99).
4.2. Tensile Strength and Elongation at Break Test
- TS:
- is the tensile strength (N/mm2).
- Fmax:
- is the maximum tensile force recorded at the moment that the specimen breaks (N).
- W:
- is the width of narrow portion of the test sample (mm) and it is specified in the standard ISO 37 [12]. For type 2 dumb-bell test piece that is used in this research, this value is equal to 4 mm.
- d:
- is the thickness of the sample (mm) (ISO 37 requires 2.0 ± 0.2 mm thickness for type 2 dumb-bell test pieces [12]).
- EB:
- is the elongation at break (%).
- LB:
- is the test length of the specimen at the moment of rupture (mm).
- L0:
- is the initial test length of the specimen before the test (mm).
4.3. Tear Strength Test
- TS:
- is the tear strength (N/mm).
- Fmax:
- is the maximum tensile force till the tearing of the sample (N).
- t:
- is the thickness of the specimen at the point where the tear occurred (mm) (ISO 34-1 requires 2.0 ± 0.2 mm thickness [13]).
4.4. Density Measurement
- p:
- is the density (g/cm3).
- pw:
- is the density of distilled water (g/cm3). All measurements in this research were conducted at 21 °C, and therefore pw = 0.997989 g/cm3 was used in all calculations [32].
- m1:
- mass of the test piece by weighing it in air (g).
- m2:
- mass of the test piece by weighing it in distilled water (g).
4.5. Inclined Plane Test
5. Discussion
5.1. Shore A Hardness Measurement
5.2. Tensile Strength and Elongation at Break Test
5.3. Tear Strength Test
5.4. Density Measurement
5.5. Inclined Plane Test
6. Conclusions
- Some useful analytical methodologies for extracting the test pieces from composite insulators (finished products) for five widely used tests are presented, taking into consideration some deviations, mainly on their dimensions, from the specified ones in the corresponding international standards. As a result, the proposed methodologies could be included to future versions of the used ISO/IEC standards, as extensions.
- The ranges of the results of these tests for new, unused and unaged HTV silicone rubber with ATH filler are presented in this study as an extension and contribution to the existing knowledge. These results in combination with the results of previous investigations, which are also presented in this article, comprise a database that can be used as a guide for future tests on composite insulators’ housing material (HTV silicone rubber with ATH filler) in terms of what the results should be expected to be, so that the material is the appropriate one.
- Shore A hardness measurement on housing material of the available insulators was in the range of 56–75 shore A hardness units. Measurements were taken on one half shed and on the top of two half sheds, layered in opposite direction.
- When measuring on one half shed, with thickness less than the required 6 mm, the result can be multiplied with a correction factor k = 0.99. In this way, the result is “converted” to the measurement on the top of two half sheds, layered in opposite direction, which meets the 6 mm requirement of ISO 48-4 [11]. Alternatively, instead of using k as a correction factor, a factor of 1% could be included in the uncertainty estimation of shore A hardness measurement, when measuring on one half shed.
- Tensile strength test results were in the range of 2.4–6.0 N/mm2. Type 2 dumb-bell test pieces [12] were used, which were cut from the sheds of the insulators.
- Elongation at break results were in the range of 150–560%. Test pieces were of the type 2 dumb-bell [12], cut from the sheds of the available composite insulators.
- Tear strength test results range was 12.5–20.0 N/mm. Test pieces were crescent-type [13], cut from the sheds of the insulators.
- Density measurements on the housing material of the tested insulators was in the range of 1.5–1.6 g/cm3. Method A of standard ISO 2781 [14] was used and specimens were taken from the sheds of insulators.
- Inclined plane test was successful for 49 out of the 50 tested samples of the available insulators. Test pieces were half sheds and method 1 (constant ac voltage of 4.5 kV for 6 h and 0.6 mL/min flow rate of the contaminant) of standard IEC 60587 [15] was used.
- According to a comparative study with previous investigations [2,4,5,6,8,16,17,18,19,20,21,22,24,26,27], variations of the results of the above-mentioned tests were revealed. These variations depend, among others, on the type of the test pieces, which are used for the tests. It is strongly recommended that the type of test pieces be mentioned in every test report. In this way, comparisons can be made among results obtained from the same test pieces.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Insulator | A1 | A2 | B1 | B2 | C1 | C2 | D1 | D2 | E1 | F1 | Avg. | Std. Dev. |
---|---|---|---|---|---|---|---|---|---|---|---|---|
k | 0.99 | 1.00 | 0.98 | 0.99 | 0.98 | 0.99 | 1.00 | 1.00 | 0.98 | 0.99 | 0.99 | 0.01 |
Insulator | Passed Samples/ All Samples | Thickness Range (mm) | Max. Depth of Erosion (mm) | Result | Notes | |
---|---|---|---|---|---|---|
Average | Std. Dev. | |||||
A1 | 5/5 | 2.82–7.13 | 0.79 | 0.18 | Pass | - |
A2 | 5/5 | 2.65–5.92 | 0.85 | 0.16 | Pass | - |
B1 | 5/5 | 2.97–4.83 | 0.62 | 0.12 | Pass | - |
B2 | 5/5 | 2.95–5.04 | 0.76 | 0.25 | Pass | - |
C1 | 5/5 | 2.85–5.37 | 0.84 | 0.09 | Pass | - |
C2 | 4/5 | 2.79–5.68 | 0.77 | 0.14 | Fail | Hole |
D1 | 5/5 | 3.58–8.15 | 0.51 | 0.05 | Pass | - |
D2 | 5/5 | 3.84–7.80 | 0.69 | 0.28 | Pass | - |
E1 | 5/5 | 2.73–4.70 | 0.59 | 0.09 | Pass | - |
F1 | 5/5 | 2.67–5.27 | 0.55 | 0.08 | Pass | - |
Reference | Range of Shore A Hardness Measurement (Shore A Units) | Test Piece |
---|---|---|
[8] | Not mentioned | Layered sheds |
[20] | 61–75 | Standard test piece (6 mm thick) |
[21] | 76.64 (no range) | Rectangular test pieces (2 mm thick) |
[22] | 73 (no range) | Standard test piece (6 mm thick) |
[27] | 65–75 | Not mentioned |
This research | 56–75 | One half shed or two layered half sheds |
Reference | Range of Tensile Strength (N/mm2 = MPa) | Range of Elongation at Break (%) | Test Piece |
---|---|---|---|
[4] | 3.4 (no range) | 321 (no range) | Not mentioned |
[6] | 2.7 (no range) | 124 (no range) | Not mentioned |
[18] | ≥3.0 | - | Dumb-bell (Type: not mentioned), cut from composite insulators’ housing material |
[19] | ≥3.0 | - | Not mentioned, cut from composite insulators’ sheds |
[20] | 4.0–5.1 | 150–345 | Standard dumb-bell (Type: not mentioned) |
[22] | 6.6 Mpa (67 kgf/cm2) (no range) | 198 (no range) | Standard dumb-bell (Type: 1) |
This research | 2.4–6.0 | 150–560 | Dumb-bell (Type: 2), cut from composite insulators’ sheds |
Reference | Range of Tear Strength (N/mm) | Test Piece |
---|---|---|
[2] | ≥6.0 | Not mentioned |
[4] | 9.6 (no range) | Not mentioned |
[19] | ≥7.0 | Not mentioned |
[20] | 13.0–25.0 | Standard angle type without nick |
[22] | 11.0 kgf/cm ≈ 10.8 N/mm (no range) | Standard angle type without nick |
[24] | ≥7.0 | Not mentioned |
[26] | >10.0 | Standard angle type without nick |
This research | 12.5–20.0 | Crescent type, cut from composite insulators’ sheds |
Reference | Range of Density (g/cm3) | Test Piece |
---|---|---|
[2] | >1.50 | Not mentioned |
[8] | >1.50 | From composite insulators’ sheds and sheath |
[20] | ≥1.52 | Not mentioned |
[22] | 1.54 (no range) | 20 g of material |
This research | 1.50–1.60 | From composite insulators’ sheds |
Reference | Result at 4.5 kV | Test Piece |
---|---|---|
[5] | Pass | Standard specimens |
[8] | Pass | From sheath |
[16] | Pass | From sheath |
[17] | Pass | Half sheds |
[20] | Pass | Standard specimens |
This research | Pass (49/50) | Half sheds |
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Kokalis, C.-C.A.; Kontargyri, V.T.; Gonos, I.F. A Proposal for the Evaluation of HTV Silicone Rubber Composite Insulators. Polymers 2021, 13, 3610. https://doi.org/10.3390/polym13213610
Kokalis C-CA, Kontargyri VT, Gonos IF. A Proposal for the Evaluation of HTV Silicone Rubber Composite Insulators. Polymers. 2021; 13(21):3610. https://doi.org/10.3390/polym13213610
Chicago/Turabian StyleKokalis, Christos-Christodoulos A., Vassiliki T. Kontargyri, and Ioannis F. Gonos. 2021. "A Proposal for the Evaluation of HTV Silicone Rubber Composite Insulators" Polymers 13, no. 21: 3610. https://doi.org/10.3390/polym13213610