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Extended Summary pp.531 536 Large Current Lightning Mimic Test for FRP Blades of Wind Turbine Generators Masahiro Hanai Member (Toshiba Corporation, masahiro.hanai@toshiba.co.

such as wind power has become popular. In Japan, power generated by wind in 1999 totaled only 2.3 MW, but by the end of fiscal year 2001 it had reached 300 MW.

FRP blade failure of a wind turbine generator caused by lightning has to be clearly reproducible in the high-voltage examination with a lightning impulse voltage-generator, and the large current

1 Extended Summary pp Large Current Lightning Mimic Test for FRP Blades of Wind Turbine Generators Masahiro Hanai Member (Toshiba Corporation, Hisatoshi Ikeda Senior Member (Toshiba Corporation, Masumi Nakadate Non-member (Toshiba Corporation, Haruo Sakamoto Non-member (Kochi University of Technology, Keywords: wind turbine generator, FRP blade, short-circuit generator, large current test, test method In response to a global trend toward environmental conservation, renewable energy technology such as wind power has become popular. In Japan, power generated by wind in 1999 totaled only 2.3 MW, but by the end of fiscal year 2001 it had reached 300 MW. There has been a large increase in the power generation capacity of wind power generators. FRP blade failure of a wind turbine generator caused by lightning has to be clearly reproducible in the high-voltage examination with a lightning impulse voltage-generator, and the large current examination with a short circuit generator. We are carrying out the examination of the large current, and clarified the destructive mechanism of the blade by lightning. In order to attain this purpose, two kinds of models were used. They were a1/2-scale test model of a 250 kw wind turbine generator blade (Fig. 1), and a full-scale 250 kw wind turbine generator blade divided into four parts. A large current examination with 1/2-scale test models of a 250 kw wind turbine generator blade (Fig. 1), and a full-scale 250 kw wind turbine generator blade divided into four parts, verified whether a FRP blade explodes as a result of the current of Fig. 2. Simulation model of pressure shock wave Table 1. Conditions and results of large current test Fig. 3. Simulation results of pressure shock wave a lightning strike. The examinations accurately reproduced actual blade failures caused by lightning in the field, and the results proved the compatibility of the measurement method. The first three experiments are for the surface current, as shown in Table 1. When the current flows on the surface of the blade, the surface is burned, and there is no explosion. Smoke and soot remain. It appears that the FRP blade is capable of being used again. However, when the lightning current flowed once into the blade, the blade exploded. When the resistance of an arc in a large current examination was measured, it was about 1 kv/m. When the quantity of heat generated inside a blade, was calculated by the resistance of an arc, the pressure makes a blade explode. Furthermore, by results of the simulation as shown in Fig. 2, it was shown clearly that there are no difference between a steep front current and 50 Hz current (Fig. 3). So it turned out that we can use the short circuit generator in large current examinations which simulate lightning. Fig. 1. Set up of 1/2-scale model specimens 11

2 FRP Large Current Lightning Mimic Test for FRP Blades of Wind Turbine Generators Masahiro Hanai, Member, Hisatoshi Ikeda, Senior Member, Masumi Nakadate, Non-member, Haruo Sakamoto, Non-member In Japan, lightning damage to FRP blades of wind turbine generators has been increasing in parallel with the recent increase in the installation of wind turbine generators. Therefore, we established a test method, while clarifying the destructive climate of lightning, and examined a method of preventing destruction. A high-voltage test clearly showed that lightning easily penetrates FRP that is not processed to be conductive. Moreover, after developing a test method, an examination with a large current successfully reproduced blade damage, and revealed the failure mechanism, which explains breakdowns of actual machines. If lightning penetrates a FRP blade, the air temperature inside the blade rises. As a result, pressure increases and the blade is damaged. Moreover, the breakdown of positive polarity (winter) lightning can be examined with a large current that is generated by a short circuit generator. FRP Keywords: wind turbine generator, FRP blade, short-circuit generator, large current test, test method 1. (1) 100 m Power & Industrial Systems Research & Development Center, Toshiba Corporation Power Systems Company 2-1, Ukisima-Cho, Kawasaki-ku, Kawasaki Hamakawasaki Works, Toshiba Corporation Power Systems Company 2-1, Ukisima-Cho, Kawasaki-ku, Kawasaki Department of Intelligent Mechanical System Engineering, Kochi University of Technology Miyanoguchi, Tosayamada-Cho, Kami (2) (3)(5) FRP B

1 IEC (5) Table 1. IEC protection level (5). 2 50 Hz 1/2 Table 2.

1. Approach to lightning with high voltage and high power equipment.

31 IEC TR 61400-24 (8) 1 IEC I 2 1 2 1 150C 2 80C 311 1/2 1/2 250 kw 12.

3 1 IEC (5) Table 1. IEC protection level (5) Hz 1/2 Table 2. Parameter values of examination with short circuit generator (50 Hz 1/2cycle). 1 Fig. 1. Approach to lightning with high voltage and high power equipment. (2)(7) GFRP FRP FRP IEC TR (8) 1 IEC I C 2 80C 311 1/2 1/2 250 kw 12.6 m 2m 1/2 1m 1/2 FRP 1/2 2 1/ /2 Fig. 2. Set up of 1/2-scale model specimens. 3 Fig. 3. Short circuit generator. φ0.2mm 312 1/4 1/ m 4 2 3m 532 IEEJ Trans. PE, Vol.127, No.3, 2007

3 Table 3. Result of a large current examination.

4 FRP 4 1/4 1m Fig. 4. Set-up of full-scale 1/4 cut model specimens (copper wire inside model is 1 m in length). 5 1/2 281 C Fig. 5. Results for 1/2-scale model specimens (surface current of 281 C). 3 Table 3. Result of a large current examination. 1/2 4 1/4 FRP 1m /2 3 3 TP-1 3 No C V 800 V 6 1/ C Fig. 6. Results for 1/2-scale model specimens (inside current of 66.4 C) C Fig. 7. Current and arc voltage waveform of large current test (inside current of 146 C). B

4 C 66.4 kj/m 100 C 1.011(J/K*g) (9) 0 C 1.293(g/l) (9) 1/2 3.6 l 66.4 C 14000 5MPa 42 9 30 cm 30 m 4 30 m 1kV/m 50 A 10 ms 0.5 C 50 Hz 0.

5 8 1/4 264 C Fig. 8. Results for full-scale 1/4 cut model specimens (inside current: 264 C). 9 Fig. 9. Simulation model of pressure shock wave V 33 1/4 1/4 1m 264 C 8 3m 4 Table 4. Conditions of pressure shock wave simulation FRP FRP (3)(6) 7 WJ W = (V I)dt = V (I)dt = V Q (1) V I Q C 1kV/m 66.4 C 66.4 kj/m 100 C 1.011(J/K*g) (9) 0 C 1.293(g/l) (9) 1/2 3.6 l 66.4 C MPa cm 30 m 4 30 m 1kV/m 50 A 10 ms 0.5 C 50 Hz C 30 m 0.5 m15 m29.5 m 10(a) 1ms MPa 300 C 1.7 Mpa 10(a)(b) 534 IEEJ Trans. PE, Vol.127, No.3, 2007

6 FRP (a) Both ends are closed, 10 ms rectangle wave 11 (10) Fig. 11. Observed waveform of positive polarity lightning current (10). (b) 0 m side end is closed, 30 m side end is opened, 10 ms rectangle wave (c) 0 m side end is closed, 30 m side end is opened, 50 Hz sine half wave 10 Fig. 10. Simulation results of pressure shock wave in blade model MPa 10(b)(c) 10 ms 50 Hz 10 ms 50 Hz π (3.14) : 2 50 µs 50 Hz 30 m (10) 50 Hz 1 IEC TR Hz I 281C IEC TR JFE T.Sorensen,M.H.Brask,P.Grabau,K. Olsen, and M.L. Olsen: Lightning Damages to Power Generating Wind Turbines, 24 th International. Conference on Lightning Protection, No.96.4 pp Brimingham, UK (1998) 2 S. Yokoyama and N. Vasa: Study on Lightning Damage of Wind Tubine Blades and Protection Method of them, The Papers of Joint Technical Meeting on Electrical Discharge and High Voltage Engineering, IEE Japan, B

ED-02-56, HV-02-40, pp.31 36 (2002) (in Japanese) N. Vasa,, ED-02-56, HV-02-40, pp.31 36 (2002) 3 H. Sakamoto, H. Kubo, Y. Hashimoto, I. Suzuki, Y. Ueda, and M.

Hanai: Reproduction and Mechanism of FRP Blades Failure for Wind Power Generators, J. JSME, Series A, Vol.48, No.4, pp.465 471 (2005-11) 5 M. Hanai, H. Koyama, N. Kubo, Y. Hashimoto, I. Suzuki, Y.

of the 28 th International Conference on Lightning Protection (ICLP), pp.1509 1514, Kanazawa, Japan (2006) 6 T. Naka, N.J. Vasa, S. Yokoyama, A. Wada, A. Asakawa, H. Honda, K. Tsutsumi, and S.

Korematsu, Y. Ueda, Y. Suguro, and S. Yokoyama: Experimental Study on Lightning Protection Methods for Wind Turbine Blades, Proc.

7 ED-02-56, HV-02-40, pp (2002) (in Japanese) N. Vasa,, ED-02-56, HV-02-40, pp (2002) 3 H. Sakamoto, H. Kubo, Y. Hashimoto, I. Suzuki, Y. Ueda, and M. Hanai: Lightning Protection of FRP Blades for Wind Power Generators, Proc World Renewable Energy Conference Denver, Colorado (2004) 4 H. Sakamoto and M. Hanai: Reproduction and Mechanism of FRP Blades Failure for Wind Power Generators, J. JSME, Series A, Vol.48, No.4, pp ( ) 5 M. Hanai, H. Koyama, N. Kubo, Y. Hashimoto, I. Suzuki, Y. Ueda, and H. Sakamoto: Reproduction and Test Method of FRP Blades Failure for Wind Turbine Generators Caused by Lightning, Proc. of the 28 th International Conference on Lightning Protection (ICLP), pp , Kanazawa, Japan (2006) 6 T. Naka, N.J. Vasa, S. Yokoyama, A. Wada, A. Asakawa, H. Honda, K. Tsutsumi, and S. Arinaga: Study on Lightning Methods for Wind Turbine Blades, IEEJ Trans. PE, Vol.125, No.10, pp ( ) 7 S. Arinaga, K. Tsutsumi, N. Murata, T. Matsushima, M. Shibata, K. Inoue, Y. Korematsu, Y. Ueda, Y. Suguro, and S. Yokoyama: Experimental Study on Lightning Protection Methods for Wind Turbine Blades, Proc. of the 28 th International Conference on Lightning Protection (ICLP), pp , Kanazawa, Japan (2006) 8 Wind turbine generator systems-part24: Lightning Protection, IEC TR Rika Nenpyo (Chronological Scientific Table), National Astronomical Observatory, Ed., Maruzen Co., Ltd. (1989) (in Japanese) 1990,, (1989) 10 K. Yamashita, Y. Mizutani, D. Tanaka, M. Yoda, and I. Miyachi: Positive and Negative Current Waveform of Rocket-Triggered Lightning, 1999 National Convention Record IEE Japan, No.1639, pp.7 30 (1999), 11, No.1639, pp.7 30 (1999) SF6 DC IEC 1 IEEE EHD 536 IEEJ Trans. PE, Vol.127, No.3, 2007

Table 1. Assumed performance of a water electrol ysis plant. Fig. 1. Structure of a proposed power generation system utilizing waste heat from factori

Table 1. Assumed performance of a water electrol ysis plant. Fig. 1. Structure of a proposed power generation system utilizing waste heat from factori Proposal and Characteristics Evaluation of a Power Generation System Utilizing Waste Heat from Factories for Load Leveling Pyong Sik Pak, Member, Takashi Arima, Non-member (Osaka University) In this paper,