Revision of lightning protection map for overhead contact line system

Transcription

1 2014 International Conference on Lightning Protection (ICLP), Shanghai, China Revision of lightning protection map for overhead contact line system Masahiro Nakayama 1, Yukio Furuyama 1, Haruki Aoyagi 1, Hiroshi Katou 1, Takehiko Nakamura 2, Yuuki Iino 2, Takeshi Yamazaki 2, Hitoshi Hayashiya 2, Dan Tsuchizawa 2 East Japan Railway Company 1 Tokyo Electrical Construction & System Integration Office, 2 Electrical & Signal Network System Department, Railway Operations Headquarters Tokyo, Japan nakayama-m@jreast.co.jp Abstract Lightning protection equipment for overhead contact line system is installed by a lightning protection map based on IKL (isokeraunic level). The IKL was created by data observed over 50 years ago, so we are planning to revise the lightning protection map. A new lightning protection map is created by data observed from 2002 to Number of lightning damage is analyzed, and the validity of the new lightning protection map is discussed. Keywords-component; lightning protection map; lightning location system; isokeraunic level; overhead contact line system; railway II. EXAMPLES OF LIGHTNING DAMAGE Examples of lightning damage from 2010 to 2013 in power supply equipment led to delay of trains are shown in Table I. In Table I, a lightning damage in overhead contact line system is only one (No.5). The mechanism of the lightning damage on Kawagoe Line that occurred on September 4, 2012 (No.5) is shown in Fig. 1. I. INTRODUCTION Cancellation or delay of trains had occurred frequently by lightning damage in power supply equipment of East Japan Railway Company in recent years, so we revised installation standards of lightning protection equipment such as surge arresters. In addition, there was an opinion that the IKL (isokeraunic level) map was outdated. The IKL is used for indices of lightning protection equipment in overhead contact line system. The IKL was created by data observed from 1954 to We are planning to create a new lightning protection map by the JLDN (Japanese lightning detection network operated by Franklin Japan Corporation) data observed from 2002 to In this paper, number of lightning strikes is analyzed, and the validity of the new lightning protection map is discussed. Figure 1. The mechanism of lightning damage (No.5) TABLE I. EXAMPLES OF LIGHTNING DAMAGE ( ) No. Date and time Place Damaged equipment Influence of traffic 1 16:52, Jul. 26th, 2010 Chuo Line, Canceled:30 Diode rectifier Sakaori substation Delayed:21 (Max 169min) 2 7:09, Sep. 2th, 2011 Senzan Line, Canceled:16 Booster transformer Tohokuhukushidaimae -Kunimi Delayed:23 (Max 147min) 3 17:15, Jun. 8th, 2012 Banetsusaisen Line, Canceled:11 High voltage cut-out Akogashima station Delayed:6 (Max 123min) 4 18:23, Aug. 17th, 2012 Shinetsu Line, Canceled: 0 Diode rectifier Nagano substation Delayed:3 (Max 22min) 5 19:44, Sep. 4th, 2012 Kawagoe Line, Canceled:47 Messenger wire Sashiogi- Minamihuruya Delayed:1 ( 329min) 6 22:29, Nov. 29th, 2012 Uetsu Line, Canceled:2 Line transformer Kosagawa station Delayed:11 (Max 641min)

2 Figure 2. Current limiting arresters for overhead contact line system As shown in Fig. 1, it is estimated that the following process has occurred: (1) lightning struck a steel pole, (2) potential of the steel pole rose by the lightning current, (3) back-flashover occurred at insulator, (4) DC current continued after the back-flashover, and messenger wire was disconnected by the arc. As a countermeasure for this damage, current limiting arresters (Fig. 2) have been introduced on a trial basis in parts of bridges which may be struck by lightning. III. REVISION OF LIGHTNING PROTECTION MAP A. Installation standards of lightning protection equipment Overhead ground wires and surge arresters are installed for lightning protection in overhead contact line system. Installation standards of the equipment are classified into three levels (lightning area A, lightning area B and other area) based on IKL values. The installation standards are shown in Table II. Overhead ground wires are installed in areas where the IKL is more than 30 days (the Tokyo metropolitan area is 25 days). The installation interval of surge arresters is defined by the IKL value. The interval is 500m in area where IKL is more than 30 days. The other area, the interval is 1000m. The lightning protection map based on the IKL is shown in Fig. 3. Lightning strikes occur often in the north Kanto area and the coastal area of the Sea of Japan. In these areas, there are large values of IKL. B. Analysis of lightning observation data We analyzed lightning strike densities and average current. TABLE II. Ground wires Surge arresters INSTALLATION STANDARD OF LIGHTNING PROTECTION EQUIPMENT Lightning area A (IKL 30) Lightning area B (30>IKL 25) Necessary Necessary a - 500m interval 1000m interval Other area (IKL<25) Figure 3. The lightning protection map based on the IKL These data were observed by the JLDN from 2002 to Distribution maps of these data are shown in Fig. 4. Lightning strike density is the number of lightning strikes per 1km 2, in one year. If there are large numbers of lightning strikes, there will be large numbers of these with large current. In the other words, there will be large numbers of these to be occurred flashover of insulators. Therefore, it is thought that lightning strike density is highly correlated with accident probability. Average current is equal to average of the peak values of lightning current. If there are large average current, there will be large peak current. So, it is thought that average current may be correlated with accident probability. Fig. 4 (a) shows lightning strike density. High densities that are assumed to be due to summer lightning are found in north Kanto area. Fig. 4 (b) shows average current. Distribution of large values that is assumed to be due to winter lightning is found in the coastal area of the Sea of Japan. a. The Tokyo metropolitan area

3 C. Revision of the lightning protection map According to Fig. 4 (a), it is thought that summer lightning area in the north Kanto will be selected to lightning area A or B for lightning protection equipment. On the other hand, it may be thought that winter lightning area in the coastal area of the Sea of Japan won t be selected to lightning area A or B because there are small numbers of lightning strikes. However, winter lightning in the coastal area of the Sea of Japan has the following characteristics: (a) Lightning strike density (b) Average current Figure 4. Distribution maps observed by the JLDN There are smaller numbers of lightning strikes. But winter thunderclouds are low altitude compared to summer ones, so lightning strikes tend to concentrate on high structures that are shorter distance from thunderclouds. Duration of lightning current can be very long. If lightning strikes directly, energy discharged to earth by surge arresters will be very large. (Winter lightning are sometimes several thousand times the energy of summer lightning.) Therefore, even if there is low lightning strike density, it is believed that winter lightning area is lightning area A or B. Based on the above, we consider the lightning protection map including both summer and winter lightning area as lightning area A or B. Summer lightning area can be taken into account by lightning strike density. Winter lightning area is taken into account by average current. The total number of equipment for lightning protection is not changed, because there were few cases that were led to delay of trains due to lightning damage (Table I). So, square measure of lightning area A and B in the new lightning protection map will be equivalent to square measure of ones in the IKL map. The new lightning protection maps are shown in Fig. 5. (a) Map1 (b) Map2 Figure 5. Lightning protection maps based on the JLDN Fig. 5 (a) is a map superimposing the lightning strike density over the average current. It includes both summer and winter lightning area as lightning area A or B. However, the north part of Aomori Prefecture, where little lightning damage occurs, is lightning area A or B. This is found to be due to large average current, and an improved map is shown in Fig. 5(b). In this map, if there is larger lightning strike density, average current will be considered. We are planning to revise the lightning protection map to Fig. 5 (b). IV. ANALYSIS OF LIGHTNING DAMAGE CASES Cases of lightning damage are analyzed, and the validity of the new lightning protection map is discussed. The targets of analysis are shown below: Target area: Service area of East Japan Railway Company (except Mito branch area) Target Equipment: Power supply equipment in East Japan Railway Company (substation equipment, overhead contact line system and distribution line system) Period: The service area of East Japan Railway Company is shown in Fig. 6. A. Number of lightning strikes per year Number of lightning strikes in power supply equipment per year is shown in Fig. 7. About 100 cases of lightning strikes occurred per year, with 469 cases in four years. Lightning strikes occurring April to October (including the summer) comprised 415 cases (88%). Lightning strikes occurring November to March (including the winter) comprised 54 cases (12%).

4 Figure 7. Number of lightning strikes per year Figure 6. The service area of East Japan Railway Company B. Case of lightning strikes per equipment type As shown in Fig. 8, the 469 cases of lightning strikes are categorized into equipment type. About 60% of the total cases were caused by power companies. In the cases of JRE s company-owned equipment, most cases occurred in low voltage equipment. Substation equipment, high voltage distribution lines, overhead contact lines, transmission lines follow. Lightning strikes that led to delay of trains amounted to 66 cases (14%). C. Occurrence of lightning strikes in each branch area Lightning strikes in overhead contact line systems is rare, so we analyzed 406 cases that occurred in power supply equipment (except low voltage equipment). Low voltage equipment includes power supply equipment such as railway crossing or observation equipment on the wayside. This equipment is also installed on non-electrified sections, and much equipment receives electric power from power companies. Lightning damage on non-electrified sections isn't necessary to consider, because there is no overhead contact line system. Therefore, lightning strike cases in low voltage equipment are excluded. Occurrence of lightning strikes in each branch area is shown in Fig. 9. There are frequent occurrences of lightning strikes in summer lightning area of Takasaki and Omiya, and in winter lightning area of Akita and Niigata. The most occurrence of lightning strike is in Nagano. Chiba area experiences about equal amounts of lightning strikes in both summer and winter. Figure 8. Case of lightning strikes per equipment type Figure 9. Occurrence of lightning strikes in each branch area

5 D. Occurrences of lightning strikes per number of equipment in each branch area Occurrences of lightning strikes per number of equipment in each branch area were reviewed, considering in substations and wayside equipment separately. Substations included cases that were caused by power companies. Wayside equipment included overhead contact line systems, distribution line systems, and affected equipment caused by power companies on the wayside such as stations. Substations were evaluated by calculating occurrences of lightning strikes per substations in each branch area. Occurrence of lightning damage at substations is shown in Fig. 10. Occurrence of lightning strikes per substation is shown in Fig. 11. Figs. 10 and 11 show the same trend. Fig. 11 shows the following: April October (summer): There are relatively large numbers in Takasaki and Omiya, matching lightning area A or B for new lightning protection map. There is a large number in Akita, lightning area A or B for winter lightning. There is a large number in Nagano, which is not in lightning area A or B. November March (winter): There are almost same numbers in Akita and Niigata. Occurrence of lightning strikes, there is a larger number in Niigata than Akita (Fig.10). It is believed because there is a smaller number of substation equipment in Akita. Wayside equipment was evaluated by calculating occurrences of lightning damage per length of overhead contact line in each branch area. Occurrence of lightning strikes on wayside equipment is shown in Fig. 12. Occurrence of lightning strikes per length of overhead contact line is shown in Fig. 13. There is less, lightning strikes on wayside equipment than at substation. Fig. 13 shows the following: Figure 10. Occurrence of lightning damage at substations in each branch area Figure 12. Occurrences of lightning damage on wayside equipment in each branch area Figure 11. Occurrences of lightning damage per substation in each branch area Figure 13. Occurrences of lightning damage per length of overhead contact line in each branch area

6 April October (summer): There is relatively a large number in Takasaki, matching lightning area A or B for new lightning protection map. There is a large number in Akita, lightning area A or B for winter lightning. There is a large number in Sendai, which is not in lightning area A or B. November March (winter): There is less lightning strikes in winter than summer. E. Discussion In summer, there are relatively frequent occurrences in Takasaki and Omiya as summer lightning area, matching lightning area A or B for new lightning protection map. In addition, there are frequent occurrences in Akita, lightning area A or B for winter lightning. In winter, there are relatively frequent occurrences in Akita and Niigata as winter lightning area, but there is less lightning strikes in winter than summer. On the other hand, winter lightning are sometimes has several thousand times the energy of summer lightning. Therefore, it is believed that winter lightning area is lightning area A or B. There are frequent occurrences in Nagano and Sendai which are not lightning area A or B. A detailed distribution map of lightning strike density is shown in Fig. 14. There are a few areas that have high values of lightning density in parts of Nagano and Sendai. We need to confirm occurrence of lightning strikes of these branch areas in the future. V. CONCLUSIONS We created a new lightning protection map by the JLDN data observed from 2002 to The lightning protection map included summer and winter lightning area as lightning area A or B. Summer lightning area could be taken into account by lightning strikes density. Winter lightning area could be taken into account by average current. Number of lightning strikes was analyzed, and the validity of the new lightning protection map was discussed. There are relatively frequent occurrences of lightning strikes in summer and winter lightning area, matching lightning area A or B for new lightning protection map. There are frequent occurrences in Nagano and Sendai which are not lightning area A or B. We need to confirm occurrence of lightning strikes of these branch areas in the future. REFERENCES [1] H.Hayashiya, N.Koguchi, T.Fujita, H.Yamamoto, S.Kikuchi, H.Tamura, S.Shimada, K.Watanabe, T.Abe: Summary of measures for lightning in traction substation and case analysis of recent lightning troubles, The Papers of Technical Meeting, IEEJ, No.HV (2011) (in Japanese) [2] H.Hayashiya, T.Fujita, H.Yamamoto, N.Koguchi, M.Hino, K.Watanabe, S.Shimada, M.Okubo, T.Kozawa, S.Yokokawa, A.Okui, H.Inoue, H.Watanabe, H.Yamashia: Outline of silicon rectifier trouble caused by lighting at DC railway traction substation. The Papers of Technical Meeting, IEEJ, No.TER (2011) (in Japanese) [3] K.Hanaoka, T.Momose, K.Matsuda, S.Chiba, Y.Yoshioka, S.Yajima, K.Nishimura, K.Sato, H.Hayashiya: Measuring results of investigation to determine the breaking process of rectifier for traction power supply system. The Papers of Technical Meeting, IEEJ, No.HV (2014) (in Japanese) [4] H.Hayashiya, S.Yokokawa, M.Onuki, K.Hanaoka, T.Momose, K.Matsuda, S.Chiba, Y.Yoshioka, S.Yajima, K.Nishimura, K.Fujita, T.Katsurayama: Overview of rectifier trouble caused by lightning at traction substation. The Papers of Technical Meeting, IEEJ, No.HV (2014) (in Japanese) [5] H.Hayashiya, T.Murakami, Y.Nishimura, K.Ishida, E.Yoshino, M.Matsumoto: Investigation and enforcement of comprehensive lightning protection in TOKYO metropolitan area railway system in Proc. of 30th International Conference on Lightning Protection (ICLP2010). Cagliari, 2010, No.9B-1147 [6] H.Hayashiya, N.Koguchi, H.Yamamoto, T.Ozaki, T.Sakurai, R.Inoue: Improvement of grounding system of DC traction substation in railway power supply system in Proc. of 31th International Conference on Lightning Protection (ICLP2012). Vienna, 2012, No.52 [7] H.Hayashiya, T.Ozaki, T.Fukano, N.Sato, N.Koguchi: Summary of Grounding System Improvement of Traction Substation around Tokyo in East Japan Railway Company in Proc. of 32nd International Conference on Lightning Protection (ICLP2014). Shanghai, 2014, No.174 [8] H.Hayashiya, T.Nakamura, K.Sato, H.Yamamoto, S.Mohri, N.Koguchi: Recent Lightning Troubles in Traction Power Supply System and Evaluation by the Data from Lightning Detection System in Proc. of 9th Asia-Pacific International Conference on Lightning (APL2015). Nahoya, 2015, TC5.3-4 Figure 14. A detailed distribution map of lightning strike density