( ) Tishreen University Journal for Research and Scientific Studies - Engineering Sciences Series Vol. (33) No. (7) %. . 20/0.

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1 2011 (7) (33) _ Tishreen University Journal for Research and Scientific Studies - Engineering Sciences Series Vol. (33) No. (7) (2011 / 11 / / 10 / 30 ). ( ) 80% /0.4 kv.. :

2 2011 (7) (33) _ Tishreen University Journal for Research and Scientific Studies - Engineering Sciences Series Vol. (33) No. (7) 2011 Testing Voltage Arrestors used in Medium Voltage Networks Dr. Mohammad Zhirah * Dr. Alaa Eldin Housam Eldin ** (Received 30 / 10 / Accepted 24 / 11 / 2011) ABSTRACT The electric network is subject to internal and external excess voltage, which makes it prone to danger because there is no possibility of economically designing its insulation to undergo these voltages. Therefore, we must make additional arrangements to protect the equipment when subjected to these voltages; this can be done by using voltage arrestor in medium voltage networks, because we cannot use the earthing line hanging on top of the towers as additional protection, as is the case in high voltage networks; because of the short distance between the earthing line and phases, this triggers a stroke between them when the earthing line is directly subjected to a thunderbolt. The statistics of fault in customers of Lattakia and Tartous electricity company has shown that 80% of faults in these networks is caused by excess voltages resulting from thunderbolts. This research aims to determine the correct selection of the type of arrestors and the necessary tests performed by the manufacture and customer before being used. This study also aims to examine the effect of the type of tower used in overhead networks on reducing the faults of power transformers (20/0.4 kv) in medium voltage networks. In this research, a simple approach has been suggested for testing the voltage arrestor used in medium voltage networks for each period of time by measuring the leakage current in carbon resistors and comparing it with allowable values. Keywords: voltage arrestors, earthing elements, overhead lines. : * Professor, Electrical Power Engineering Department, Faculty of Mechanical & Electrical Engineering, Tishreen University, Lattakia, Syria. ** Associate Professor, Electrical Power Engineering Department, Faculty of Mechanical & Electrical Engineering, Tishreen University, Lattakia, Syria. 22

3 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33)..[1]. 80 %.. : 20 kv ) ( ). (. ( ). 20/0.4 kv.[2] : : -1 ( ) ( ) ( 2 µ s ) sec 23

4 k = U 2 max U h 3. :k -U max. -U h.[3] ( ) (3-10) k 5 P.u. 4 : (1) ( ) (-) (1).. [4] IEC : -2 [4] 20/0.4 kv 125 kv 95 kv.[5] sec 10 5 µ s m s s hour 1.2.(2). : : SiC SiC 24

5 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33) a) b). (2) :.(3).2-3 cm 80 mm ZnO 0 10 ms a) b).zno (3). (3,b) (2,b)... SiC 25

6 .[6]. (2,a) ZnO (1).SiC SiC ZnO (1).SiC.SiC.. (-).. )..(... ZnO..1 ma... ).(... : -3 ZnO ( ) (4) P. 26

7 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33).T P, Q 2 Q P T.T ( ) (4) P > θ 2. (5) 4 /10 µ s. 2 θ.100 ka t / sec [2] (5) 27

8 ... : -4. : (5). o 45 C U C ( ) U C.[5] T. 5 2 % U C U C 1.25 ( T U ) C :[7] : : U C U U n U C U C n. -U n U 3 n 3 :.T : T =1.4 U C 20 sec U n U = C 3 T.C f < 1.4 : U n U Tov < 3 : T = sec U C 28

9 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33) 1.4 U n U C VDE (0675-2) (2)..VDE (0675-2) (2) U N [kv] 20. U n [kv] >24 U C [kv] >30 U C 80 5 %.U C.[8] 1.05 U n / 3. [2] : -5 IEC : 1-5 :. 5 ka 2.5 ka ka 1.5 :(3) (3) 65 ka 25 ka A 10 4 /10 µ s o 1000 h 115 C. U C. 1 ma.20 kv 29

10 . U r. (4). : 2-5 : U C.5 PC. : 3-5.8/ 20 µ s :.. : 1µ s ( ) : -6 8/ 20 µ s.1.13 U P 30/ 60 µ s 500 A. ( ).8/ 20 µ s : -7 ). ( 30

11 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33) :[9] 1-7 (6). v = 300m / µ s :U P :U. :a,b :v. :E :S.E (6) U E S 1 : µh/m 2S ( a + b) U = U + E P v.( ) -U P U W 1.2. UW 2 S l U = U + E P 1.2 v. l = a + b UW U P l = 1.2 v (1) : 2 S :[du/dt]s 2-7.(i/2) 31

12 S Z (i / 2) Z :. di > 32 ka/ µ s dt [6] 10% S 7200 kv 20 kv.[9]. S [kv/µs]..[7] [5] (4) 20 kv.20 kv (4) [9] 40.10%. l = 2. 3m. (1) l = 4. 5m ( ).. ( ) ).[1] ( 32

13 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33) : 3-7 : (7) U = U + U + U T P b E ZnO -U P : : -U b di U = L dt. -U E U B l max D. (7).(8) U B l max D. (8) 33

14 : ( 20 % )... ( ) m.( ).. ( ). : -8 [9] DIN A. (9). : -9 (-)..[10] (9). 34

15 Tishreen University Journal. Eng. Sciences Series 2011 (7) (33) : :... 5 cm :..(10) :. 1 ma A.(10). (4 :). : : 20/0.4 kv ( ). 35

16 /0.4 kv 100 kv.125 kv 95 kv.125 kv (. (-).. : : /1/ DIN EN ( ; VDE : Norm, : Metalloxidableiter ohne Funkenstrecken für Wechselspannungsnetze (IEC :2004). 3. SCHUFFT W., Taschenbuch der Elektrischen Energietechnik-2009, DIN EN ( ; VDE : Norm, :Isolationskoordination- Teil2 (IEC :1996). 5. Niemexer P., Grohs A. Freileitung, 2 Auflage VDE VERLAG-2008, Hinrichsen V. Metalloxid, Ableitse (Grundlagen), SIEMEN-2000,104. -ABB Küchler A. Hochspannungs, Technik springer Verlag-2009, Hilgarth G. Hochspannung, Technik, 3 Auflag B-G,Tebner-1997, DIN EN ( ); IEC ): Fremdschicht Prüfüngen an Hochspannung, Isolatorn Zur Anwendung in Wechselspannung systemen. 36

Tishreen University Journal for Research and Scientific Studies - Arts and Humanities Series Vol. (31) No. (1) 2009

2009(1) (31) _ Tishreen University Journal for Research and Scientific Studies - Arts and Humanities Series Vol. (31) No. (1) 2009 ( ) * ** (2009 / 2 / 18.2008 / 10 / 27 ) ) ( ) : ( ) (......... :. -.