IEEE WG C Nashville, March 13, APPLICATION OF DUVAL TRIANGLES 2 TO DGA IN LTCs. Michel Duval

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1 IEEE WG C Nashville, March 13, 2012 APPLICATION OF DUVAL TRIANGLES 2 TO DGA IN LTCs Michel Duval 1

2 Normal operation of LTCs may involve: -arc-breaking-in-oil between contacts, producing arcing gases D1. -switching of selectors and valves, also producing sparking discharges D1. -current dissipation in resistors, increasing their temperature and producing hot spot gases T3, T2 or T1. -combinations of the above, producing mixtures of the corresponding gases. 2

3 Faulty operation of LTCs may involve: -an increase in the resistance and temperature of contacts, with the production of hot spots T3 and T2, and coking on contacts, through carbonization of oil. -abnormal arcing D2 or D1 on metallic parts of the LTC. 3

4 Examples of LTC failures: (heavy coking in a ABB UZC) 4

5 Examples of LTC failures: (heavy coking in a Federal Pioneer TC546) 5

6 Examples of LTC failures: (moderate coking in a GE LR83) 6

7 Examples of LTC failures: (arcing/short-circuit in a GE LR83) 7

8 Examples of LTC failures: (arcing/short-circuit in a GE LR65) 8

9 To be able to distinguish between normal and faulty operation of LTCs: -gases formed as a result of normal operation should be identified as precisely as possible under different power operating conditions. -deviation from normal operation will indicate faulty operation. 9

10 Mostly arcing gases are formed during normal operation of a large majority of LTCs, such as: -LTCs of the reactive-type in oil or vacuum from: -Westinghouse: UN, UR, UV series, UTS, UTN, UTT. -Cooper, McGrawEdison: series 394, 396, 494, 550, 995, General Electric: LR and LRT series. -Reinhausen: RM series. -Allis Chalmers, Siemens: TLH series. -Federal Pacific: TC series. -Ferranti Packard: RT series. 10

11 -also, in LTCs of the resistive-type in oil or vacuum from: -ABB: UB, UC, UZ series. -Reinhausen: OilTaps C, R, V, Y. -Westinghouse: UTH. -Hyundai: RS series. 11

12 Duval Triangle 2 can be used for all these types of LTCs, with: -arcing gases D1 appearing on the left side of the Triangle, -hot spot gases T3, T2 and T1 on the right side. 12

13 The Duval Triangle 2 for LTCs (inspected cases) Fault zones: N = normal operation T3 = Thermal faults T > 700 C T2 = Thermal faults 300 < T < 700 C X3 = Fault T3/T2 in progress X3 = abnormal arcing D2 D1 = abnormal arcing D1 Inspected cases of: : Normal operation; : Severe coking; : Light coking; : Heating ; : Strong arcing D2; : Arcing D1 13

14 HQ Data - All ABB Ref. for all HQ data: M.Foata 14

15 HQ Data ABB In-tank cylinder 15

16 HQ Data ABB Selector switch UZE change-over selector problem 16

17 Altalink UZCRT 17

18 HQ Data - GE LR83 18

19 HQ Data Ferranti Packard? Model known to be susceptible to coking in the inverter switch 19

20 HQ Data Westinghouse URS 20

21 HQ data - OilTaps V 21

22 OilTaps R The use of methane in addition to acetylene and ethylene indicates some normal overheating T1 of the resistors during the operation of these LTCs. 22

23 Triangle 2 applied to large databases by J.Dukarm Siemens Westinghouse 23

24 Triangle 2 applied to large databases by J.Dukarm McGraw Edison Cooper 24

25 Other types of normal operation -Some resistive LTCs such as OilTaps Y and M and VacuTaps VV operate normally in either zone N or zone T3 or zone T2, depending on operating conditions. -The use of methane in addition to acetylene and ethylene allows to distinguish between faulty and normal operation in such LTCs. 25

26 HQ data - OilTaps D: Faulty operation 3 phases - Y 1 phase - Normal operation of resistors 26

27 VacuTaps VV: In service, normal operation of selectors During high power tests, normal (in blue) and faulty operation (in red) of resistors. Ref: R.Frotscher, CIGRE 27

28 VacuTaps VR: Normal operation in zone T2 is probably due to operation of selectors and resistors. Ref: R.Frotscher (Orlando) 28

29 -A few other resistive LTCs such as OilTaps G and some UZBs of ABB (ref.john Pruente) operate normally in zone X3 (mixture of arc-breaking-in-oil and high-temperature operation of resistors), depending on operating conditions. 29

30 HQ data - OilTaps G: OilTaps G are high-currents application models. Normal gases occur in zone X3 (mixture of arcing and hot spots). 30

31 Different versions of Triangle 2 should therefore be used for some LTCs, indicating the normal zone(s) of operation depending on power operating conditions: -Triangle 2a and 2b for OilTaps M-Y and VacuTaps VR-VV. -Triangle 2c for OilTaps G and some UZBs. 31

32 Finally, reactive LTCs of the vacuum-type: -Arc-breaking activity occurs in the vacuum bottle only. Normal operation in the surrounding oil used for cooling the bottle does not involve sparking of selector or resistor heating. -Triangle 1 should be used for these LTCs. Overheating in oil suspected Ref: Paul Boman 32