HADHASOD
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Nature of Faults in Electrical Systems: Books: 1.Elements of Power System Analysis by William D. Stevenson, Jr. 2.Power System Engineering by Nagrath Kothari. 3.Power system Engineering by J.B. Gupta (for problem). Summary of this topic: This topic consists of 3 chapters viz (a) Symmetrical fault analysis (b) Symmetrical components& (c) Unsymmetrical fault analysis. (a) Symmetrical fault analysis: This chapter is devoted to abnormal system behavior under conditions of symmetrical short circuit(symmetrical three phase fault).Such conditions are caused in the system accidentally through insulation failure of equipment or flashover of lines initiated by a lightning stroke or through accidental faulty operation. i) Introduction (Nagrath kothari) ii) Transient on a Transmission line (page 2 & 489 of M.G.Say 3 rd edition) Short circuit reactance (page 492 of M.G.Say 3 rd edition) Two reaction theory: X d x q (page 444 of M.G.Say 3 rd edition) iii) Short circuit of a synchronous machine (on no load)[nagrath Kothari & page 489 of M.G.Say 3 rd edition ] Damper Winding(page 484 of M.G.Say 3 rd edition) iv) Short circuit of a loaded syschronous machine (Nagrath kothari) v) Selection of circuit breakers (Nagrath kothari) (b) Symmetrical components: (Stevenson) It is a convenient method of analyzing unbalanced operation through symmetrical components where the three phase voltages and currents which may be unbalanced are transformed into three sets of balanced voltages and currents called symmetrical components. i) Synthesis of Unsymmetrical phasors from their symmetrical components (Fortescue’s Theorem) ii) Operator( a=1<120 o ) iii) The symmetrical components of Unsymmetrical phasors V ao =1/3(V a +V b +V c ) V a1 =1/3(V a +aV b + a 2 V c ) V a2 =1/3(V a + a 2 V b + aV c ) Derive similarly for currents iv) Unsymmetrical Series impedances v) Sequence impedances and Sequence Networks vi) Sequence networks of unloaded generators vii) Sequence impedances of circuit elements (Stevenson &Nagrath Kothari) viii) Sequence impedances of Transmission Lines (Nagrath Kothari) ix) Sequence impedances and networks of transformers (Nagrath Kothari) x) Zero sequence networks for y connected loads(Stevenson) xi) Construction of sequence networks of a power system(stevension page300,301) (c) Unsymmetrical fault analysis. It is of two types. 1.shunt type fault [Its classification:(a)Single line to ground fault(LG)(b)Line-to-line fault(LL)(c) Double line to Ground fault(LLG)]
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Transcript of HADHASOD
Nature of Faults in Electrical Systems: Books: 1.Elements of Power System Analysis by William D. Stevenson, Jr. 2.Power System Engineering by Nagrath Kothari. 3.Power system Engineering by J.B. Gupta (for problem). Summary of this topic: This topic consists of 3 chapters viz (a) Symmetrical fault analysis (b) Symmetrical components& (c) Unsymmetrical fault analysis.
(a) Symmetrical fault analysis: This chapter is devoted to abnormal system behavior under conditions of symmetrical short circuit(symmetrical three phase fault).Such conditions are caused in the system accidentally through insulation failure of equipment or flashover of lines initiated by a lightning stroke or through accidental faulty operation.i) Introduction (Nagrath kothari)ii) Transient on a Transmission line (page 2 & 489 of M.G.Say 3rd edition)
Short circuit reactance (page 492 of M.G.Say 3rd edition)Two reaction theory: Xd xq (page 444 of M.G.Say 3rd edition)
iii) Short circuit of a synchronous machine (on no load)[nagrath Kothari & page 489 of M.G.Say 3rd edition ]Damper Winding(page 484 of M.G.Say 3rd edition)
iv) Short circuit of a loaded syschronous machine (Nagrath kothari)v) Selection of circuit breakers (Nagrath kothari)
(b) Symmetrical components: (Stevenson) It is a convenient method of analyzing unbalanced
operation through symmetrical components where the three phase voltages and currents which may be unbalanced are transformed into three sets of balanced voltages and currents called symmetrical components.i) Synthesis of Unsymmetrical phasors from their symmetrical components (Fortescue’s
Theorem)ii) Operator( a=1<120o)iii) The symmetrical components of Unsymmetrical phasors
Vao=1/3(Va+Vb+Vc)Va1=1/3(Va+aVb+ a2Vc)Va2=1/3(Va + a2Vb+ aVc) Derive similarly for currents
iv) Unsymmetrical Series impedancesv) Sequence impedances and Sequence Networksvi) Sequence networks of unloaded generatorsvii) Sequence impedances of circuit elements (Stevenson &Nagrath Kothari)viii) Sequence impedances of Transmission Lines (Nagrath Kothari)ix) Sequence impedances and networks of transformers (Nagrath Kothari)x) Zero sequence networks for y connected loads(Stevenson)xi) Construction of sequence networks of a power system(stevension page300,301)
(c) Unsymmetrical fault analysis. It is of two types. 1.shunt type fault [Its classification:(a)Single line
to ground fault(LG)(b)Line-to-line fault(LL)(c) Double line to Ground fault(LLG)]
2.Series type fault [Open conductor:one fault: one or two conductors open]i)Introduction(Nagrath Kothari)ii)Single line to ground fault(L-G) (Nagrath Kothari)iii)Line-to-Line fault (LL) (Nagrath Kothari)iv)Double line to ground fault(LLG) (Nagrath Kothari) Relevant questions: 1.When zero sequence fault current is absent ?2.What do you mean by symmetrical & unsymmetrical faults in a 3-phase power system?
