Won-member GOVERNMENT EWGIWEERIWGJAGDALPUR I-494005 IWDIA
' . AbstractA complicated sequential fault on a multiphase power system may involve grounding of some phases, short circuit between some phases in one or more bunches and isolation of some phases. All these faults may take place in any sequence. This paper presents a generalized method for analysing such faults. Two matrices which may be called 'the terminal voltage co-efficient matrix' and 'the ground fault co-efficient matrix' are employed for the analysis. The elements o f these natrices can immediately be written for any state if the system. The method presented imposes no *estriction either on the sequence in which the :omplicated fault develops or on the instants on ;he voltage waves at which the faults develop. k t u a l phase variables are employed for the inalysis and expressions for transient phase :urrents, transient terminal voltages and the transient neutral current are gjven. By suitably adjusting certain constants and the summation indices in the general expressions, the method can be applied to an n-phase power system. As an application of the proposed method, the results for an arbitrary sequential fault on a six phase system are given.
E .List o f Symbols d : ground fault co-efficient matrix D : phase fault co-efficient matrix ek k i ' k N i : e.m.f. of phase k : current in phase k : terminal voltage o f phase k : neutral current at any time 3. COLLEGE (M.P. 1 i * neutral current at time t i,v,e : current, terminal voltage and e.m.f. (n)N n vectors i : current in phase j at time t i (n)j (n) : current vector at time t n L r M S t t i x 1 x O B P w a z1 2 Z ci : self Inductance o f each phase, assumed constant : resistance o f each phase, assumed constant : mutual inductance between any two phases, assumed constant : number o f phases already grounded at any instant : variable time : fault instants : positive sequence reactance = w(L-M) : zero sequence reactance = u(Lt5M) : phase current co-efficient matrix : terminal voltage co-efficient matrix : circular frequency other variables used = M/(L-M), x = X /X y = 6tS(x-l) 0 1' = J(r 2 + X 2 2 y /36), 0 = arctan(X1y/6r) 1 1 0 = arctano( /r) 2 2 2 1 = J(r +xl), = l/(L-M), y = act/(l+aS) 0 = rs(t-t 1(x-13/X y 1 a-yS = 6~/X,y, n