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Electrical & Computer Engineering: An International Journal (ECIJ) Volume 3, Number 2, June 2014

Where,

_{M =} MęmgMrmg

M_T = 'Y_jM_i

5 = 5,_mP - 5rr

^rmgYji.kecmg^i^-k^ik ^cmg

w_r

p _ Mrmg Tiiecmg Pmi ~ ^cmg

^m~    M_t

P_max = yJC² + D²

Yij,lermg

Yjjermg Pmj

' ‘rmg ^1,1 cmg

^Vlrmg ^ir‘cmg

M\

Z.

Z.

lecmg.jermg

The accelerating and decelerating areas are given by [12]:

EiEjGy

EiEjBij

Aacc = (.Pm - Pcd)(Ect ~ So) + P_maxD [cos(.5_cr - y_D) - cos(«„ - y_D)]    (8)

Adec = (Pcp-Pm)(n-S_cr-dp+2yp) + P_rtlllxp[cos(S_cr-yp) + cos(6p-Yp)](?')

Where 0 denotes original (pre-fault), D during fault, and P post-fault, S_cr is the critical clearing time.

The transient stability margin: n = A_acc — A_dec, at the critical clearing time t_cr, fi = A_acc — Adec ⁼ 0

Solving the eąuations (13) & (14), the critical clearing angle S_cr can be computed. The value of critical clearing time (CCT) can be computed [17] by following formula:

tcr = J^(Scr-So) (10)

Where,

P₀ = generator output before fault S₀ = pre-fault angle

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