Fault t is considered as the malfunction of the nebJOrk usually due to the short circuit between the conductors or the conductor and the ground3. The fault voltages of the connected buses and the fault currents flowing through the connected lines. Here is reference bus at ground 'Ipotential, V and I are the zero sequence. The" total zero-sequence impedance, Zo is given by
The voltage source eL is connected in series with an added element for recalculating the elements of the bus impedance matrix. ADJUSTMENT OF ZBUS FOR CHANGES IN NET1WmC. Once the ZBUS is built, it can be easily modified for changes in the network configuration, such as If an element is removed, its impedance changes Hit.ll. bus impedance matrix for a composite network containing one branch as shown in Fig.
The partia1 network is shown in Fig- 3.7. Partia1 network after adding element 1-3. Partial network after addition of element ) - 4. The partial network after this addition is shown in Fig. ).9 shown. The short circuit matrix approach requires the. calculation of the: Z:SUS of the entire neb.,ork. The three-phase current in the network element i-j can be calculated in terms of the voltages, vt'<> (F) acroSs.
The phase components of the fault current at bus p can be obtained by pre-multiplying both sides of equation (4.41).
LINE TO GROUND FAULT CALCULATION
34; The currents in the network elements during the fault can be calculated from equation (4.34). ij then the currents in net-. Bus number, element number, Bus. name, Bus code p~q, .Generator- HVA. and Xd., and Xo per cent, Transfor-. get HVA and percentage reactance, transmission line type, distance and line impedances etc. Positive and zero sub-matrices of the positive-sequence bus resistance are formed for the p-th bus and the connected buses.
Form +Vo a H'O 'oouooco bus impedOoc. Fi9, 4'4 FIQW ChQrt fqr !i'art circuit calculation. fault currents flowing into the lines connected to the pth bus are also calculated using equations.
INTRODUCTION
THAKURGOAN
RANGPUR
PALASHBARI
TONGI-132
ISHURDI-132
BOGRA
BOTTAIL
FARIOPUR
MADARIPUR
GJCTI
MIRPUR o .99{-99
JHENAIDA
JESSORE
BARISAL
POSTAGOLA
NOAPARA
BAGERHAT
GOALPARA
FENI TO COMILt~I_9.3
SHAHJIBAZAR
SYLH
ASHUGANJ -132
SRIMANGA
FENCHUGAN
ASHUG:2 0
JAMALPUR
MYMENSHING
KISHOREGANJ
TONGI-230 1.04/-4.0
104/-5.2 GHORASAL-132
KULSI ROAD
DRAWING NO. I
TONGI-
ULLON
MIRPUR
MANGLA
PURBASADIPUR
SAIDPUR
BHERAMARA
COMPUTER PROGRAM
A computer program has been developed for 3-phase to earth and 1ine to earth short circuit calculations. The effect of the opening of each line connected to this, .fau1t bus is then studied and for which the total. To perform this c81cu1ation, a sm811 submatrix containing the faulty bus and its adjacent buses is formed.
811 1ines connected to the faulty bus is modified by adding a new 1ine, with the negative impedance of the 1ine to be opened. The ZBUS thus 'formed' turned out to be 'identical' with the known result. 'Another' program was developed to 'reform ZBUS by reversing YBUS.' The subroutine 'subrut' was used ~ or inversion of YBUS~'The.inversion method was also used to solve ~.:_ZBUS~or the same problem. It turns out that the computer time required for the a1.gorithm method is much smaller than that of the invert method.
This check was taken to 'variify' the program' developer or .this work. Short circuits :inMega-v01t - amps (MVA) are calculated_for.each bus and tabulated with the appropriate station name. currents and the voltage of the bus. zi Three-phase and 1ine to earth fault contribution,. in each 1-line connected to the faulty bus and v01taken by the adjacent buses. currents and the corresponding 1ine contributions and also the voltages of the adjacent buses when 1lines connected to the faulted bus are opened one at a time. The computer results of the short-circuit investigation of the BPDB network are given in Tab1e -5.10. to ground -and sing1e 1ine to ground fault I. its __phase angle and the phase voltages in per unit for the faulty bus •. b) Error VAT Contribution~ from the connected buses. the associated buses in faulty condition.
It is also observed that all error levels for the 1987 network have become higher than the corresponding values for the network for the year 1984. This is due to the increase in the self-impedances and the decrease in the transfer impedances of the bus impedance matrix for , the gap : off the line. TO LINE TO LINE TO LINE TO LINE TO LINE TO LINE TO.
CONCLUSION
Previously, the computer aided short circuit study was done by an iterative method using ZBUS. The ZBUS of the BPDB network is formed in steps by fetching one element at a time. To study the effect of opening any line connected to the faulty bus, the corresponding parts of the bus resistance matrix o~y are being modified.
In this study, fault calculations are made for both three-phase earth faults and single-line faults. The results of the short-circuit study show that the short-circuit MVA for three-phase electricity is higher than that of a single line to ground. It is also observed that the error level on each bus decreases, but the error contributions in MVA of the connected bus.
The BPDB usually investigates three-phase short circuits at various buses in its network using a program developed for this type of short circuit investigation. Also, in the relay setting, there are usually fault currents due to single line to ground. It can also be mentioned that BPDB follows the convehtional_a.pproa.ch (-matrix inversion).
The program developed here for short-circuit calculations will make available to Engineers much more information for protection -or 'the, existing network, and luso for. In the program developed, the system conditions during the fault at any bus are studied for a 3-phase. to ground and single line to ground fault for opening any line connected to the faulty bus. Further extension of this work may include studying the following I. 3) Short-circuit calculations with two or more lines opened after the occurrence of fault.
