DC Distribution Systems For certain applications, d.c. supply is absolutely necessary. For example, d.c. supply is required for the operation of variable speed. || || || COURSE: POWER SYSTEMS-II LECTURE NOTES. Power system monitoring/control; large networks; automatic generation control; programs for transients, short-circuit, and transient stability analysis. [].

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It is mainly used for power systems 2 the general circuit parameters and performing load flow analysis. As we can see here, VS and VR is the supply and receiving end voltages respectively, and Is is the current flowing through the supply end.

IR is the current flowing through the receiving end of the circuit.

Power systems 2 and I3 are the values of currents flowing through the admittances. And I2 is the current through the impedance Z. Now applying KCL, at node P, we get. Nominal T representation of a medium power systems 2 line In the nominal T model of a medium transmission line the lumped shunt admittance is placed in the middle, while the net series impedance is divided into two equal halves and and placed on either side of the shunt admittance.

## Power System II Notes (PS II) - Notes | Smartzworld

The circuit so formed resembles the symbol of a capital T, and hence is known as the nominal T network of a medium length transmission line and is shown in the diagram below. Here also Vs and Vr is the supply and receiving end voltages respectively, and Is is the current flowing through the supply end.

Ir is the current flowing through the receiving end of the circuit. Let M be a node power systems 2 the midpoint of the circuit, and the drop at M, be given by Vm.

Calculations related to circuit parameters ABCD parameters of such a power transmission is not that simple, as was the case for a short or medium transmission line. The reason being that, the effective circuit length in this case power systems 2 much higher than what it was for the former models long and medium line and, thus ruling out power systems 2 approximations considered there like.

Rather, for all practical reasons we should consider the circuit impedance and admittance to be distributed over the entire circuit length as shown in the figure below.

The calculations of circuit parameters for this reason is going to be slightly more rigorous as we will see here. For accurate modeling to determine circuit parameters let us consider the circuit of the long transmission line as shown in the diagram below.

### Subject Name: POWER SYSTEMS-II

Substituting power systems 2 conditions to equation 7 and 8 respectively. The diagram overcomes the difficulty of otherwise keeping track of the multiplicity of successive reflections at the various junctions. Consider a transmission line having a resistance r, an inductance l, a conductance g and a capacitance c, all per unit length.

If is the propagation constant of the transmission line, and E is the magnitude of the power systems 2 surge at the sending end, then the magnitude and phase of the wave as it reaches any section distance x from the sending end is Ex given by.

It is also common for an attenuation factor k to be defined corresponding to the length of a particular. In traversing the second line, if the attenuation factor is k, then on reaching the termination at the end of the second line its amplitude would be reduced to N.

The lattice diagram may now be constructed as follows. Set the ends of the lines at intervals equal to the time of transit of each line. If a suitable time scale is chosen, then the diagonals on the diagram power systems 2 the passage of the waves.

It is possible to find where it came from and just what other waves went into its composition. Along the line the wave is attenuated and a wave of amplitude k reaches the open end at time 2.

At the open end, this wave is reflected without a loss of magnitude or a change of sign. The wave is again attenuated and at power systems 2 2 reaches the generator end with amplitude 2 k. In order to keep the generator voltage unchanged, the surge is reflected with a change 2 3 of sign -kand after a time 32 reaches the open end being attenuated to -k.

The whole process is now repeated for the wave of amplitude 4 k. Such a phenomena does power systems 2 have much role to play in case of a very short line, but with increase in the effective length of the conductors, skin effect increases considerably. So the modifications in line calculation needs to be done accordingly.

The distribution of current over the entire cross section of the conductor is quite uniform in case of a dc system.