Notes: The Basic Theory Of Power Transfer Network

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Basic theory of power transfer network

We know that AC lines are operated at voltage level between 10kv to 800kv. The distribution network operates voltage level below the 100kv. For protection against fault circuit breakers are used. Power flow is obtained by receiving end power or sending end power. Ex. Consider a transmission line connected between load centre and generating station. We assume line is loss less and ignore line charging, then the power flow (P) is,

P=V1V2 sin⁡(θ1-θ2)/X

X= transmission line reactance
V1= sending end voltage
V2= receiving end voltage
Assume V1 and V2 are remain constant
Power flow in the transmission line is obtained by the power injected throw power station. If
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Due to instability voltage in transmission line there is an uncontrollable and continuous drop in system voltage. So, removing this effect we compensate the transmission line by different fact controllers.

Transient stability:

It occurs after large fault in a transmission line Due to this load is bypassed and system is unbalanced.
Reactive power control

There is a reactive power in transmission line with active power. There will be a necessity of reactive power in transmission line but not much more. So, remove the effects due to reactive power in transmission line we control the reactive power by connection of shunt capacitors and types of FACTS controller. Active power control

To control the reactive power, we connect the capacitor in transmission line but increasing capacitor active power is also increase. But after some time there is no effect of increased active power.

Damping oscillation

If suddenly load is increased the frequency of supply is decreasing. But decrease in frequency there is an affect the power transmission line. there is oscillation in system so we need to damped this oscillation by compensating of transmission
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Exchange of real power between shunt and series controllers through dc power link.

(Figure 2.3.4)


3.1 Data of uncompensated transmission line

The Simulink diagram of uncompensated transmission line is given below. We do this simulation in MATLAB software. The data of uncompensated transmission line is given below, 11kv transmission line (supply voltage) Source impedance = (0.01+0.001) Ω Series impedance = (5+0.023) Ω Load is constant at 25MW and 50MVAR

We take different measurement block to measure different quantity like load current, source current, load voltage, source voltage, reactive power, and active power block. We measure in scope: 1 = source voltage, source current. scope: 2 = load voltage, load current. scope: 3 = active and reactive power.

Figure 3.1 (Simulink model of uncompensated line)

3.2 MATLAB simulation waveforms

After simulation we get different waveform of different parameters. It is given below:

Figure 3.2a (Source voltage)

Figure 3.2b (source

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