CONCEPT OF REACTIVE POWER AND REACTIVE POWER COMPENSATION



RPC theory
The beer mug analogy is useful to understand the
BEER MUG ANALOGY
theory of reactive power compensation. If the mug capacity is the apparent power (kVA) that we can transmit through a system, then the foam is the reactive power (kvar) and the beer is the real power (kW). Power factor = beer (kW) divided by mug capacity (kVA) or the efficiency that we can achieve of beer volume to mug capacity
           If we use capacitors to provide the foam (kvar) when we drink the beer, then we free up mug capacity so you don't have to buy a bigger mug and/or so you can pay
less for your beer. Most loads and delivery apparatus (e.g., lines and transformers) are inductive in nature and operate at
a lagging power factor. They need the reactive power component, but that's not to say, that we need to constrain the power system by transmitting the reactive power
through the system.

The benefits of reactive power compensation in the transmission and distribution system include:
  •  Voltage improvement
  • Increase power flow capacity
  •  Release system capacity
  •  Reduced losses
The cost of RPC equipment is normally a fraction of the cost of alternative options of increasing the capacity of the transmission and distribution system (eg. additional lines, transformers, etc.).

Capacitors increase the voltage
Applying capacitors to a system will result in a voltage rise in the system from the point of installation back to the voltage source. This occurs because capacitors reduce the amount of current being
carried through the system, reducing I · R and I · X voltage drops. Fixed capacitor banks don't change the amount of voltage variation (without switching), they only increase the average voltage.
                    The volt drop in transmission system is determined using the formula I · (R+JX). The
voltage rise associated with the installation of a capacitor bank is approximated using the formula:
Where DV is the voltage rise, Q is the capacitor bank size in Mvar, Ssc is the 3 phase symmetrical fault level in MVA.

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