Facts and Custom Power Devices

• The document discusses facts and custom power devices, focusing on real and reactive power, power factor correction, and compensation techniques in transmission lines.
• It also covers Static VAR Compensators (SVCs) and Thyristor-Controlled Series Capacitors (TCSCs).

Real and Reactive Power

• Real power (P) is primarily responsible for supplying energy to perform work in an electrical power system.
• Reactive power (Q) is required to maintain voltage levels and enable energy storage in the form of electric and magnetic fields.
• The unit of real power is Watts (W)
• The unit of reactive power is Volt-Ampere Reactive (VAR)
• Control of real power is achieved by varying the generator output or load demand.
• A synchronous condenser is commonly used for reactive power compensation in transmission lines.

Power Factor Correction

• Power factor correction is important because it decreases the need for reactive power.
• In a power transmission system, a capacitor bank is used to generate reactive power.
• The main purpose of controlling reactive power in power transmission lines is to regulate the voltage and maintain system stability.
• In an uncompensated transmission line, the line's inductive reactance is primarily responsible for the voltage drop across the line.
• The main disadvantage of using an uncompensated transmission line is increased voltage regulation and power losses.
• Installing synchronous condensers at the receiving end is typically used to compensate for the reactive power in an uncompensated transmission line.
• The primary effect of an uncompensated transmission line on power delivery to the load is reduced transmission efficiency and stability.
• Reactive power in an uncompensated transmission line can cause voltage sag and higher transmission losses.
• Shunt compensation compensates for the reactive power demand of a transmission line by injecting capacitive reactive power at the line's receiving end.
• The main purpose of series compensation in a transmission line is to increase the overall transmission capacity and reduce the line impedance.
• A key advantage of using shunt compensation is that it improves the transmission efficiency by reducing voltage drops.
• When using series compensation, the line's reactance is reduced.
• In a system with both shunt and series compensation, shunt compensation raises the voltage at the receiving end, and series compensation minimizes voltage drop across the line.
• A disadvantage of using series compensation is that it may cause overvoltage if not controlled properly.

Static VAR Compensator (SVC)

• The primary purpose of an SVC in voltage control is to maintain a constant voltage at the bus.
• The slope of the dynamic characteristics of an SVC controls the rate of change of reactive power with respect to voltage.
• A positive slope in the dynamic characteristics of an SVC provides smoother voltage regulation without excessive oscillations.
• A direct benefit of a well-designed slope in the dynamic characteristics of an SVC reduces voltage fluctuations and oscillations during load changes.
• In the context of SVC, a high slope in the voltage-reactive power characteristic indicates a very rapid increase in reactive power with a small voltage decrease.
• The damping of oscillations in voltage is improved by the slope of the dynamic characteristic in an SVC.
• A negative slope in the dynamic characteristic of an SVC would typically result in the SVC supplying reactive power as the voltage rises.
• The desired speed of voltage regulation is one of the key factors in determining the slope of an SVC's dynamic characteristic.
• A steeper slope improves the transient response by enabling quicker voltage control of an SVC system.
• Having no slope (flat dynamic characteristic) the SVC would fail to regulate voltage effectively.

Thyristor-Controlled Series Capacitor (TCSC)

• The primary purpose of a Thyristor-Controlled Series Capacitor (TCSC) in a power system is to control the reactive power flow in the transmission line.
• Both fixed and adjustable reactance modes of operation are possible for a TCSC.
• In capacitive mode, the TCSC behaves like a fixed capacitor in a transmission line.
• The main benefit of the TCSC operating in the capacitive mode is that it increases the system's stability by improving the power transfer capacity.
• In inductive mode, the TCSC acts as an inductive reactance.
• The reactance of the TCSC can be dynamically adjusted by controlling the thyristor firing angles.
• The primary role of the thyristors in the operation of a TCSC is to vary the reactance of the series capacitor.