FLOW CONTROL EQUIPMENT USED IN HYDROELECTRIC POWER PLANT

The flow through the turbine is controlled by wicket gates on reaction turbines and by needle nozzles on impulse turbines. A turbine inlet valve or penstock intake gate is provided for isolation of the turbine during shutdown and maintenance.

Spillways and additional control valves and outlet tunnels are provided in the dam structure to pass flows that normally cannot be routed through the turbines.

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Breaker Schemes in Substations

Breaker Schemes in Substations — Types, Design, Advantages, Disadvantages, and Comparison Author: Engr. Aneel Kumar Figure 1: Infographic overview of breaker schemes commonly used in substations. Introduction The breaker scheme or busbar arrangement in a substation defines how incoming feeders, outgoing feeders, and power transformers are connected to the bus. The choice of scheme has a direct impact on system reliability, maintainability, safety, and cost . A simple bus scheme is economical but vulnerable to outages, while advanced schemes such as breaker-and-a-half or double-bus/double-breaker provide very high reliability but at much higher cost and design complexity. Engineers select breaker schemes considering fault tolerance, maintenance needs, space requirements, expansion possibilities, protection coordination, and capital investment . Below, we explain eac...

Advantages of Per Unit System in Power System Analysis | Electrical Engineering

Advantages of Per Unit System in Power System Analysis In electrical power engineering, the per unit (p.u.) system is one of the most widely used techniques for analyzing and modeling power systems. It is a method of expressing electrical quantities — such as voltage, current, power, and impedance — as fractions of chosen base values rather than their actual numerical magnitudes. This normalization technique provides a universal language for system calculations, minimizing errors, simplifying transformer modeling, and enabling consistency across multiple voltage levels. Because of these benefits, the per unit system is essential in fault analysis, load flow studies, transformer testing, and short-circuit calculations . ⚡ What is the Per Unit System? The per unit system is defined as: Q u a n t i t y ( p u ) = A c t u a l V a l u e B a s e V a l u e Quantity_{(pu)} = \dfrac{Actual \ Value}{Base \ Value} Q u an t i t y ( p u ) = B a se ...

PRINCIPLE OF OPERATION OF UNIFIED POWER FLOW CONTROLLER UPFC

UPFC consist of two back to back converters named VSC1 and VSC2, are operated from a DC link provided by a dc storage capacitor. These arrangements operate as an ideal ac to ac converter in which the real power can freely flow either in direction between the ac terminals of the two converts and each converter can independently generate or absorb reactive power as its own ac output terminal. Figure: Basic UPFC scheme One VSC is connected to in shunt to the transmission line via a shunt transformer and other one is connected in series through a series transformer. The DC terminal of two VSCs is coupled and this creates a path for active power exchange between the converters. VSC provide the main function of UPFC by injecting a voltage with controllable magnitude and phase angle in series with the line via an injection transformer. This injected voltage act as a synchronous ac voltage source. The transmission line current flows through this voltage source resulting in reactive an...

PRIMARY SECONDARY AND TERTIARY FREQUENCY CONTROL IN POWER SYSTEMS

Primary, Secondary and Tertiary Frequency Control in Power Systems Author: Engr. Aneel Kumar Keywords: frequency control, primary frequency control, automatic generation control (AGC), tertiary control, load-frequency control, grid stability. Frequency control keeps the power grid stable by balancing generation and load. When generation and demand drift apart, system frequency moves away from its nominal value (50 or 60 Hz). Grids rely on three hierarchical control layers — Primary , Secondary (AGC), and Tertiary — to arrest frequency deviation, restore the set-point and optimize generation dispatch. Related: Power System Stability — causes & mitigation Overview of primary, secondary and tertiary frequency control in power systems. ⚡ Primary Frequency Control (Droop Control) Primary control is a fast, local response implemented by generator governors (dro...

AC Transmission Line and Reactive Power Compensation: A Detailed Overview

Introduction The efficient operation of modern power systems depends significantly on the management of AC transmission lines and reactive power. Reactive power compensation is a vital technique for maintaining voltage stability, improving power transfer capability, and reducing system losses. This article explores the principles of AC transmission lines, the need for reactive power compensation, and its benefits in power systems. Keywords: Reactive Power Compensation Benefits, STATCOM vs SVC Efficiency, Power Transmission Stability Solutions, Voltage Stability in Long-Distance Grids, Dynamic Reactive Power Compensation. Fundamentals of AC Transmission Lines AC transmission lines are the backbone of modern power systems, connecting generation stations to distribution networks. They have distributed electrical parameters such as resistance ( R R R ), inductance ( L L ), capacitance ( C C ), and conductance ( G G ) along their length. These parameters influence ...

CLASSIFICATION OF HVDC LINKS

HVDC links may be broadly classified into the following categories: Monopolar Links Bipolar Links Homopolar Links The basic configuration of a monopolar link is shown in figure. It uses one conductor, usually of negative polarity. The return path is provided by ground or water. Cost considerations often lead to the use of such systems, particularly for cable transmission. This type of configuration may also be the first stage in the development of a bipolar system. Instead of ground return, a metallic return may be used in situation where the earth resistivity is too high or possible interference with underground/ under water metallic structures is objectionable. The conductor forming the metallic return is at low voltage.

MAIN AND PILOT EXCITER

Main Exciter The exciter (sometimes called the main exciter) is a synchronous generator that has its stator and rotor windings inverted. Its field winding is fixed in the stator, and the rotor carries the armature or AC . In addition the rotor carries the semiconductor bridge rectifier that converts the armature voltages to a two-wire DC voltage system. The AC voltages and currents in the armature are often alternating at a higher frequency than those in the main generator, e.g. 400 Hz. The higher frequency improves the speed of response of the exciter. The DC power circuit is coupled to the field of the main generator by the use of insulated conductors that pass coaxially inside the rotor of the exciter and the rotor of the main generator. This eliminates the use of slip rings, which were traditionally used before shaft mounted rectifiers were developed. A slight disadvantage of this technique is that the derivative feedback cannot be taken from the output of the exciter. Howeve...

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