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  • Basic Elements of a Digital Controller for a Steam-Turbine Driven Generator

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    John Mulindi
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    The block diagram below illustrates the basic elements of a minicomputer system for speed and voltage control as well as data acquisition of a steam-turbine driven generator unit. Typical output variables of the generator are speed, rotor angle, terminal voltage, field (excitation) current, armature current, and real & reactive power. A number of output variables…

  • Types of Busbar Arrangements in Grid Stations and Substations

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    John Mulindi
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    The arrangement and connection of incoming and outgoing feeders in grid stations and substations and the number of busbars have a significant influence on the supply reliability of the power system. Grid stations and substations, and the topology of the power systems must be designed in a similar way and must therefore be included in…

  • Key Factors to Consider In Substation Design

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    John Mulindi
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    Substations are the points in the power network where transmission lines and distribution feeders are connected together through circuit breakers or switches via busbars and transformers. This permits the control of power flows in the network and the normal switching operations for maintenance purposes. We discuss the key factors to consider when designing substations as…

  • Types of Insulators used in Power Systems

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    John Mulindi
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    We have various types of overhead line and substation insulators. Generally they can be classified as: Post Insulators The post insulators comprise of pedestal posts and solid core cylindrical types. Pedestal post insulators The pedestal post insulator stacks employed in substations are available as single units with a range of lighting impulses withstand ratings (LIW)…

  • How Ground Fault Interrupter (GFI) is used as a Safety Device

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    John Mulindi
    in

    The function of a ground fault interrupter (GFI) is to disconnect the power if a current leakage to ground is detected. GFI is also termed to as Ground fault circuit interrupter (GFCI). We have two types of ground fault interrupters: those designed for life protection and those designed for equipment protection. GFI used for life…

  • Single-phase and Three-phase Power Systems

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    John Mulindi
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    Single-phase Power System To help us understand single-phase power system, consider the sine wave shown in figure 1(a) below of a 120 Vac single-phase power connected to a plug. We know very well that, voltage is the difference in potential between two points. Therefore the sine wave in figure 1(a) shows only the voltage difference…

  • Alternating Currents and Voltages

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    John Mulindi
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    Alternating current generator Let’s consider a signal turn coil rotating freely at a constant angular velocity symmetrically between the poles of a magnet as illustrated below: The ends of the loop are terminated in slip rings. As the loop rotates, side A will have an emf induced first in one direction and then in the…

  • Surge Suppression in Power Systems

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    John Mulindi
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    Causes of Power Surges Transient overvoltages in power systems may arise from a number of sources. Power disturbances resulting from lightning strikes or switching operations on transmission and distribution lines. The switching of power factor correction capacitors for voltage control is the main cause of switching transients. All utility lines are designed to certain basic…

  • Switchgear Equipment

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    John Mulindi
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    Switchgear can be defined as equipment used for controlling, regulating and switching ON and OFF power circuits. Switchgear units range from the small moulded-case unit circuit breakers in a household panel board to the huge, air break switches on 750 kV transmission lines. Switchgear equipment is generally divided into four groups, namely: Disconnect/Isolator Switches Disconnect…

  • Power Measurement in AC Circuits (Single-phase & Polyphase Systems)

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    John Mulindi
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    Introduction to AC Power Measurement In alternating current circuits, the instantaneous power varies continuously as the voltage and current varies while going through a cycle. In this case the power at any instant is given by: p(t) = v(t) x i(t) Where, p(t), v(t) and i(t) are the values of instantaneous power, voltage and current…