Tie-Line Control

Tie-line is used to control frequency for the power station and power transfer from one station to an another station in interconnected system. It is also to avoid overload in the system as a result from accidental power exchange.

Formula derivation
Lets look at this example,

Generation Control

Principles of Generation Control

  • In an interconnection system, power stations are connected synchronous and the frequency should be the same.
  • The load in power system always change, sometimes change rapidly.
  • The generator must able to increase its ouput from zero to full load quickly
  • It is impossible for the generator output equal to the load in the system.
  • When the generator output exceeds the demand load, the  generator speed and frequency will increase and vice versa.
  • The frequency for each station is not always fixed, but the change is very small.
  • To overcome the change of frequency, then it must be monitored based on the standard resources.
  • If any frequency changes, the generator's output control action should be taken.
Conditions for the two generators that can be operated in the interconnection system is:

  1. Same sequence.
  2. Same frequency.
  3. Same busbar voltage.
  4. Generator must be able to increase output from zero to full load quickly.
Generation Control System

  1. Tie-line control
  2. Automatic Generation Control
  3. Turbine speed control

Electronic Voltage regulator

Voltage regulator

Voltage regulator is designed to maintain constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.

Electronic voltage regulators are found in devices such as:
  • Computer power supplies.
  • Automobile alternators
  • Central power station generator plants, 
  • Substation or along distribution lines

Lenz's law

Lenz's law

Lenz's law is a way of understanding how electromagnetic circuits obey Newton's third law and the conservation of energy. Lenz's law is named after Heinrich Lenz, and it says:

An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.
The Induced current is such as to oppose the change in applied field
Lenz's Law is all about conservation of energy. It guarantees that induced currents get their energy from the effect creating the change. The force acting against the conductor being moved earlier is actually an invocation of Lenz's Law. ( As the conductor moves down, the flux increases, so the induced field opposes this which leads to the direction of the Induced current - which in turn shows the direction of the force back on the current.)

Faraday's law of induction

Faraday's law

Faraday's law of induction dates from the 1830s, and is a basic law of electromagnetism relating to the operating principles of transformers, inductors, and many types of electrical motors and generators.

Faraday's law is applicable to a closed circuit made of thin wire and states that:

"The induced electromotive force (EMF) in any closed circuit is equal to the time
rate of change of the magnetic flux vector through the circuit"
"The EMF generated is proportional to the rate of change of the magnetic flux vector"



A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors or namely the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding.

This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling. If a load is connected to the secondary, current will flow in the secondary winding, and electrical energy will be transferred from the primary circuit through the transformer to the load.

In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp) and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

(Vs/Vp) = (Ns/Np) = (Ip/Is)

Basic principle of transformer

Current Transformer


In electrical engineering, a current transformer (CT) is used for measurement of electric currents. Current transformers, together with voltage transformers (VT) (potential transformers (PT)), are known as instrument transformers.
Current Transformer (CT) 

What is energy


In physics, energy is an indirectly observed quantity that understood as ability of a physical system to do work. Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of a certain length.

Distinction between energy and power

Power is not at all the same as energy, but is the rate at which energy is converted (or, equivalently, at which work is performed).

By allowing the water above the dam to pass through turbines, converts the water's potential energy into kinetic energy and ultimately into electric energy, whereas the amount of electric energy that is generated per unit of time is the electric power generated. The same amount of energy converted through a shorter period of time is more power over that shorter time.

How to test diode


Sounds easy right? But guest what? Even so at some point when doing lab work we also forgot how to test the diode whether it is okay or not. Okay, here i would like to give you some tips on how you should test your diode by using multimeter.

To determine the diode polarity

1. Set you multimeter to resistance measurements
2. Connect your diode to the multimeter
3. Now see the indicator whether it is Low resistance or High resistance
4. Low resistance means that the diode is in forward bias, whereas the high resistance indicates that it is in reverse bias.

In theory views, we know that diode only operates in forward bias. So, when the diode is in forward bias, it is like an close circuit, while in reverse bias, the diode is like in an open circuit.

Hey, guest what? you can also determine the diode polarity by making a simple circuit to help you more understanding how the diode operates. Its easy, all you need is a diode, a battery (at least 9V), a switch (optional), and L.E.D.

Here are the example circuit for you to test the diode.

You can also determine whether the diode is in good condition or not.

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Partial Discharge Theory


Partial discharge (PD) is also refer to dielectric breakdown of a small portion of a solid or fluid electrical insulation system under high voltage.

PD can occur in a gaseous, liquid or solid insulating medium. It often starts within gas voids, such as voids in solid insulation or bubbles in transformer oil. Protracted partial discharge can erode solid insulation and eventually lead to breakdown of insulation.
a short videos about PD on Youtube

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