What is a Prime Mover for an Electrical Generator?

Fig-Prime Mover for an Electrical Generator

Prime Mover Who Rotates the Electrical Generator Shaft Constantly to Generate Electrical Energy Converting the Mechanical Rotating force:

A simple idea about the prime mover that can be anything to provide mechanical input to a machine.

With a better understanding we can say, Yes, even a human can act as a prime mover if anyone rotates the machine by himself and give mechanical input to the machine.

But for machines, a good prime mover is something that maintains to provide a constant speed irrespective of the load applied to a generator.

Actually, the prime mover is a primary source of power, which means all the machinery that provides power for performing different mechanical work.

So, the prime mover is a group of machines that transform energy from thermal, electrical, or pressure into mechanical form for use in different sources for some mechanical work to generate electrical energy by an electrical generator.

Wikipedia Prime mover (locomotive): In engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. In an engine-generator set, the engine is the prime mover, as distinct from the generator.

What are the Common types of Prime Mover for Electrical generators?

AC synchronous generator at a power plant will be driven/turned/spun by the prime mover. In the field of the electrical generator the more common types of energy resources used to generate electricity and their associated prime movers' classes are as below:

Steam turbines

Fossil fuels (coal, gas, oil)

Nuclear

Geothermal

Solar-heated steam 

Hydro turbines

Dams and rivers

Pump storage 

Combustion turbines

Diesel

Natural gas

Combined cycle

Wind turbines

Solar direct (photo-voltaic)

Major Classification of Prime Mover

Prime movers are classified as follows: 

1. Engines: 

a.External combustion engine. Ex. Steam Engine b.Internal Combustion engine i) Petrol engine ii) Diesel engine 

2. Turbines: 

a.Steam turbine b.Gas turbine c.Water turbine d.Wind turbine

Electric Motor Also Called a Prime Mover

A Prime mover is something that provides motion/rotation or mechanical power to move a shaft; converts energy from source energy, into mechanical energy, usually, as a motive power source providing traction to move a vehicle.

An electric motor is an electrical machine that converts electrical energy into mechanical energy. The reverse of this is the conversion of mechanical energy into electrical energy and is done by an electric generator, which has much in common with a motor.

The fan over the stove and in the microwave oven;

The blender;

The mixer; etc. are an example of an electric motor used as the prime mover.

What Happens If Electric Generator Prime Mover Rotates in Opposite Direction?

The electric generator generates electricity that maintains phase sequence and its direction is universal. Phase 1,2,3 or R-Y-B is apart 120 degrees from each other, following these rules all generators synchronize together.

Now consider one generator's prime mover rotating opposite direction, the phase difference between phases remains the same but the phase sequence of the power generated will change :)

Suppose R-Y-B is the phase sequence in normal operation than after rotating of prime mover in the opposite direction phase sequence would be R-B-Y because the magnetic field of rotor poles will be firstly cut by R winding then B and then Y.

Operation & Installation Guide For Scroll Compressor, Frequency Converter & Temperature Controller

This operation, installation & maintenance complete guide for Danfoss refrigeration and air-conditioning main equipment such as scroll compressor, frequency converter, and temperature controller EKC204A & EKC102. This refrigeration control system manual will make happy for any technician or operation and maintenance engineer who works with heating ventilating and air conditioning (HVAC) systems.

Scroll Compressor Using Guide

A quick reference to the Danfoss compressor manual will cover the working principle of the scroll compressor and the Danfoss full product range with performance data.

Commissioning and Test Procedure of Power Cable and Equipment

Commissioning and Test Procedure:

Testing methods for power cable insulation depend basically on the type and material of cable insulation. Cross-linked Polyethylene (XLPE) is now spreading widely for power cable insulation at the rated voltage of 66 to 500 kV worldwide.

Quick and easy understanding of commissioning tests for transmission lines and major equipment. Here specially focused on the underground power transmission line, underground cable megger testing, cable fault location and main causes of cable fault, and some manufacturing faults. You also find some megger test procedures for transformer or circuit breakers or common methods for insulation tests or megger tests.   

To see the slide view click the below link,

Commissioning and Test Procedure of Power Line

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Typical Electrical Test for Power Cable

01. Resistance measurements through bolted connections with a low-resistance ohmmeter;

02. Insulation-resistance test individually on each conductor with all other conductors and shields grounded. Apply voltage in accordance with the manufacturer’s published data;

03. Shield-continuity test on each power cable;

04. In accordance with ICEA, IEC, IEEE, and other power cable consensus standards, testing can be performed by means of direct current, power frequency alternating current, or very low-frequency alternating current. These sources may be used to perform insulation-withstand tests, and baseline diagnostic tests such as partial discharge analysis, and power factor or dissipation factor.

HVDC or HVAC, Which Test is the best for XLPE Power Cable?

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We propose to take the HVAC test1.            

HVAC Soak Test is also a suitable way for testing insulation as per IEC 62067 There are 2 ways of HVAC Test mentioned in IEC 62067

(1.7 U0 HVAC Test / U0 HVAC Soak Test)

 2.    HVAC Soak Test doesn’t require additional cost for equipment and complex testing progress, It is the way to keep the testing cost as the HVAC Soak Test doe.  
We not recommend to take HVDC test

There are several reports that DC Testing is ineffective and could even be dangerous for the system under test.

v IEC 62067 : The clause regarding HVDC Test for insulation is changed to HVAC Test for insulation after it is revised

v IEEE 400 : HVDC is not effective in detecting certain types of insulation defects in a bable system when compared with AC Test.

              sn’t need the equipment to make 1.7 U0 for testing

1. DC test can’t detect some problems which can be detected during in HVAC Test.

ü  AC Electrical stress is influenced by capacitance in insulation instead DC Electrical stress is influenced by resistivity

ü  So, the problems in AC system can be different with DC system because of Electrical stress difference.

ü  The reason of some problem in AC system can’t be detected in DC test.

2. DC test can’t detect some problem regarding partial discharge which can be the worst problem in Cable system.

ü  AC voltage makes many kinds of partial discharge pulses in 1 cycle of AC current and it’s repeated

ü  But, DC voltage makes constant value so the number of partial discharge pulses and the value are very normal as compared with AC voltage.

ü  So, even big defection can’t be detected in DC voltage test.

3. Space Charge

ü  In the case of applying DC voltage, Normally Space charge is accumulated in insulation layer.

ü  However, when there is a defection, more charges got into the insulation layer and will be accumulated more than in normal situation because of unequal electrical stress as compared with equal electrical stress.

ü  Because of space charge, unequal electrical stress caused by defection can be released so We can’t detect even big problem when we take DC Test

Cable Parameters: Insulation Resistance,Charging Current, Dielectric Losses

Cable Parameters: Insulation Resistance, Charging Current, Dielectric Losses

Before we formulated cable basic parameters resistance, inductance, and capacitance, now we will try to 3 more parameters like Insulation Resistance, Charging Current and Dielectric Losses.

Cable Insulation Resistance:

Using the following formula you can calculate insulation resistance in mega-ohm per kilometer of cable, to do this you consider the insulation material, diameter of cable including a semiconductor layer, and the diameter of the insulated core.

R =K In (D/d )  MΩ/km

Where

R = Insulation resistance in MΩ/km;

K = Constant depends on the insulation material;

d = Diameter of the conductor in mm including the semiconducting layer;

D = Diameter in mm of the insulated core;

MΩ- mega ohm, km- kilo meter, mm- mili meter.

Cable Charging Current:

The charging current is the capacitive current that flows when AC voltage is applied to the cables as a result of the capacitance between the conductor and earth, and for a multi-core cable in which cores are not screened, between conductors. The value can be calculated from the following equation.

IC = Uo ωC 10^-6   A/km

Where

IC = Charging current in Ampear/km;

Uo =Voltage in volt between phase and earth;

ω= 2 π f (π=22/7, f= frequency in hertz) Hz;

C= Capacitance in micro-farad per kilo-meter to neutral;

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Cable Dielectric Losses:

To calculate the dielectric losses of an AC cable are proportional to the Capacitance, the frequency, the phase voltage and the power factor. The value in watt per kilo-meter per phase can be calculated from the following equation.

WD = 2 π f C Uo² tanδ 10^-6   watt/km/phase

Where 

WD = Dielectric losses in watt/km/phase;

f = Frequency in hertz;

C = Capacitance in micro-farad per kilo-meter to neutral;

Uo = Voltage in volt between phase and earth;

tanδ=Dielectric power factor.

Switching and Earthing Operating Procedure

Switching and Earthing Operative Procedure in Electrical Energy Network

 

The keywords of this article are Switching & Earthing; we are not going to learn technical details about switching and earthing procedures in this piece, but we would like to keep in limit our focus on the key points to the safe operation of switching & earthing system.

The Switching

How keep your switching system safe and healthy in the electrical energy transmission and distribution network? Let’s review some important points that will keep you a smarter switching operator.

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Circuit Breakers and Isolator Operation

1.     Don’t allow switching or any operation in a system without clear permission of the controlling authority except in an emergency case for personnel or property;

2.     System control authority should directly communicate with an authorized person who will operate the switching;

3.     If direct contact is not possible for controlling authorities, the message may be relayed by a third party with written down without any alteration or abbreviation;

4.     If a switching or operating message send by any wireless devices then the receiver will write the message and readout to the sender to ensure that it has been received accurately;

5.     The circuit Breakers or Isolators operator should carry on the message from control authorities without delay  regarding switching or operation;

6.     If emergency switching is required to save the life or property, the report must be relayed to control authority as soon as possible;

7.     If any fault is visible to any equipment, operator must  inform to controlling authority immediately before operation or switching;

8.     Very details switching and operation record must maintain in a station Log.

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The Earthing

The earthing switch is very much related to switching or operating the circuit breakers and isolators. To ensure life and property isolator and earthing switch must be operated safely.

Circuit Main Earth or CME Operation

The Circuit Main Earth or CME must be operated under the supervision of authorized seniors and after clear instruction from the controlling authorities. The position of the earthing and location of each connection must be recorded in the station Log.

If you have many more ideas about switching and earthing operations, you can share them in the comments space. If you think others should know this for safe work, please don’t forget to hit the like or share button below.

Voltage Drop Calculation for Electrical Power Cable

What is Voltage Drop for Cable?

When current flows in a cable conductor a voltage drop is developed in between the ends of the conductor which is the product of flowing current and the impedance of the cable.

Why Calculation Voltage Drop?

It is a common obligation for the designer to calculate the voltage drop as requirements are the main factor in determining the minimum conductor sizes (cross-sectional area) that can be used for a particular electrical circuit.

How to Calculate Voltage Drop?

Calculating the voltage drop of a circuit the designer has two options to choose of them depending on the project requirements. These pretty two options are as below:

Simple Design Approach

Accurate Design Approach

The simple design approach is a rough estimated one which sometimes leads to the use of larger conductor cross-sectional areas than are necessary for the project. If you consider a simple approach, then basically the following information is needed:

·        

•     Type of cable;
•     Conductor cross-sectional area;
•     Method of installation (for AC circuits only);
•     Circuit route length;
•    Type of circuit (DC, single-phase AC or three-phase  AC);
•     Load on the circuit.

Information is not needed for a simple approach:

•   Type and nominal current rating of the associated overcurrent device;
•   Ambient temperature;
•   Whether the circuit is run singly or grouped with other  circuits;
•    The power factor of the load.

On the other hand, an accurate design approach takes more into consideration conductor operating temperature. Above mentioned four “not needed information” for a simple approach should consider for a more accurate approach, especially two factors namely:

•    The ambient temperature
•    Whether the circuit is to be run singly or grouped with other circuits.

Calculate Voltage Drop Smartly:

We who work with cable system sometimes have to calculate voltage drop in short and very smartly. Considering this point of view following two formulas may be helpful for voltage drop calculation smartly.

Voltage Drop Calculation Formula for Single Phase Circuit:

V_d=2Il (R cos ø + X sin ø)  V

Voltage Drop Calculation Formula for Three Phase Circuit:

V_d=√ 3 I l (R cos ø + X sin ø)  V

Where

V_d = Voltage drop in Volt;

I = Load current in Amper;

R =A C Resistance in Ω/km;

X =Reactance in Ω/km;

cos ø = Power factor;

l  = Length in km;

X = ^ωL10-3

 ^ω=2 π f

L = from table mh/km

The limit of voltage drop depends on national code and standards which vary from country to country, and hope we got some basic idea on Voltage Drop for Electrical Power Cable.