Transformer Rectifier Unit

    • Transformer Rectifier Units (TRUs) are utilized to 115 VAC, 400Hz into 28 VDC
    • A transformer is used to reduce the voltage from 115 volts to 28 volts
    • At this point the 28 volts is still AC current
    • To change the current from AC to DC, a rectifier is used
    • Each aircraft AC bus feeds a TRU which feeds a DC bus

    Blogger Labels: Transformer,Rectifier,Unit,TRUs,voltage,aircraft,Units,volts

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Constant Speed Drive

    • The purpose of the Constant Speed Drive (CSD) is to take rotational power from the engine and, no matter the engine speed, turn the generator at a constant speed
    • This is necessary because the generator output must be 400Hz
    • CSD Operation
      • The engine turns the CSD which uses a differential assembly and hydraulic pumps to turn the generator

    Integrated Drive Generator

    • Another method of regulating the generator speed is with the use of an Integrated Drive Generator (IDG)
    • An IDG is simply a CSD and generator combined into one unit
    • There are two ways to mount the IDG:
      • Co-axially
      • Side-by-side

    Blogger Labels: Constant,Drive,purpose,engine,generator,output,Operation,differential,Another,method,unit,Side

ALTERNATING CURRRENT

  • More common in electrical work
  • Changes rapidly in both direction and value
  • Power companies produce power cheaper with alternating current

ELECTRICAL HAZARDS

  • SHOCK. Electric shock occurs when the human body becomes part of the path through which current flows.
  • The direct result can be electrocution.
  • The indirect result can be injury resulting from a fall or movement into machinery because of a shock
  • BURNS. Burns can result when a person touches electrical wiring or equipment that is energized.
  • ARC-BLAST. Arc-blasts occur from high- amperage currents arcing through the air. This can be caused by accidental contact with energized components or equipment failure.

High Voltage Circuit Breakers

  • Electrical power transmission networks are protected and controlled by high-voltage breakers.
  • SF6 gas filled and spring mechanism operated CBs are widely used in modern EHT systems
  • Basic operating principle of these breakers does not vary from any other LV or MV CBs
  • Sulphur hexafluoride (SF6) gas is a good arc quenching medium due to its low ionization property
  • SF6 has good insulation properties too
  • The chambers and the supporting hollow insulators are filled with SF6 gas
  • In the previous picture, the breaker is operated using a gang operated single mechanism box
  • CBs with separate operating mechanism box for each pole are also in use.High Voltage Circuit Breakers
SF6 High Voltage Circuit Breakers

AutoCAD Electrical 2013 Service Pack 1

You can apply this update to AutoCAD Electrical 2013 running on all supported operating systems and languages. 


Be sure to install the correct update (32-bit or 64-bit) for your software and operating system.

The Readme contains the latest information regarding the installation and use of this update. It is strongly recommended that you read the entire document before you apply the update to your product. For your reference, you should save the Readme to your hard drive or print a copy.

This Service Pack can be applied to AutoCAD Electrical 2013 installed as a standalone application as well as AutoCAD Electrical 2013 installed from Autodesk Product Design Suite 2013.

Ace2013_SWL_SP1.exe (exe – 23053Kb)

Ace2013_SWL_SP1_x64.exe (exe – 29499Kb)



Initiate site activities in scope of site management

Project management group and O and M management group plan various preparatory activities to meet L1 demands These include ;

  • Acquiring land,right off way for line/land               – Schedule for finalizing subcontracts
  • Case inflow and case outflow schedule                            – Billing schedule
  • Schedule for training
  • Schedule of submission of drawing documents,check lists to site
  • Schedule of equipment delivery to site
  • Schedule for inputs from the other sources (Governments agencies ,land owners,main customers etc )
  • Communication facilities,telephones,telex,wireless,fax,internet,radio communication,power line carrier communication
  • Personal computer facility and networking .                – Survey of transportation route
  • Insurance policies for plant equipment and third party for ETC phase and O and M phase
  • Schedule for safety facilities                           – Schedule for safety procedures
  • Schedule for site organization and manning for ETC phase and O and M phase
  • These schedules are also monitored on monthly basis

ANSI / IEEE Codes for Protection Functions

ANSI / IEEE Codes for Protection Functions
Code
Function Description
Application Area
Feedes
Transformers
Generators
Motors
Cap. Banks
2
Time delay
x
x
x
x
x
12
Over speed
x
x
21
Impedance Relay (Distance Protection)
x
x
21G
Distance Relay – earth Fault
24
Over excitation
x
x
25
Synchronising check
x
x
26
Over / under temperature
x
x
x
27 / 59
Under voltage / Over Voltage – ac
x
x
x
x
x
30
Annunciator
x
x
x
x
x
32
Reverse Power (Directional Power)
x
x
32P
Reverse Power (Directional Power) – Active
x
x
32Q
Reverse Power (Directional Power) – Reactive
x
x
37
Under Power / Under curent
x
x
38
Bearing Temperature
x
x
39
Bearing Vibration
x
x
40
Loss of field
x
x
43
Manual transfer switch
x
x
45
DC Over voltage
x
46
Reverse phase / phase balance current relay
x
x
x
x
x
47
Phase sequence / phase reversal voltage
x
x
x
49
Thermal Over load
x
x
x
x
50
Instantaneous Over Current
x
x
x
x
x
50N
Instantaneous Earth Fault
x
x
x
x
x

OPERATION INDICATOR

 Generally, a protective relay is provided with an indicator that shows when the relay has operated to trip a circuit breaker. Such “operation indicators” or “targets” are distinctively colored elements that are actuated either mechanically by movement of the relay’s operating mechanism, or electrically by the flow of contact current, and come into view when the relay operates. They are arranged to be reset manually after their indication has been noted, so as to be ready for the next operation. One type of indicator is shown in Fig. 2. Electrically operated targets are generally preferred because they give definite assurance that there was a current flow in the contact circuit. Mechanically operated targets may be used when the closing of a relay contact always completes the trip circuit where tripping is not dependent on the closing of some other series contact. A mechanical target may be used with a series circuit comprising contacts of other relays when it is desired to have indication that a particular relay has operated, even though the circuit may not have been completed through the other contacts.

FUNDAMENTAL RELAY-OPERATING PRINCIPLES AND CHARACTERISTICS

Protective relays are the “tools” of the protection engineer. As in any craft, an intimate knowledge of the characteristics and capabilities of the available tools is essential to their most effective use. Therefore, we shall spend some time learning about these tools without too much regard to their eventual use.

GENERAL CONSIDERATIONS

All the relays that we shall consider operate in response to one or more electrical quantities either to close or to open contacts. We shall not bother with the details of actual mechanical construction except where it may be necessary for a clear understanding of the operation. One of the things that tend to dismay the novice is the great variation in appearance and types of relays, but actually there are surprisingly few fundamental differences. Our attention will be directed to the response of the few basic types to the electrical quantities that actuate them.

OPERATING PRINCIPLES

There are really only two fundamentally different operating principles:
(1) electromagnetic attraction, and
(2) electromagnetic induction.

Electromagnetic attraction relays operate by virtue of a plunger being drawn into a solenoid, or an armature being attracted to the poles of an electromagnet. Such relays may be actuated by d-c or by a-c quantities. Electromagnetic-induction relays use the principle of the induction motor whereby torque is developed by induction in a rotor; this operating principle applies only to relays actuated by alternating current, and in dealing with those relays we shall call them simply “induction-type” relays.

Understanding ground resistance testing soil resistivity

Why Measure Soil Resistivity?


Soil resistivity measurements have a threefold purpose. First, such data are used to make sub-surface geophysical surveys as an aid in identifying eor locations, depth to bedrock and other geological phenomena. Second, ersistivity has a direct impact on the degree of corrosion in underground pipelines. A decrease in resistivity relates to an increase in corrosion activity and therefore dictates the protective treatment to be used. Third, soil resistivity directly affects the design of a grounding system, and it is to that task that this discussion is directed. When designing an extensive grounding system, it is advisable to locate the ar ea of lowest soil resistivity in order to achieve the most economical grounding installation.

Effects of Soil Resistivity on Ground Electrode Resistance Soil resistivity is the key factor that determines what the ersistance of a grounding electrode will be, and to what depth it must be driven to obtain low ground resistance. The resistivity of the soil varies widely thorughout the world and changes seasonally. Soil resistivity is determined largely by its content of electrolytes, which consist of moistur e, minerals and dissolved salts. A dry soil has high resistivity if it contains no soluble salts 
Resistivity (approx), W-cm
Soil
Min
Average
Max
Ashes,cinders,brine,waste
590
2370
7000
Clay,shale,gumbo,loarn
340
4060
16300
Same with varying proportions of sand and gravel
1020
15800
135000
Gravel ,sand,stones with little clay or loarn
59000
94000
458000