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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What type of fluid can be used to top off a wecosol transformer?
Wecosol Fluid is no longer manufactured or available. It was a fire resistant insulating oil manufactured in the 1980s by Westinghouse. It was made from a mixture of chlorinated solvents and mineral oils. Wecosol Fluid was a very good heat transfer fluid, so a low viscosity hydrocarbon should be used for retrofill, such as Alpha-1 Fluid (PAO based) or a synthetic ester such as Midel 7131 or Cargill Envirotemp 200. Silicone fluid should not be used. .
What is required to turn a LED into a laser diode?
you can't. they are two different things. however you might be able to focus it to a small point with a lens.
It is possible to use an array of hundreds or thousands of high intensity LEDs to pump a dye LASER. But this does not make the LED itself a LASER, just the source of energy for a different type of LASER.
What are the advantages and disadvantages of electrostatic instruments?
What are the advantages and disadvantages manx iron instrument
What is difference between balanced and unbalanced load?
three phase load is said to be balanced when the impedance and power factor of each load is equal.in this condition phasor sum of currents and phase voltages add up to zero.
What is pressure test for transformmer and how to test?
On installed transformer a test is performed to check weather it has any oil leakage or not, the test is called pressure test, more precisely pressure leakage test.
What is bleeding of steam in thermal power plant?
Bleeding of steam means Extracting steam from Turbines for heating the feed-water.
Normally, there are High Pressure Heaters & Low Pressure heaters in Condensate cycle. Steam bleed out from the turbine gets into these heaters and heats up the feed-water (generally termed as Sensible Heat Addition).
The steam that was bled can be re-used as condensate in Deaerators.
Steam Extractions although reduce net work output but helps in overall gain in efficiency in terms of Reduced Fuel Consumption.
What is 8 mega ohms equal to in kilo ohms?
Mega is 8 X 10^6 and Kilo is 8000 X 10^3.
For every 3 you go down in powers you divide by 1000, so 8 Mega ohms is 8,000,000 ohms. 8,000 Kilo ohms or 0.008 Giga ohms.
the first google prank directing users to project their thoughts and visualize what they wanted to see on google
What happens when lagging Power Factor changes to leading PF?
when lagging
Power Factor changes to leading
PF, then the voltage across the circuit in which capacitor bank is connected, is increased.
How is reverse current in a diode produced?
The main reason for produce reverse current in a diode is "MINORITY CARRIERS". For reverse bias diode i.e negative terminal connected to p side and positive to n side the electrons in p side(minority charge carriers) attracted towards the positive polarity i.e towards positive terminal. Hence the current (reverse saturation) flows.Holes also contributed the current by attracting towards negative side.
What are the different types of braking in dc motors?
plugging
rheostatic or dynamic braking
regenerative braking
How do you convert amps to mVA?
You cannot. An ampere (A) is used to measure current. A millivolt ampere (mV.A) is used to measure apparent power. These are two different quantities, so you cannot convert one unit into the other!
Refer to:
International Electrotechnical Commission IEC 836"Specifications for silicone liquid for electrical purposes" (Silicone Fluid Type T-1) and
ASTM D 4652 "Silicone Fluids for Electrical Insulation" specifications for repair or top-off of existing liquid-filled units.
These standards cover both the physical and electrical properties of fluid suitable for dielectric applications.
Also refer following:
IS-335/1993 - Specification for uninhibited new insulating oils.
IS-12463/1988 - Specification for inhibited mineral insulating oils.
IEC -60296/2003 - Specification for unused mineral insulating oils for transformers and switchgear. This standard cover both uninhibited and inhibited oils.
ASTM - D3487/2000-StandardSpecification for Mineral Insulating Oil used in Electrical apparatus. This standard also covers both uninhibited and inhibited oils.
Unused Mineral Insulating oils filled inNew transformers
IS -1866/2000-Code of Practice for Electrical Maintenance and supervision of Mineral Insulating oil in Equipment. (Refer Table.1 for limiting values of various parameters)
IEC -60422/1998-Supervision and maintenance guide for mineral insulating oils in electrical equipment.
In service Mineral Insulating oils:
IS -1866/2000 -Code of Practice for Electrical Maintenance and supervision of Mineral Insulating oil in Equipment.(Refer Table for limiting values of various parameters)
IS-335/1993
Appearance ------------ Clear and transparent
Density at 29.5 deg.C (Max) 0.89 g/cm2
Kinematic Viscosity (Max)
1) at 27deg.C ------------------ 27 cSt
2) at 40deg.C ------------------ Under consideration
IFT at 27deg.C (Min) ---------0.04 N/m
Flash Point (Min) --------- 140deg.C
Pour Point (Max) ---------- 6deg.C
Neutralization Value
1) Total Acidity (Max) ---- 0.03 mg KOH/gm
2) Inorganic acidity ------ Nil
Corrosive Sulphur ------- Non-corrosive
Electric Strength (BDV)
1) New unfiltered Oil (Min) 30 KV (rms)
2) After filteration (Min) If the above value is not attained, the oil shall be filtered to 60 KV (rms)
Dielectric dissipation factor (tan ) at 90deg.C(max) 0.002
Specific resistance (Resistivity)
1) at 90deg.C (Min) 35 x 10 12 ohm-cm
2) at 27deg.C (Min) 1500 x 10 12 ohm-cm
Oxidation Stability
1) Acidity (max) 0.4 mg KOH/gm
2) total sludge (max) 0.1 % by weight
Ageing characteristics
a) Resistivity (Min)
1) at 27deg.C 2.5 x 10 12 ohm-cm
2) at 90deg.C 0.2 x 10 12 ohm-cm
b)Tanδ at 90deg.C (Max) 0.20
c) Total acidity (Max) 0.05 mg KOH/gm
d) Total sludge (Max) 0.05 % by weight
Presence of Oxidation inhibitor -The oil shall contain natural anti oxidant additives.
Water content - 50 ppm
S K value - Under consideration
IS-1866/2000-Recommended Limits of Unused Mineral Oil filled in NewTransformer
Property
Highest Voltage of Equipment (KV)
< 72.5
72.5-170
>170
Appearance
Clear, free from sediment and suspended matter
Density at 29.5 deg.C (g/cm2), Max.
0.89
0.89
0.89
Viscosity at 27 deg C (cst), Max
27
27
27
Flash Point deg. C, Min
140
140
140
Pour Point Deg. C , Max
-6
-6
-6
Total acidity (mg KOH/gm), Max
0.03
0.03
0.03
Water Content (ppm), Max
20
15
10
IFT at 27 degC,(mN/m), min
35
35
35
Tanδ at 90 deg C, Max
0.015
0.015
0.01
Resistivity at 90 deg.C (x10e12 ohm cm Min.
6
6
6
BDV Kv Min
40
50
60
IS-1866/2000-Violation Limits for in service oils
Property
Highest Voltage of Equipment (KV)
< 72.5
72.5-170
>170
Flash Point deg. C, Min
Maximum decrease of 15deg.C from initial value
Pour Point Deg. C , Max
-6
-6
-6
Total acidity (mg KOH/gm), Max
0.3
0.3
0.3
Water Content (ppm), Max
No free water
40
20
IFT at 27 degC, (mN/m), min
1
1
1
Tanδ at 90 deg C, Max
1
1
0.2
Resistivity at 90 deg.C (x10e12 ohm cm Min.
1
1
1
BDV Kv Min
30
40
50
Sediment and Sludge
No sediment or precipitable sludge should be detected.
Results below 0.02% by mass may be neglected
IS-1866/2000 - Frequency of testing
Property
Frequency of Testing
Appearance
In conjunction with other Quantitative tests
Water content
After filling or refilling prior to energizing, then after
three and 12 months, subsequently along with DGA
BDV
After filling or refilling prior to energizing, then yearly
Total acidity
Yearly
IFT
After filling or refilling prior to energizing, then yearly
Resistivity
After filling or refilling prior to energizing, then yearly
Tanδ
After filling or refilling prior to energizing, then yearly
Flash Point
Yearly
Sediment and sludge
Yearly
IS-1866/2000-Recommended Actions
Property
Recommended Actions
Appearance
As dictated by other tests
Water content
Check Source of water and consider reconditioning
BDV
Recondition the oil or alternatively, if more economical or other tests dictate replace oil
Total acidity
Replace or reclaim oil
IFT
Replace or reclaim oil
Resistivity
Replace or reclaim oil
Tanδ
Replace or reclaim oil
Flash Point
Replace the oil, equipment may require inspection
Sediment and sludge
Where sediment is detected recondition the oil
IS-1866/2000 - Classification of oils in service.
Group 1:
This group contains oils that are in satisfactory condition for continued use. The frequency can be followed as described earlier.
Group 2:
This group contains oils that requires reconditioning for further service. (LOW BDV and High water content). The frequency can be followed as described earlier after reconditioning.
Group 3:
This group contains oils in poor condition that it can restore satisfactory properties only after reclaiming. Insulating oils this group should be reclaimed or replaced depending on economic considerations.
Group 4:
This group contains oils, in such poor state that it is technically advisable to dispose of them.
IEC -60296 - General Specification
Functional Properties: Viscosity, Pour point, Water content, BDV, Density, Tan.
Stability Properties: Appearance, Acidity, IFT, corrosive Sulfur, Antioxident additive
Performance Properties: Oxidation Stabillity, Sludge
HSE Properties: Flash Point, PCB content, PCA content
Ashok
Head Engineering & Project Execution
EVI, INDIA
Why are stator cores laminated?
Thin metal laminations are used to minimize the magnetic flux eddy current loss in the stator cores of high-speed, high-performance induction motors.
How do you calculate electric cable copper weight?
wire weight = material_density * 3.14159 * (0.5 * cable_diameter)² * cable_length
example for copper with 152 meter length:
----------------------------------------
material_density for copper = 8960 kg/m³
cable_diameter=0.006 meter
cable_length=152 meter
weight of wire = 8960 kg/m³ * 3.14159 * (0.5 * 0.006)² * 152 = 38.51 kg
lenght and diameter must be calculated in "meters"
density must be in "kg/m³"
How much power can a transmission line carry?
700 Billion volts
AnswerFirst of all, power is expressed in watts, not in volts! Your answer cannot be answered in any straightforward way, because it depends upon too many variables. For example: At what voltage is the transmission line operating? What is the current-rating of its conductors? How many conductors comprise each line? Etc.
When the length is increased 2 times the value for resistivity will be?
The value for resistivity will remain unchanged (provided temperature remains constant). Resistivity is a property of the material. The resistance, however, will double. Remember that resistance is directly proportianal to the length of the conductor and inversely proportional to the cross-sectional area of the conductor.
How do you UNCHARGE a capacitor?
Connect it, in series, to a resistor or a dummy load and a switch. And then throw the switch.
If a 9.0 volt battery is connected to a 4.0-ohm and 5.0-ohm resistor connected in series, the current in the circuit is 1.0 amperes.
If a 9.0 volt battery is connected to a 4.0-ohm and 5.0-ohm resistor connected in parallel, the current in the circuit is 0.5 amperes.
Connected in series or parallel will each bulb glow brighter?
In parallel, each bulb will have full voltage applied across them. However, in series, the voltage across each bulb won't be the same as supply voltage. Thereby, bulbs connected in parallel will glow brighter.
