Transformer life time

This picture show that after the design life time and/or reaching the 60% substances level only a short time of suitable and reliable service is possible.


















The preservation measure resulting in reduction the a going accelerators. The result is that the curve (green) of the residual life time is kept in high levels. A improvement of 5 - 15 years of the useful life time is typical.



Copy from DTC (Daemisch Transformer Consult).

Transformer Oil Test

Periodic inspection on Transformer for example take oil sample for test may prevent abnormalities from being detected early, resulting in malfunction or deterioration of performance.


Procedure:
1. Use glass receptacles so that if any water present it may be readily observed.


2. Rinse sample containers with dry non-leaded gasoline or dry water-white kerosene until they are entirely clean.

Invert and drain to remove excess solvent, and then wash them with strong soapsuds, rinse throughout with water and dry them preferably in an oven at 105C to 110C.


After drying, store them un-stoppered in a dry, dust free cabinet or compartment at a temperature of not less than 35C.

If they are not stored in a hot cabinet, cork or cap the containers immediately after drying.

3. Take samples when the oil is at least as warm as the surrounding air.

Insulating oil is not hygroscopic but cold oil may condense enough moisture from a humid atmosphere to seriously affect its insulating properties.

Take sample from outdoors transformer on a clear day only, and guard against contamination by wind-blown dust, etc.


4. Before taking samples from the transformer, carefully clean the sampling valve and allow enough oil to run out so that any contamination that may have collected in the valve will be removed.


5. Rinse the container several times with the same oil as the sample to remove any contamination that may have collected in the container.

Do not mix these rinsing with oil sample.


6. Carefully seal the containers to prevent leakage or exposure of the oil to atmosphere. Use glass stoppers, clean corks or screw caps to seal the glass receptacles.

If corks are used or if the screw caps contain cork disc inserts, the cork should be covered with tin or aluminum foil.


Testing For Dielectric Strength.
Since the oil is major insulation of the transformer, its dielectric strength must be kept up to the specific values.

If the oil fails to withstand the minimum breakdown kV specified, it is a sign that impurities, particularly moisture have entered it. In this event the oil no longer safe for use as an insulating medium and must be filtered to remove and bring it back to its original conditions.


Colour Test.
The colour test is not too reliable a test in itself, since darkening of the oil does not indicates any particular conditions with certainty.

Discolouration is a rough indication of oxidation but this should be verified by making an acidity (neutralization) test.

In general, the best indication that a colour test can give is that the condition of the oil is doubtful and further test should be made.


These tables below related with Dielectric strength of oil before oil filing and vacum treatment.















These tables below related with degree of vacuum under oil filling, final check of oil quality, energization and dielectric strength of oil for on load tap changer.














Adopted from Toshiba.


















Adopted from Fortum

More info about transformer life time, please click http://idpowerstation.blogspot.com/2011/10/transformer-life-time.html

Note:
IEEE C57104-1991 is Institute of Electrical and Electronic Engineer (IEEE).
TDCG is Total dissolved Combustible Gas.

More information click this http://www.satcs.co.za/Transformer_Oil_Analysis.pdf

Transformator Theory

Transformator consist of two coil electricity insulated from one another and wound on the same iron.

An alternating current in one winding sets up an alternating magnetic flux in the core. Most of this flux links with the other winding and induces in it an alternating electromotive force (emf).

Power is thus transferred from one winding to the other via the flux in the core. The winding to which power is supplied is called the primary that from which power is delivered is called secondary.

The power output of a transformer is necessarily less than power input because of unavoidable losses in the form of heat. The losses consist of I^2.R heating in the primary and secondary winding (the copper losses) and hysteresis and eddy current heating in the core (the core losses). In the spite of these losses, transformer efficiency are usually well over than 90% and in large installation may reach 99%.

For simplicity we shall first consider and idealized transformer in which there are no losses and no leakage flux. Let the secondary circuit be open. The primary winding then functions merely as an inductor. The primary current which is small lags the primary voltage by 90degree and is called the magnetizing current, Im.

Since the same flux links both primary and secondary, the induced emf per turn is the same in each. The ratio of primary to secondary induced emf is therefore to the ratio primary to secondary turns έ2/έ1 = N2/N1

In the idealized case assumed, the induce emf’s έ1 and έ2 are numerically equal to corresponding terminal voltage V1 and V2. Hence by properly choosing the turn ratio N2/N1, any desired secondary voltage may be obtained from a given primary voltage. If V2 > V1, we have step-up transformer; if V2 < V1, a step down transformer.
The vector diagram of the idealized transformer is given picture beside for a turn ratio of N2/N1 =2. The induced emf’s in both primary and secondary, since they proportional to the negative rate of change of flux, will be lag 90degree behind the flux, but since the induce emf in the primary έ1 is back emf, the primary terminal voltage V1 is opposite to it phase (V1 = -έ1).


Consider next the effect of closing the secondary circuit. The secondary current I2 (picture beside) and its phase angle έ2 will, of course, depend on the nature of the secondary circuit. It has been assumed that the load is inductive and hence I2 lags V2. As soon the secondary circuit is closed, some power must be deliver by the secondary (except when έ2 = 90degree) and from energy consideration an equal amount of power must be supplied to the primary.

The process by which the transformer is enable to draw the requisite amount of power is as follows. When the secondary circuit is open, the core flux is produced by the primary current only. But when the secondary circuit is closed, both primary and secondary current step up a flux in the core. The secondary current by Lenz’s law, tends to weaken the core flux and there fore to decrease the back emf in the primary. But (in the absence of losses) the back emf in the primary must equal the primary terminal voltage which is assumed to be fixed.

The primary current therefore increases until the core flux is restored to its original no load magnitude. The vector I1’ represent the change in the primary current that takes place when the secondary delivers the current I2. It is opposite in phase to the secondary current I2 and of such magnitude that its magnetomotive force (N1 I1’) is equal and opposite to the magnetomotive force of the secondary current (N2 I2) that is

N2 I2 = N1 I1’ or

I2 / I1’ = N1 / N2

The resultant primary current I1 is the vector sum of I1’ and magnetizing current Im, But in practice the magnetizing current is never more than a few percent of the full loaf current. Hence I1 and I1’ are practically equal and one may write approximately

I2 /I1 = N1 / N2

That is the primary current and secondary current are inversely proportional to the primary and secondary turn.

The effect of leakage flux and resistance of the winding requires that the primary terminal voltage shall be somewhat large than the primary induced emf and not exactly 180degree out of phase with it. Similarly the secondary terminal voltage is somewhat smaller than and out of phase with the secondary emf.

More info about transformer oil test, please click http://idpowerstation.blogspot.com/2012/04/transformer-oil-test_02.html

Spiritual Journey

For previous please visit http://anto-hendarto.blogspot.com/2013/04/3rd-time-line.html

Leave our routine for a moment and let's pray to God.

1. Preparation to Umrah.
New year 2014 I fell no satisfied in the work, and I didn't enjoy to do my hobbies. I didn't know what should I do. And My wife suggest to me to do something like spiritual thing to refresh our brain. We decided to register to went Umrah at 13 February 2014.

Passport and Visa to Saudi Arabia was not easy to proposed due to many happen to us. First I got dengue fever, second thing my father got stroke and the last thing we got flooded that make my city in Jepara isolation from nearby city especially we have no gasoline and last thing that we had bad news that quota Umrah at 13 February was full.

For a moment I though that God didn't release to me to go Umrah yet but finally that was wrong cause we have quota at 01 February and the rain was not hard anymore. We have a chance to went to Semarang for our Passport and Visa, after that we did meningitis and influenza vaccination. We were ready to went Umrah.



2. Madinnah.

1st Day we gathered together at Semarang at 06:30 and then went to Jakarta for transit. Jakarta - Jeddah take 9 hours by plane and Jeddah - Madinnah take 5 hours by bush.

Here is a beautiful Nabawi mosque that we were there for three days.



We were pray five times per day at this beautiful mosque (06:00Subuh; 12:45Dzuhur; 15:45Ashar; 18:15 Maghrib and 19:30 Isya). We late came once for Maghrib due we thought that time for prayer always delay one hour compare to Indonesia. time. We learn for not look down.


Here is Nabawi Mosque yard with Hotel and Martket as background.




Here in front of Umar bin Khattab Nabawi Mosque gate.



Here is interior if Nabawi Mosque.


















Uhud valley will be appear in heaven. That location for Uhud war where the prophet of Muhammad lead the war against Quraish. In that location too we take a picture together.




2. Macca

As prophet Muhammad went to Mekkah with peace to Quraisy people by wear Ihrom uniform.






Here took from King Abdul Azis Haram mosque gate




Adam down to India and Eva down to Jeddah. They met each other on this location.







Continue to My The 4th Time Lines....

Our Spiritual Journey

Leave our routine for a moment and let's pray to God.

1. Preparation to Umrah.
New year 2014 I fell no satisfied in the work, and I didn't enjoy to do my hobbies. I didn't know what should I do. And My wife suggest to me to do something like spiritual thing to refresh our brain. We decided to register to went Umrah at 13 February 2014.

Passport and Visa to Saudi Arabia was not easy to proposed due to many happen to us. First I got dengue fever, second thing my father got stroke and the last thing we got flooded that make my city in Jepara isolation from nearby city especially we have no gasoline.

We had bad news that quota at 13 February was full. For a moment I though that God didn't release to me to go Umrah yet but finally that was wrong cause we have quota at 01 February and the rain was not hard anymore. We have a chance to went to Semarang for our Passport and Visa, after that we did meningitis and influenza immunization. We were ready to went Umrah.