This document discusses modern technology trends in power transformers, including on-load tap changers and bushings. It focuses on assessing the condition of transformer insulation using furan analysis. Furan compounds are produced from degradation of cellulose insulation and can indicate the degree of polymerization (DP) remaining. A DP below 200 indicates unsafe insulation conditions. The document recommends regularly performing residual life assessments (RLA) using furan analysis on transformers older than 30 years to determine remaining life without dismantling the unit. This helps ensure grid reliability by identifying transformers in need of replacement.

1. Conference on
MODERN TECHNOLOGY TRENDS IN POWER
TRANSFORMERS INCLUDING OLTC,BUSHINGS ETC,
on 27-28 February 2019 at CBIP Conference Hall, New Delhi

2. SYNOPSIS
 Transformer’s Life above 100kVA - 25 yrs as per MOP’s
notification (March1994).
 40 yrs as per depreciation chart of Company's Act 2013
 EHV Grid network Consists of Large Generator Step-up
Transformers & EHV Transformers.
 RLA studies advised for Grid transformers which rendered
continuous service of more that 30 yrs.
 Shall obviate Grid Disturbance, Grid failure ,Power deficit in
the Grid &/or Unscheduled Load-shedings.
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By K.K.Murty

3. SOLID INSULATIONS IN A TRANSFORMER
 Kraft paper.
 Other paper products;
conductor wraps, crape paper tapes. press board, spacers
and wedges of press-board, barrier boards, and clamps etc.
Major constituents of the paper ;
 Cellulose (about 90%),
 Lignin (about 6.0%) and
 the remainder (about 4.0%).
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4. STRUCTURAL FORMULA OF CELLULOSE
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By K.K.Murty

5. Degradation factor of Cellulose & by-products
Degradation factor of cellulose is mainly thermal.
 When Cellulose is subjected to higher temperature , the beta
linkages ( Glycosidic bonds) tend to break and open the
glucose molecule rings and thereby lose mechanical
strength.
 By-products of this reaction –
i) Free glucose molecules,
ii) Moisture,
iii) CO, CO2,
&
iv) Organic acids.
5By K.K.Murty

6. FURANS
The free glucose molecules degrade further into aromatic
components known as FURANS.
Following are the Furans;
 5H2F (5-Hydroxymethyl-2 Furaldehyde)
 2-Furaldehyde (2FAL)
 5 Methyl-2 Furaldehyde (5M2F)
 2-Acetyl furan (2ACF)
 2 Furfuryl alcohol (2FOL)
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By K.K.Murty

7. Cont;
 2FAL(2Furaldehide) stays stable for several years.
 Other furans are unstable under normal operating
conditions and get converted/degrade into 2FAL in a few
months time.
 The molecular structure of 2-Furaldehyde (2FAL) is shown
in the figure below.
7By K.K.Murty

8. PRIMA- FACIE ANALYSIS OF FURANS.
Prima-facie prevailing condition of the Cellulosic
insulation of Transformers as soon as oil sample is
extracted is as per table below;
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Type of Furan Chemical
identification
Effect of abnormality
5-Hydroxymethyl-2
furaldehyde.
5H2F Oxidation
2-Furaldehyde. 2FAL Overheating, old
faults
5 Methyl-2-
furaldehyde.
5M2F Local sever over heat.
2-Acetyl furan 2ACF lightening
2 Furfuryl Alcohol 2FOL High moisture
By K.K.Murty

9. DP(Degree of Polymerization)
 Analysis of paper insulation for its DP values requires
removal of a few strips of paper from the in-service
Transformers, which is practically not possible.
 Calculation of D P: Some of the scientists of Transformer
Chemistry namely Chendong, Stabins, De Publo and
Pahlav Anppour have innovated different models of
FURAN Contents Vs DP through different empirical
formulae/equations.
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By K.K.Murty

10. FURAN Vs DP - EQUATIONS BY SCIENTISTS;
1) Chendong’s equation;
, where 2FAL in ppm
2) De Pablo’ equation;
, where 2FAL in ppm
3) Pahlav annpour’s equation;
, where 2FAL in ppm
4) Stebbin’s equation
, where 2FAL in ppb
By K K
Murty
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11. GRAPHICAL REPRESENTATION OF DIFFERENT MODELS
OF FURAN Vs DP (Ref.: Slide No.10)
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By K.K.Murty

12. FURAN , DP & % REMNANT LIFE
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Table along side is based on the
Chendong’s model which is widely
used for accessing the remnant life
of a Transformer.
By K.K.Murty

13. NOTE;
 An average DP value of new kraft paper is 1,000 to 1,200.
 During manufacturing and transformer drying process new
paper in a new transformer, has a DP value of 800(approx).
 DP value<200 indicates precarious condition of the paper
(cellulosic) insulation.
 FURANs as diagnostic tool, reasons thereof;
(i)Degradable by-products of paper which are soluble in
Transformer Oil.
(ii)Cannot be produced by Transformer oil.
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By K.K.Murty

14. FLOW CHART OF RLA OF TRANSFORMERS
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15. SPECIMEN PHOTOGRAPHS OF DETERIORATED
PAPER INSULATION
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16. CONCLUSIONS;
 Power Transformers served >30 yrs may be taken up for
RLA studies.
 Since it is a non- invasive test ,thus does not call for
dismantling of transformer for evaluation of condition of
Paper insulation-Degree of Polymerization (DP).
 This test should be included in the Transformer’s
Maintenance schedule at least once in 2-years and data
should be reviewed in conjunction with DGA, Oil
Insulation tests and maintenance history.
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By K.K.Murty

17. END OF PRESENTATION;
 The author expresses his gratitude towards the honorable
distinguish Guests, eminent Engineers, Scientists & other
audiences for patient listening.
 This paper is dedicated to his beloved wife Late Mrs.
K.Vijaya Murty.
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By K.K.Murty