FOR IN-SERVICE INSULATING FLUIDS
OIL Dielectric > 27KV Acceptable
Water Content < 35 ppm (69 KV or less) Acceptable
< 25 ppm (69 KV-288 KV) Acceptable
< 20 ppm (greater that 228K KV) Acceptable
IFT > 27.1 dynes/cm Acceptable
24.0-27.0 Marginal
18.0-23.9 Bad
14.0-17.9 Very Bad
9.0-13.9 Extremely Bad
< 8.9 Poor
Neutralization# 0.01-0.10 mg KOH/g Good
0.05-0.15 Marginal
0.16-0.30 Bad
0.31-0.60 Very Bad
0.61-1.50 Extremely Bad
> 1.50 Poor
Power Factor < 0.5% Acceptable
DBPC > 0.01% Acceptable
PCB Dielectric > 27 KV Acceptable
Water Content < 75 ppm Acceptable
Neutralization# < 0.040 mg KOH/g sample Acceptable
Silicone Dielectric >27 KV Acceptable
Water Content < 100 ppm Acceptable
Neutralization# < 0.20 mg KOH/g sample Acceptable
ON –SITE TEST REPORTS
ABBREVIATIONS
LIQUID LEVEL
N………………………………………………………………………NORMAL
L……………………………………………………………………….LOW
H………………………………………………………………………HIGH
OTHER ACCESS
TIP…………………………………………………………………….TOP INSPECTION PLATE
CT…………………………………………………………………….CONSERVATOR TANK
PT……………………………………………………………………..POP TOP
Exp. Vnt……………………………………………………………..EXPLOSION VENT
Brthr………………………………………………………………….BREATHER
AP…………………………………………………………………….ACCESS PLATE
COLOR – ASKAREL/SILICONE
WW………………………………………………………………….. WATER WHITE
P/Y…………………………………………………………………… PALE YELLOW
D/Y……………………………………………………………………DARK YELLOW
P/G……………………………………………………………………PALE GREEN
D/G…………………………………………………………………...DARK GREEN
P/B…………………………………………………………………….PALE BLUE
D/B……………………………………………………………………DARK BLUE
PINK…………………………………………………………………..PINK
Amb………………………………………………………………….AMBER
VISUAL
Clr…………………………………………………………………… CLEAR
Cldy………………………………………………………………… CLOUDY
S/Sd………………………………………………………………… SLIGHT SEDIMENT
M/Sd……………………………………………………………….. MODERATE SEDIMENT
H/Sd………………………………………………………………… HEAVY SEDIMENT
S/Cb………………………………………………………………… SLIGHT CARBON
M/Cb………………………………………………………………. MODERATE CARBON
H/Cb……………………………………………………………….. HEAVY CARBON
S/Pt…………………………………………………………………. SLIGHT PARTICULATE
M/Pt………………………………………………………………… MODERATE PARTICULATE
H/Pt………………………………………………………………… HEAVY PARTICULATE
CLASS
GOOD………………………………………………………………GOOD
MARG……………………………………………………………….MARGINAL
BAD………………………………………………………………….BAD
V.BAD……………………………………………………………….VERY BAD
EX.BAD………………………………………………………………EXTREMELY BAD
D.F.F………………………………………………………………….DRAIN, FLUSH, FILL
TC…………………………………………………………………….THERMAL CLEAN
DIELECTRIC
F/Wt………………………………………………………….FREE WATER
DISSOLVED GAS ANALYSIS
IEEE 90% PROBABILITY NORMS (ANSI/IEEE C57.104-1991)
MINERAL OIL FILLED TRANSFORMERS
GAS SYMBOL TRANSMISSION
EQUIPMENT (ppm)
ACETYLENE C2H2 35
HYDROGEN H2 100
METHANE CH4 120
ETHANE C2H6 65
ETHYLENE C2H4 10
CARBON DIOXIDE CO 350
KEY COMBUSTIBLE GASES AND GENERATING CONDITIONS
ACETYLENE: High Energy Arcing
HYDROGEN: Corona (Partial (Discharge)
Electrolysis of Free Water
Arcing (If Acetylene is also present)
METHANE: Generalized Overheating
Secondary Gas
ETHANE: Generalized Overheating
Secondary Gas
ETHYLENE Hot Spot
Severe Localized Overheating
CARBON MONOXIDE Aging/Thermal Decomposition of Cellulose
NON-COMBUSTIBLE GASES
OXYGEN: Less than 5% of Total – Normal Operation
Greater than 5% - Check for tightness of Nitrogen Seal
CARBON DIOXIDE: Check Ratio of CO2/CO
Ratio less than 7 - Cellulose Breakdown
Ratio greater that 7 - Normal
(Note: CO> 500 & CO2 > 500 to improve certainty factor)
NITROGEN: Normal
WHAT IS FURAN ANALYSIS?
The questions often arise,: what are Furans, and is Furan testing beneficial to my existing preventive maintenance plans?”
The solid insulation of a power transformer consists basically of paper in the form of sheets, tapes and other pressed shapes, Heat,
moisture and oxygen primarily cause degradation (aging) of cellulose insulation, which adversely affects the life if the paper.
Degradation of this paper causes it to lose its tensile strength and results in the release of furans.
The main goal of furan testing is to determine whether the paper in a given transformer has been or is being damaged by heat.
Furans produced from temperature buildups are generated in two ways; the first being a localized area of high heat and paper
damage, and the second being the general overall heating of the entire transformer. Early detection of paper insulation breakdown
can prevent major damage of failure to you power transformer.
Before furan analysis, Dissolved Gas Analysis in oil was the only non-invasive test performed on transformers that could indicate
internal problems. By monitoring the ration on CO and CO2 found dissolved in the oil, the paper condition was thought to be
determined. The major disadvantage of this method is that CO & CO2 generation is not entirely s[specific to pare degradation.
Many customers would like to know the present aged condition of their transformers and be able to estimate life expectancy so that
replacement or repair costs can be managed. The systematic use of furan analysis to monitor paper insulation condition promises
to be a useful and complementary technique to dissolved gas analysis (DGA) and other monitoring techniques. A furan test should
be included with annual oil testing programs and trends developed to monitor the condition of the paper.
The preferred method of furanic analysis is by HPLC (High Performance Liquid Chromatography), and ASTM Standard (D5837-95)
has been approved which outlines methodology. It is now possible to measure furanic compounds in the parts per billion levels.
Damage to as little as a few ounces of paper is discernible in an oil sample, even in large transformers.
SUMMARY
1. Furanic compounds are the byproducts if the degradation of the cellulose (paper) insulation.
2. Heat, moisture, and oxygen most often cause paper degradation, with eat being the main factor.
3. Furan Analysis gives an accurate indication of the rate of aging in the insulation system in a transformer.
4. Furan Analysis can help prevent major damage or failure.
5. Furan Analysis can help determine when to rewind or retire a transformer.
INTERPRETATION OF RESULTS
0-100 parts per billion = Acceptable
101-1000 parts per billion = Marginal
Greater than 1000 parts per billion = Unacceptable
OIL CLASSIFICATION SHEET
TEST METHODS AND INTERPRETATIONS
Dielectric D877
This test is capable of revealing just two things; the momentary resistance of a liquid sample to the passage of current, and the
relative amount of free water, dirt or conducting particles present in the sample. Although standards vary from system to system,
most systems accept 27 KV or better as good. A lower break is an indication of damp or dirty oil.
Neutralization Number (Acid Content) D974
The first oxidation product formed in deteriorating oil is peroxide or a series or peroxides. The cellulose of which cotton and paper
are composed react readily with peroxides. The result is oxy-cellulose, a compound which is lacking in mechanical strength.
Embrittlement is the usually applied to the results of attack of peroxides on cellulose. Embrittled insulation cannot withstand the
mechanical shock produced by surges, and the useful life of transformer decreases as this process of embrittlement proceeds. It is
commonly accepted in industry that when the neutralization number exceeds 0.10 mg KOH per gram of oil it is time to take the
corrective action on the oil.
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