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Title: TRANSFORMER%20OIL%20PROCESSING


1
  • TRANSFORMER OIL PROCESSING
  • Paul J. Hodgson B.Sc (Hons) (Wales), M.Sc
    (Edinburgh) Executive Vice-President, Redragon
    Oil Gas Systems International Inc., Cambridge,
    Ontario, Canada
  • Introduction
  • Techniques in Processing Electrical Oils
  • Processing on Energised Transformers
  • Regeneration of Used Electrical Oil
  • PCB Dechlorination
  • Tests

2
Introduction
  • Electricity is transmitted at very high voltages
    to minimise losses
  • High voltages are not practical for everyday use
  • Voltages are transformed to lower, safer levels
    in a number of steps
  • - Power, transmission and distribution
    transformers

Transmission transformer- Incoming (primary)
voltage 150,000 V, 121 A Outgoing (secondary)
voltage 20,000 V, 909 A
3
Function of oil
  • Insulation very high voltage
  • differences between different parts of the
    transformer
  • Cooling conversion from one voltage to another
    is not 100 efficient. There are losses caused
    by the transformation process that are
    manifested as heat

4
1. Techniques in Processing Electrical Oils
5
  • Impurities in transformer oil are unavoidable
  • Primary impurities are moisture and dissolved
    gases and usually accompanied by solids
  • Secondary impurities consist of solids
    (colloidal), acidity, gas and moisture (product
    of oxidation)

6
Moisture
  • Sources of moisture in transformer oil are
  • - residual moisture of new transformer oil
  • - residual moisture in insulation
  • - moisture adsorbed from surrounding atmosphere
  • - moisture as a by-product of oxidation
  • Major transformer manufacturers recommend
    insulation dryness be below 0.5 and oil dryness
    below 10 ppm of water
  • When transformer paper temperature increases,
    some of its moisture is released and absorbed by
    oil until equilibrium is reached

7
Moisture (cont)
8
Moisture (cont)
9
Moisture (cont)
10
Moisture (cont)
11
Air Gas
  • Individual components of air are found in oil in
    the following composition
  • Non-fault gases
  • - nitrogen approximately 70
  • - oxygen approximately 30
  • Oil solubility at static equilibrium at
  • 760 mm Hg and 25oC
  • - hydrogen 7 by volume
  • - nitrogen 8.6
  • - oxygen 16
  • - methane 30
  • - acetylene 400
  • - carbon dioxide 1200
  • - butane 2000
  • Transformer oils normally are stored under dry
    air or dry nitrogen atmospheres. The advantage
    of nitrogen blanketing is that in the absence of
    oxygen transformer oil cannot deteriorate

12
Air Gas
(Fault gases)
From DiGiorgio, NTT, 2005
13
Solids - Noncolloidal
  • Mechanical particles gt0.1 micron are considered
    non-colloidal
  • Solid particle contamination in transformer oil
    influences the dielectric strength
  • Two main sources of solids contamination
  • - cellulose insulation
  • - dust during transformer manufacture

14
Solids Non-colloidal
15
Solids - Colloidal
  • Solid particles lt0.1 micron are considered
    colloidal. These particles are small enough to
    be kept in suspension indefinitely
  • Aging process of the oil is the main source of
    colloidal contamination
  • Flocculation process creates colloidal particles
  • In flocculation, particles of a few Angstroms in
    diameter unite into larger complexes of a max.
    diameter of 0.05 to 0.1 micron

16
Acidity
  • Aging of transformer oil is accelerated by
    temperature and the presence of oxygen and
    moisture
  • Process of aging starts from oxidation of oil by
    dissolved oxygen
  • Initial products of oxidation include organic
    acids of low molecular weight, peroxides,
    alcohols and ketones
  • Later polymerization of unsaturated hydrocarbons
    precipitates into a sludge

17
Acidity (cont)
  • Sludge depositions and a increase in oil
    viscosity are the main factors in insulation
    overheating and the formation of colloidal carbon
  • Acidity increases the affinity of oil for
    moisture and accelerates the process of
    flocculation
  • The acceptable acidity limit of transformer oil
    in operation is 0.3 mg KOH/mg oil. New
    transformer oil acidity should be below 0.03 mg
    KOH/mg oil

18
Acidity increase with time
19
Definition of terms
  • Filtration particle removal
  • Dehydration water removal
  • Degasification removal of gas
  • Purification all of the above
  • Regeneration acidity, colour
  • Desludging sludge dissolution
  • Anti-oxidant DBPC blend-back

20
Oil Processing Techniques
  • Maintenance of transformer oils falls into two
    categories
  • - preventative maintenance
  • - restorative maintenance
  • Regular preventative maintenance includes regular
    care for desiccant breathers, nitrogen blanketing
    systems and monitoring of proper additives level
  • Restorative maintenance represents an attempt to
    return the contaminated oil and insulation to its
    original or as-new quality

21
Filtration
  • Main purpose to remove solids from transformer
    oil
  • Cartridge type filters most popular
  • Surface type filter cartridges with ratings of
    0.5 to 15 microns most practical for transformer
    oil applications
  • Pleated paper design gives very large filtration
    area in a limited amount of space

22
Processing of Oils with Fullers Earth
  • The term Fullers Earth is applied to any clay
    which has an adequate decolorizing and purifying
    capacity
  • Attapulgus clay deposits found in Georgia and
    Florida possess superior decolorizing and
    adsorption powers
  • Activated Fullers Earth structure is highly
    porous and its active structure reaches more than
    100 m2/gram

23
Processing of Oils with Fullers Earth (cont)
  • The order of sorbtivity of various substances by
    Fullers Earth
  • - water
  • - alcohols
  • - acids
  • - aldehydes
  • - ketones
  • - n-olefins
  • - neutral esters
  • - aromatics
  • - cycloparaffins
  • - paraffins

24
Processing of Oils with Fullers Earth (cont)
  • Purification of oils by Fullers Earth includes
    the following actions
  • - filtration
  • - adsorption
  • - catalytic activity
  • Different methods of Fullers Earth purification
  • - contact method
  • - fixed bed method
  • - throwaway cartridges
  • - re-fillable canisters or bags

25
Fullers Earth Flow Schematic
26
Fullers Earth equipment
27
Thermo-Vacuum Treatment of Transformer Oils
  • Most economical method in the removal of
    dissolved water and gases in EHV transformers
  • Water present in oil in excess of the soluble
    water could be removed by heating oil to 120oC
  • With the use of vacuum, water can be boiled out
    of oil at room temperature
  • This vacuum process prevents overheating and
    oxidation of the oil
  • Removal of air and other gases from oil is an
    added benefit of vacuum treatment

28
Thermo-Vacuum Flow Schematic
29
Thermo-Vacuum Treatment of Transformer Oils (cont)
  • The maximum oil surface exposure to the effect of
    vacuum for a certain length of time is the most
    important factor in effective removal of
    dissolved water and gas
  • Methods to expose oil to vacuum
  • - spray nozzle (high surface tension of oil
    droplets causes problems)

30
Thermo-Vacuum Treatment of Transformer Oils (cont)
  • Raschig rings (adhesion of oil to surface of
    rings causes problems)
  • - fibreglass coalescing (vacuum depth penetration
    an issue)
  • - centrifuge bowl spray (not very effective)

31
Mobile Transformer Oil Treatment Plant
  • Most newer transformers are designed for full
    vacuum therefore suited for dry-out by vacuum
    technique
  • Typical single pass performance 100 ppm to lt10
    ppm
  • 12 to lt0.25
  • Mobile transformer oil treatment plant can
    consist of the following
  • - Thermo-vacuum unit
  • - Fullers Earth filtration system
  • - Extra capacity vacuum pump
  • - Extra capacity oil heater
  • - Additive (DBPC) injection package
  • - Electric cables, oil and vacuum hoses
  • - Instrumentation for continuous automatic
    monitoring of oil quality (e.g. hygrometer,
    vacuum controller, BDV, etc.)

32
Mobile Transformer Oil Treatment Plant
33
  • Primary contamination in transformers is water,
    gas and solid particles
  • Secondary contamination (aging of oil) develops
    under electrical stress in the presence of
    primary contamination
  • Complete removal of primary contamination can
    only be accomplished by the thermo-vacuum
    technique

34
  • Adsorption treatment by Fullers Earth treatment
    removes products of aging
  • Designed concept of packed columns of Fullers
    Earth cost effective
  • Thermo-vacuum process along with Fullers Earth
    treatment reconditions oil as well as facilitates
    transformer dry-out

35
Summary of effects of treatment on a transformer
36
Section end
37
2. Processing on Energised Transformers
38
WARNING! WARNING!
It can be extremely dangerous to work on live
transformers Utmost care must be taken Use
experienced personnel only Fatal injury could
occur
39
Grounding
  • Ensure that the oil processing system is earthed
  • Dangerous voltages can, under exceptional
    circumstances, be transmitted from the
    transformer to the oil processing system,
    resulting in the oil processing system floating
    up to these voltages. The system must be
    properly earthed. At the very least the grounding
    rod should be made from 10mm diameter galvanised
    steel and connected to the system with suitable
    copper braided flex.
  • A connection to the transformer grounding cable
    should also be made.
  • It is also advisable to ensure that any earth
    cable brought into the system for the purpose of
    supplying power is firmly connected at both ends
  • Use wire braided hoses

40
Grounding Hotstick/Barehand clearances
41
Grounding
42
Grounding
43
Before starting (1)
  • Ensure that the oil processing system is filled
    with oil to
  • just below the High Oil Level point in the
    vacuum
  • chamber.
  • It is imperative that when the system is first
    switched on and oil flow begins that there is no
    net loss of oil into the system as this runs the
    risk of draining the conservator and exposing the
    bushings in the transformer.

44
Chamber oil level
45
Before starting (2)
  • Ensure that both the inlet and outlet oil hoses
    are filled with
  • oil.
  • For the same reason, there must not be a net loss
    of oil from
  • the transformer and the possibility of
    introducing air into the
  • transformer must be minimised
  • (This can be easily accomplished with the TOLMS)

46
Before starting (3)
  • Ensure that top up oil is available and close to
    hand.
  • Under certain conditions, where the transformer
    is very wet, there will be settling out of
    free water at the bottom of the transformer. It
    is advisable to drain as much of this free water
    as possible before connecting to the oil
    processing
  • equipment. This must be done slowly. It is
    critical to observe
  • the transformer oil level when draining
    water as the fluid level will drop.

47
Before starting (4)
  • Under no circumstances must the fluid level drop
    below the
  • minimum level indicated on the conservator
    tank, as there is a
  • risk that the bushings will become exposed,
    resulting in a
  • flashover.
  • If a great deal of water is being drained it is
    advisable to
  • top-up the transformer from the top-up oil
    supply via the oil
  • processing plant. Recirculate oil within the
    oil processing
  • system to heat it and degasify it and then
    slowly top-up the
  • transformer. Repeat until all the free water
    has been drained
  • from the transformer.

48
Operating procedure (1)
If using the TOLMS, attach the level sensor and
inlet solenoid valve assembly to outlet
connection on the bottom of the
transformer. The level sensor is a pressure
sensor that will operate on transformers that are
up to 20m high. The absolute sensor output is not
critical, the concern is only for changes to the
reading. It is important to allow the sensor
reading to stabilise for 30 minutes prior to
using the automatic shut-off system. Changes in
the level of the oil in the transformer will
produce changes in the output of the sensor. If
the sensor reading moves too much the plant will
close the inlet solenoid valve and shutdown as it
assumes that there is a leak of oil out of the
system. Small changes in the oil level in the
transformer are permitted, as they are not
critical and will happen as the oil processing
system cycles between high and low level
49
Operating procedure (2)
Attach a one-way (check) valve on the far end of
the outlet hose, ensuring flow is from the oil
processing system into the conservator. This
valve will prevent any possibility of the vacuum
level in the oil processing system from draining
the conservator. If the TOLMS is available then
this step is not required see flow schematic
50
Operating procedure (3)
Connect the oil hoses to the transformer Make
sure the hoses are filled with oil! This
requires great care and is potentially one of the
most dangerous aspects, especially connecting the
outlet hose from the oil processing system to the
top of the transformer or conservator tank if
flange on body is not available. It is highly
recommended that the transformer should be
switched off to make these connections Great
care is needed to avoid approaching the live
terminals too closely. (10kV will jump 3cm)
51
Visualization
52
TOLMS
53
TOLMS
54
TOLMS
55
TOLMS
56
TOLMS
57
Start slowly!
Prior to opening the valves on the transformer it
is advisable to prepare the oil processing system
by internally recirculating oil that is in the
system i.e. having bypass open and inlet and
outlet closed. If the TOLMS is used then the
oil should be circulated around with V-203, V-204
open and V-201, V-202 closed. Once this oil has
reached temperature, processing of the
transformer can begin.
58
Start slowly!
Monitor the conservator oil level at all times at
this early stage. Slowly open the inlet valve
and outlet valve on the oil processing system and
also any manual valve on the inlet and outlet
from the bottom of the transformer. Slowly close
the recirculating valve. Oil is now flowing
through the system and the level will be
monitored automatically
59
Start slowly!
Important note If the transformer is relatively
small compared to the oil processing equipment
then do not process on full flow. Throttle the
inlet and outlet valves down or partially open
the internal recirculation valve. As a rule of
thumb, do not exceed 10 of the oil volume,
expressed as a flow rate e.g. 10,000 litres of
oil maximum flow rate 1,000 litres per hour
60
During processing. (1)
  • If the TOLMS is not used then a great deal of
    vigilance is required!
  • The conservator level must be monitored at all
    times !
  • The condition of the hoses must be monitored at
    all times!
  • The flow rate must be monitored at all times

61
During processing. (2)
Oil volume in a transformer changes with
temperature The volume of oil in the transformer
changes significantly between day time and night
time. It may be necessary to temporarily top-up
the oil during night time operation, especially
if the TOLMS is being used. This oil can be
drained during the day time shift. Take care
when introducing oil into the unit, minimise the
chance of air getting into the system.
62
Shutdown
Normal Shutdown Switch off the heaters, wait 30
minutes. Open the recirculating valve on the
degasifier. Close the outlet valve at the bottom
of the transformer and the inlet valve on the oil
processing system. Continual running oil out of
the degasifier until the oil level is at the
desired level in the transformer. Control this
via the recirculating valve and the outlet valve.
Remember that this level will drop when the
transformer cools down. Close the inlet valve on
the transformer. The transformer is now isolated
(deep breath!)
63
Shutdown (continued)
Switch off the inlet pump. Close the outlet valve
and switch off the outlet pump. Close the
recirculating valve. If possible shutdown the
transformer for 5 minutes. If not possible then
carefully remove the hoses from the transformer
and remove the oil level sensor and inlet
solenoid valve assembly.
64
Shutdown
EMERGENCY Once the oil level in the conservator
reaches the Minimum oil level, it is crucial to
prevent any further drop in oil level. CLOSE
THE OUTLET VALVE AT THE BOTTOM OF THE TRANSFORMER
FIRST and worry about the oil processing system
last! Once the outlet valve of the transformer is
closed no more oil will leave the transformer and
there is time for an orderly evaluation of the
problem that caused the oil level to drop
65
What Can Go Wrong?
  • Tripping of the Bucholtz relay the relay will
    not trip on a small or infrequent
    release of bubbles but will if the amount of
    introduced air is large. Proper design of the
    degasifier will minimise this possibility.
  • Oil leakage from burst hoses the TOLMS will
    minimise the risk of the transformer flashing
    over internally through lack of oil.
  • Float-up of the degasifier proper grounding
    and wire-braided hoses will minimise this.
  • Flash-over of the transformer through dumping
    of contaminants into the transformer e.g. sludge,
    free water. Correct operational procedure will
    minimise this risk

66
Remember.
  • Not every transformer can be processed energised
    if the oil test shows poor results, process
    off-line! It is not worth getting killed to
    process online.

67
Heads Up! Oil parameters..
  • Free water where possible do not process
    on-line where free water exists. If it must be
    processed on-line, drain as much free water as
    possible from the transformer, taking all
    precautions to maintain the correct oil-level in
    the transformer. Free water introduced into the
    degasifier will destroy the vacuum level.
  • Dissolved water a limit of 50 PPM should be
    observed. Over this value, consider off-line
    processing.
  • Acidity if higher than 0.2 mg KOH/mg, check
    for physical appearance of sludge. If present,
    consider off-line processing.

68
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69
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70
Section end
71
3. Regeneration of Used Electrical Oil
72
WHAT IS REGENERATION ?
  • Regeneration is the procedure followed if oil
    purification is insufficient to return the oil to
    an acceptable condition
  • Regeneration is the restoration of the oil to, or
    better than, virgin oil specifications

73
HISTORY OF REGENERATION
  • 1940 Burmah-Castrol in UK
  • 1975 Castrol South Africa
  • 1980 Fluidex (SA), Filtervac (Canada)
  • 1994 Enviroil (SA)
  • 1998 Enervac (Canada)
  • 2004 Redragon (Canada)

74
WHEN TO REGENERATE ?
75
WHEN TO REGENERATE
  • Usually, but not exclusively, determined by
    acidity level of oil

76
IFT vs. NN
Courtesy TMI
77
OIL PROPERTIES
Courtesy TMI
78
Why is NN important
  • Acidity dissolves transformer components
  • Leads to build-up of sludge
  • Reduces cooling effects of oil
  • Transformer overheats, leading to more rapid
    build-up

79
When to regenerate (2)
  • Critical Neut Number is around 0.2, above this
    point increase in acidity is exponential
  • Many utilities will consider regenerating oil as
    low as 0.05
  • Generally, the larger the transformer the lower
    the NN

80
Two methods of regeneration
81
Two methods of regeneration (cont)
82
Two methods of regeneration (cont)
83
Operational oil parameters
84
Typical Before and After
by Rondar. Results are per Rondar test reports T
2003-0565 and T 2003-0566 on oil scrapped by GE
Burlington
85
Overview
86
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87
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88
A panacea? No..
89
Waste streams - 2,000,000 litres of oil recovered
  • Gaseous none
  • (clean air)
  • Liquid 8,000 litres
  • (acidic oil)
  • Solid 850 kg
  • (spent activated carbon can be regenerated)

90
Other applications
  • Polishing stage of used engine oil recycling
    plant
  • Replacement of disposable Fullers Earth in palm
    oil refining

91
Used engine oil recycling
  • Polishing stage of thin film vacuum distillation
    plant that produces as new N100 and N300 cuts
    (and asphalt filler) from used crankcase oil

Courtesy PESCO
92
PROS' CONS' OF REGENERATION ?
  • LIFE EXTENSION OF A LIMITED RESOURCE
  • It is environmentally criminal not to recycle and
    reuse a limited resource.
  • Regeneration technology has a long history which
    shows that recycled oil is as good as, if not
    better than new. The same oil that has been aged,
    regenerated, aged and regenerated 6 times shows
    no decrease in efficiency showing an effective
    lifetime for oil-in-use of over 100 years.
  • Modern waste stream technologies and management
    minimise the environmental loading from the
    reactivation technique to a fraction of
    replacement oil and traditional non-reactivation
    technique loading.

From work by George Hodgson and ESKOM, South
Africa, 2001
93
PROS' CONS' OF REGENERATION ?
  • ECONOMICALLY ADVANTAGEOUS
  • The price of purchasing regenerated oil is
    typically less than 80 of new oil and can be as
    low as 50.
  • Ancillary savings increment when considering
    there is no downtime when reclaiming on energised
    equipment. Replacement with new oil and hot oil
    flush requires equipment switch off.

94
PROS' CONS' OF REGENERATION ?
  • CONTROL OF ASSET RETAINED
  • Oil in use is an asset.
  • Use of regeneration technology removes dependence
    on oil companies to deliver replacement supplies
    and isolates from wildly fluctuating external
    market prices.
  • Large organisations with their own reclamation
    systems are further insulated.

95
PROS' CONS' OF REGENERATION ?
  • PCB contamination is not removed
  • Level of the contaminant is only negligibly
    affected.
  • Virgin oil does not contain PCB. PCBs can be
    removed from regenerated oil through chemical
    treatment of the oil at an added cost.

96
PROS' CONS' OF REGENERATION ?
  • Initial equipment capital cost could be high
  • Minimum oil quotas are required to offset the
    capital cost.
  • New system costs typically start around
  • US 400,000

97
MOBILE CONFIGURATION
98
MOBILE CONFIGURATION
99
MOBILE CONFIGURATION
100
SEMI-MOBILE CONFIGURATION
101
STATIC CONFIGURATION
102
STATIC CONFIGURATION
103
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104
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105
Summary of effects of treatment on a transformer
106
WHAT ITS ALL ABOUT!
107
Section end
108
4. PCB Dechlorination
109
The PCB Story
  • Polychlorinated biphenyls were first synthesized
    in 1881
  • Excellent properties fire-resistant, very
    stable, insulating, low volatility
  • Generic name Askarel (40 to 70 PCB)
  • Brand names Aroclor (US) Kanechlor (Japan)
    Pyranol (US) Santotherm (Japan) Pyroclor (US)
    Fenchlor (Italy) Phenoclor (France) Apirolio
    (Italy) Pyralene (France) Clophen (Germany)
    Sovol (USSR) Elaol (Germany)

110
The PCB Story (cont)
  • However found to be toxic and by-products fatal
  • Production banned in North America in 1977
  • /- 635,000,000 kg produced in North America
  • Used in transformers, capacitors plus other
    non-electrical applications

111
The PCB Story (cont)
  • Most countries have a maximum allowable limit of
    50 PPM but this is coming down (2 PPM?)
  • Even developed countries have problems (UK,
    Spain)
  • Two main treatment options
  • Incineration (gt1200C, O2 rich, gt2s)
  • Chemical treatment (Na, K)

112
The PCB Story (cont)
  • Polychlorinated biphenyls, commonly known as
    chlorobiphenyls or PCBs, are a group of
    halogenated aromatic hydrocarbons (arenes)
    characterized by the biphenyl structure (two
    phenyl rings (C6H5)2) and at least one chlorine
    atom substituted for hydrogen. The chlorine
    atoms can be attached at any of the ten available
    sites. In theory there are 209 congeners but
    only approximately 130 congeners have actually
    been used in chemical formulations (Holoubek,
    2000). Typically 40-60 of the 10 possible
    substitution sites are occupied with chlorine
    atoms (four to six chlorine atoms) (Environment
    Canada, 1988). Some regulatory agencies only
    regulate those congeners that have at least two
    chlorine atoms attached. They are virtually
    insoluble in water and very resistant to thermal
    and biological degradation.
  • Source Basel Convention, September 2002

113
Chemical Treatment
  • Continuous

114
Chemical Treatment
  • Batch

115
Frequently Asked Questions
  • Who developed the process
  • In which countries has the technology been
    used.
  • How long has the process been in successful
    operation
  • Detailed description of the process and
    technology
  • Total waste from 1500 litres at 50 PPM PCB
  • What are the waste products
  • What is the operational cost of the unit
  • What is the cost to buy the unit

116
Who developed the process
  • The process was developed in Canada by
    Ontario Hydro and BC Hydro. The process was
    developed in 1982. Both utilities have been
    operating units since the mid-1980s and have
    current Canadian Ministry of Environment
    approval.
  • The process was independently developed in the
    US around the same time.

117
In which countries has the technology been
used.
  • Canada, United States, Mexico, Japan, United
    Kingdom, France, Spain and Australia are
    countries that have used or use this technology.

118
How long has the process been in successful
operation
  • For approximately 20 years. The first Ontario
    Hydro unit was delivered in 1982.
  • By 2001, BC Hydro had reclaimed 15,000,000
    litres of contaminated oil for re-use.

119
Detailed description of the process and
technology
  • General
  •  
  • A PCB treatment system comprises of several steps
    and the unit is comprised of several modules to
    achieve this end-
  •  
  • A degassification module primary function is to
    remove any water in the oil down to a known level
    of around 10 PPM
  • A sodium dispersion system this module controls
    the amount of sodium introduced into the mixing
    tanks
  • The mixing tanks this is the section of the
    system where the PCB contaminated oil is mixed
    with the sodium dispersion and the PCBs are
    converted to harmless by-products

120
Detailed, comprehensive description of the
process and technology
  • The nitrogen purge system this module controls
    the nitrogen blanket above the mixed volume and
    also in the sodium module
  • The chiller package is used to take out any
    remaining condensables in the treated oil and
    reduce the temperature of the oil prior to
    treatment in the (optional) centrifuge module
  • The centrifuge module this option is used to
    accelerate the return of treated oil back into
    service. If a tank farm principle is used then
    this is not required.

121
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122
Total waste from 1500 litres at 50 PPM PCB
  • Total waste will be approximately 7 kilograms
    based on above parameters.

123
What are the waste products
  • 49.8 filterable oil   
  • 30.9 sodium chloride   
  • 10.0 un-saponifiables   
  • 5.4 NaOH   
  • 0.8 Fatty acid esters   
  • 0.8 sodium carbonate   
  • 1.3 sodium soap   
  • 0.1 asphalt and tar   
  • Non-detectable PCB, dioxin and di-benzo furane   
       
  • 60 of sludge is water soluble. SG 0.95, flash
    point gt100C, pH between 12 - 14

124
What is the operational cost of the unit
  • This is dependent on local labour rates but in
    a study performed by Ontario Hydro, based on two
    operators, shows the cost to recover 1 litre of
    oil contaminated at 200 PPM PCB is US 20 cents,
    excluding capital financing costs.

125
Federal discharge criteria
126
Section end
127
5. Tests
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Significance of tests
  • Aniline Point (D 611) The aniline point is the
    temperature at which a mixture of aniline and oil
    separates. It provides a rough indication of the
    total aromatic content, and relates to the
    solvency of the oil for materials which are in
    contact with the oil. The lower the aniline
    point, the greater the solvency effect.
  • Carbon Type Composition (D 2140) The carbon type
    composition characterizes an insulating oil in
    terms of the percentage of aromatic, naphthenic,
    and paraffinic carbons. It can be used to detect
    changes in oil composition and to relate certain
    phenomena that have been demonstrated to be
    related to oil composition.
  • Color (D 1500) The color of a new oil is
    generally accepted as an index of the degree of
    refinement. For oils in service, an increasing or
    high color number is an indication of
    contamination, deterioration, or both.

From Doble Engineering, 2005
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Significance of tests
  • Corrosive Sulfur (D 1275) This test detects the
    presence of objectionable quantities of elemental
    and thermally unstable sulfur-bearing compounds
    in an oil. When present, these compounds can
    cause corrosion of certain transformer metals
    such as copper and silver.
  • Dielectric Breakdown (D 877, D 1816) The
    dielectric breakdown is the minimum voltage at
    which electrical flashover occurs in an oil. It
    is a measure of the ability of an oil to
    withstand electrical stress at power frequencies
    without failure. A low value for the
    dielectric-breakdown voltage generally serves to
    indicate the presence of contaminants such as
    water, dirt, or other conducting particles in the
    oil. Method D 1816 is more sensitive than Method
    D 877 to contaminants that lower the
    dielectric-breakdown voltage and is the preferred
    method for assessing the intrinsic breakdown
    strength of an oil.

From Doble Engineering, 2005
130
Significance of tests
  • Water Content (D 1533) A low water content is
    necessary to obtain and maintain acceptable
    electrical strength and low dielectric losses in
    insulation systems.
  • Flash Point (D 92) The flash point is the minimum
    temperature at which heated oil gives off
    sufficient vapor to form a flammable mixture with
    air. It is an indicator of the volatility of the
    oil.
  • Furanic Compounds (D 5837) Furanic compounds are
    generated as byproducts of the degradation of
    cellulosic materials such as insulating paper,
    pressboard, and wood. These compounds serve as
    indicators of insulation degradations. Because
    they are dissolved in the oil, furanic compounds
    can readily be sampled and tested by high
    performance liquid chromatography (HPLC). No
    significant quantity should be detected in new
    oils.

From Doble Engineering, 2005
131
Significance of tests
  • Impulse Breakdown Voltage (D 3300) The impulse
    breakdown voltage is the voltage at which
    electrical flashover occurs in an oil under
    impulse conditions. It indicates the ability of
    an oil to resist transient voltage stresses such
    as those caused by nearby lightning strokes and
    high-voltage switching surges. The results are
    dependent on electrode geometry, spacing, and
    polarity.
  • Interfacial Tension (D 971) The interfacial
    tension of an oil is the force in dynes per
    centimeter required to rupture the oil film
    existing at an oil-water interface. When certain
    contaminants such as soaps, paints, varnishes,
    and oxidation products are present in the oil,
    the film strength of the oil is weakened, thus
    requiring less force to rupture. For oils in
    service, a decreasing value indicates the
    accumulation of contaminants, oxidation products,
    or both. It is a precursor of objectionable
    oxidation products which may attack the
    insulation and interfere with the cooling of
    transformer windings.

From Doble Engineering, 2005
132
Significance of tests
  • Neutralization Number (D 974) The neutralization
    number of an oil is a measure of the amount of
    acidic or alkaline materials present. As oils age
    in service, the acidity and therefore the
    neutralization number increases. A used oil
    having a high neutralization number indicates
    that the oil is either oxidized or contaminated
    with materials such as varnish, paint, or other
    foreign matter. (A basic neutralization number
    results from an alkaline contaminant in the oil.)
  • Pour Point (D 97) The pour point is the lowest
    temperature at which oil will just flow. A low
    pour point is important, particularly in cold
    climates, to ensure that the oil will circulate
    and serve its purpose as an insulating and
    cooling medium. It may be useful for identifying
    the type (naphthenic, paraffinic) of oils.

From Doble Engineering, 2005
133
Significance of tests
  • Power Factor (D 924) The power factor of an
    insulating oil is the cosine of the phase angle
    between a sinusoidal potential applied to the oil
    and the resulting current. Power factor indicates
    the dielectric loss of an oil thus the
    dielectric heating. A high power factor is an
    indication of the presence of contamination or
    deterioration products such as moisture, carbon
    or other conducting matter, metal soaps and
    products of oxidation.
  • Specific Gravity (D 1298) The specific gravity of
    an oil is the ratio of the weights of equal
    volumes of oil and water determined under
    specified conditions. In extremely cold climates,
    specific gravity has been used to determine
    whether ice, resulting from the freezing of water
    in oil-filled apparatus, will float on the oil
    and possibly result in flashover of conductors
    extending above the oil level. The specific
    gravity of mineral oil influences the heat
    transfer rates. Oils of different specific
    gravity may not readily mix when added to each
    other and precautions should be taken to ensure
    mixing.

From Doble Engineering, 2005
134
Significance of tests
  • Oxidation Inhibitor Content (D 2668, D 4760)
    These tests provide a method for the quantitative
    determination of the amount of oxidation
    inhibitor (2,6-ditertiary butyl-paracresol or 2,6
    ditertiary phenol) present in an inhibited oil.
    Control of the inhibitor content is an important
    factor in maintaining long service life of
    inhibited insulating oils.
  • Power Factor Valued Oxidation (PFVO) This test,
    developed by the Doble Engineering Company,
    periodically measures the power factor of an oil
    while it is being aged at 95C in the presence of
    copper and air. Consequently, it indicates the
    dielectric-loss characteristics of insulating oil
    as a function of accelerated aging conditions.
    The resulting graph of power factor versus time
    characterizes a given oil. It is applicable as a
    continuity test, as well as a measure of oil
    quality. The test is run concurrently with the
    Doble Sludge-Free Life test which measures the
    time until the oil forms sludge.

From Doble Engineering, 2005
135
Significance of tests
  • Oxidation Stability (acid/sludge) (D 2440) The
    acid/sludge test is a method of assessing the
    oxidation resistance of an oil by determining the
    amount of acid/sludge products formed when tested
    under certain prescribed conditions. Oils which
    meet or exceed the requirements tend to preserve
    insulation system life and ensure acceptable heat
    transfer. The test may also be used to check the
    performance consistency of this characteristic of
    production oils.
  • Oxidation Stability (D 2112) This test is a rapid
    method for the evaluation of the oxidation
    stability of new insulating oils containing an
    oxidation inhibitor. It is used as a control test
    for evaluating the response characteristics of
    new oils to oxidation inhibitors. It may also be
    used to check the performance consistency of
    production oils. Good oxidation stability is a
    principal requirement for long service life of
    transformer oils.

From Doble Engineering, 2005
136
Significance of tests
  • Gassing Under Electrical Stress (D 2300) The
    gassing tendency is defined as the rate of gas
    evolved or absorbed by an insulating oil when
    subjected to electrical stress of sufficient
    intensity to cause ionization. The characteristic
    is positive if gas is evolved and negative if gas
    is absorbed. Correlation of results with
    equipment performance is limited at present.
  • Polychlorinated Biphenyls (D 4059) Regulations
    prohibiting the commercial distribution of
    polychlorinated biphenyls (PCBs) mandate that
    insulating oils be examined for PCB contamination
    levels to assure that new products do not contain
    detectable amounts.
  • Viscosity (D 445) Viscosity is the resistance of
    oil to flow under specified conditions. The
    viscosity of oil used as a coolant influences
    heat transfer rates and consequently the
    temperature rise of an apparatus. The viscosity
    of an oil also influences the speed of moving
    parts in tap changers and circuit breakers. High
    viscosity oils are less desirable, especially in
    cold climates. Standard viscosity curves can be
    generated using Method D 341 by measuring two or
    three data points and plotting the data on
    special chart paper. The resulting curve can be
    used to interpolate or extrapolate values at
    temperatures where the viscosity is not measured
    directly.

From Doble Engineering, 2005
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Section end
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