SITRAM® DRY Cabinet, Frame und Smart
Transforming know-how into solutions.
Siemens Transformers.
Intern © Siemens AG 2014 Alle Rechte vorbehalten.
Answers for energy.
Scope of Activities / Portfolio of Transformer Service
Condition Assessment & Diagnostic
Online Monitoring
Consulting & Expertise
Maintenance & Lifecycle Extension
Spare Parts & Accessories
Repair & Retrofit
Transport, Installation & Comissioning
© Siemens AG 2014 All Rights reserved.
Seite 2
May 2014
Energy Transmission Transformer
Structure of Transformers
Transformer oil
Transformer wood
Laminated
pressboard
Pressboard
Grain-oriented
electrical steel
Gasket material
Copper winding
Coating
Insulating paper
Transformers are comprised substantially of organic materials
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Ageing processes of transformer insulation system
Moisture
Oxygen
Temperature
Oil/Cellulose - Insulation
Chemical degradation, acids,
peroxides, ...
add. water, oxygen
Mechanical Degradation
Lightning-SwitchingImpulses
Accelerated Aging
of Insulation
Dielectric Degradation
Insulation failure
Short Circuits
The ageing of oil and cellulose is strong depending from each other
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Ageing in transformers
The service life of a transformer is determined
by the life its solid insulation
End of life is reached as soon as the mechanical
strength has lost 50% of initial value which commonly
appear at degree of polymerization (DP) values < 200
( -75%) (IEEE C57.91-1995)
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Ageing processes in the solid insulation
Paper ageing duration until a DP value of 150 is reached (end of life)
at 120ºC depending on humidity content in the paper
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Moisture in transformers
Cause of moisture
• Ageing of solid insulation
• Diffusion of moisture from the external environment:
• Free breathing systems with poorly maintained air dehumidifier
• Damaged gasket
A sustainable low water content in the cellulose and insulating oil
extend the life of the transformer considerably.
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May 2014
Energy Transmission Transformer
Overview options for actions
If the latest transformer oil analysis reports high water content
and/or low breakdown voltage:
The customer has six options, each with different characteristics and
consequences:
1. Do nothing
2. Retrofill
3. Conventional dehydration
4. Field vacuum dehydration
5. Oven drying
6. Stationary transformer drying
© Siemens AG 2014 All Rights reserved.
Seite 8
May 2014
Energy Transmission Transformer
Options for actions (1)
Option
Process description
Conclusion
1. Do nothing
This is as simple as the results are predictable:
continuous degradation and failure of the unit. Water
in the paper insulation breaks down the designed
value of the insulation, resulting in premature failure,
outage and replacement.
Inexpensive at first, then
extremely costly
2. Retrofill
Exchange the wet oil with dry oil. The problem: the
moisture is still bound deep within the transformer`s
insulation/paper. So after the retrofit the moisture will
slowly leach from the paper into the new oil.
Eventually, high moisture will reappear in testing. In
the end, this approach treats the symptom but does
not solve the problem.
Moisture remains in the paper
The risk is unchanged and
hidden behind temporary good
oil values after processing
Outtake costs
3. Conventional
dehydration
This temporary solution circulates and heats the
transformer oil, removing the moisture from the outer
layers of the insulation. However, most of the
moisture stays deep within the paper. After removal of
the dehydration unit, the moisture will slowly leach
from the paper into newly processed oil. Over time,
this will lower the breakdown voltage again.
Only temporary good results
Moisture remains in the paper
High power consumption
Risk is unchanged and hidden
behind temporary good oil
values after processing
© Siemens AG 2014 All Rights reserved.
Seite 9
May 2014
Energy Transmission Transformer
Options for action (2)
Option
4. Field vacuum
dehydration
(LFH)
Process description
Conclusion
Process can take from days to
In the transformer tank is rated for full vacuum, the
weeks
transformer can be de-energized and disconnected from
Unit stays de-energized
the system. Typical approaches heat up the core an coil
Afterwards, has to be refilled with
assembly by heating the circulated oil. After reaching the
oil and electrically tested
nominal temperature, the unit is drained and placed
Vacuum in the tank could lead the
under vacuum. The combination of heat and vacuum
failure in the sealings
begins to remove moisture from the internal components
High outage costs
including the paper. For full and proper moisture removal,
Very effective at moisture removal
this process requires constant or periodic application. It is
also recommended that a cold trap be utilized to measure
the amount and rate the moisture removal.
5. Oven Drying
Wet transformers can be dried in an oven - just as in the
factory during initial assembly. Of course, this means
disconnecting the transformer and transporting it to a
drying oven. There it has to be drained and put in the
oven for a period of days or weeks, until it finally
becomes dry. Afterward, the transformer must be refilled,
the previous steps repeated in reverse, and (eventually)
the power turned back on.
Effective for small distribution TX,
but very costly in time and money
for bis units (transportation costs
for shipping to repair shop)
6. Stationary
transformer
drying device
A small, highly efficient unit is permanently placed on the
energized transformer and slowly but continuously
removes the moisture from the oil and paper completely.
Low cost, low risk. Maximum
benefit. It`s just that simple.
© Siemens AG 2014 All Rights reserved.
Seite 10
May 2014
Energy Transmission Transformer
Conclusion regarding drying of transformers
• Oil has the property to absorb only a low
water quantity (<2%)
• The main part of moisture remains in
the solid insulation and this accelerates
the irreversible degradation of the
cellulose.
• Conventional drying methods are
causing only a temporary reduction of
moisture in oil
Continuous oil dehydration is necessary to ensure moisture removal
from the paper insulation
© Siemens AG 2014 All Rights reserved.
Seite 11
May 2014
Energy Transmission Transformer
What is molecular sieve?
A molecular sieve is a material containing tiny pores of a uniform size
that is used as an adsorbent for gases and liquids.
Internal surface of the content of
3 cartridges amount approx. 25 km2
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Experimental result (1)
SITRAM® DRY in operation
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Experimental result (2)
SITRAM® DRY in operation
H2O-Adsorption [Liter]
Moisture in oil [ppm]; Temp. [°C]
Temperature entry[ºC]
Moisture entry [ppm]
Temperature entry[ppm]
H2O-Adsorption [Liter]
© Siemens AG 2014 All Rights reserved.
Seite 14
May 2014
Energy Transmission Transformer
SITRAM® DRY Stationary Drying System
Two product versions for all standard applications
SITRAM® DRY Cabinet/Frame
SITRAM® DRY SMART
• Target segment: Power transformers with
conservator oil level of min. 2.5 m above ground
• Target segment: Distribution transformers with
conservator oil level of min. 1.5 m above ground
• Typical application: Power generation and
Transmission Utilities/Industry
• Typical applications: D-Utilities and Industry
• Water capacity: 3 x 3 liter
• PLC functionality
• Water capacity: 2 x 1.5 liter
• PLC functionality
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
SITRAM® DRY Versions
Main Customer Benefits
• Graded product approach
• Reduced total costs of ownership and higher availability
- Automatic cartridge replacement signal
- Self-monitoring of pump and moisture sensors
- Leakage control (optional at SITRAM® DRY Cabinet)
- Potential free alarm contact (live contact) to SCADA
• Extended field of application: ambient temperature range
(-20ºC to +60ºC)
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
SITRAM® DRY Cabinet
The unit for customers with special requests
Speziell for customers, …
• With transformers far away
- From the daily access of their
personnel,
- E.g. substation transformers
Target Segment
• Power transformers with conservator
oil level of min. 2.5 m above ground
• Typical application: Power generation
and Transmission Utilities/Industry
• Who set a high value on
- The protection of their device
- Information about the operation
conditions
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Customer‘s benefits
• Automatic reaction if an error occurs
• In case of an error, avoidance of leakage by
- Closing the magnetic valves
- Switching off the pump
• Actual information about the operating
conditions and the measurement values by
text messages
• Recording and storage of measurement
data by data logging
• Good overview about the operating
conditions by enhanced visualization
© Siemens AG 2014 All Rights reserved.
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May 2014
Energy Transmission Transformer
Functions with and without stop of operation
Leakage inside/outside, pump error
Control of moisture/pressure sensors
• Stop of pump operation
• Message via text message and Panel
• Magnetic valves get closed to avoid a
leakage of oil
• SITRAM® DRY continues in operation
© Siemens AG 2014 All Rights reserved.
Seite 19
May 2014
Energy Transmission Transformer
Cartridge Saturation
• Detailed display about the cartridge saturation
• Error message if the cartridges are saturated
• Text messages
© Siemens AG 2014 All Rights reserved.
Seite 20
May 2014
Energy Transmission Transformer
SMS with information about operating conditions
and error messages
Four different text messages in German or
English
• Error leakage inside / outside
• Pump error
• Transmission of measurement values
- SITRAM DRY operating condition
- Temperatures, absolute moisture in ppm
and relative moisture as aw-value at the
inlet and the outlet
• Cartridges saturated
© Siemens AG 2014 All Rights reserved.
Seite 21
May 2014
Energy Transmission Transformer
Data Logging
• Storage of the measurement values with
time stamp
- Absolute moisture in ppm
- Relative moisture as aw-value
- Temperature of the transformer oil
• Acces with Ethernet connection using a
common web browser
© Siemens AG 2014 All Rights reserved.
Seite 22
May 2014
Energy Transmission Transformer
SITRAM® DRY Versions
Cartridge Saturation and Exchange
• Message for cartridge exchange
If the incoming transformer oil is higher than 10 ppm and the cartridges are
saturated a signal for cartridge exchange will automatically occur on the plc.
• Operating experience
For a wet transformer the sets of cartridges last for:
- 6 months for the first set
- 12 months for the second set
- 18 months for the third and all other sets
These values depend strongly on different parameters like the size of the
transformer, the oil volume, the moisture in the oil, the load and the
temperature in the transformer.
© Siemens AG 2014 All Rights reserved.
Seite 23
May 2014
Energy Transmission Transformer
SITRAM® DRY Cabinet
How to install SITRAM DRY at the transfomer?
Pipe connection
to transformer
Electrical connection
Pipe connection
from transformer
© Siemens AG 2014 All Rights reserved.
Seite 24
May 2014
Energy Transmission Transformer
SITRAM® DRY Cabinet
General Overview and monitoring functions
Vent tank with vent valve
Oil filter
Cartridges
Control box
with PLC
Moisture in oil sensor
© Siemens AG 2014 All Rights reserved.
Seite 25
May 2014
Energy Transmission Transformer
SITRAM® DRY Cabinet
Leakage Monitoring
Vent valve
Leakage control
© Siemens AG 2014 All Rights reserved.
Seite 26
May 2014
Energy Transmission Transformer
Examples of installation
© Siemens AG 2014 All Rights reserved.
Seite 27
May 2014
Energy Transmission Transformer
SITRAM® DRY Cabinet, Frame und Smart
Thank you for your attention.
Intern © Siemens AG 2014 Alle Rechte vorbehalten.
Answers for energy.