ABB Relion 670 Series Applications Manual page 482

Section 17
Monitoring
Insulation aging or deterioration is a time function of temperature, moisture content, and oxygen
content. With modern oil preservation systems, the moisture and oxygen contributions to
insulation deterioration can be minimized, leaving insulation temperature as the controlling
parameter.
Temperature distribution is not uniform in transformers, the part that is operating at the highest
temperature normally undergoes the greatest deterioration. Therefore, in aging studies it is usual
to consider the aging effects produced by the highest (hottest-spot) temperature. Since many
factors influences the cumulative effect of temperature over time which causes transformer
insulation deterioration, it is difficult to predict the useful life of the insulation in a transformer
with great degree of accuracy. However, this function will help in reducing the accelerated aging of
power transformers during overload conditions and thus maximize the transformer operating life.
17.11.2 Setting guidelines
The parameters for the estimation of transformer insulation life function LOLSPTR (26/49HS) are
set via the local HMI or PCM600.
Minimum information about the transformer parameters which are required to decide the
transformer insulation life are:
1. Top oil temperature rise over ambient temperature at rated load
2. Average conductor temperature rise over ambient temperature at rated load
3. Winding hot spot temperature rise over ambient temperature
4. Load losses at rated load
5. No-Load (core) loss
6. Oil flow design (Directed or non-directed)
7. Weight of core and coil assembly
8. Weight of tank and fittings
9. Weight of oil in the tank and cooling equipment (excluding load tap changer, oil expansion
tanks)
For information about 1 to 5, the conditions (load, ambient temperature, tap, etc.) under which the
measurements are made should be known. In order to have more precise calculations, load loss at
rated and tap extremes or all possible tap connection combinations are required.
Operation : Disabled or Enabled .
TrafoRating : Rated transformer power in MVA.
TrafoType : This setting is used to set the number of phases in the transformer. The options are:
Three Phase Trafo : The function considers the given transformer as three phase transformer.
•
Single Phase Trafo : The function considers the given transformer as single phase transformer.
•
Based on the settings
temperature calculations. Both IEEE and IEC standards defines the transformer parameters based
on three categories of transformer rating.
In the case of three phase transformers:
476
TrafoRating and TrafoType , transformer parameters are selected for
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Bay control REC670
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