S4 Elements745
Transformer Management Relay
Setpoints
http://www.GEindustrial.com/multilin
5–78
GE Multilin
Insulation Aging a) Main Menu
PATH: SETPOINTS !" S4 ELEMENTS !" INSULATION AGING
The 745 Insulation Aging/Loss of Life feature is based on the computational
methods presented in IEEE standards C57.91–1995, IEEE Guide for Loading
Mineral-Oil-Immersed Transformers, and C57.96–1989, IEEE Guide for Loading
Dry-Type Distribution and Power Transformers. These standards present a method
of computing the top oil temperature, the hottest spot inside the transformer, the
aging factor, and the total accumulated loss of life. The computations are based on
the loading of the transformer, the ambient temperature, and the transformer data
entered. The computations assume that the transformer cooling system is fully
operational and able to maintain transformer temperatures within the specified
limits under normal load conditions.
The computation results are a guide only. The transformer industry has not yet been
able to define, with any degree of precision, the exact end of life of a transformer.
Many transformers are still in service today, though they have long surpassed their
theoretical end of life, some of them by a factor of three of four times.
Three protection elements are provided as part of the Loss of Life feature. The first
element monitors the hottest-spot temperature. The second element monitors the
aging factor and the third monitors the total accumulated loss of life. Each element
produces an output when the monitored quantity exceeds a set limit.
The Insulation Aging/Loss of Life feature is a field-upgradable feature. For the
feature (and associated elements) to operate correctly, it must first be enabled
under the factory settings using the passcode provided at purchase. If the feature
was ordered when the relay was purchased, then it is already enabled. Note that
setting this feature using the enerVista 745 Setup software requires that it be
enabled the under File > Properties > Loss of Life menu. If the computer is
communicating with a relay with the feature installed, it is automatically detected.
For the computations to be performed correctly, it is necessary to enter the
transformer data under
S2 SYSTEM SETUP ! TRANSFORMER. The transformer load is
taken from the winding experiencing the greatest loading. All transformer and
winding setpoints must be correct or the computations will be meaningless.
The preferred approach for ambient temperature is to use an RTD connected to the
745. If this is not feasible, average values for each month of the year can be
entered as settings, under
S2 SYSTEM SETUP !" AMBIENT TEMPERATURE !" AMBIENT
RTD TYPE and selecting By Monthly Average.
! INSULATION [!]
AGING
! HOTTEST-SPOT [!]
LIMIT
See page 5–79.
MESSAGE
! AGING FACTOR [!]
LIMIT
See page 5–80.
MESSAGE
! LOSS OF LIFE [!]
LIMIT
See page 5–81.
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