Monitor - Qualitrol 111-300 Series Instruction Manual

known, then the values for each stage should be made the same. At no time
should zeros be entered as values for these variables.
NOTE: The current is entered as a % of full-scale current. The full scale current
A winding rise time constant must also be entered. One time constant is defined
as the time to reach 63.2% of the ultimate value for the load current. The
winding temperature reaches 98% of its ultimate value in 4 time constants after a
step change in current. A typical time constant is 5 to 8 minutes.
NOTE: The Time Constant can NOT be set to zero. If a very short time constant
An example:
A 30/40/50 MVA 132/32kV single phase transformer with a instrumentation CT
In ONAN mode:
In first stage cooling mode:
In second stage cooling mode: 50MVA/32kV*5/2400=3.25 amps
The full scale current for the CT secondary is 5 amps which corresponds to a:
100%*2400Amps*32kV/50MVA=153% overload rating for the CT.
From the transformer manufacturers heat rise test data you obtain the average
winding rise temperature above oil temperature, or the hottest spot winding
temperature above oil temp (you must decide which gradient is to be used to turn
on cooling). Let's say the gradient is average winding temp, and for no cooling
the temperature rise above oil temperature is 15°C, for first stage cooling the
gradient is 10°C, and for both stages of cooling the gradient is 8°C.
In this case, the values to enter into the "Winding Rise" table would be:
No cooling: 15°C and 100%*1.95/5.00=39%
One stage of cooling: 10°C and 100%*2.60/5.00=52%
Both cooling stages: 8°C and 100%*3.25/5.00=65%
Get Data from Unit – This uploads data from an ETM that can then be
downloaded to another ETM

Monitor

Monitor
Monitor Monitor
The 111W models send out continuous data on the RS232 port.
Display Values from Unit – When the START button on this screen is pressed
stored temperature readings are displayed.
is the 100% value used in the "Calibrate CT" screen, which typically is
the secondary CT current at the extreme overload condition.
is desired, set it 0.1 minutes
of 2400/5 on the secondary side is to configured.
30MVA/32kV*5/2400=1.95 amps
the data from the ETM is displayed. This data is updated several times a
second until the DONE button is pressed. The values displayed vary with
the model, but in all cases the present temperature readings and max
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E l e c t r o n i c T e m p e r a t u r e M o n i t o r
40MVA/32kV*5/2400=2.60 amps