Clear menu. The temperature is stored in a nonvolatile memory and restored if the
IED is restarted.
The Max temperature setting defines the maximum temperature of the transformer
in degrees Celsius (°C). The value of the Max temperature setting is usually given
by transformer manufacturers. The actual alarm, operating and lockout
temperatures for T2PTTR are given as a percentage value of the Max temperature
setting.
When the transformer temperature reaches the alarm level defined with the Alarm
temperature setting, the ALARM output signal is set. When the transformer
temperature reaches the trip level value defined with the Operate temperature
setting, the OPERATE output is activated. The OPERATE output is deactivated
when the value of the measured current falls below 10 percent of the Current
Reference value or the calculated temperature value falls below Operate
temperature.
There is also a calculation of the present time to operation with the present current.
T_OPERATE is only calculated if the final temperature is calculated to be above
the operation temperature. The value is available in the monitored data view.
After operating, there can be a lockout to reconnect the tripped circuit due to the
thermal overload protection function. The BLK_CLOSE lockout output is activated
when the device temperature is above the Reclose temperature lockout release
temperature setting value. The time to lockout release T_ENA_CLOSE is also
calculated. The value is available in the monitored data view.
4.1.6.5 Application
The transformers in a power system are constructed for a certain maximum load
current level. If the current exceeds this level, the losses are higher than expected.
This results in a rise in transformer temperature. If the temperature rise is too high,
the equipment is damaged:
• Insulation within the transformer ages faster, which in turn increases the risk
of internal phase-to-phase or phase-to-earth faults.
• Possible hotspots forming within the transformer degrade the quality of the
transformer oil.
During stressed situations in power systems, it is required to overload the
transformers for a limited time without any risks. The thermal overload protection
provides information and makes temporary overloading of transformers possible.
The permissible load level of a power transformer is highly dependent on the
transformer cooling system. The two main principles are:
Section 4 1YHT530004D05 D
Protection functions
236 615 series
Technical Manual
To Next Page
Loading...
Need help?
General
