Application - ABB RELION 620 Series Technical Manual

1MRS757644 F
4.1.7.5
620 series
Technical Manual
The ambient temperature can be measured with RTD measurement. The measured
temperature value is connected, for example, from the AI_VAL3 output of the X130
(RTD) function to the AMB_TEMP input of T2PTTR.
The Env temperature Set setting is used to define the ambient temperature if the
ambient temperature measurement value is not connected to the AMB_TEMP input.
The Env temperature Set setting is also used when the ambient temperature
measurement connected to T2PTTR is set to "Not in use" in the X130 (RTD) function.
The temperature calculation is initiated from the value defined with the Initial
temperature and Max temperature setting parameters. The initial value is a percentage
of Max temperature defined by Initial temperature. This is done when the protection
relay is powered up or the function is turned off and back on or reset through the Clear
menu. The temperature is stored in a nonvolatile memory and restored if the protection
relay 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.

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.
Section 4
Protection functions
329