Application - ABB RELION 620 Series Technical Manual

1MAC504801-IB E
4.5.1.5
620 series ANSI
Technical Manual
setting) via a control parameter that is located under the clear menu. This is useful during
testing when secondary injected current has given a calculated false temperature level.

Θ
= − ⋅ ln
t 
τ
lockout release _


A070783 V3 EN
Here the final temperature is equal to the set or measured ambient temperature.
In some applications, the measured current can involve a number of parallel lines. This is
often used for cable lines where one bay connects several parallel cables. By setting the
Current multiplier parameter to the number of parallel lines (cables), the actual current on
one line is used in the protection algorithm. To activate this option, the ENA_MULT input
must be activated.
The ambient temperature can be measured with the RTD measurement. The measured
temperature value is then connected, for example, from the RTD/mA output of the X130
(RTD) function to the AMB_TEMP input of 49F.
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 49F is set to "Not in use" in the X130 (RTD) function.
The temperature calculation is initiated from the value defined with the Initial
temperature setting parameter. This is done in case the protection relay is powered up, the
function is disabled and enabled back or reset through the Clear menu. The temperature is
also stored in the nonvolatile memory and restored in case the protection relay is restarted.
The thermal time constant of the protected circuit is given in seconds with the Time
constant setting. Please see cable manufacturers manuals for further details.

Application

The lines and cables in the power system are constructed for a certain maximum load
current level. If the current exceeds this level, the losses will be higher than expected. As
a consequence, the temperature of the conductors will increase. If the temperature of the
lines and cables becomes too high it can cause damage. For example:
• The sag of overhead lines can reach an unacceptable value.
• An aluminum conductor will be destroyed if the temperature becomes too high
• Overheating can damage the insulation on cables which in turn increase the risk of
phase-to-phase or phase-to-ground faults.
 
− Θ
final lockout release _


Θ − Θ
final n 
Section 4
Protection functions
(Equation 23)
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