The measured current used by the function is available as a service value.
Overload characteristics
Stator winding temperature increases with the current. Thus, it is logical to apply over current
elements with inverse time-current characteristics for overload protection. The function operating
characteristic is designed in accordance with the American standard IEEE-C50.13: 2014. This
standard specifies the following operating points:
Table 324: Operate time in accordance with IEEE-C50.13: 2014 standard
Current (% of IBase) Trip time (s)
115 120
127 60
150 30
218 10
In order to obtain such operating characteristic the stator overload function utilizes the following
formula in order to calculate the operate time:
GUID-7CF0FE5A-F5CE-44EC-A2D7-F1E05849171C V1 EN-US (Equation 164)
Where:
t
tr
is trip time in seconds
TD1 is a multiplier (it shall have default value of 37.5 in order to get the operating points as prescribed by the
standard, see Table 324)
I is measured current by the function
IBase is base current (stator winding rated current)
In addition to this equation based operating characteristic, the stator overload function has some
additional cut-off features. The actual overall operating characteristic of the stator overload
function is shown in Figure
312
Section 8 1MRK 502 066-UUS B
Current protection
582
Technical manual
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