Application And Setting Notes - Siemens 6MD85 Manual

Siprotec 5 high-voltage bay controller

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Protection and Automation Functions

7.8 Overcurrent Protection, 1-Phase

An integrating method of measurement totalizes the weighted time. The weighted time results from the char-

acteristic curve. For this, the time that is associated with the present current value is determined from the

characteristic curve. Once the weighted time exceeds the value 1, the stage operates.

When the measured value falls short of the pickup value by a factor of 1.045 (0.95 x 1.1 x threshold value),

the dropout is started. The pickup will be indicated as clearing. You can influence the dropout behavior via

setting parameters. You can select between instantaneous dropout (totalized time is deleted) or dropout

according to the characteristic curve (reduction of totalized time depending on the characteristic curve). The

dropout according to characteristic curve (disk emulation) is the same as turning back a rotor disk. The

weighted reduction of the time is initiated from 0.9 of the set threshold value.

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Figure 7-125

Note that the currents that are lower than the current value of the smallest characteristic-curve point do

not extend the operate time. The pickup characteristic runs in parallel to the current axis up to the smallest

characteristic-curve point. Currents that are larger than the current value of the largest characteristic-curve

point do not reduce the operate time. The pickup characteristic runs in parallel to the current axis from the

largest characteristic-curve point.

Application and Setting Notes

This stage is structured the same way as the stage with the inverse-time characteristic curve. The only differ-

ence is that you can define the characteristic curve as desired. This chapter only provides application and

setting notes for setting characteristic curves.

Parameter: Current/time value pairs (from the operate curve)

Use these settings to define the characteristic curve. Set a current/time value pair for each characteristic-curve

point. The setting depends on the characteristic curve you want to realize.

Set the current value as a multiple of the threshold value. Siemens recommends that you set the Threshold

parameter to 1.00 in order to obtain a simple relation. You can change the threshold value setting afterwards

if you want to displace the characteristic curve.

Set the time value in seconds. The characteristic curve is displaced using the Time dial parameter.

Pickup Behavior and Dropout Behavior when Using a User-Defined Characteristic Curve

SIPROTEC 5, High-Voltage Bay Controller, Manual

C53000-G5040-C015-9, Edition 11.2017