Siemens Reyrolle 7SR5 Manual page 233

Parameter Value
RMS
Fundamental
Parameter: 51‑n Dir.Control
•
Default setting: Non-Dir
This setting is used to define whether the element will operate for overcurrent detection in the Forward
or Reverse direction based on the 67 directional element decision or for any overcurrent regardless of
the 67 direction. This allows the overcurrent protection to have different current and time settings for
forward and reverse faults by using 2 elements. Additional non‑directional elements can be used for
backup or high set and will still be active if the main directional elements are inhibited by VTS etc.
This parameter is not provided in devices that do not have voltage inputs or for current inputs that are
not polarized by the voltage inputs.
If a protection element is set as non-directional then it will operate independently of the output of the
directional detector. However, if a protection element is programmed for forward directional mode then
operation will occur only for a fault lying within the forward operate zone. Conversely, if a protection
element is programmed for reverse directional mode then operation will occur only for a fault lying
within the reverse operate zone. Typically the forward direction is defined as being "away" from the
busbar or "towards" the protected zone.
Parameter Value
Non-Dir
Forward
Reverse
Parameter: 51‑n Setting
•
Default setting: 1 x I
This setting defines the operating current threshold of the element. The applied phase current must
exceed this setting by a factor of 1.05 for pickup of the element. The operation timing will then be
dependent on the selected characteristic for the element setting. The element pickup will reset when the
current is reduced by a factor of 0.97, the setting and the reset characteristic will be applied. This factor is
always applied for 51 elements including when the Char is selected as DTL.
This setting should be set to suit the individual application.
Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
Description
Select this method of measurement if it is required to consider the effects of
harmonic currents. This method may be required if there is significant harmonic
content such as at capacitor banks or filter networks. This method is required for
correct grading with fuses or electromechanical overcurrent relays.
This method is used:
•
When harmonic components are not to be considered in the current evalua-
tion
•
For current/time grading with devices which also measure fundamental
current
•
For unbalance type protection where the unbalance applies at fundamental
frequency and the risk of errors in transient response measurement can be
avoided
Description
Select this setting if the element is to operate regardless of the current direction
or presence of voltage.
Select this setting if the element is to operate only in a forward direction.
Select this setting if the element is to operate only in a reverse direction.
(1 ⋅ I )
n rated
Protection and Automation Functions
5.14 51 Time-Delayed Overcurrent – Phase
233