Alstom MiCOM P546 - 2.3.20 Trip on reclose mode (Distance option only); 2.3.21 Setup of DEF (Distance option only); 2.3.22 DEF negative sequence polarization (Distance option only); 2.3.23 General setting guidelines for DEF (directional ground overcurrent) (Distance option only)

P54x/EN AP/La4 Application Notes
(AP) 6-32 MiCOM P543, P544, P545 & P546
AP
2.3.20 Trip on reclose mode (Distance option only)
To ensure fast isolation of all persistent faults following the circuit breaker reclosure. It is
recommended this feature is enabled with appropriate zones selected and/or ‘Current No
Volt’ (CNV) level detectors.
TOC Delay
the TOR is activated after ‘TOC Delay’ has expired. The setting
must not exceed the minimum AR Dead Time setting
to make
sure that the TOR is active immediately upon reclose
command.
TOC reset delay
- 500 ms is recommended as a typical setting (as per SOTF).
2.3.21 Setup of DEF (Distance option only)
DEF ze
ro sequence polarization
In practice, the typical zero sequence voltage on a healthy system can be as high as 1%
(i.e.: 3% residual), and the VT error could be 1% per phase. A VNpol Set setting between
1% and 4%.Vn is typical, to avoid spurious detection on standing signals. The residual
voltage measurement provided in the Measurements column of the menu may assist in
determining the required threshold setting during commissioning, as this will indicate the
level of standing residual voltage present. The Virtual Current Polarizing feature will create a
VNpol which is always large, regardless of whether actual VN is present.
With DEF, the residual current under fault conditions lies at an angle lagging the polarizing
voltage. Hence, negative characteristic angle settings are required for DEF applications.
This is set in cell ‘DEF Char Angle' in the relevant earth fault menu.
The following angle settings are recommended for a residual voltage polarized relay:-
Distribution systems (solidly earthed)  -45°
Transmissions systems (solidly earthed)  -60°
2.3.22 DEF negative sequence polarization (Distance option only)
For n
egative sequence polarization, the RCA settings must be based on the angle of the
upstream negative phase sequence source impedance. A typical setting is -60
o
.
2.3.23 General setting guidelines for DEF (directional ground overcurrent) (Distance option only)
DEF forward threshold
- This setting determines the current sensitivity (trip sensitivity) of
the DEF aided scheme. This setting must be set higher than
any standing residual current unbalance. A typical setting will
be between 10 and 20% In.
DEF reverse threshold
- This setting determines the current sensitivity for the reverse
ground fault. The setting must always be below the DEF forward
threshold for correct operation of Blocking scheme and to
provide stability for current reversal in parallel line applications.
The recommended setting is 2/3 of DEF forward setting. Note
that this setting has to be above the maximum steady state
residual current unbalance.
2.3.24 Delta directional comparison principle and setup (Distance option only)
For d
elta directional decisions, the RCA settings must be based on the average source + line
impedance angle for a fault anywhere internal or external to the line. Typically, the Delta
Char Angle is set to 60
o
, as it is not essential for this setting to be precise. When a fault
occurs, the delta current will never be close to the characteristic boundary, so an
approximate setting is good enough.