Setting The Enabling Pick-Up Levels - ABB RELION REB500 Technical Manual

1MRK 505 406-UEN B
• I-Setting: current enabling level
• MeasBwd: fault in backwards direction including Transient blocking
• MeasBwd': fault in backwards direction
• MeasFwd: fault in forwards direction
• Rx: receive
• T: trip
• t TransBlk: blocking time
• TB: transient blocking
• t
Basic
• t
Wait
• Tx: send
• V-setting: reference voltage
5.9.6.4

Setting the enabling pick-up levels

The setting of the current enabling
normal operation arising from system asymmetries.
The pick-up setting for the voltage enabling signal
asymmetries on the secondary side (VT tolerances, asymmetrical burdens etc.).
The ability to read voltage and current values on the relay is a useful aid for determining these
settings.
For example, if the enabling current setting
continuously (current circuit enabled).
Since a ground fault causes asymmetrical voltages in the vicinity of the fault, the current
flowing via the system capacitances also has a zero-sequence component. A capacitive current
of this kind on a long line lies within the setting range of the sensitive ground fault protection
function.
The pick-up level
of 0.7 ×
currents of the line.
The following procedure is recommended for setting the pick-up levels:
• The enabling current for the directional measurement must be set to at least twice the
maximum possible asymmetrical current, which can occur in normal operation.
• The voltage pick-up must be set to 1.6 times the level of the spurious voltages, which can
occur due to asymmetries in the VT secondary circuit.
V Setting
where:
• I
asymm
• I : primary CT rated current
N
• I-Setting: setting of the enabling current
Bay protection functions REB500
Technical manual
: basic time
: waiting time
I-dir of the current circuit for the directional measurement has a fixed setting
I-Setting to take account of influences, such as CT errors and the capacitive charging
I

asymm
I -Setting 2.0
I
N
U

sec.asymm
1.6
-
U
: current component 3I
© Copyright 2019 ABB. All rights reserved
I-dir must take account of the zero-sequence component in
V-Setting is determined by the level of
I-Setting is too low, the pick-up signal lights
N
caused by asymmetrical load currents
0
Section 5
Bay protection functions
GUID-E1B70D52-C69A-43A2-AA45-C8502F086DE2 v1
165