Seg HighTECH MRG3 - Residual Voltage; Behavior of MRG3 under Different Operating Conditions; Blocking Function Set in Compliance with Requirements

Manual MRG3 SEG Electronics GmbH
DOK-TD-MRG3, Rev. D 33
In compensated mains the earth fault direction cannot be determined from the reactive current
components because the reactive part of the earth current depends upon the compensation level of
the mains. The ohmic component of the total current (calculated by cos  adjustment) is used in
order to determine the direction.
The resistive component in the non-faulted line is in phase with the residual voltage, while the re-
sistive component in the faulted line is opposite in phase with the residual voltage.
By means of an efficient digital filter harmonics and fault transients in the fault current are sup-
pressed. Thus, the uneven harmonics which, for instance, are caused an electric arc fault, do not
impair the protective function.
4.7.4 Residual voltage
In the MRG3-IER – relay, the detection of residual voltage has only a warning function because re-
sidual voltage here is used for the directional detection. The MRG3-IUO implies a two-step protec-
tion.
4.7.5 Behavior of MRG3 under different operating conditions
Nr.
Dynamic Behaviour
U</<<
U>/>>
f
1
, f
2
, f
3

df/dt
1
voltage to external
blocking input is ap-
plied
free pro-
grammable
free pro-
grammable
free pro-
grammable
free pro-
grammable
free pro-
grammable
2
blocking input is
released
released
instantane-
ously
released
instanta-
neously
released
after 1 s
released
after 5 s
released
after 5 s
3
supply voltage is
switched on
blocked for
200 ms
blocked for
200 ms
blocked for 1
s
blocked for
1 s
blocked for
1 s
4
3ph measuring volt. is
suddenly applied
released
released
blocked for 1
s
blocked for
5 s
blocked for
5 s
5
one or several meas-
uring voltages are
switched off suddenly
(phase failure)
released
released
blocked
blocked
blocked
6
measuring voltage
smaller U
B
< (adjusta-
ble voltage threshold
value)
released
released
blocked
blocked
blocked
Table 4.2: Dynamic behaviour of functions for the mains decoupling in the MRG3
Nr.
Dynamic Behaviour
I>
I>>
IE>
ER>
UO>*
1
voltage to external
blocking input is ap-
plied
free pro-
grammable
free pro-
gramma-
ble
free pro-
grammable
free pro-
grammable
free pro-
grammable
2
blocking input is
released
released
instantane-
ously
released
instanta-
neously
released
instantane-
ously
released
instantane-
ously
released
instantane-
ously
*not MRG3-IER
Table 4.3: Dynamic behavior of functions for the current protection in the MRG3
4.7.6 Blocking function set in compliance with requirements
The MRG3 has an external blocking input. By applying the auxiliary voltage to input D8/E8, the re-
quested protection functions of the relay are blocked (refer to 5.9.1).