Areva MiCOM P125, Техническое руководство

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Application Guide P12y/EN AP/D32
MiCOM P125/P126 & P127 Page 19/74
2.4 Directional Earth Fault Protection (P125, P126 & P127)
The MiCOM P125, P126, P127 relays have a directional/non directional earth fault
protection.
It provides three directional/non directional earth overcurrent thresholds and two wattmetric
and active earth fault current thresholds.
The first and second threshold can be set as definite or inverse delay time using the IEC,
IEEE/ANSI, CO2-8, RI and RECT curves as shown in the Technical Data of the relays; for
the wattmetric protection ( Pe / IeCos ) only the first threshold can be set as definite or
inverse delay time, always using IEC, IEEE/ANSI, CO, RI and RECT curves.
The directional earth fault overcurrent protection element compares the earth fault current,
residual voltage with the set thresholds Ie>, Ue>, Ie>>, Ue>>, Ie>>>, Ue>>> and the relevant
angle between the Ie and Ue for each threshold. Once all the following listed requirements
are met the tripping command is set:
−
thresholds for Ie and Ue are exceeded (earth fault OC protection element)
−
Ie current vector is in the tripping area (Ie^Ue)
−
Ie [mA] + Ue [V] > 18 (Ien=1A) or Ie [mA] + Ue [V] > 90 (Ien=5A)
−
the tripping timer expires .
The protection's tripping area is defined by a tripping zone settable form ± 10° to ± 170° in
steps of 1° for each tripping threshold and a settable angle from 0° to 359° in steps of 1°
named torque/RCA angle (Ie^Ue), which can be separately set for each tripping threshold
and
The same threshold can be set as non-directional with definite or inverse delay time.
The third current threshold can be set as directional or non-directional but with only definite
delay time setting. The same applies to the Pe or IeCos second threshold.
The third threshold can work on the measured peak by an opportune choice in the dedicated
submenu. (See the FT part of the TG)
The peak detection is applied where a CT saturation condition occurs and the measure is not
more trustworthy.
The reset delay time for each threshold provides protection against intermittent faults.
Ue
Ie
RCA
Tripping zone is settable from:
±10˚ to ±170˚ in step of 1˚ with reference
to RCA (Torque angle)
RCA (Torque angle) is settable from
0˚ to 359˚ in step of 1˚
Forward
tripping zone
Backward
tripping zone
P0083ENa
The close figure shows the forward and
reverse tripping zone for the directional
earth fault protection.
The protection element also provides a non-sensitive area to avoid instability due to small
asymmetries and unbalances that can generally be present in the network system. This
condition is represented by the characteristic reproduced below, where the hatched area is
the tripping zone.
The tripping zone is limited by the equation Ie +(k x Ue) < (k x 18). (18 is a value derived
experimentally where stability is guaranteed).