ABB RET670 Applications Manual page 378

Section 3
IED application
372
Time delay for the overreaching power swing zone is not an important parameter, if the
zone is used only for the protection purposes at power-swings.
Consider the normal time grading, if the overreaching zone serves as a time delayed back-
up zone, which is not blocked by the operation of Power swing detection (ZMRPSB,
68) function.
Timers within the power swing logic
Settings of the timers within Power swing logic (ZMRPSL) depend to a great extent on
the settings of other time delayed elements within the complete protection system.
These settings differ within different power systems. The recommended settings
consider only the general system conditions and the most used practice at different
utilities. It is always necessary to check the local system conditions.
The carrier send timer tCS is used for safety reasons within the logic. It requires
continuous presence of the input signal PUPSD, before it can issue a carrier send
signal. A time delay between 50 and 100 ms is generally sufficient.
The trip timer tTrip is used for safety reasons within the logic. It requires continuous
presence of the input signal PUPSD, before it can issue a tripping command during the
power swings. A time delay between 50 and 100 ms is generally sufficient.
The blocking timer tBlkTr prolongs the presence of the BLKZMOR output signals,
which can be used to block the operation of the power swing zones after the detected
single-phase-to-ground faults during the power swings. It is necessary to permit the O/
C EF protection to eliminate the initial fault and still make possible for the power
swing zones to operate for possible consecutive faults. A time delay between 150 and
300 ms is generally sufficient.
Blocking and tripping logic for evolving power swings
The second part of a complete Power swing logic (ZMRPSL) functionality is a
blocking and tripping logic for evolving power swings, see figure
The simplified logic is presented in figure 165. The logic controls the operation of the
underreaching distance protection zone (Zone 1) at power swings, caused by the faults
and their clearance on the adjacent power lines. The logic should generally be
configured between distance protection zones 1 and 2.
Configuration
The fault impedance should be detected within the external boundary of Power Swing
Detection (ZMRPSB, 68) function without power swing detected during the entire
fault duration. Configure for this reason the PUZMPSD to the functional output signal
of ZMRPSB (68) function, which indicates the measured impedance within its external
boundaries.
1MRK504116-UUS C
162 and figure 163.
Application manual