Table Of ContentMICOM P437
Distance Protection
Version -307 –408+409 –611
Upgrade
Documentation
P437/EN AD/AB7
(AFSV.12.09960 EN)
(Issue A)
In the new version of P437 several new features and changes on existing features have
been added. These are described with reference to the documentation listed below.
References
Release Version Documentation
26.02.2006 P437-307-408/409-610 Manual P437_EN_M_Ba7
(AFSV.12.09910)
P437 Upgrade Documentation
(continued)
1 Overview
Version Changes
P437-307-408/409-611 Hardware No changes
Release: 28.02.2007 Diagram No changes
Software
IEC Enhancements of protocol implementation:
GOOSE
(cid:133) 2nd SNTP server
GSSE
(cid:133) VLAN priority
COMM1 Bug fixing:
The following spontaneous messages were missing:
034.047 MAIN Manual trip signal A
034.048 MAIN Manual trip signal B
034.049 MAIN Manual trip signal C
DIST Improved measuring logic to provide fast 3-pole tripping in case of
phase-phase-ground faults, with one phase-ground loop impedance
getting significantly slower into zone 1.
The underimpedance starting logic has been improved to pick up faster
in case of faults with almost no change in current magnitude.
The directional characteristic is now settable.
PSB Separate counters for number of stable swings as well as number of pole
slips have been implemented. These counters are accomplished by
settable levels at which binary signals are raised that could be used for
tripping purposes.
Bug fixing:
(cid:133) The ∆Z detection did not operate in all cases, if the apparent
impedance moved “from the left to the right” into the power swing
detection zone.
(cid:133) The maximum blocking timer was not correctly re-triggered each time
when entering the power swing detection zone. Thus it could by
chance time out during a consecutive power swing cycle.
SOTF The SOTF dead line detection logic could now be enabled or disabled.
PSIG Weak-Infeed Logic blocking feature has been modified to provide pole-
selective blocking by CB auxiliary contact information (52a inputs).
The scheme logic has been enhanced to cope 3-ended line applications.
The distance dependent send logic has been modified for improved
operation in case of 2pG faults: If fault direction signals forward and
backward are present at the same time, the send signal is based on the
selective Z1 decision only (not on Z1e).
Bug fixing:
In distance-dependent blocking scheme, the PSIG tripping time was not
started, if the zone timing setting was
001.236 DIST Zone timer start = ‘With zone starting’.
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P437 Upgrade Documentation
(continued)
Version Changes
ARC Zone 1 extension tripping during reclosing is now executed from ARC,
even if PSIG is in operation.
The duration of the zone extension is as long as the set reclose
command (015.067 MAIN Close cmd.pulse time), ifen if the
reclose command is stopped because of the close-signal from the CB
(015.042 MAIN RC inhib.by CB close = ‘Yes’).
ASC The selection of voltage control conditions (operating modes) has been
enlarged by an exclusive-OR condition, i.e. (re-)closing is enabled, if
exactly one side is “dead” while the other side must be “live”
(setting abbreviated “N V&Vref or V&n Vref”
means “(NOT V AND Vref) OR (V AND NOT Vref)”).
In operating mode “Vref & Z1 but not V” the meaning of Z1 has been
changed to “DIST zone Z1 trip OR protective signaling Z1e trip”, so
reclosure is possible if the primary fault is on the line.
GFSC The user settable blocking condition of the function has been changed to
an m-out-of-n selection, using the same enlarged list as for GSCSG.
Consequentially, the previous setting 002.137 GFSC: Block. w.
DIST start is removed.
For ground faults with small neutral displacement voltage an optional
‘virtual current polarisation’ has been implemented. This feature uses a
faulty phase selector, which is based on the measured change of phase
currents.
Along with the signaling scheme (GSCSG) the priority of the function has
been changed to provide faster 1-pole trips.
GSCSG The selection list for user defined blocking conditions (002.180 GSCSG:
Fct.assign. blocking) has been further expanded by internal trip decisions
as well as parallel and transfer trip signals.
The tripping timer is now started from 039.088 GFSC IN> triggered
signal only.
Transient blocking timer is now always started upon reset of a GSCSG
backward direction decision.
P<> Directional power protection function is now available.
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P437 Upgrade Documentation
(continued)
2 Functional Details
2.1 Distance Protection (Function Group DIST)
Based on recent RTDS (Real Time Digital Simulator) simulated type test cases, distance
protection operation for specific conditions has been improved.
Distance decision for
2pG-faults
To provide correct operation for cross-country faults or inter-system faults on double
circuit lines (2pGG faults), it is mandatory to evaluate only the both phase-ground loop
impedances. This is possible by setting, yet during tests this setting resulted in
staggered tripping for very close 2pG faults, because one PG loop impedance could
appear in backward direction. The reason for this is that the impedance is calculated by
using the ground factor k of the line, yet as no line impedance is involved in the
G
measuring loop any more and as the source ground factor was significantly smaller than
the line factor, thus one PG loop impedance is “misleading”.
With version –611 the following solution is implemented:
If starting identifies a 2pG fault condition, and “PG loops” evaluation is selected, than the
phase-phase voltage is used to determine whether it is a close fault, which is the case ir
V < 10% V . In this case, the PG-loop impedances (for the distance and directional
PP nom
measurement) are calculated with k = 0; otherwise normal equation with set k is used.
G G
Additionally to the 2 PG impedances the PP impedance is calculated, too, to secure
simultaneous 3-pole tripping, because it could happen that the 2 PG impedances settle
in zone 1 (or Z1e) with different “speed” – just depending on the fault transients. Always
all 3 impedances (e.g. BN, CN and BC for a BCN fault) are calculated, and the zone
decisions are then compared:
1) If both PG impedances are in zone 1, P437 immediately trips 3-pole.
2) If one PG and the PP impedance are in zone 1 and the 2nd PG loop is in forward
direction, then P437 trips 3-pole, too.
Taking care for the directional decision acertains, that – just in case of cross-country
and intersystem faults (2pGG faults) – both PG faults are on the protected line. The
zone 1 decision of the PP loop then is sufficient to secure that both faults are in zone
1, too.
In applications with parallel lines, during intersystem faults one PG fault could be on
the parallel line, but then either its direction is backwards or the PP loop impedance is
outside zone 1.
3) If after the first calculation loop just one zone 1 decision is determined, than the DIST
processing task duration is prolonged and all 3 impedances are calculated again.
This is done to make shure that normal 2pG faults are immediately tripped 3-pole and
the risk of staggered tripping is minimized.
The disadvantage is that for parallel line applications in case of cross-
country/intersystem faults the correct 1pole trip could be delayed by up to ~7 ms.
So in order to get a proper balance of speed and correct 1p/3p trip decision, this
measuring repitition is only done once.
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P437 Upgrade Documentation
(continued)
1pG starting during
2pG faults
In some cases a fast 1pG starting was observed during a 2pG fault. This incomplete
fault type determination also forced an initial 1-pole trip. During the 2nd processing cycle
the correct type of fault was identified and 3-pole trip was issued, thus a unfortunate
staggered tripping took place.
To solve this problem, the starting conditions are now checked again during the first
distance measuring cycle.
Settable directional
characteristic
In some cases with external phase-phase faults with a high intermediate infeed at the
remote busbar, the apparent directional angle (calculated from memorised voltage and
fault current) appeared at about –40°...-70°, i.e close to the directional line, sometimes
even in the forward section. This resulted from a severe phase shift of V voltage upon
AB
fault inception.
The solution implemented for this condition is a settable directional characteristic angle
as figure below.
Figure 1 New settable distance directional characteristic
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P437 Upgrade Documentation
(continued)
2.2 Power Swing Blocking (Function Group PSB)
New counters
Two new counters are implemented to count stable and unstable swings:
(cid:133) 006.025 PSB No. stab. PSwing
This counter is incremented after each stable power swing cycle,
i.e. if the positive sequence impedance leaves the power swing detection polygon on
the same side as it entered (equal signs of resistive component R )
pos
(cid:133) 006.026 PSB No. OOS
This counter is incremented after each unstable power swing cycle
(= upon out-of-step condition),
i.e. if the positive sequence impedance leaves the power swing detection polygon on
the opposite side as it entered (unequal signs of resistive component R )
pos
Counter reset timer
Upon each incrementing the counter, a dedicated timer stage is triggered. If this timer
elapses while no further incrementing of the same counter takes place, then it is
supposed that the power swing condition has stopped and this counter gets reset to 0.
For this timer stage the existing setting 014.055 PSB Max. blocking time is
used, which is already recommended to be set to the anticipated maximum power swing
cycle time.
Counter comparators
For each counter comparative thresholds are provided:
(cid:133) 006.027 PSB Perm. no. stab. PS [setting range 1 ... 10 / blocked]
is the number of stable power swings, after which the signal
006.030 PSB Perm. no. PS reach is raised
(cid:133) 006.028 PSB Perm. no. OOS [setting range 1 ... 10 / blocked]
is the number of unstable power swings, after which the signal
006.035 PSB Perm. no. OOS reach is raised
These binary signals remain active (value “Yes”) until their associated counter resets.
They are freely configurable to any physical output relays, LED’s and communication
outputs (InterMiCOM, GOOSE, GSSE). They are logged in fault recording and –
depending on the communication protocol and signal mapping – messaged through the
information communication interfaces (COMM1).
Also these signals can be directly linked into the general trip command, e.g. to provide
delayed tripping if a power swing does not get removed in due time by the generator
control equipment.
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P437 Upgrade Documentation
(continued)
2.3 Switch on to Fault Protection (Function Group SOTF)
Dead line detector
The dead line detection logic implemented in version -610 was not useful, as SOTF
protection remained operative as long as the CB was signaled in 3-pole open condition,
even if the line was already energized (from remote CB or from local 2nd CB in 1½ CB
schemes. Therefore the CB status input is no longer taken into consideration.
On the other hand, in few cases CT failures occurred from picking up load current. For
such cases it is not desirable to inhibit SOTF, even if the line is already energized. To
take care for this condition, too, the dead line inhibit logic can now be enabled or
disabled by setting.
Figure 2 Decision 'Line dead' in the 'Switch on to fault protection' function
Note: Internal signal name ‘Dead line’ remained unchanged to as it is required in figure 3-129 in the referenced full manual.
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P437 Upgrade Documentation
(continued)
2.4 Protective Signaling (Function Group PSIG)
Refinement of Weak-Infeed
blocking logic
The weak-infeed blocking logic has been modified so that phase-selective blocking is
raised upon the CB pole open condition.
Figure 3 Phase-selective blocking of the weak infeed logic (replaces fig. 3-165 of the referenced manual)
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