of the capability curve of the transformer/generator. Setting should be above the knee-
point when the characteristic starts to be straight on the high side.
XLeakage: The transformer leakage reactance on which the compensation of voltage
measurement with load current is based. The setting shall be the transformer leak
reactance in primary ohms. If no current compensation is used (mostly the case) the setting
is not used.
t_TripPulse: The length of the trip pulse. Normally the final trip pulse is decided by the
trip function block. A typical pulse length can be 50 ms.
CurveType: Selection of the curve type for the inverse delay. The IEEE curves or tailor
made curve can be selected depending of which one matches the capability curve best.
TDforIEEECurve: The time constant for the inverse characteristic. Select the one giving
the best match to the transformer capability.
t_CooolingK: The cooling time constant giving the reset time when voltages drops below
the set value. Shall be set above the cooling time constant of the transformer. The default
value is recommended to be used if the constant is not known.
t_MinTripDelay: The operating times at voltages higher than the set Pickup2. The setting
shall match capabilities on these high voltages. Typical setting can be 1-10 second.
t_MaxTripDelay: For overvoltages close to the set value times can be extremely long if a
high K time constant is used. A maximum time can then be set to cut the longest times.
Typical settings are 1800-3600 seconds (30-60 minutes)
AlarmPickup: Setting of the alarm level in percentage of the set trip level. The alarm level
is normally set at around 98% of the trip level.
tAlarm: Setting of the time to alarm is given from when the alarm level has been reached.
Typical setting is 5 seconds.
10.4.3.3 Service value report
A number of internal parameters are available as service values for use at commissioning
and during service. Remaining time to trip (in seconds) TMTOTRIP, flux density
VPERHZ, internal thermal content in percentage of trip value THERMSTA. The values
are available at local HMI, Substation SAsystem and PCM600.
10.4.3.4 Setting example
Sufficient information about the overexcitation capability of the protected object(s) must
be available when making the settings. The most complete information is given in an
overexcitation capability diagram as shown in figure
292.
Section 10 1MRK 506 369-UUS -
Voltage protection
584 Line distance protection REL670 2.2 ANSI
Application manual
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