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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.
kForIEEE: The time constant for the inverse characteristic. Select the one giving the best
match to the transformer capability.
tCooling: 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.
tMin: The operating times at voltages higher than the set V/Hz>>. The setting shall match
capabilities on these high voltages. Typical setting can be 1-10 second.
tMax: 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)
AlarmLevel: 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.
9.4.3.3
Service value report
M6496-144 v4
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.
9.4.3.4
Setting example
M6496-108 v5
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
.
The settings
V/Hz>> and V/Hz> are made in per unit of the rated voltage of the transformer
winding at rated frequency.
Set the transformer adapted curve for a transformer with overexcitation characteristics in
according to figure
.
V/Hz> for the protection is set equal to the permissible continuous overexcitation according
= 105%. When the overexcitation is equal to
V/Hz>, tripping is obtained after a
time equal to the setting of t1.
This is the case when
UBase is equal to the transformer rated voltages. For
other values, the percentage settings need to be adjusted accordingly.
When the overexcitation is equal to the set value of
V/Hz>>, tripping is obtained after a time
equal to the setting of t6. A suitable setting would be
V/Hz>> = 140% and t6 = 4 s.
The interval between
V/Hz>> and V/Hz> is automatically divided up in five equal steps, and the
time delays t2 to t5 will be allocated to these values of overexcitation. In this example, each
step will be (140-105) /5 = 7%. The setting of time delays t1 to t6 are listed in table
.
1MRK 505 343-UEN B
Section 9
Voltage protection
481
Application manual
Содержание Relion 670 series
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