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
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
298.
The settings Pickup2 and Pickup1 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 298.
Pickup1 for the protection is set equal to the permissible continuous overexcitation
according to figure 298 = 105%. When the overexcitation is equal to Pickup1, tripping
is obtained after a time equal to the setting of t1.
This is the case when VBase 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 Pickup2, tripping is obtained after
a time equal to the setting of t6. A suitable setting would be Pickup2 = 140% and t6 =
4 s.
The interval between Pickup2 and
Pickup1 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
48.
Table 48: Settings
V/f op (%) Timer Time set (s)
105 t1 7200 (max)
112 t2 600
119 t3 60
126 t4 20
133 t5 8
140 t6 4
1MRK 504 163-UUS A Section 10
Voltage protection
Transformer protection RET670 2.2 ANSI 631
Application manual
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