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
292.
Pickup1 for the protection is set equal to the permissible continuous overexcitation
according to figure 292 = 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
42.
Table 42: 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
Information on the cooling time constant T
cool
should be retrieved from the power
transformer manufacturer.
1MRK 506 369-UUS - Section 10
Voltage protection
Line distance protection REL670 2.2 ANSI 585
Application manual
To Next Page
Loading...
