ABB ret650 - Page 202

IECEQUATION2294 V2 EN-US (Equation 46)
DA
D
U
=
D
EQUATION1986 V1 EN-US (Equation 47)
t
1
tMin
D
=
EQUATION1848 V2 EN-US (Equation 48)
Where:
DA absolute voltage deviation from the set point
D relative voltage deviation in respect to set deadband value
For the last equation, the condition t1 > tMin shall also be fulfilled. This practically
means that tMin will be equal to the set t1 value when absolute voltage deviation
DA is equal to ΔU ( relative voltage deviation D is equal to 1). For other values see
figure
72. It should be noted that operating times, shown in the figure 72 are for 30,
60, 90, 120, 150 & 180 seconds settings for t1 and 10 seconds for tMin.
t1=180
t1=150
t1=120
t1=90
t1=60
t1=30
IEC06000488_2_en.vsd
IEC06000488 V2 EN-US
Figure 72: Inverse time characteristic for TR1ATCC and TR8ATCC
The second time delay, t2, will be used for consecutive commands (commands in
the same direction as the first command). It can have a definite or inverse time
characteristic according to the setting t2Use (Constant/Inverse). Inverse time
Section 11 1MRK 504 169-UEN A
Control
196 Transformer protection RET650 2.2 IEC
Application manual