Maximum Slip Frequency - ABB REG650 Technical Manual

1MRK 502 043-UUS B
7.3.7.3
Technical Manual
results in a tendency to miss the 1st pole-slip, that one immediately after the fault has
been cleared.) The above timing is used to discriminate a fault from an out-of-step
condition. In Figure 68, some important points on the trajectory of Z(R, X) are
designated. Point 0: the pre-fault, normal load Z(R, X). Point 1: impedance Z under a
three-phase, low-resistance fault. Z lies practically on, or very near, the Z-line.
Transition of the measured Z from point 0 to point 1 takes app. 20 ms, due to Fourier
filters. Point 2: Z immediately after the fault has been cleared. Transition of the
measured Z from point 1 to point 2 takes approximately 20 ms, due to Fourier filters.
The complex impedance then travels in the direction from the right to the left, and exits
the lens on the opposite side. When the complex impedance exits the lens on the side
opposite to its entrance, the 1st pole-slip has already occurred and more pole-slips can
be expected if the generator is not disconnected.
Figures like Figure 68 and
analog output data from the pole-slip function, and are of great help with eventual
investigations of the performance of the out-of-step function.

Maximum slip frequency

The maximum slip frequency fsMax in Hz where a pole-slip can be detected when
using a specific value of the setting (parameter) PickupAngle (which determines the
width of the lens characteristic) is as follows. A parameter in this calculation routine is
the value of the minimum traverse time, traverseTimeMin. The minimum traverse time
determines the minimum time, the complex impedance Z(R, X) must travel through the
lens from one side to the other, in order to recognize that a pole-slip has occurred. The
value of the internal constant traverseTimeMin is a function of the set PickupAngle.For
values of PickupAngle <= 110°, traverseTimeMin = 50 ms. For values PickupAngle >
110°, traverseTimeMin = 40 ms. The expression which relates the maximum slip
frequency fsMax and the traverseTimeMin is as follows:
1000
[ ]
≅
fsMax Hz
traverseTimeMin ms
ANSIEQUATION2319 V1 EN
The maximum slip frequency fsMax for traverseTimeMin = 50 ms is:
PickupAngle = 90° → fsMax = 20 ⋅ 0.500 = 10.000 Hz
PickupAngle = 100° → fsMax = 20 ⋅ 0.444 = 8.888 Hz
PickupAngle = 110° → fsMax = 20 ⋅ 0.388 = 7.777 Hz
The maximum slip frequency fsMax for traverseTimeMin = 40 ms is:
PickupAngle = 120° → fsMax = 25 ⋅ 0.333 = 8.333 Hz
Figure 68
Figure 70 are always possible to draw by means of the

PickupAngle
⋅
 
1 000 . -
[ ] [ [ ]
°
180

Section 7
Impedance protection
shows two pole-slips.
[ ]
° 
 

(default 110°)
(Equation 32)
157