Maximum Slip Frequency - ABB Relion Technical Manual

1MRK 502 048-UUS A
7.4.7.3
Technical manual
milliseconds. (To require that the impedance Z(R, X) travels through each of the two
halves of the lens, for example, in 25 milliseconds, 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
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 76 and
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:
Figure 78 are always possible to draw by means of the analog

PickupAngle
⋅
 
1 000 . -
[ ] [ [ ]
°
180

Section 7
Impedance protection
Figure 76, some important points
Figure 76 shows two pole-slips.
[ ]

°
 

(default 110°)
(Equation 40)
183