Maximum Slip Frequency - ABB REL650 Technical Manual

Section 6
Impedance protection
6.4.7.3
144
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.
shows two pole-slips. Figures like
draw by means of the 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

A pole-slip may be detected if it has a slip frequency lower than a maximum value
fsMax. The specific value of fsMax depends on the setting (parameter) StartAngle
(which determines the width of the lens characteristic). A parameter in this
calculation routine is the value of the minimum traverse time, traverseTimeMin.
The minimum traverse time is the minimum time that the travel of the complex
impedance Z(R, X) through the lens, from one side to the other, must last in order
to recognize that a pole-slip has occurred. The value of the internal constant
traverseTimeMin is a function of the set StartAngle.For values of StartAngle <=
110°, traverseTimeMin = 50 ms. For values StartAngle > 110°, traverseTimeMin =
40 ms. The expression which relates the maximum slip frequency fsMax and the
traverseTimeMin is as follows:
1000
[ ]
≅
fsMax Hz
traverseTimeMin ms
IECEQUATION2319 V1 EN-US
The maximum slip frequency fsMax for traverseTimeMin = 50 ms is:
StartAngle = 90° → fsMax = 20 × 0.500 = 10.000 Hz
StartAngle = 100° → fsMax = 20 × 0.444 = 8.888 Hz
StartAngle = 110° → fsMax = 20 × 0.388 = 7.777 Hz
The maximum slip frequency fsMax for traverseTimeMin = 40 ms is:
StartAngle = 120° → fsMax = 25 × 0.333 = 8.333 Hz
StartAngle = 130° → fsMax = 25 × 0.277 = 6.944 Hz
The minimum value of fsMax is 6.994 Hz. When StartAngle = 110 degrees, fsMax
= 7.777 Hz. This implies, that the default StartAngle = 110 degrees covers 90% of
cases as, the typical final slip frequency is between 2 - 5Hz. In practice, however,
before the slip frequency, for example 7.777 Hz, is reached, at least three pole-slips
have occurred. In other words, if we consider a linear increase of frequency from
50 Hz to 57.777 Hz, at least three pole-slips will occur (in fact: (57.777 - 50) / 2 =
3.889). The exact instantaneous slip-frequency expressed in Hz (corresponding to
Figure 61 and Figure 63
[ ]

StartAngle
⋅
 
1 000 . -
[ ] [ ] ]
°
180

(default 110°)
Line distance protection REL650 2.2 IEC
1MRK 506 382-UEN A
Figure 61
are always possible to
GUID-1311529F-21F8-40A0-8D01-0296BD9B4F00 v5

°
 

(Equation 14)
Technical manual