105
Two step definite and inverse time-
delayed residual
overcurrent protection (TEF1 and TEF2)
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on the other lines gives a time difference of 0.3-0.4 seconds. A logarithmic characteris-
tic is generally the most suitable for this purpose, because the time difference is constant
for a given ratio between the currents.
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In the directional comparison scheme, information of the fault current direction must be
transmitted to the other line end. A short operate time enables auto-reclosing after the
fault.
A communication logic block for residual overcurrent protection can be included in the
REx 5xx terminal to provide this feature. The function contains circuits for blocking
overreach and permissive overreach schemes. See the section
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.
In the permissive directional comparison system, the forward direction measuring ele-
ment will send a permissive signal to the other line end if a fault is seen in the forward
direction. The direction element at the other line end must wait for a permissive signal
before it can trip.
The total operate time for the system will be the sum of the pick-up time of the measur-
ing element and the transmission time of the permissive signal. An operate time of 50-
60 ms, including a channel transmission time of 20 ms, can be achieved. This short op-
erate time allows auto-reclosing after the fault.
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The functions (TEF1 andTEF2) measures the residual current I
N
and the residual volt-
age U
N .
Figure 47 shows the current measuring, time delay and logic circuits of this
protection function. The two functions are identical except that TEF1 uses the current
I4 and TEF2 the current I5. References will therefore only be made to TEF1 in the fol-
lowing description, but the also apply for TEF2.
Summary of Contents for REO 517
Page 10: ... RQWHQWV ...
Page 16: ...6 Introduction to the application manual KDSWHU QWURGXFWLRQ ...
Page 64: ...54 Blocking of signals during test KDSWHU RPPRQ IXQFWLRQV ...
Page 88: ...78 Scheme communication logic ZCOM KDSWHU LQH LPSHGDQFH ...
Page 146: ...136 Unbalance protection for capacitor banks TOCC KDSWHU XUUHQW ...
Page 166: ...156 Dead line detection DLD KDSWHU 3RZHU V VWHP VXSHUYLVLRQ ...
Page 378: ...368 Monitoring of DC analog measurements KDSWHU 0RQLWRULQJ ...
Page 384: ...374 Pulse counter logic PC KDSWHU 0HWHULQJ ...
Page 412: ...402 Serial communication modules SCM KDSWHU DWD FRPPXQLFDWLRQ ...
Page 440: ...430 LED indication module KDSWHU DUGZDUH PRGXOHV ...