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3BTELECONTROL FUNCTIONS
PROTECTION, CONTROL AND METERING FUNCTIONS
When B trips but for some reason A takes longer to act, relays C and D experience a
change in the direction of the power flow since the fault has not been cleared. In this
case two adverse scenarios are possible which could cause relays C and D to open
the healthy line.
There is a delay in the communication channel between C and D. When B trips
D has permission to trip it observes the change in the power flow direction
(sees the fault in the trip direction) and the current magnitude is enough to trip.
The moment when relays C and D realize the current inversion is not
simultaneous. Besides C takes longer to realize the change in the power flow
direction. In this case the trip signal may arrive from D when C is still observing
a power flow towards the trip zone.
When the problem is examined it can be seen that in both cases the trip signal is not
related with the real fault condition and its duration is related in one case to the delay
in the communication channel and in the other case with a processing delay in the
farthest end(C here).
In order to avoid this, the POTT scheme shown in Figure 2-57 is slightly modified as
can be seen in Figure 2-61.
Tx
Rx
Tx
Rx
Trip
50H/67
Trip
50H/67
Trip
C
Trip
D
Figure 2-61 Modified POTT diagram
“Pick-up/Drop out” (PU/DO) blocks have been added to the trip outputs. These blocks
represent configurable delays for the signals to appear and disappear.
In this case a pick-up time needs to be configured whose duration should not be
smaller than 8ms. This time is enough to ensure that both relays have seen the
change in direction. A higher delay may be necessary depending on the
communication channel used to connect the relays. Slow channels would require
proportionally higher delays.
Summary of Contents for smART P500
Page 1: ...Instruction Manual Multifunction Protection Relay smART P500...
Page 23: ...2BTABLES INDEX THIS PAGE HAS BEEN LEFT BLANK INTENTIONALLY...
Page 39: ...5BHARDWARE FEATURES INTRODUCTION Figure 1 9 Wye Wye Connection measured neutral...
Page 40: ...5BHARDWARE FEATURES INTRODUCTION Figure 1 10 Wye Wye Connection sensitive neutral...
Page 41: ...5BHARDWARE FEATURES INTRODUCTION Figure 1 11 Open Delta Connection measured neutral...
Page 42: ...5BHARDWARE FEATURES INTRODUCTION Figure 1 12 Open Delta Connection sensitive neutral...
Page 511: ...2BANSI CURVES 0BCURVES FOR TIME CHARACTERISTICS Figure I 6 Moderately ANSI curve...
Page 513: ...2BANSI CURVES 0BCURVES FOR TIME CHARACTERISTICS Figure I 7 Very inverse ANSI curve...
Page 515: ...2BANSI CURVES 0BCURVES FOR TIME CHARACTERISTICS Figure I 8 Extremely inverse ANSI curve...
Page 532: ...4BRECLOSER CURVES 0BCURVES FOR TIME CHARACTERISTICS Figure I 14 Recloser Curves 101 119...
Page 535: ...4BRECLOSER CURVES 0BCURVES FOR TIME CHARACTERISTICS Figure I 15 Recloser Curves 120 142...
Page 538: ...4BRECLOSER CURVES 0BCURVES FOR TIME CHARACTERISTICS Figure I 16 Recloser Curves 151 202...