Substation Automation and Protection Training
REL 670 Line Distance Protection IED
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ABB AB, 2007
Switch Onto Fault (SOTF)
2007-10-03
Substation Automation and Protection Training
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©
ABB AB, 2007
Switch Onto Fault (SOTF)
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Substation Automation and Protection Training
SOTF – What happens What happens from the IED’s point of view:
Pre-fault
Fault
Pre-fault: Voltage is zero, Current is zero. Fault: fault voltages and currents.
THIS is NOT a normal situation. In a normal situation:
U
I
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ABB AB, 2007
Pre-fault: Healthy voltages and load current Fault: fault voltages and currents.
2007-10-03
Substation Automation and Protection Training
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SOTF IED 670 Directional Measurement is based on memory voltage, to ensure correct directional detection even at close-in faults, where the level of faulty voltages is too low to ensure a correct measurement of the phase angles (directionality). The memory voltage is based on pre-fault voltage. In case of Switch Onto Fault: pre-fault voltage is zero Æ Memory Voltage is zero Directionality cannot be measured or it can be measured with a longer time delay.
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ABB AB, 2007
For Switch onto Fault fast trip must be ensured: Æ Switch Onto Fault needs a non-directional fault detection from an overreaching impedance zone: ZM02-STND (Non Directional Start)
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Substation Automation and Protection Training
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ABB AB, 2007
SOTF - settings
Internal Dead Line Detection Settings: IPh < Iset AND UPh < Uset Æ Dead Line 2007-10-03
Substation Automation and Protection Training
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SOTF Switch onto fault must also know that the Circuit Breaker is going to be closed. This is done by an external signal (Close Command to CB) or by Automatic Dead Line Detection.
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ABB AB, 2007
DeadLine Detection
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Substation Automation and Protection Training
SOTF
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ABB AB, 2007
When CB is going to be closed SOTF opens one time-window of 1s (default value). This is done by monitoring the built-in dead line detection signal. If during this window a non-diretional fault (ZM02-STND) is detected THEN Æ SOTFTRIP signal is issued.
2007-10-03
Substation Automation and Protection Training
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SOTF Information that Circuit Breaker is going to be closed can be done by an external signal (Close Command to CB).
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ABB AB, 2007
When CB is going to be closed SOTF opens one time-window of 1s. If during this window a non-directional fault (ZM02-STND) is detected THEN Æ SOTF-TRIP signal is issued.
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Substation Automation and Protection Training
SOTF With these settings:
SOTF is initiated by: - DEAD LINE DETECTION OR CB CLOSING CONTACT INFORMATION
With these settings:
SOTF is initiated by: - CB CLOSING CONTACT INFORMATION ONLY!
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ABB AB, 2007
FAULT DETECTION IS ALWAYS BASED BY NON DIRECTIONAL IMPEDANCE START (ZM02-STND in A32 configuration).
2007-10-03
Substation Automation and Protection Training
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SOTF – settings UILevel fault detection
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ABB AB, 2007
Current higher then IPh< and voltage below the UPh< in any of the three phases for more than tDuration time Æ fault detection 2007-10-03 10
Substation Automation and Protection Training
SOTF Information that Circuit Breaker is going to be closed can be done by an external signal (Close Command to CB).
©
ABB AB, 2007
When CB is going to be closed SOTF opens one time-window of 1s (default value). If during this window a fault is detected (UI Level algorithm) THEN Æ SOTF-TRIP signal is issued.
2007-10-03
Substation Automation and Protection Training
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SOTF Information that Circuit Breaker is going to be closed can be done by built-in dead line detection.
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ABB AB, 2007
When Dead Line Detection signal goes from 1 to 0, one time-window of 1s (default value) is opened. If during this window a fault is detected (UI Level algorithm) THEN Æ SOTF-TRIP signal is issued.
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Substation Automation and Protection Training
SOTF With these settings:
SOTF is initiated by: - DEAD LINE DETECTION OR CB CLOSING CONTACT INFORMATION
With these settings:
SOTF is initiated by: - CB CLOSING CONTACT INFORMATION ONLY!
©
ABB AB, 2007
FAULT DETECTION IS BASED BY UI Level Algorithm
2007-10-03
Substation Automation and Protection Training
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SOTF With these settings:
SOTF is initiated by: - DEAD LINE DETECTION OR CB CLOSING CONTACT INFORMATION
With these settings:
SOTF is initiated by: - CB CLOSING CONTACT INFORMATION ONLY!
©
ABB AB, 2007
FAULT DETECTION IS BASED BY UI Level Algorithm or by Non Directional Impedance detection (ZM02-STND)
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Substation Automation and Protection Training
SOTF– Automatic CB close detection If Automatic detection of CB closing is desired, the GATE GT01 should be set OFF. Dead Line Detection is built-in in SOTF function block.
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ABB AB, 2007
If GATE GT01 = GT02 = OFF, this logic is not used.
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Substation Automation and Protection Training
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SOTF– Activation by CB contact If GATE GT01 = ON and GATE GT02 = OFF, then activation of SOTF by auxiliary contact of the circuit breaker is enabled (Automatic detection is always enabled).
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ABB AB, 2007
Time delay: to avoid that too fast auxiliary Normally Closed CB contacts enable SOTF before the tripped protection function (and also ZM02-STND) resets with consequence the A/R attempt is blocked by SOTF.
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Substation Automation and Protection Training
SOTF – Activation by CLOSE command
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ABB AB, 2007
If GATE GT02 = ON and GATE GT01 = OFF, then activation of SOTF by Close Command to circuit breaker (automatic by A/R or manual) is achieved. Automatic detection is always enabled.
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Substation Automation and Protection Training