![background image](http://html.mh-extra.com/html/abb/615-series-ansi/615-series-ansi_technical-manual_4665139.webp)
Section 4
1MAC050144-MB C
Protection functions
132
615 series ANSI
Technical Manual
Reliable operation requires both the operating and polarizing quantities to exceed certain
minimum amplitude levels. The minimum amplitude level for the operating quantity
(current) is set with the
Min trip current
setting. The minimum amplitude level for the
polarizing quantity (voltage) is set with the
Min trip voltage
setting. If the amplitude level
of the operating quantity or polarizing quantity is below the set level, the direction
information of the corresponding phase is set to "Unknown".
The polarizing quantity validity can remain valid even if the amplitude of the polarizing
quantity falls below the value of the
Min trip voltage
setting. In this case, the directional
information is provided by a special memory function for a time defined with the
Voltage
Mem time
setting.
The three phase directional over current protection functions is provided with a memory
function to secure a reliable and correct directional IED operation in case of a close short
circuit or an ground fault characterized by an extremely low voltage. At sudden loss of the
polarization quantity, the angle difference is calculated on the basis of a fictive voltage.
The fictive voltage is calculated using the positive phase sequence voltage measured
before the fault occurred, assuming that the voltage is not affected by the fault. The
memory function enables the function to operate up to a maximum of three seconds after
a total loss of voltage. This time can be set with the
Voltage Mem time
setting. The voltage
memory cannot be used for the "Negative sequence voltage" polarization because it is not
possible to substitute the positive sequence voltage for negative sequence voltage without
knowing the network unsymmetry level. This is the reason why the fictive voltage angle
and corresponding direction information are frozen immediately for this polarization mode
when the need for voltage memory arises and these are kept frozen until the time set with
Voltage Mem time
elapses.
When the voltage falls below
Min trip voltage
at a close fault, the fictive voltage is used
to determine the phase angle. The measured voltage is applied again as soon as the voltage
rises above
Min trip voltage
and hysteresis. The fictive voltage is also discarded if the
measured voltage stays below
Min trip voltage
and hysteresis for longer than
Voltage Mem
time
or if the fault current disappears while the fictive voltage is in use. When the voltage
is below
Min trip voltage
and hysteresis and the fictive voltage is unusable, the fault
direction cannot be determined. The fictive voltage can be unusable for two reasons:
• The fictive voltage is discarded after
Voltage Mem time
• The phase angle cannot be reliably measured before the fault situation.
Summary of Contents for 615 Series ANSI
Page 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
Page 2: ......
Page 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Page 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Page 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Page 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Page 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
Page 712: ......