• Single phase railroad load
• Unbalanced system faults such as
•
Line to ground faults
• Double line to ground faults
• Line to line faults
• Open conductors, includes
• Broken line conductors
• Malfunction of one pole of a circuit breaker
.
9.16.3 Setting guidelines
GUID-2E6EBD7C-108F-49F1-A577-2730089B638D v1
GUID-F7AA2194-4D1C-4475-8853-C7D064912614 v4
When inverse time overcurrent characteristic is selected, the trip time
of the stage will be the sum of the inverse time delay and the set
definite time delay. Thus, if only the inverse time delay is required, it is
important to set the definite time delay for that stage to zero.
9.16.3.1
Operate time characteristic
GUID-0F3D5C8B-B485-4FEC-8448-CEAA1F6710D6 v6
Negative sequence time overcurrent protection for machines NS2PTOC
(46I2)
provides two operating time delay characteristics for step 1 and 2:
• Definite time delay characteristic
• Inverse time delay characteristic
The desired operate time delay characteristic is selected by setting CurveType1 as
follows:
• CurveType1 = Definite
• CurveType1 = Inverse
Definite time delay
[1]
is independent of the magnitude of the negative sequence
current once the pickup value is exceeded, while inverse time delay characteristic do
depend on the magnitude of the negative sequence current.
This means that inverse time delay is long for a small overcurrent and becomes
progressively shorter as the magnitude of the negative sequence current increases.
[1] The definite time delay is described by the setting t1, which is the time between activation of pickup and trip outputs.
Section 9 1MRK 504 163-UUS A
Current protection
604 Transformer protection RET670 2.2 ANSI
Application manual
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