OperationStepn: This is to enable/disable operation of step n.
Characteristicn: Selected inverse time characteristic for step n. This parameter gives the
type of time delay to be used. The setting can be, Definite time or Inverse curve A or
Inverse curve B or Inverse curve C or Prog. inv. curve. The choice is highly dependent of
the protection application.
Pickupn: Set operate overvoltage operation value for step n, given as % of residual voltage
corresponding to VBase:
ANSIEQUATION2290 V1 EN (Equation 513)
The setting depends on the required sensitivity of the protection and the type of system
grounding. In non-effectively grounded systems, the residual voltage cannot be higher
than three times the rated phase-to-ground voltage, which should correspond to 100%.
In effectively grounded systems, this value depends on the ratio Z0/Z1. The required
setting to detect high resistive ground faults must be based on network calculations.
tn: time delay of step n, given in s. The setting is highly dependent on the protection
application. In many applications, the protection function has the task to prevent damage
to the protected object. The speed might be important, for example, in the case of the
protection of a transformer that might be overexcited. The time delay must be co-
ordinated with other automated actions in the system.
tResetn: Reset time for step n if definite time delay is used, given in s. The default value
is 25 ms.
tnMin: Minimum operation time for inverse time characteristic for step n, given in s. For
very high voltages the overvoltage function, using inverse time characteristic, can give
very short operation time. This might lead to unselective trip. By setting t1Min longer than
the operation time for other protections such unselective tripping can be avoided.
ResetTypeCrvn: Set reset type curve for step n. This parameter can be set:
Instantaneous,Frozen time,Linearly decreased. The default setting is Instantaneous.
tIResetn: Reset time for step n if inverse time delay is used, given in s. The default value
is 25 ms.
TDn: Time multiplier for inverse time characteristic. This parameter is used for co-
ordination between different inverse time delayed undervoltage protections.
ACrvn, BCrvn, CCrvn, DCrvn, PCrvn: Parameters for step n, to set to create
programmable undervoltage inverse time characteristic. Description of this can be found
in the technical reference manual.
1MRK 506 369-UUS - Section 10
Voltage protection
Line distance protection REL670 2.2 ANSI 579
Application manual
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