Hitachi Relion 670 Series Applications Manual page 170

Section 8
Current protection
IEC16000129 V1 EN-US
Figure 67:
DirMode is set Forward or Reverse to set the direction of the operation for the directional function
selected by the OpMode.
All the directional protection modes have a residual current release level setting INRel> which is set
in % of IBase. This setting should be chosen smaller than or equal to the lowest fault current to be
detected.
All the directional protection modes have a residual voltage release level setting UNRel> which is set
in % of UBase. This setting should be chosen smaller than or equal to the lowest fault residual
voltage to be detected.
tDef is the definite time delay, given in s, for the directional residual current protection.
tReset is the time delay before the definite timer gets reset, given in s. With a tReset time of few
cycles, there is an increased possibility to clear intermittent earth faults correctly. The setting shall be
much shorter than the set trip delay. In case of intermittent earth faults, the fault current is
intermittently dropping below the set value during consecutive cycles. Therefore the definite timer
should continue for a certain time equal to tReset even though the fault current has dropped below
the set value.
The characteristic angle of the directional functions RCADir is set in degrees. RCADir is normally set
equal to 0° in a high impedance earthed network with a neutral point resistor as the active current
component is appearing out on the faulted feeder only. RCADir is set equal to -90° in an isolated
network as all currents are mainly capacitive.
ROADir is Relay Operating Angle. ROADir is identifying a window around the reference direction in
order to detect directionality. ROADir is set in degrees. For angles differing more than ROADir from
RCADir the function is blocked. The setting can be used to prevent unwanted operation for non-
faulted feeders, with large capacitive earth fault current contributions, due to CT phase angle error.
INCosPhi> is the operate current level for the directional function when OpMode is set 2I0Cosfi. The
setting is given in % of IBase. The setting should be based on calculation of the active or capacitive
earth fault current at required sensitivity of the protection.
164
RCADir = 0º
ROADir = 80º
Characteristic for RCADir = 0° and ROADir = 80°
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IEC16000129-1-en.vsdx
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Application manual