Hitachi Relion 670 Series Applications Manual page 144

Section 8
Current protection
DirMode is set Forward or Reverse to set the direction of the operation for the directional function
selected by the OpModeSel.
All the directional protection modes have a residual current release level setting INRelPU 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 VNRelPU which is set in
% of VBase. 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 ground faults correctly. The setting shall be much
shorter than the set trip delay. In case of intermittent ground 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 grounded 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 ground fault current contributions, due to CT phase angle error.
INCosPhiPU is the pickup current level for the directional function when OpModeSel is set 3I0Cosfi. The
setting is given in % of IBase. The setting should be based on calculation of the active or capacitive
ground fault current at required sensitivity of the protection.
SN_PU is the pickup power level for the directional function when OpModeSel is set 3I03V0Cosfi. The
setting is given in % of SBase. The setting should be based on calculation of the active or capacitive
ground fault residual power at required sensitivity of the protection.
The input transformer for the Sensitive directional residual over current and power protection function has
the same short circuit capacity as the phase current transformers. Hence, there is no specific
requirement for the external CT core, i.e. any CT core can be used.
If the time delay for residual power is chosen the delay time is dependent on two setting parameters.
SRef is the reference residual power, given in % of SBase. TDSN is the time multiplier. The time delay
will follow the following expression:
=
t
inv
3I 3V cos (measured)
EQUATION2030-ANSI V1 EN-US
INDirPU is the pickup current level for the directional function when OpModeSel is set 3I0 and fi. The
setting is given in % of IBase. The setting should be based on calculation of the ground fault current at
required sensitivity of the protection.
OpINNonDir is set Enabled to activate the non-directional residual current protection.
138
×
TDSN Sref
× × j
0 0
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1MRK511407-UUS Rev. N
(Equation 56)
Phasor measurement unit RES670
Application manual