ABB RELION REX640 Technical Manual page 595

1MRS759142 F
and then compared with setting
validity check are called as transient resistive and reactive components and noted as
Transient Ris Comp and Transient React Comp in Recorded data and TR_RIS_COMP
and TR_REACT_COMP in Monitored Data.
Validity of earth-fault current estimate is indicated by VALID_EF = TRUE.
In case
is confirmed by evaluating the polarity of the resistive part of measured admittance
(real(Y
phase of fault). The measured "transient admittance" is converted into equivalent
current value by multiplying it with nominal phase-to-earth voltage value and then
compared with setting
valid in compensated systems regardless of compensation degree and also in
high resistance earthed systems. Note that situation, when the compensation coil
becomes unintentionally disconnected, may result to condition where measured
resistive component is not sufficient for validity confirmation. In such case
validity Op mode should be selected as 'Resistive, Reactive'.
In case
current estimate is confirmed by evaluating the polarity of the resistive (real(Y
= real(I
admittance during the fault ignition moment (during the transient phase of fault).
The measured "transient admittance" is converted into equivalent current value
by multiplying it with nominal phase-to-earth voltage value and then compared
with setting
admittance is used to confirm validity of earth-fault current estimate.
Op mode = 'Resistive, Reactive' is valid in compensated, unearthed and in high
resistance earthed systems. In compensated systems this criterion is applicable
unless the protected feeder is over-compensated i.e. earth-fault current produced
by protected feeder is inductive. In such case
'Resistive'.
In case
estimate is not confirmed and protection operates based on estimated earth-fault
current or touch voltage magnitude.
applied e.g. when current measurement is at incomer and when compensation coil
with parallel resistor is located at dedicated earthing transformer bay. In this case,
during an earth fault in the network, residual current at incomer is zero and thus
validity evaluation based on resistive or reactive component is not possible. Thus in
order to apply IFPTOC at the incomer,
selected.
Setting
primary current as base value. The value should be selected based on following
principles:
• In compensated networks
known system damping value, in practice e.g. based on the ampere value of the
parallel resistor of the coil. For example, if parallel resistor of the coil has rating
of 10A, then
for example 5A. Based on practical experience, value of 3A is found to be suitable
for most applications. The value of
than the transient resistive component generated by the protected feeder during
post-fault oscillation to avoid false activations of validity check module in healthy
feeders during an earth fault.
Transient resistive component can be approximated with following equation:
REX640
Technical Manual
EF validity Op mode = 'Resistive', then validity of earth-fault current estimate
) = real(I /U )) during the fault ignition moment (during the transient
o o o
EF validity Min Curr . EF validity Op mode = 'Resistive' is
EF validity Op mode = 'Resistive, Reactive', then validity of earth-fault
/U )) and reactive (imaginary) part (imag(Y
o o
EF validity Min Curr . Either one, resistive or reactive part of measured
EF validity Op mode = 'No validity", then validity of earth-fault current
EF validity Min Curr is given in per unit format with residual current channel
EF validity Min Curr should be smaller than this value with margin,
EF validity Min Curr . The current values used in
EF validity Op mode must be set to
EF validity Op mode = 'No validity' can be
EF validity Op mode = 'No validity', must be
EF validity Min Curr should be selected based on the
EF validity Min Curr should also be set higher
Protection functions
) = imag(I /U )) of measured
o o o
EF validity
EF
)
o
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