1. set k equal to the IEC or ANSI standard generator capability value
2. set parameter
A_OC1
equal to the value 1/x2
3. set parameter
C_OC1
equal to the value 1/x2
4. set parameters
B_OC1
= 0.0 and
P_OC1
=2.0
5. set
StartCurr_OC1
equal to the value x
then the OC1 step of the CVGAPC function can be used for generator negative
sequence inverse overcurrent protection.
1. select positive sequence current as measuring quantity for this CVGAPC
function
2. make sure that the base current value for CVGAPC function is equal to the
generator rated current
3. set k = 37.5 for the IEC standard or k = 41.4 for the ANSI standard
4. set
A_OC1
= 1/1.162 = 0.7432
5. set
C_OC1
= 1/1.162 = 0.7432
6. set
B_OC1
= 0.0 and
P_OC1
= 2.0
7. set
StartCurr_OC1
= 116%
Proper timing of CVGAPC function made in this way can easily be verified by
secondary injection. All other settings can be left at the default values. If required
delayed time reset for OC1 step can be set in order to insure proper function
operation in case of repetitive overload conditions.
Furthermore the other built-in protection elements can be used for other protection
and alarming purposes.
In the similar way rotor overload protection in accordance with ANSI standard can
be achieved.
6.1.3.4
Open phase protection for transformer, lines or generators and circuit
breaker head flashover protection for generators
M13088-142 v3
Example will be given how to use one CVGAPC function to provide open phase
protection. This can be achieved by using one CVGAPC function by comparing the
unbalance current with a pre-set level. In order to make such a function more
secure it is possible to restrain it by requiring that at the same time the measured
unbalance current must be bigger than 97% of the maximum phase current. By
doing this it will be insured that function can only pickup if one of the phases is
open circuited. Such an arrangement is easy to obtain in CVGAPC function by
enabling the current restraint feature. The following shall be done in order to insure
proper operation of the function:
1. Connect three-phase currents from the protected object to one CVGAPC
instance (for example, GF03)
2. Set
CurrentInput
to value
UnbalancePh
3. Set
EnRestrainCurr
to
On
4. Set
RestrCurrInput
to
MaxPh
5. Set
RestrCurrCoeff
to value 0.97
1MRK 511 423-UEN A
Section 6
Multipurpose protection
Bay control REC650 2.2 IEC
85
Application manual
