Hitachi Relion 670 Series Applications Manual page 183

1MRK511407-UUS Rev. N
In order to achieve such protection functionality with one CVGAPC functions the following must be done:
1. Connect three-phase generator currents to one CVGAPC instance (for example, CVGAPC:1)
2. Set parameter CurrentInput to value NegSeq
3. Set base current value to the rated generator current in primary amperes
4. Enable one overcurrent step (for example, OC1)
5. Select parameter CurveType_OC1 to value Programmable
=
t TD
op
EQUATION1742-ANSI V1 EN-US
where:
top
TD
M
A, B, C and P are user settable coefficients which determine the curve used for Inverse Time Overcurrent TOC/IDMT
When the equation
is obvious that if the following rules are followed:
1. set TD equal to the generator negative sequence capability value
2.
set A_OC1 equal to the value (1/x)
3. set B_OC1 = 0.0, C_OC1=0.0 and P_OC1=2.0
4. set PickupCurr_OC1 equal to the value x
then the OC1 step of the CVGAPC function can be used for generator negative sequence inverse
overcurrent protection.
For this particular example the following settings shall be entered to insure proper function operation:
1. select negative sequence current as measuring quantity for this CVGAPC function
2. make sure that the base current value for the CVGAPC function is equal to the generator rated
current
3. set TD_OC1 = 20
4.
set A_OC1= (1/0.07)
5. set B_OC1 = 0.0, C_OC1 = 0.0 and P_OC1 = 2.0
6. set PickupCurr_OC1 = 7%
Proper timing of the 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 ensure proper function operation in case of repetitive unbalance conditions.
Furthermore the other built-in protection elements can be used for other protection and alarming
purposes (for example, use OC2 for negative sequence overcurrent alarm and OV1 for negative
sequence overvoltage alarm).
Phasor measurement unit RES670
Application manual
æ ö
A
+
×
B
ç ÷
-
P
è M C ø
is the operating time in seconds of the Inverse Time Overcurrent TOC/IDMT algorithm
is time multiplier (parameter setting)
is ratio between measured current magnitude and set pickup current level
calculation
87 is compared with the equation
2
= 204.0816
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89 for the inverse time characteristic of the OC1 it
2
Section 11
Multipurpose protection
(Equation 90)
177