ABB Relion 670 Series Applications Manual page 254

Section 10
Multipurpose protection
10.1.4.4 Open phase protection for transformer, lines or generators and circuit
breaker head flashover protection for generators
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,
CVGAPC:3)
2. Set CurrentInput to value UnbalancePh
3. Set EnRestrainCurr to On
4. Set RestrCurrInput to MaxPh
5. Set RestrCurrCoeff to value 0.97
6. Set base current value to the rated current of the protected object in primary amperes
7. Enable one overcurrent step (for example, OC1)
8. Select parameter CurveType_OC1 to value IEC Def. Time
9. Set parameter PickupCurr_OC1 to value 5%
10. Set parameter tDef_OC1 to desired time delay (for example, 2.0s)
Proper operation of CVGAPC function made in this way can easily be verified by secondary injection. All
other settings can be left at the default values. However it shall be noted that set values for restrain
current and its coefficient will as well be applicable for OC2 step as soon as it is enabled.
Furthermore the other built-in protection elements can be used for other protection and alarming
purposes. For example, in case of generator application by enabling OC2 step with set pickup to 200%
and time delay to 0.1s simple but effective protection against circuit breaker head flashover protection is
achieved.
10.1.4.5 Voltage restrained overcurrent protection for generator and unit step-up
transformer
Example will be given how to use one CVGAPC function to provide voltage restrained overcurrent
protection for a generator. Let us assume that the time coordination study gives the following required
settings:
• Inverse Time Over Current TOC/IDMT curve: ANSI very inverse
• Pickup current of 185% of generator rated current at rated generator voltage
• Pickup current 25% of the original pickup current value for generator voltages below 25% of rated
voltage
This functionality can be achieved by using one CVGAPC function. The following shall be done in order
to ensure proper operation of the function:
1. Connect three-phase generator currents and voltages to one CVGAPC instance (for example,
CVGAPC:5)
2. Set CurrentInput to value MaxPh
3. Set VoltageInput to value MinPh-Ph (it is assumed that minimum phase-to-phase voltage shall be
used for restraining. Alternatively, positive sequence voltage can be used for restraining by selecting
PosSeq for this setting parameter)
4. Set base current value to the rated generator current primary amperes
5. Set base voltage value to the rated generator phase-to-phase voltage in kV
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1MRK 505 370-UUS Rev. K
M13088-142 v4
M13088-158 v5
Busbar protection REB670
Application manual