ABB Relion 670 Series Applications Manual page 196

Section 11
Multipurpose protection
11.1.3.4 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, GF03)
2. Set
3. Set
4. Set
5. Set
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
9. Set parameter
10. Set parameter
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.
11.1.3.5 Voltage restrained overcurrent protection for generator and 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,
GF05)
2. Set
3. Set
be used for restraining. Alternatively, positive sequence voltage can be used for restraining by
selecting
4. Set base current value to the rated generator current primary amperes
190
CurrentInput to value UnbalancePh
EnRestrainCurr to On
RestrCurrInput to MaxPh
RestrCurrCoeff to value 0.97
CurveType_OC1 to value IEC Def. Time
PickupCurr_OC1 to value 5%
tDef_OC1 to desired time delay (for example, 2.0s)
CurrentInput to value MaxPh
VoltageInput to value MinPh-Ph (it is assumed that minimum phase-to-phase voltage shall
PosSeq for this setting parameter)
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1MRK 511 407-UUS Rev. J
M13088-142 v3
M13088-158 v4
Phasor measurement unit RES670
Application manual