Voltage Elements - GE F35 Instruction Manual

CHAPTER 5: SETTINGS
The negative-sequence instantaneous overcurrent element is used as an instantaneous function with no intentional delay
or as a definite time function. The element responds to the negative-sequence current fundamental frequency phasor
magnitude (calculated from the phase currents) and applies a positive-sequence restraint for better performance: a small
portion (12.5%) of the positive-sequence current magnitude is subtracted from the negative-sequence current magnitude
when forming the operating quantity:
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious negative-sequence
currents resulting from:
• System unbalances under heavy load conditions
• Transformation errors of current transformers (CTs) during three-phase faults
• Fault inception and switch-off transients during three-phase faults
The positive-sequence restraint must be considered when testing for pickup accuracy and response time (multiple of
pickup). The operating quantity depends on the way the test currents are injected into the relay (single-phase injection:
 ; three-phase injection, opposite rotation:
I = 0.2917 I
op injected

5.7.8 Voltage elements

5.7.8.1 Menu
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  VOLTAGE ELEMENTS
 VOLTAGE ELEMENTS

F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL

I = I_2 K I_1 where K
–
op
Figure 5-85: Negative sequence IOC1 logic
 PHASE

 UNDERVOLTAGE1

 PHASE

 UNDERVOLTAGE3
 NEUTRAL OV1



 NEUTRAL OV3


 AUXILIARY UV1



 AUXILIARY UV3


1 8 
=
).
I = I
op injected
See below
See page 5-178
See page 5-178
GROUPED ELEMENTS
Eq. 5-20
5
5-175