Wattmetric Ground Fault - GE F35 Instruction Manual

GROUPED ELEMENTS
The neutral instantaneous overcurrent element can be used as an instantaneous function with no intentional delay or as a
definite time function. The element essentially responds to the magnitude of a neutral current fundamental frequency
phasor calculated from the phase currents. A positive-sequence restraint is applied for better performance. A small portion
(6.25%) of the positive-sequence current magnitude is subtracted from the zero-sequence current magnitude when
forming the operating quantity of the element as follows:
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious zero-sequence currents
resulting from:
• System unbalances under heavy load conditions
• Transformation errors of current transformers (CTs) during double-line and three-phase faults
• Switch-off transients during double-line and 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 how test currents are injected into the relay (single-phase injection:

I = 0.9375 I
op injected
5

5.7.5 Wattmetric ground fault

5.7.5.1 Wattmetric zero-sequence directional (ANSI 32G, IEC PSDE)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  WATTMETRIC...  WATTMETRIC GROUND FAULT 1(4)
 WATTMETRIC
 GROUND FAULT 1
5-166
NEUTRAL IOC1

TARGET: Self-reset
NEUTRAL IOC1

EVENTS: Disabled
 
I = 3 I_0 K
–
op
; three-phase pure zero-sequence injection:
Figure 5-79: Neutral IOC1 logic
WATTMETRIC GND FLT 1

FUNCTION: Disabled
WATTMETRIC GND FLT 1

SOURCE: SRC 1
WATTMETRIC GND FLT 1

VOLT: Calculated VN
WATTMETRIC GND FLT 1

OV PKP: 0.20 pu
WATTMETRIC GND FLT 1

CURR: Calculated IN
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
  
I_1 where K = 1 16

I = 3 I
op injected
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
Range: Calculated VN, Measured VX
Range: 0.02 to 3.00 pu in steps of 0.01
Range: Calculated IN, Measured IG
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
).
Eq. 5-16