Admittance; Neutral Admittance (21Yn) - GE 850 Instruction Manual

ADMITTANCE

Admittance

Neutral Admittance (21YN)

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In a medium voltage (MV) network, the compensating reactor is used to compensate the
capacitive fault current ideally to zero at the fault point. However, detection of low ground
fault current in such networks is challenging when using the conventional current-based
ground fault detection methods. This element uses neutral admittance based criteria to
successfully detect the ground fault in the compensated or isolated MV networks.
Measured or calculated values of neutral current (I
calculate the shunt neutral admittance (Y
element uses one of the three modes (Y
Path:
Setpoints > Protection > Group 1(6) > Admittance > Neutral Admittance 1(X)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
This setting enables the Neutral Admittance functionality.
CURRENT INPUT
Range: J1 I0, J1 Ig, K1 I0, K1 Ig
Default: J1 I0
Current input can be programmed to be either the zero-sequence current, J1 I0 and K1
I0, calculated from the phase currents or measured ground current, J1 Ig and K1 Ig,
supplied externally at ground CT input. The setting range provides flexibility of selecting
the current source bank; currents J1 I0 and J1 Ig correspond to Bank 1 – Slot J1, while
currents K1 I0 and K1 Ig correspond to Bank 2 – Slot K1.
Selection of K1 I0 and K1 Ig, is only available with a Slot K bank order code. Otherwise, the
neutral admittance is calculated from the Slot J options only.
VOLTAGE INPUT
Range: J2 V0, J2 Vaux, K2 V0, K2 Vaux
Default: J2 V0
Voltage input can be programmed to be either the zero-sequence voltage, J2 V0 and K2
V0, calculated from the phase voltages, or the measured voltage, J2 Vaux and K2 Vaux,
supplied externally at auxiliary VT input. The setting range provides the flexibility of
selecting the voltage source bank; voltages J2 V0 and J2 Vaux correspond to Bank1 -
Slot J2, while currents K2 V0 and K2 Vaux corresponds to Bank2 - Slot K2.
When Voltage Input is set to J2 Vaux or K2 Vaux, it is required that the setpoint Aux VT
Connection (under
Setpoints > System > Voltage Sensing
otherwise the element operation will be blocked by the relay.
When Voltage Input is set to J2 V0 or K2 V0, phase voltages must be wye-connected,
and setpoint Phase VT Connection (under
set to "Wye."
Selection of K2 V0, K2 Vaux, is only available with the Slot K Bank order code. Otherwise,
the neutral admittance is calculated from Slot J options only.
CHAPTER 6: PROTECTION SETPOINTS
) and neutral voltage (V
0
), conductance (G ) and susceptance (B
0 0
, G , B ) to operate or block the output operands.
0 0 0
) be set to "VN" for this element,
Setpoints > System > Voltage Sensing
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
) are used to
0
). The
0
) must be