ABB RELION REX640 Technical Manual page 533

1MRS759142 C
REX640
Technical Manual
times of stages 1 and 2 avoid unnecessary breaker operations during self-
extinguishing earth faults.
• Fast tripping of low-ohmic permanent earth faults regardless of their type
(continuous or intermittent), stage 1
• Delayed tripping of higher-ohmic permanent earth faults regardless of their type
(continuous or intermittent), stage 2
• Alarms (but no tripping) about high-ohmic earth faults in order to monitor the
insulation status of the network and provide early indication of evolving faults
before they cause tripping (by stages 1 or 2), stage 3.
Besides the internal start condition based on residual zero-sequence overvoltage,
MFADPSDE can also be externally released by using the RELEASE input. In this
case, the external release signal overrides the Voltage start value setting and sets the
internal limit to the minimum value.
Multi-frequency admittance calculation
The Multi-frequency admittance calculation module calculates neutral admittances
using fundamental frequency and the 2nd, 3rd, 5th, 7th and 9th harmonic components
of residual current and zero-sequence voltage. The fundamental frequency admittance
(conductance and susceptance) is calculated if the magnitude of a harmonic in residual
current and zero-sequence voltage is measurable by the relay.
1
I
3
⋅
1 1 1
0
Y G j B
= = + ⋅
0 o o
1
U
−
0
GUID-1269F862-9B49-4122-B2F4-9C5324D4F51C V1 EN
Fundamental frequency neutral admittance phasor
1
Y
0
Fundamental frequency zero-sequence current phasor
1
I
0
1 1 1
I I I
( )
+ +
A B C
( )
=
3
Fundamental frequency zero-sequence voltage phasor
1
U
0
1 1 1
U U U
( )
+ +
A B C
(
=
3
Fundamental frequency conductance,
1
G
o
1
Re Y
( )
0
Fundamental frequency susceptance,
1
B
o
1
Im Y
( )
0
)
Section 4
Protection functions
(Equation 76)
527