ABB RELION REX640 Technical Manual page 531

1MRS759142 C
REX640
Technical Manual
The operation of MFADPSDE can be described using a module diagram. All the
modules in the diagram are explained in the following sections.
Transient
detector
I
o
IRES Multi-
frequency
admittance
U
URES o
calculation
General
fault
criterion
RELEASE
RESET
BLOCK
GUID-535CD424-8114-4120-A86A-92AEB21682C1 V2 EN
Figure 286: Functional module diagram
General fault criterion
The General fault criterion (GFC) module monitors the presence of earth faults in the
network. It is based on the value of the fundamental frequency zero-sequence voltage
defined as the vector sum of fundamental frequency phase voltage phasors divided by
three.
1 1 1
U U U
( )
+ +
A B C
1
U
=
0
3
GUID-4786964D-2390-4A96-AA24-DFCFA57F50DE V1 EN
MFADPSDE supports zero-sequence voltage monitoring based on measurement
(from open-delta winding) or calculated (derived from phase-to-earth voltages).
When the magnitude of
detected. The GFC module reports the exceeded value to the Fault direction
determination module and Operation logic. The reporting is referenced as General
Fault Criterion release.
The setting Voltage start value defines the basic sensitivity of MFADPSDE. To avoid
unselective start or operation, Voltage start value must always be set above the
maximum healthy-state zero-sequence voltage value, considering network topology
changes, compensation coil and parallel resistor switching status and compensation
degree variations. The setting Voltage start value can be easily selected based on the
resonance curve calculated by the coil controller in corresponding network conditions
(see Figure 287).
Fault
Operation
direction
logic
determination
1
U exceeds setting Voltage start value, an earth fault is
0
Section 4
Protection functions
PEAK_IND
INTR_EF
DIRECTION
FAULT_DIR
START
OPERATE
Timer
BLK_EF
(Equation 75)
525