Ver 1710 Rev 1
Protrol AB
Tel: 031- 45 82 00
Ullevigatan 19
internet: www.protrol.se
411 40 Göteborg
5
e-mail: [email protected]
4 Functional Description
4.1 Detector Function
True Fault Pass Through Earth Fault Detection
Protrol’s patented Fault Pass Through earth fault detection
is suitable for all indirectly earthed networks. It
is capable of detecting high impedance and arcing earth faults. It analyses the transient nature of phase and
neutral currents and points reliably out the fault direction with respect to the measurement point. Note
that no voltage measurement is necessary for good selectivity at very low currents. The sensitivity is
comparable with that of a directional earth fault protective relay.
At an earth fault the detector will set itself into
Trig
state and evaluate if the fault is upstream or
downstream the unit. If the fault is downstream, it will switch to
Start
state. In this mode, the detector
evaluates the I
0
residual current until the
Operation Delay
has passed. If the residual is high after the set
time, the detector will enter
Trip
state.
Note that both a
Start
and a
Trip
indication means that an earth fault has occurred downstream the
detector. A
Start
without a subsequent
Trip
indication means that either the fault current is too low, or the
fault was of transient type and was gone after the
Operation Delay
time. Thus, the
Start
object, available
remotely, can be used as an early indication of an incipient fault.
Some periods after the disturbance has vanished, the detector returns to its normal state.
High I
0
Detection
The IPS2 supervision alarm for high residual current if the steady-state
I
0
current exceeds 16 times
the
I
0
pickup level
, as specified by the rotary switch on the front panel
1
.
The main purpose of this alarm is to indicate that something is wrongly connected, either wrong polarity or
missing phase.
An alarm is indicated by flashing the
I
0
>
LED, also see the Section 5.2 IPS2 24 VDC Top Printed Circuit
Board.
Overcurrent Detection
The IPS2 unit has one overcurrent stage that can be configured using the rotary switch at the front panel.
Phase Break Detection
The phase break detection alarm is activated - if one phase is
“dead”
while the other two are
“alive”
, a
phase break is signaled locally and on the system interface.
A phase is considered “dead” if the current is
lower than the
I
0
pickup level
, and “alive” if the current is higher than
4 x the
I
0
pickup level.
2
An alarm is indicated by flashing the
I>
LED, also see the Section 5.2 IPS2 24 VDC Top Printed Circuit
Board.
1
If the earth fault stage is deactivated, the High I
0
steady-state limit is set to 160 A.
2
If the earth fault stage is deactivated, the “dead” threshold is set to 5 A while “alive” is 20 A.