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Design
The earth fault indicator type
TERRA is used in open ring networks or in radial networks with one
input. For measuring the earth fault current, the sensor has to be
mounted on the three-core cable. |
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Usually,
the symmetric sum current of a three-core system is approximately 0 A
and will become as-symmetric due to an earth fault.
This assymmetric current will be detected by the sensor and transmitted
to the reading instrument.
If this fault current reaches
the preadjusted opera-ting point (current), the evaluation will be
started and the fault will be indicated by a flag indication.
The earth fault is located between the last indicating instrument (X)
and the next instrument in stand-by-mode (O) (confer figure 1).
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Assembling
The
sensor has to be mounted around the three cores of the three-phase
supply network. It is very important that the screen current will not
be detected in case of a fault. There are two ways to achieve this.
(Please look at the assembling instructions before starting to
assemble.) |
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1st
Possibility (figure 2)
The sensor has to be mounted on the screen of the cable. The screen is
insulated against the earth fault. The screen must be led back within
the frame belt. In this way the screen current is neutralized, and the
real earth fault current will be detected. The capacitve protection is
achieved by earthing
the system on the input side. |
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2nd Possibility (figure
3)
The sensor has to be mounted on the screen of the cable. For this
purpose, the screen below
the sensor has to be removed all around the cable.The
removed section must have a width of at least 15 mm.
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this way the sensor cannot detect the screen current because the screen
current is derived before reaching the sensor. The mounting site of the
sensor is capacitively protected via the system. |
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| Technical Data |
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reading instrument:
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dimensions
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(W*H*D): |
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TERRA
E1+ E3 (panel-mounted):
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96x48x63
mm |
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TERRA
A1+A3 (surface-mounted):
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77
x 140 x 45 mm |
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material:
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ABS
DIN 40 050 |
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protection
class:
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panel-mounted IP 52
surface-mounted IP 65 |
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minimum
operating current:
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10
A +/-10% |
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electric
strength:
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5
kV |
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auxiliary
voltage:
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220
- 240 V AC, 50 Hz |
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reset
time :
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5
- 10 sec.(with voltage reset) |
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maximum
current load:
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5000A
for 5 sec. |
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current
peak:
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20
kA |
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relay:
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1
x changer relay, max. 230 VAC (50...150W)
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Sensor:
dimensions (W*H*D): 39 x 39 x
26 mm
material: ABS DIN 40 050
protection class: IP 67
fixing belt: plastic-sheathed laminated
transformer plate
for cable diameter: 70 - 100 mm
connection cable: length 3000 mm (standard)
( TypeLiYY 2 x 0.5 sqmm, 0.15 Ohm/m).
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