LEGRAND IME Delta D4-h Mode D'emploi page 34

Delta D4-h
Ring Current Transformers
Choice of the ring current transformer for differential relays series DELT
depending on the minimum value of the leakage current to be detected and the diameter
of the hole in which have to pass all the active conductors of the line to be protected.
Mounting with strong transient currents (max. 6In) according to IEC/EN 60947-2
enclosure M.
In order to avoid ill-timed interventions (caused by transient currents and not by real
insulation defects), the standards provide for a test 6 times the rated current; for installations
in conformity with what provided by the standard, you have to stick to the values shown in
the table
Diameter: transformer inner hole diameter (passing cables/bars)
IDn min: min. IDn value which can be loaded on the differential relay linked to the ring
current transformer
In: switch or disconnector rated current
The shown values are valid only if the conductors are exactly passing in the middle of the
ring current transformer
Ex. choice of the ring current transformer for switch rated current
Respecting the parameters provided by the standard IEC/EN 60947-2 enclosure M.
you have to use a transformer model Del-80
Current In = 170 - Current 6In = 1020
Model Del-28
Code TDG 2
Diameter
28mm
IDn *
0,03A
In
65A
6In
390A
6
(In) = 125
(code TDGC2)
Del-35 Del-60 Del-80
TDGB2 TDGH2 TDGC2
35mm 60mm 80mm
0,03A 0,05A 0,1A
70A 90A 170A
420A 540A 1020A
For plants with poor transient currents
with lower rated currents, following this formula:
6In (value shown in the table)
Is (rated current of used switch)
Using a transformer Del -310
rated current In = 1250
3780
= 3,024
1250
The highest admitted overload corresponds to 3,024 times the switch rated
current
* Values measured according to normal load PF = 0.5 - dt = 0 - t = 2 sec.
Del-110 Del-140 Del-210
TDGD2 TDGE2 TDGF2
110mm 140mm 210mm
0,15A 0,15A 1A
250A 250A 400A
1500A 1500A 2400A
(< 6In ) it is possible to use ring current transformers
= Max. allowed overload
(code TD C2) with value 6In = 3780
Del -110 Del -150
TD 2 TD B2
110mm 150mm
1A 0,3A
250A 250A
1500A 1500A
LE12570AA_E 10/20 - 01IM cod.RDD421..
with switch with
Del -310
TD C2
310mm
3A
630A
3780