14
Protection Features
Long Time Protection
Long time protection is provided in accordance to the IEC 947-
4 Class 20 curve; trip times are defined as:
Current at 1.5 x Ir
Current at 7.2 x Ir
480s (max)
20s (max)
The pickup point, Ir is switch adjustable from 0.4 times the
breaker rating (In) to 1.0 x In in steps of 0.1. There is a
tolerance on the trip time of +0, -20% expressed in terms of
current.
Short Time Protection
M-PRO 17 offers adjustable short time protection with
selectable trip time delay. All the short time settings are
configured via front panel switches. The pickup point is in
terms of the long time setting Ir, and can be set to 2.0, 3.0, 4.0,
6.0, 8.0, 10.0 or 12.0 x Ir. Trip delays of INST, 0.1, 0.2, 0.4,
0.6, 0.8 and 1s are available. A setting of ‘INST’ causes M-
PRO 17 to initiate an instantaneous trip in a minimum of 40ms.
Earth Fault Protection (OPTIONAL)
Earth fault current is measured by summing the current in all
phases and neutral (where used) to give a value equal to the
earth leakage current which is present downstream of the
circuit breaker.
The M-PRO can be set to provide trip delays of INST, 0.1, 0.2,
0.4, 0.6, 0.8 and 1s, with pickup points or OFF, 0.4, 0.6, 0.8
and 1.0 x In, the breaker rating. This protection can be
switched off when not required.
NB see section “Neutral Rogowski Coil Mounting Details”
for external coil orientation.
Making-Current Release (MCR)/High-Set Instantaneous
Short Circuit (HSISC) Protection
The M-PRO 17 will perform an instantaneous trip if the breaker
is closed onto a fault exceeding its making-current capability.
When the circuit breaker is closed, it can carry a current equal
to Icw. The M-PRO 17 will however perform an instantaneous
trip if Icw is exceeded.
Both these thresholds are factory set and are not
adjustable by the operator.
M-PRO 17 IEC 947 Class 20 Long Time Protection
0.01
0.1
1
10
100
1000
10000
1
10
100
CURRENT IN MULTIPLES OF Ir
TIME TO
TR
IP IN
SEC
O
N
D
S
Ir = 0.4 to 1.0 x In
in steps of 0.1In
Inst
0.1
0.2
0.4
0.6
0.8
1.0
Trip delay settings
Min/max settings
show n in BOLD
