Specifications

Depending on the selected type the M-PRO
protection relays offer the following features:
• Overload protection
• Short circuit protection
• Earth fault protection
•I
2
t cropping
• Neutral protection
• Thermal memory
• Communication
• Trip history and indication
• Manual or automatic reset
• Watch dog in case of microprocessor malfunction
• Plant Associated Memory Module (PAMM)
• Outputs
• Programmable inputs
• Load monitoring, Pre-trip alarm/Load shedding
Long time protection
M-PRO17: Curve speed fixed to class 20 (480 sec at
1.5 Ir, 20 sec at 7.2 Ir ) in accordance with IEC 947-4.1
M-PRO20-40: Curve speed adjustable and meets
the requirements of IEC 947-4.1 (class 40).
Choice between the curve characteristics in
accordance with IEC 255:
• Standard inverse
• Very inverse
• Extremely inverse general/motor (default)
• HV fuse compatible for transformer-fed circuits
involving discrimination with primary side high
voltage fuses
The operating time of each type can vary in 16
increments, from curve speed 1 (shortest time) to
curve speed 16 (longest time).
Short time protection
Maximum operating time is 80ms from initiation of
the fault to contacts part. Operating time of the I
2
t
cropping on M-PRO20-40 is fixed at 0.1 times the
selected long time characteristic.
A.9
A
M-PACT
Making Current Release (MCR)
Instantaneously trips the M-PACT air circuit breaker
should an attempt be made to close onto a short-
circuit fault current greater than the detected
making capacity of 50kA. This trip becomes
inoperative once the circuit breaker has been
closed.
High Set Instantaneous Short Circuit (HSISC)
Provides immediate protection against high value
short circuit currents by tripping the circuit breaker.
HSISC pickup level is factory set depending on
M-PACT air circuit breaker performance.
Earth Fault Protection
Three types of earth fault protection are available:
• Unrestricted (UEF) - protects downstream cables
and equipment
• Restricted (REF) - protects upstream cables and
equipment forming the main supply to the breaker
• Standby (SEF) - provides general back-up
protection against earth faults affecting upstream
or downstream cables and equipment
M-PRO17: Unrestricted protection only
M-PRO30-40: Any combinations of two or three
types of protection can be factory pre-set
Earth fault curve cropping: available for unrestricted
or stand-by earth fault options. This feature enables
the user to vary the tripping time in accordance with
the prospective earth fault detected.
A ‘Cropping Factor’ may be selected which is a
multiple of the chosen earth fault pick-up current.
This selects the desired level of current at which the
fixed time delay becomes effective.
Earth fault protection zone diagram