50
I N S TA L L AT I O N , O P ER AT I O N S A N D M A I N T EN A N C E M A N UA L
For generic wiring diagram, please see
.
To ensure proper functionality the following wiring
limitation are adhered to:
• Phase and neutral current transformers to
primary side of auxiliary current transformer wire
to be 14 AWG, twisted pair with a maximum one-
way length of 30 ft.
• Summing to summing current transformer wiring
to be 14 AWG, twisted pair with a maximum loop
length of 31,000 ft.
• Summing current transformer to secondary
disconnect terminal wiring to be 16 AWG, twisted
pair with a maximum one-way length of 49 ft.
Caution:
To ensure intended
functionality of a given breaker
within the MDGF scheme, the
breaker rated current, rating plug
and phase & neutral current
transformers shall have matching
primary current ratings. The
summing current transformer's
primary current rating is to match
the secondary current rating of the
phase & neutral current
transformers.
NEC 240.95 requires that all ground fault
protection schemes be performance tested prior to
going into service. For field testing procedures
please see
For specific wiring diagrams related to your order,
please review the As-Built documentation.
For specific wiring diagrams related to your order,
please review the As-Built documentation.
Zone selective interlocking (ZSI) - ZSI be used to
minimize circuit- breaker trip times closer to the
fault. The protection is provided by connecting all
the zone selectivity outputs of the trip units
belonging to the same zone and taking this signal
to the trip unit input that is immediately upstream.
Each circuit breaker that detects a fault reports it
to the circuit breaker upstream; the circuit-breaker
thus detects the fault but does not receive any
communication from those downstream and opens
without waiting for the set delay to elapse. It is
possible to enable zone selectivity if the fixed-time
curve has been selected and the auxiliary supply is
present.
Prior to operation ensure that breakers utilizing ZSI
protection are properly configured and NEC 240.87
requires field testing be completed for arc
mitigation protections. Please see
for setup and test instructions.
For specific wiring diagrams related to your order,
please review the As-Built documentation.
Modified Differential Ground Fault (MDGF) - For
each breaker in a MDGF protection scheme the
equipment is fashioned with corresponding
compartment mounted phase current
transformers, neutral mounted current
transformer, a compartment mounted summing
current transformer and a secondary disconnect
terminal block. The summing current transformers
are interconnected to form a loop with an output
connected to the secondary disconnect terminal
block of the circuit breakers.
DANGER
WARNING
CAUTION
NOTICE