![background image](http://html1.mh-extra.com/html/eaton/digitrip-520mcv/digitrip-520mcv_instructions-manual_524797024.webp)
Effective 8/2006
Page 24
I.L. 66A7534H04
8.0 RECORD KEEPING
Use the forms shown in Figures 8.1 and 8.2 for record
keeping. Fill in these forms, giving the indicated reference
information and initial time-current trip function settings. If
desired, make a copy of the form and attach it to the
interior of the breaker cell door or another visible location.
Figure 8.3 provides a place for recording test data and
actual trip values.
Ideally, sheets of this type should be used and maintained
by those personnel in the user’s organization that have the
responsibility for protection equipment.
9.0 REFERENCES
9.1 Medium Voltage Type VCP Circuit Breakers
I.B.
#69C3067
ANSI Breaker Instructions
I.B.
#69C3066
IEC Breaker Instructions
9.2 Time-Current Curves
The Time-Current Curves are listed below for particular trip
unit models. All protection function time-current settings
should be made following the recommendations of the
specifying engineer in charge of the installation.
#5720B80
Digitrip 520V/520MCV (LS) Curve
#5720B81
Digitrip 520V/520MCV (I) Curve
#5720B82
Digitrip 520V/520MCV (G) Curve
#5721B77
Digitrip 520MCV Maintenance
Mode Trip Curve
WARNING
BEFORE YOU FIT THE RATING PLUG INTO THE TRIP
UNIT, BE SURE TO CHECK THAT EACH BREAKER
POLE HAS AN EXTERNALLY MOUNTED SENSOR THAT
IS WIRED TO THE CIRCUIT BREAKER’S SECONDARY
CONTACTS. THESE SENSOR RATINGS MUST MATCH
THAT PRINTED ON THE RATING PLUG. INSTALLING A
RATING PLUG THAT DOES NOT MATCH THE SENSOR
RATING CAN PRODUCE SERIOUS MISCOORDINATION
AND/OR FAILURE OF THE PROTECTION SYSTEM.
7.0 FRAME RATINGS (SENSOR RATINGS AND RATING
PLUGS)
The frame rating
of a circuit breaker is the maximum RMS
current it can continuously carry. The maximum short-
circuit current rating of the circuit breaker is usually related
to the frame rating as well.
There are two frame ratings for this circuit breaker using
the Digitrip 520V and 520MCV trip units as follows:
A current value, (
I
n), that is less than the full frame rating
may be chosen to be the basis for the coordination of the
protection function of the breaker without affecting its
short-circuit current capability. For Digitrip units, this is
implemented by changing the CH Type-V current sensors
and the corresponding
rating plug. These sensors and
rating plugs are available in kit form.
The CH Type-V current sensor rating is the maximum
current the circuit breaker can carry with the specified
sensors installed. Their rating can be the same or less
than the frame rating, but not greater.
This value, (
I
n), is the basis for the trip unit current set-
tings:
1.
The Instantaneous Current Settings are multiples of
(
I
n)
(See Sections 4.6).
2.
The Ground Current Settings
are multiples of (
I
n)
(See
Section 4.7)
. The one exception would be if the Zero
Sequence sensor is employed. It is a tapped sensor
with 100A and 200A selections.
3.
The Long Delay Current Setting, (
I
r), is a fractional
multiple of (
I
n): Long Delay Current Setting = (
I
r) = LD
x (
I
n)
(See Section 4.2).
4.
The Short Delay Current Setting is a multiple of (
I
r):
Short Delay Current Setting = SD x (
I
r) = SD x [LD x
(
I
n)]
(See Section 4.4).