Utility Relay Company AC-PRO-II, Instruction Manual

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AC-PRO-II
®
Instruction Manual www.utilityrelay.com
Page 25
The security code is the last four (4) digits of the serial
number. See Section 4.0 for location of serial number. See
Figure 11.2.
After the Security Code is entered, the first setting is the CT
Tap (rating) in amps. The CT tap can range from 50 amps
to 5,000 amps in 25 amp steps.
The CT rating entered into the trip unit
must correspond to
the actual rating of the phase and neutral CT taps. See
Figure 11.2.
The CT secondary rating settings are entered in Amps and
must correspond to the actual CT ratings. See Figure 11.2.
The Phase CT secondary rating is set in Amps with the
following setting options:
1.0, 0.5, 0.4, 0.25, 0.20, 0.18 Amp
The Neutral CT secondary rating is set in Amps with the
following setting options:
2.0, 1.5, 1.0, 0.5, 0.4, 0.25, 0.20, 0.18 Amp
Note: the 0.18 CT secondary rating is an abbreviated
representation of 0.185. The associated settings and
performance are based on 0.185.
The power flow direction setting only applies when a VDM is
connected. When the CT wiring polarity matches Figure 5.3,
the power flow direction should be set to “NORMAL”. When
the CT wiring polarity is the opposite of Figure 5.3, the power
flow Direction should be set to “REVERSE”.
Note: This setting affects the KVA and KVAHr values
displayed by the trip unit. See Section 13.0.
Set the AC-PRO-II frequency to match the power system
frequency. The setting options are 50 Hertz and 60 Hertz.
See Figure 11.2.
The Long Time (LT) settings screen includes the following
settings: Enabled (ON or OFF), pick-up, delay, and thermal
memory.
See Figure 11.2 for Long Time protection settings notes,
ranges, steps, and options.
Long Time (LT) protection is ON, unless the trip unit is
ordered with the “LT can be turned OFF” option.
Please note that the LT trip time is not a constant value, but
is a function of breaker current. For lower currents the trip
time is longer, and for higher currents the trip time is shorter.
See Figure 18.1 for Time Current Curve.
See Section 18.1 for LT Trip Times.
The AC-PRO-II trip unit has a thermal memory feature for
the following protective functions:
Long Time (LT) (set at Long Time screen)
Short Time (ST)
Ground Fault (GF) (always on)
Neutral Overload (set at Neutral Overload screen)
The thermal memory feature for LT and ST can be turned on
or off at the LT screen. See Figure 11.2.
Thermal memory for the GF function is always on and
cannot be turned off.
The GF thermal memory feature
provides protection against “sputtering” ground faults.
Except for unusual conditions, it is recommended that
the thermal memory feature for LT and ST should be
turned on.
Cycling overloads that are not above the LT Pick-Up long
enough to cause a trip can still lead to thermal damage to
wiring and equipment. With thermal memory turned on, a
cycling overload can still produce a LT trip to protect cables
and equipment even if any individual overload event did not
persist long enough to directly cause a LT trip.
With thermal memory turned off, an overload that drops
below the LT Pick-Up will reset the LT trip register. If the
current goes above the LT Pick-Up again, the LT trip register
starts from zero.
The Short Time (ST) settings screen includes the following
settings: enabled (ON/OFF), pick-up, delay, and I
2
T ramp
(ON/OFF).
See Figure 11.3 for ST protection settings, notes, ranges,
steps, and options.
**** NOTE ****
The trip unit does not allow setting both the ST and
Instantaneous to be set to OFF at the same time.
See Figure 18.1 for the Time Current Curve.
See Section 18.2 for ST Trip Times.
The Instantaneous (I) settings screen includes the following
settings: enabled (ON/OFF) and pick-up.
Figure 11.3 for Instantaneous settings, ranges, and steps.
**** NOTE ****
The trip unit does not allow setting both the ST and
Instantaneous to be set to OFF at the same time.
See Figure 18.1 for the Time Current Curve.
In addition, the Instantaneous settings screen displays the
Instantaneous override and Instantaneous-on-close features
if they are enabled. These features are fixed and set at the
factory. See below:
11.4 Security Code
11.5 CT Tap
11.6 CT Secondary Rating
11.7 Power Flow Direction
11.8 Frequency
11.9 Long Time (LT)
11.10 Thermal Memory
11.11 Short-Time (ST)
11.12 Instantaneous (I)