Utility Relay Company AC-PRO-II, Instruction Manual

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AC-PRO-II
®
Instruction Manual www.utilityrelay.com
Page 26
Instantaneous Override (I-OVRD): The AC-PRO-II is
configured at the factory with this feature either ON or OFF.
If the feature is ON, a fixed Instantaneous pickup of 12 times
the CT rating is applied. In some applications, this feature is
enabled at the factory to protect the specific breaker this trip
unit is paired with. Additionally, this feature can be enabled
if requested at the time of order. Unless specified or
specifically required to protect the breaker, AC-PRO-II trip
units are normally configured with this feature OFF.
Instantaneous-on-Close (I-CLOS): The AC-PRO-II is
configured at the factory with this feature ON or OFF. If this
feature is ON, a fixed Instantaneous pickup of 12 times the
CT rating is applied for only the first 10 cycles (166ms for
60Hz, 200ms for 50Hz) after the trip unit is powered up.
Unless specified at the time of order, AC-PRO-II trip units
are normally configured with this feature ON.
Note: When AC-PRO-II is configured with a Voltage Divider
Module (VDM), the VDM will provide trip unit power when
the line side of the breaker is energized, even when the
breaker is open. If the trip unit is already powered by the
VDM, the I-CLOS feature does not apply.
Note: The AC-PRO-II uses a unique algorithm to determine
if RMS currents greater than 12 times the CT rating are
present, in which case the CTs may be saturated. The
AC-PRO-II then corrects the effect of CT saturation on the
LT and ST trip functions.
The AC-PRO-II features redundant Instantaneous protection.
The primary Instantaneous is an analog peak-detecting
circuit that directly trips the actuator, regardless of the state
of the microprocessor. The microprocessor provides digital
backup Instantaneous protection for the analog circuit.
The Ground Fault screen includes the following settings: GF
type, pick-up, delay, and slope.
GF type can be set to residual, ground return, or OFF)
The residual GF method calculates a vector sum of the three
phase currents (and neutral current if applicable) and
determines the fundamental frequency component.
The ground return method is used for applications where a
ground return CT directly measures the GF current, and the
AC-PRO-II calculates the fundamental value.
See Section 5.1.1 for typical wiring diagrams of the two
ground fault methods.
Figure 11.3 for Ground Fault settings notes, ranges, steps,
and options.
See Figure 18.2 for Ground Fault Time Current Curve.
**** NOTE ****
On a 4-wire system, a neutral CT must be installed to
avoid nuisance GF trips.
**** NOTE ****
Due to possible CT saturation, RMS currents greater than
12 times the CT rating are not considered in the GF
protection calculations. The ST and/or Instantaneous
functions will provide protection for these currents.
**** CAUTION ****
24VDC Aux Power is required for GF protection with
5000A CTs & larger that use 0.2A or 0.18A CTs.
**** IMPORTANT ****
To implement GF protection on the main breakers and
the tie breaker of a double ended 4-wire substation, see
the following Technical Bulletin:
http://www.utilityrelay.com/Side_Bar/Technical_Bulletins.
html
The neutral overload (NOL) screen includes the following
settings: enabled (ON/OFF), pick-up, delay, and NOL
thermal memory.
Figure 11.3 for NOL settings notes, ranges, steps, and
options.
See Figure 18.2 for the NOL Time Current Curve (TCC).
The NOL thermal memory feature operates the same as the
LT and ST thermal memory feature. See Section 11.10 for a
description.
**** NOTE ****
Neutral Overload (NOL) protection cannot be enabled if
the Ground Fault (GF) type is set to ground return. This
is because with the ground return method, the neutral CT
input is used for GF protection and thus cannot be used
for NOL protection.
This setting only applies if the AC-PRO-II QUICK-TRIP
switch module is installed and connected. See Section
7.0 for details.
The QT-I pickup range and steps are the same as the
Instantaneous pickup range and steps.
See Figure 18.4 for the QUICK-TRIP Time Current Curves
(TCC).
The QT- I function does not have an OFF setting. It is turned
ON or OFF using the QUICK-TRIP ON-OFF selector switch.
If the AC-PRO-II QUICK-TRIP switch module is not installed,
then this function is always off.
This setting only applies if the AC-PRO-II QUICK-TRIP
switch module is installed and connected. See Section
7.0 for details.
The QUICK-TRIP GF feature has two settings: QT-GF type
and QT-GF pick-up.
If GF type is set to OFF, QT-NG type can be set to residual,
return, or OFF. If GF type is set to residual or return, the
QT-GF type can only match it or be turned OFF.
The QT-GF pick-up range and steps are the same as the GF
pickup range and steps.
See Figure 18.4 for the QUICK-TRIP Time Current Curves
(TCC).
11.13 Ground Fault (GF) Protection
11.14 Neutral Overload (NOL) Settings
11.15 QUICK-TRIP
®
Instantaneous (QT-I)
11.16 QUICK-TRIP Ground Fault (QT-GF)