EMR-5000
IM02602012E
27M - Undervoltage Protection
Available elements:
27M[1] ,27M[2]
M is for “Main” referring to protection metered by the Main Voltage transformer in the
System Configuration.
All undervoltage elements are identically structured.
Definition of Vn: Vn is dependent on the System Parameter setting of "Main VT con".
In case that within the System Parameters "Main VT con" is set to "Open-Delta":
Vn
=
Main VT sec
.
In case that "Main VT con" is set to "Wye":
Vn
=
MainVT sec
3
This is the 27 device undervoltage setting for the main three phase VT. This function consists of a Phase, a Pickup, a
Delay setting. The Phase setting allows the User to select at which phase (any one, any two, or all) the undervoltage
function operates. The Pickup setting is the magnitude at which the undervoltage element operates. The Delay setting
is the time period an undervoltage must occur before the device initiates a trip. Depending on the settings within the
System Parameters, the element works based on phase-to-phase (»
Open-Delta«) or phase-to-ground (»wye«)
voltages. This element will operate depending on the phase setting: if any one, any two, or all of the voltage(s) that
is/are selected by the Phase setting drop(s) below the set point. This element works based on True RMS values.
An undervoltage pickup occurs when the measured voltage drops below the UV Threshold setting. The undervoltage
trip is set when the voltage stays below the threshold setting for the delay time specified (within the number of phases
specified by the phase setting). The undervoltage pickup and trip is reset when the voltage rises above the dropout
ratio specified in Specifications section for the undervoltage protection.
If the element should be blocked in the event of a “Loss of Potential”, the »LOP B
LO
« parameter must be set to
»
active«.
www.eaton.com
639
