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PROTECTION
Auxiliary Overvoltage
Protection
4–220
The 869 relay provides one Auxiliary Overvoltage (OV) element per protection group, or a
total of 6 elements. Each Auxiliary OV element is used to protect voltage sensitive loads
and system components against sustained overvoltage conditions. This element can be
used for monitoring zero-sequence voltage (from an "open corner delta" VT connection),
permissive functions, the source transfer schemes, restoration and similar functions.
The Auxiliary OV element may be set as an instantaneous element with no time delay or
may be set as a definite time element, Inverse Time, or with FlexCurves. The input voltage
is the auxiliary voltage.
The settings of the Auxiliary OV Protection function are applied to the auxiliary voltage
input to produce pickup and trip flags. The Auxiliary OV pickup flag is asserted, when the
voltage on auxiliary input is above the PKP value. The Auxiliary OV trip flag is asserted if the
element stays picked up for the time defined by pickup time delay, Inverse Time, or
FlexCurves. The element drops from pickup without operation, if the measured voltage
drops below 97-98% of the pickup value, before the time for operation is reached.
This element may be used to give a desired time-delay operating characteristic versus the
applied voltage or as a definite time element. For the inverse time setpoint, the
overvoltage pickup delay setpoint defines a family of curves as shown below.
The operating time is given by:
T= D/((V/V
) - 1) when V>V
pickup
Where:
T = trip time in seconds
D = Overvoltage Pickup Delay setpoint
V = actual phase-phase voltage
V
= Overvoltage Pickup setpoint
pickup
The element reset rate is a linear reset time from the threshold of trip.
Figure 4-76: Overvoltage Curves
Path:
Setpoints > Protection > Group 1(6) > Voltage > Auxiliary OV
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
pickup
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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