Overvoltage Protection; Overvoltage Protection Implementation - GE P24DM Technical Manual

P24xM
3

OVERVOLTAGE PROTECTION

Overvoltage conditions are generally related to loss of load conditions, whereby the supply voltage increases in
magnitude. This situation would normally be rectified by voltage regulating equipment such as AVRs (Auto Voltage
Regulators) or On Load Tap Changers. However, failure of this equipment to bring the system voltage back within
permitted limits leaves the system with an overvoltage condition which must be cleared.
Note:
During earth fault conditions on a power system there may be an increase in the healthy phase voltages. Ideally, the system
should be designed to withstand such overvoltages for a defined period of time.
3.1

OVERVOLTAGE PROTECTION IMPLEMENTATION

Overvoltage Protection is implemented in the VOLT PROTECTION column of the relevant settings group. The
Overvoltage parameters are contained within the sub-heading OVERVOLTAGE.
The product provides three stages of overvoltage protection with independent time delay characteristics.
Stages 1 and 3 provide a choice of operate characteristics, where you can select between:
● An IDMT characteristic
A range of user-defined curves
●
DT (Definite Time)
●
You set this using the V>1 Function and V>3 Function cells depending on the stage.
The IDMT characteristic is defined by the following formula:
t = K/( M - 1)
where:
K = Time multiplier setting
●
● t = Operating time in seconds
M = Measured voltage setting voltage (V> Voltage Set)
●
The overvoltage stages can be configured either as phase-to-neutral or phase-to-phase voltages in the
V> Measure't mode cell.
There is no Timer Hold facility for Overvoltage.
Stage 2 has definite time characteristics only. This is set in the V>2 status cell.
Three stages are included in order to provide multiple output types, such as alarm and trip stages. Alternatively,
different time settings may be required depending upon the severity of the voltage increase.
Outputs are available for single or three-phase conditions via the V> Operate Mode cell for each stage.
P24xM-TM-EN-2.1
Chapter 10 - Voltage Protection Functions
207