Signals - ABB RELION REX640 Technical Manual

1MRS759142 C
4.5.4.7
REX640
Technical Manual
applied to power system elements, such as generators, transformers, motors and
power lines, to detect overvoltage conditions.
PSPTOV can be used in combination with low-current signals or a directional reactive
overpower function to identify the distribution line with an open remote end. PSPTOV
can also be used to initiate voltage correction measures, such as insertion of shunt
reactors or switching out capacitor banks, to control the voltage.
Overvoltage faced by the power transformer can lead to an overexcitation problem.
Overexcitation normally occurs when the voltage-to-frequency ratio increases much
above the design value resulting into transformer operation under a nonlinear region.
A transformer can be in such an overvoltage situation during a sudden loss of load due
to underfrequency load shedding. Overexcitation results in an increase of the exciting
current which leads to core heating and thus to transformer damage. PSPTOV along
with the underfrequency protection can be used for the protection of the transformer
during overexcitation.
Some common reasons leading to positive-sequence overvoltages are:
• Broken conductor falling to a crossing overhead line, transformer flash overfault
from high-voltage winding to low-voltage winding
• Malfunctioning of a voltage regulator or wrong settings under manual control
(symmetrical voltage increase)
• Low load compared to the reactive power generation (symmetrical voltage
increase)
PSPTOV prevents sensitive equipment from running under overvoltage conditions
which cause equipment overheating or stress on insulation material.

Signals

Table 738: PSPTOV Input signals
Name Type
U3P SIGNAL
BLOCK BOOLEAN
Table 739: PSPTOV Output signals
Name Type
OPERATE BOOLEAN
START BOOLEAN
Protection functions
Default Description
- Three-phase voltages
0=False Block signal for activating the blocking mode
Description
Operate
Start
Section 4
789