9.14 Voltage-restrained time overcurrent protection
VRPVOC
(51V)
GUID-613620B1-4092-4FB6-901D-6810CDD5C615 v4
9.14.1 Identification
GUID-7835D582-3FF4-4587-81CE-3B40D543E287 v4
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Voltage-restrained time overcurrent
protection
VRPVOC I>/U< 51V
9.14.2 Application
GUID-622CDDDD-6D03-430E-A82D-861A4CBE067C v7
A breakdown of the insulation between phase conductors or a phase conductor and
ground results in a short-circuit or a ground fault. Such faults can result in lar
ge fault
currents and may cause severe damage to the power system primary equipment.
A typical application of the voltage-restrained time overcurrent protection is in the
generator protection system, where it is used as backup protection. If a phase-to-phase
fault affects a generator, the fault current amplitude is a function of time, and it
depends on generator characteristic (reactances and time constants), its load conditions
(immediately before the fault) and excitation system performance and characteristic.
So the fault current amplitude may decay with time. A voltage-restrained overcurrent
relay can be set in order to remain in the picked-up state in spite of the current decay,
and perform a backup trip in case of failure of the main protection.
The IED can be provided with a voltage-restrained time overcurrent protection
(VRPVOC, 51V). The VRPVOC (51V) function is always connected to three-phase
current and three-phase voltage input in the configuration tool, but it will always
measure the maximum phase current and the minimum phase-to-phase voltage.
VRPVOC (51V) function module has two independent protection each consisting of:
• One overcurrent step with the following built-in features:
• Selectable definite time delay or Inverse Time IDMT characteristic
• Voltage restrained/controlled feature is available in order to modify the pick-
up level of the overcurrent stage in proportion to the magnitude of the
measured voltage
• One undervoltage step with the following built-in feature:
• Definite time delay
Section 9 1MRK 502 071-UUS A
Current protection
426 Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Application manual
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