Alarm Function - ABB RELION RET670 Applications Manual

Section 9
Current protection
9.16.3.3
9.17
9.17.1
9.17.2
606

Alarm function

The alarm function is operated by PICKUP signal and used to warn the operator for an
abnormal situation, for example, when generator continuous negative sequence current
capability is exceeded, thereby allowing corrective action to be taken before removing
the generator from service. A settable time delay tAlarm is provided for the alarm
function to avoid false alarms during short-time unbalanced conditions.
Voltage-restrained time overcurrent protection
VRPVOC (51V)
Identification
Function description
Voltage-restrained time overcurrent
protection
Application
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 large 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:
IEC 61850 IEC 60617
identification identification
VRPVOC I>/U<
Transformer protection RET670 2.2 ANSI
1MRK 504 163-UUS A
GUID-1B932D89-3233-4841-977A-5B61346B057B v2
GUID-613620B1-4092-4FB6-901D-6810CDD5C615 v4
GUID-7835D582-3FF4-4587-81CE-3B40D543E287 v4
ANSI/IEEE C37.2
device number
51V
GUID-622CDDDD-6D03-430E-A82D-861A4CBE067C v7
Application manual