ABB Relion 670 Series Applications Manual page 216

Section 8
Current protection
tMin_HOL_IDMT = 0.1s ; Minimum time delay for IDMT stage. Selected value gives operate time in
accordance with international standards
8.15.3.1 Restrike detection
Opening of SCBs can be quite problematic for certain types of circuit breakers (CBs). Typically
such problems are manifested as CB restrikes.
In simple words this means that the CB is not breaking the current at the first zero crossing after
separation of the CB contacts. Instead current is re-ignited and only braked at consecutive current
zero crossings. This condition is manifested as high current pulses at the moment of current re-
ignition.
To detect this CB condition, the built in overcurrent feature can be used. Simply, any start of the
overcurrent feature during breaker normal opening means a restrike. Therefore simple logic can be
created in the Application Configuration tool to detect such CB behavior. Such CB condition can be
just alarmed, and if required, the built in disturbance recorder can also be triggered.
To create this logic, a binary signal that the CB is going to be opened (but not trip command) shall
be made available to the IED.
8.16 Voltage-restrained time overcurrent protection VRPVOC
(51V)
8.16.1 Identification
Function description
Voltage-restrained time overcurrent
protection
8.16.2 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.
210
IEC 61850
identification
VRPVOC
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IEC 60617 ANSI/IEEE C37.2
identification device number
I>/U< 51V
1MRK 511 401-UUS F
GUID-114747A5-0F7C-4F48-A32D-0C13BFF6ADCE v1
GUID-613620B1-4092-4FB6-901D-6810CDD5C615 v4
GUID-7835D582-3FF4-4587-81CE-3B40D543E287 v4
GUID-622CDDDD-6D03-430E-A82D-861A4CBE067C v7
Bay control REC670
Application manual