Thermal Overload Protection, One Time Constant Lpttr; Breaker Failure Protection Ccrbrf; Stub Protection Stbptoc; Pole Discordance Protection Ccrpld - ABB RED670 Product Manual

Line differential protection RED670 ANSI
Customized
Product version: 1.2

Thermal overload protection, one time constant LPTTR

The increasing utilizing of the power system closer to the
thermal limits has generated a need of a thermal overload
protection also for power lines.
A thermal overload will often not be detected by other
protection functions and the introduction of the thermal
overload protection can allow the protected circuit to operate
closer to the thermal limits.
The three-phase current measuring protection has an I
characteristic with settable time constant and a thermal
memory..
An alarm pickup gives early warning to allow operators to take
action well before the line is tripped.
Breaker failure protection CCRBRF (50BF)
Breaker failure protection (CCRBRF) ensures fast back-up
tripping of surrounding breakers in case the own breaker fails to
open. CCRBRF (50BF) can be current based, contact based, or
an adaptive combination of these two conditions.
Current check with extremely short reset time is used as check
criterion to achieve high security against inadvertent operation.
Contact check criteria can be used where the fault current
through the breaker is small.
CCRBRF (50BF) can be single- or three-phase initiated to allow
use with single pole tripping applications. For the three-phase
version of CCRBRF (50BF) the current criteria can be set to
operate only if two out of four for example, two phases or one
phase plus the residual current pickups. This gives a higher
security to the back-up trip command.
CCRBRF (50BF) function can be programmed to give a single-
or three-phase re-trip of the own breaker to avoid unnecessary
tripping of surrounding breakers at an incorrect initiation due to
mistakes during testing.
Stub protection STBPTOC (50STB)
When a power line is taken out of service for maintenance and
the line disconnector is opened in multi-breaker arrangements
the voltage transformers will mostly be outside on the
disconnected part. The primary line distance protection will thus
not be able to operate and must be blocked.
The stub protection STBPTOC (50STB) covers the zone
between the current transformers and the open disconnector.
The three-phase instantaneous overcurrent function is released
from a normally open, 89b auxiliary contact on the line
disconnector.
20
Pole discordance protection CCRPLD (52PD)
An open phase can cause negative and zero sequence currents
which cause thermal stress on rotating machines and can
cause unwanted operation of zero sequence or negative
sequence current functions.
Normally the own breaker is tripped to correct such a situation.
If the situation warrants the surrounding breakers should be
tripped to clear the unsymmetrical load situation.
2 The Polediscrepancy protection function CCRPLD (52PD)
t
operates based on information from auxiliary contacts of the
circuit breaker for the three phases with additional criteria from
unsymmetrical phase currents when required.
Directional over/underpower protection GOPPDOP/GUPPDUP
(32/37)
The directional over-/under-power protection GOPPDOP (32)/
GUPPDUP (37) can be used wherever a high/low active,
reactive or apparent power protection or alarming is required.
The functions can alternatively be used to check the direction of
active or reactive power flow in the power system. There are a
number of applications where such functionality is needed.
Some of them are:
• detection of reversed active power flow
• detection of high reactive power flow
Each function has two steps with definite time delay. Reset
times for both steps can be set as well.
Broken conductor check BRCPTOC (46)
The main purpose of the function Broken conductor check
(BRCPTOC, 46) is the detection of broken conductors on
protected power lines and cables (series faults). Detection can
be used to give alarm only or trip the line breaker.

6. Voltage protection

Two step undervoltage protection UV2PTUV (27)
Undervoltages can occur in the power system during faults or
abnormal conditions. Two step undervoltage protection
(UV2PTUV, 27) function can be used to open circuit breakers to
prepare for system restoration at power outages or as long-time
delayed back-up to primary protection.
UV2PTUV (27) has two voltage steps, each with inverse or
definite time delay.
Two step overvoltage protection OV2PTOV (59)
Overvoltages may occur in the power system during abnormal
conditions such as sudden power loss, tap changer regulating
failures, open line ends on long lines etc.
1MRK505226-BUS D
ABB