ABB RELION REX640 - Page 1010

Mho circle entirely and the setting Zone 3 enable is also set to “Yes”. Increment of
the slip counter triggers also the Reset timer. All of the zone slip counters reset after
the set Reset time has elapsed and the impedance does not cross into the outer
blinder again, or on activation of the OPERATE output.
When the “Way out” or "Adaptive" option is selected, the breaker open time, if
known, can be incorporated to optimize breaker trip time when a way out trip
command is issued. The ideal time for the breaker to interrupt current is when the
swing angle approaches zero. If the swing angle is δ
0
when the impedance exits the
outer blinder, the dynamic Trip delay, T
od
, can be set as shown in Equation 273 .
T
f T BrkropenTm
f
od
slip co
slip
=
− ⋅ ⋅ +
⋅
1 2
2
( )
(Equation 273)
T
od
Dynamic Trip delay
T
co
The time for the impedance to travel from the center impedance line (where
the swing angle is π radians) to the outer blinder on the opposite side from
which it entered.
BrkopenTm Set Breaker open time
f
slip
Slip frequency
The Breaker open time setting should include the time from when the relay issues
a trip command to the time when the breaker receives the command. The function
uses the Breaker open time setting to determine the trip delay time if it is not set
to “0”. If the Breaker open time is set to “0”, the function does not dynamically
calculate a trip delay but uses the fixed Operate delay time before activating the
OPERATE output.
The slip frequency is calculated using Equation 274 .
f
T
slip
i
oi
=
−
⋅ ⋅
δ δ
π
0
2
(Equation 274)
f
slip
Slip frequency
T
oi
The time for the impedance to pass from the outer to the inner blinder.
δ
0
Swing angle at the outer blinder
δ
I
Swing angle at the inner blinder
The swing angles, δ
0
and δ
I
, are estimated from the measured impedance when
crossing the blinders. It is the difference in these quantities that is important for
determining the slip frequency.
If the “Adaptive” option is selected, after detecting an OSB condition, the function
further examines the slip frequency f
slip
, V dip time setting, and swing angle at the
outer blinder (δ
0
) to determine if the operate is asserted on the way in or on the
way out. OPERATE is activated on the way in, entering the mho circle from an inner
blinder, if the relationship in Equation 275 is true.
Protection functions
1MRS759142 F
1010 REX640
Technical Manual