Os Tripping - GE ALPS Instruction Manual

2 CALCULATION OF SETTINGS
1606: BLOCKZ3 - Block All Zone 3 Functions
Set BLOCKZ3 = YES to block tripping by any of the Zone 3 distance functions, otherwise set BLOCKZ3 = NO.
1607: BLOCKZ4 - Block All Zone 4 Functions
Set BLOCKZ4 = YES to block tripping by any of the Zone 4 distance functions, otherwise set BLOCKZ4 = NO.
The ALPS can be supplied with optional out-of-step tripping in addition to out-of-step blocking. For a complete description
of the out-of-step tripping logic see Section 1.10: OUT-OF-STEP TRIPPING (OPTIONAL) on page 1–41. Out-of-step trip-
ping is implemented using positive sequence distance functions (separate from the regular ALPS distance functions) as
shown in Figure 2–15: OST CHARACTERISTIC. Briefly, for an out-of-step condition, the apparent impedance seen by the
relay will follow a typical swing line as shown. An out-of-step condition is recognized by sensing that the apparent imped-
ance seen by the system first enters the outer characteristic, then the middle characteristic and finally the inner characteris-
tic. The traversal from characteristic to characteristic occurs in a finite time directly related to the slip frequency of the power
system during an out-of-step condition.
The following settings must be made (refer to above and 2–16: OST REACH CHARACTERISTIC). It will most likely be nec-
essary to run load flow and system swing studies to determine the settings that must be made in any given application. The
example used below is provided only for use as a guide in describing each of the settings.
1701: USE_OST - Select OST
Set USE_OST = YES if out-of-step tripping is to be used, otherwise set USE_OST = NO.
1702: NUMBRCHAR - Select Number Of Characteristics
Depending on the application, it may not be possible to use all three of the characteristics, and the MIDDLE characteristic
must be bypassed. If only two characteristics are to be used (MIDDLE characteristic bypassed), set NUMBRCHAR = 2,
otherwise set NUMBRCHAR = 3.
1703: TRIPIN_OUT - Trip Entering Inner Or Leaving Outer
The OST function can be set so that tripping will be initiated shortly after the impedance enters the inner characteristic
(pickup time of TLOS3), or to trip shortly after the swing leaves the outer characteristic (dropout time of TLOS1). Which set-
ting to use is determined by the capability of the breakers used in the power system:
1. If the circuit breaker is capable of interrupting when the systems are approximately 180× apart (around twice voltage
across the breaker contacts) set TRIPIN_OUT = IN.
GE Power Management
X
Zf
Middle
Inner
Zr
Figure 2–15: OST CHARACTERISTIC
ALPS Advanced Line Protection System
2.3 PROTECTION SETTINGS
Outer
R

2.3.19 OS TRIPPING

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