Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

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9.31
Date Code 20170814 Instruction Manual SEL-700G Relay
Analyzing Events
Event Reporting
Conditions When CLOSEX Asserted
The SYN report shows the generator and system conditions at the time the
CLOSEX was initiated. Conditions displayed include present slip frequency,
actual generator and system frequencies, percent voltage difference, and
actual generator and system voltages. Next, the slip-compensated and
uncompensated phase angle differences are shown. The uncompensated phase
angle difference is simply the phase angle between the system and generator
voltages when CLOSEX was initiated. The relay uses Equation 9.3 to
calculate the slip-compensated phase angle difference:
Equation 9.3
The result of SLIP • TCLOSDX • 360° is the number of degrees that the
generator voltage travels, with respect to the system voltage, during the time
that it takes the breaker to close (TCLOSDX), assuming a constant slip
frequency equal to SLIP.
When you supervise CLOSEX initiation with the 25C Relay Word bit, the
relay asserts 25C when the slip-compensated phase angle is approximately
equal to the CANGLE setting. Thus, when you review a SYN report from a
25C supervised CLOSEX, the slip-compensated angle should closely equal
the CANGLE setting. The slip-compensated angle tells us what the relay
expects the phase angle to be when the breaker actually closes TCLOSDX
seconds after CLOSEX initiation.
SYN Report Closure
For the vast majority of breaker close operations, the breaker will close and
the three-pole-open condition, 3POX, will deassert. If this occurs within about
99 seconds of CLOSEX initiation, the relay records the time 3POX
deasserted, calculates and displays the breaker close time, advances the close
operation counter, and accounts for the new close time in the breaker close
time average.
If the breaker does not close and slip is not close to 0 Hz, the generator voltage
rotates away from the system voltage until the phase angle exceeds the close-
failure angle, CFANGLE, setting. If this occurs within about 99 seconds of
CLOSEX initiation, the relay reports the message
Close Failed
in the place
of the breaker close time and stores the SYN report.
If 3POX does not deassert and the uncompensated phase angle difference does
not exceed the CFANGLE setting within about 99 seconds of CLOSEX
initiation, the relay reports the message
Close Failed
in the place of the
breaker close time and stores the SYN report.
Use the Breaker Close Time Average
You can use the breaker close time average to refine the TCLOSDX setting.
By setting TCLOSDX closer to the actual breaker closing time, the
where
Ang (VPX) = the generator voltage phase-angle, degrees
Ang (VS) = the system voltage phase-angle, degrees
SLIP = present slip frequency, Hz
TCLOSDX = breaker close time-delay setting, seconds
Slip-Compensated Angle
Ang VPX
 
Ang VS
 
SLIP TCLOSDX

360
  
+ –
=