CHAPTER 9: THEORY OF OPERATION
OVERVIEW
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
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Figure 9-26: Alignment logic (relay COMTRADE record)
Being communication-dependent, a phase comparison relay needs to treat information delivered from the remote
terminals with the same criticality as the local AC currents. This includes monitoring for troubleshooting purposes,
accountability, and continuous improvement capability for products and installations. Modern microprocessor-based
phase comparison relays that sample their binary DC input voltages for analog level at the same high sampling rate as
they do for analog signal inputs provide great analysis tools: they include all the measured and derived instantaneous
signals in their oscillography records (COMTRADE files). This includes flags driving transmission, received DC voltage, local
AC currents, and all relevant instantaneous signals leading towards the trip/no-trip condition. Having four receive
channels, it is even possible to loop back the transmit voltages to monitor both the signal connected to a local carrier
equipment, and received at the remote location.
After all the local and remote pulses are aligned and conditioned, a coincidence condition X is established as per the
number of terminals and type of the scheme (tripping versus blocking). For example, for a three-terminal permissive
scheme the condition becomes:
•
X = FDH AND LOC AND REM1 AND REM2
This logic is executed for the positive polarity in single-comparison schemes, and it is executed independently for positive
and negative polarities in dual-comparison schemes.
The coincidence condition is driving an explicitly implemented integrator (summator). In the L60, the integrator counts up
by 10 units if the coincidence input is logic 1, counts down by 5 counts if the coincidence input is momentarily logic 0, and
counts down by 20 if the input is in logic 0 for extended periods of time. This provides extra security for chattering inputs,
allowing for eventual trips in clear situations, and provides for full reset of the integrator before the next coincidence
period.
The output of the integrator (or two integrators in dual-comparison schemes) is compared with the coincidence timer
setting yielding the final trip/no-trip flag.
The following figure shows an example of the coincidence integration for an internal fault as recorded in a COMTRADE file
by the relay under test.
Содержание L60
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Страница 14: ...1 4 L60 LINE PHASE COMPARISON SYSTEM INSTRUCTION MANUAL FOR FURTHER ASSISTANCE CHAPTER 1 INTRODUCTION 1 ...
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Страница 590: ...5 382 L60 LINE PHASE COMPARISON SYSTEM INSTRUCTION MANUAL TESTING CHAPTER 5 SETTINGS 5 ...
Страница 632: ...7 12 L60 LINE PHASE COMPARISON SYSTEM INSTRUCTION MANUAL TARGETS MENU CHAPTER 7 COMMANDS AND TARGETS 7 ...
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