Channel Asymmetry Compensation Using Gps; Introduction; Compensation Method 1 - GE L30 Instruction Manual

CHANNEL ASYMMETRY COMPENSATION USING GPS

• For relay 3, channel 1 communicates to relay 1 and channel 2 communicates to relay 2
Consequently, to achieve the maximum sensitivity of 0.2 pu at the terminal with a CT ratio of 2000/5 (400 amps line
primary differential current), the following pickup values are chosen:
Choosing relay as a reference with a breakpoint value of 5.0 pu, breakpoints for relays 2 and 3 are calculated as follows:
To verify the calculated values, we have:
This satisfies the equality condition indicated earlier.
During on-load tests, the differential current at all terminals should be the same and generally equal to the charging
current if the tap and CT ratio settings are chosen correctly.
8.3 Channel asymmetry compensation using GPS

8.3.1 Introduction

As indicated in the Settings chapter, the L30 provides three basic methods of applying channel asymmetry compensation
using GPS. Channel asymmetry can also be monitored with actual values and an indication signalled (FlexLogic operands
87L DIFF 1(2) MAX ASYM
philosophy, the relay can be programmed to perform the following on the loss of the GPS signal:
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• Enable GPS compensation on the loss of the GPS signal at any terminal and continue to operate the 87L element
(using the memorized value of the last asymmetry) until a change in the channel round-trip delay is detected.
• Enable GPS compensation on the loss of the GPS signal at any terminal and block the 87L element after a specified
time.
• Continuously operate the 87L element but only enable GPS compensation when valid GPS signals are available. This
provides less sensitive protection on the loss of the GPS signal at any terminal and runs with higher pickup and
restraint settings.

8.3.2 Compensation method 1

Enable GPS compensation on the loss of the GPS signal at any terminal and continue to operate the 87L element until a
change in the channel round-trip delay is detected.
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asserted) if channel asymmetry exceeds preset values. Depending on the implemented relaying
CHAPTER 8: APPLICATION OF SETTINGS
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
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