108
1MRS751802-MUM
Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
7.1.18. FUSEF
Some voltage-based protection functions may maloperate if a voltage measurement
circuitry is damaged or if the miniature circuit breaker (MCB) of the measurement
circuitry has opened for example due to an operation of the short-circuit protection.
A failure in the voltage measurement circuitry should, however, be repaired as soon
as possible to restore the blocked protection functions into use.
Fig. 7.1.18.-1 Function block symbol of FUSEF
1
When BSOUT output is used for blocking function blocks that are executed in a slower task interval
than FuseFail, an additional delay has to be included in the block activation time
2
When BSOUT output is used for blocking function blocks that are executed in a slower task interval
than FuseFail, an additional delay has to be included in the reset time
Fuse failure supervision
Ratio U2/U1> 10...50%
Ratio I2/I1> 10...50%
FuseFail Not in use
In use
Operation accuracies Depends on the frequency of the current and voltage
measured:
f/fn = 0.98...1.02: ±2.0 percentage units (of settings Ratio
U2/U1> and Ratio I2/I1<)
f/fn = 0.95...1.05: ±4.0 percentage units (of settings Ratio
U2/U1> and Ratio I2/I1<)
BSOUT activation time (when task interval is
10 ms)
1
Injected negative-sequence voltage = 2.00 x Ratio
U2/U1>:
f/fn = 0.98...1.02 <35 ms (within the same task)
Reset time (when task interval is 10 ms)
2
20 ms (within the same task)
Reset ratio 0.8...0.96 (for Ratio U2/U1>)
1.04...1.2 (for Ratio I2/I1<)
BSOUT
FUSEF
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