Supervision Functions
238 PRS-7367
The current operating characteristics can be selected with the CTS_3Io_Calc_Ena value. Detailed
contents of differential current and operate value have been given out in the upper part.
When the highest phase current is less than 2.0 × In, if the differential current exceeds the operate
value and the internally calculated residual voltage is below 10V, the CT_InsALM output signal is
activated instantly. VT_Alm output signal is activated with a fixed 10s delay. CT_InsALM signal
needs to be active during the delay.
When the highest phase current is more than 2.0 × In, The function is internally blocked. When the
internal blocking activates, the CT_InsALM output is deactivated immediately, however the
VT_Alm output deactivates after a fixed delay of 3s. The internal blocking is used for avoiding false
operation during a fault situation when the current transformers are saturated due to high fault
currents.
The function resets with a fixed delay of 3s when the differential current is below the value of
0.9*Op_Val and highest phase current is more than five percent of the nominal current (0.05 × In).
4.3.3 CTS Application Scope
Open or short-circuited current transformer cores can cause unwanted operation in many
protection functions such as differential, earth-fault current and negative sequence current
functions. So, when an error in any CT circuit is detected, the protection functions concerned can
be blocked and an alarm is given.
It must be remembered that the blocking of protection functions at an occurring open CT circuit
means that the situation remains unchanged and extremely high voltages stress the secondary
circuit which may damage the insulation and cause further problems.
4.3.4 CTS Settings
Table 4.3-3 CTS settings
4.4 Fuse failure supervision PTS
4.4.1 PTS Overview
The fuse failure supervision feature is used to detect failure of the AC voltage input circuit of this
relay.
The fuse failure supervision logic in the relay is designed to detect the voltage failure and
automatically adjust the configuration of protective elements whose stability would otherwise be
compromised. A time delay alarm output is also available.
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