Fuse-failure supervision function
ABB Network Partner AB
1MRK 580 169-XEN
Page 5 - 51
Version 1.0-00
The function has built in a phase-segregated voltage and current measur-
ing function. It sets the value of internal signal UICH to logical one, if the
voltage in any phase decreases under the set value at the same time as the
current in the same phase decreases under 10% of its rated value.
This current and voltage check function inhibits the operation of the FFS
function for 200 ms after the line energization in order to prevent its oper-
ation for unequal pole closing. The same function also blocks the FFS
function during single-pole auto-reclosing.
The voltage check function seals the fuse-failure condition if the condi-
tion exists more than five seconds. UCHL1, UCHL2, and UCHL3 assist
the function. The seal-in condition occurs until the normal voltage condi-
tions are achieved.
If any of the fuse-failure conditions are fulfilled and the voltage is
decreased under the pre-set value in all three phases, a corresponding
FUSE-VTF3PH output signal receives its value equal to logical one. The
condition seals in as long as the voltages in all three phases remain low.
This condition remains in the permanent memory of a terminal, even if the
auxiliary DC voltage is switched off during the fuse-failure condition.
This way, the terminal checks the VTF3PH memory value and establishes
the corresponding starting conditions during the new start-up procedure.
3.1 Settings The setting procedure for the FFS function occurs under the menu:
Settings
Functions
Group n
Fuse Failure
The use of a negative-sequence mode of operation is recommended for
the terminals used in isolated or high-impedance earthed networks.
The operating value for the voltage check function is the same as the oper-
ating value of the undervoltage function, independent of whether the func-
tion is built in the terminal as an option. The setting of the operating value
occurs under the submenu:
Settings
Functions
Group n
UnderVoltage
Some values of the zero-sequence or negative-sequence voltages and cur-
rents always exist due to different non-symmetries in the primary system
and differences in the current and voltage instrument transformers. The
minimum value for the operation of the current and voltage measuring
elements must always be set with a safety margin of 10 to 15%, depend-
ing on the system operating conditions.
To Next Page
Loading...
Need help?
General
