Toshiba GRZ100-211B, Instruction Manual

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6 F 2 S 0 8 3 4
Element Range Step Default Remarks
THM 2.0 – 10.0 A
(0.40 – 2.00 A)(*) 0.1 A
(0.01 A) 5.0 A
(1.00 A) Thermal overload setting.
(THM = I
AOL
: allowable overload current)
THMIP 0.0 – 5.0 A
(0.00 – 1.00 A)(*) 0.1 A
(0.01 A) 0.0 A
(0.00 A) Previous load current
TTHM 0.5 - 300.0 min 0.1 min 10.0 min Thermal time constant
THMA 50 – 99 % 1 % 80 % Thermal alarm setting. (Percentage of THM setting.)
[THMT] Off / On Off Thermal OL enable
[THMAL] Off / On Off Thermal alarm enable
(*) Current values shown in the parenthesis are in the case of a 1 A rating. Other current
values are in the case of a 5 A rating.
Note: THMIP sets a minimum level of previous load current to be used by the thermal element,
and is typically used when testing the element. For the majority of applications, THMIP
should be set to its default value of zero, in which case the previous load current, Ip, is
calculated internally by the thermal model, providing memory of conditions occurring
before an overload.
2.4.7 Switch-Onto-Fault Protection
In order to quickly remove a fault which may occur when a faulted line or busbar is energized, the
switch-onto-fault (SOTF) protection functions for a certain period after the circuit breaker is
closed.
The SOTF protection is performed by a non-directional overcurrent element and distance
measuring elements. The overcurrent protection is effective in detecting close-up three-phase
faults on the line in particular when the voltage transformer is installed on the line side. This is
because the voltage input to the distance measuring elements is absent continuously before and
after the fault, and thus it is difficult for the distance measuring elements to detect the fault.
The distance measuring elements can operate for faults other than close-up three-phase faults. One
of the zone 1 to zone ND elements can be used for the SOTF protection.
Scheme logic
The scheme logic for the SOTF protection is shown in Figure 2.4.7.1. The SOTF protection issues
a three-phase tripping signal SOTF-TRIP for the operation of an overcurrent element OCH or
distance measuring elements Z1 to ZND for 500 ms after the circuit breaker is closed (CB-OR = 1)
and/or for 500ms after the undervoltage dead line detector resets. The method of controlling the
SOTF protection by CB closing and/or by undervoltage dead line detection is selected by scheme
switch [SOTF-DL]. Elements UVFS and UVLG provide undervoltage dead line detection.
Tripping by each element can be disabled by the scheme switches [SOTF-OC] to [SOTF-ZND].
When a VT failure is detected (NON VTF = 0), tripping by the distance measuring elements is
blocked.
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