Toshiba GRZ100 B Series, Instruction Manual

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6 F 2 S 0 8 4 6
SY1UV = upper voltage setting
The phase difference is checked by the following equations.
VB
⋅
VL cos
θ ≥
0
VB
⋅
VL sin (SY1
θ
s)
≥
VB
⋅
VL sin
θ
where,
θ
= phase difference between VB and VL
SY1
θ
s = phase difference setting
A detected slip cycle is determined by the following equation:
where,
f = slip cycle
TSYN = synchronism check timer setting
2.5.7 Current Change Detection Elements OCD and OCDP
As shown in Figure 2.5.7.1, the current change detection element operates if the vectorial
difference between currents IM and IN observed one cycle apart is larger than the fixed setting.
Therefore, the operating sensitivity of this element is not affected by the quiescent load current
and can detect a fault current with high sensitivity.
The OCD element is used for the VT failure supervision circuit and the OCDP element used for
the fault detection during a power swing.
Figure 2.5.7.1 Current Change Detection
The operation decision is made by the following equation.
|IM
−
IN|
>
Is
where,
IM = present current
IN = current one cycle before
Is = fixed setting (10% of rated current)
Is
IM
IN
f =
180°
×
TSYN
θs