Toshiba GRZ100 B Series, Instruction Manual, Page: 41 / 447

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effect of charging current cannot be ignored. It appears as a distance measurement error in the
fault.
To suppress the effect of the charging current and maintain the highly accurate distance
measurement capability, the GRZ100 has a charging current compensation function.
The compensation is recommended if the minimum fault current can be less than three times the
charging current.
The setting value of ZIC should be the charging current at the rated voltage Vn.
Element Range Step Default Remarks
ZIC 0.00 - 5.00 A 0.01 A 0.0 0 Charging current setting
( 0.00 - 1.00 A 0.01 A 0.00 A) (*)
Vn 100 - 120 1 V 110 V Rated line voltage
(*) Current values shown in the parentheses are in the case of 1 A rating. Other current values are in
the case of 5 A rating.
Setting of phase selection element
Phase selection is required only for faults on the protected line. Therefore, impedance reach
setting UVCZ is set to 120% of the positive-sequence impedance of the protected line. Impedance
angle setting UVC
θ
is set the same as the protected line angle.
Undervoltage setting UVCV is set higher than the estimated maximum fault voltage at the fault
point for a single-phase earth fault.
2.4.2 Zone 1 Extension Protection
Application
The disadvantage of time-stepped distance protection is that faults near the remote end of the
protected line can only be cleared in zone 2 time, thus high speed protection cannot be performed
for all faults on the protected line. If telecommunication is available, this disadvantage can be
solved by command protection. If telecommunication is not available, zone 1 extension protection
using autoreclose will implement high speed protection at both terminals.
Zone 1 extension (zone 1X) has a complex characteristic combining the reactance element, mho
element and blinder element, and its characteristic is the same as zone 1.
Zone 1X for earth faults is provided with the same residual current compensation as zone 1 and
zone 2.
As shown in Figure 2.4.2.1, zone 1X is set to overreach the protected line and performs
instantaneous tripping. This tripping is followed by autoreclose. In the selected autoreclose mode,
one of three-phase tripping and autoreclose, single-phase tripping and autoreclose, or single- and
three-phase tripping and autoreclose is executed.
The zone 1 extension protection clears a fault on the protected line including an end zone fault at
high speed, displaying the performance equivalent to that of command protection.
On the other hand, unlike command protection, overreaching zone 1X also acts instantaneously
for a fault on adjacent lines and executes tripping. If the fault is a transient fault, power
transmission can be recovered by autoreclose with a transient loss of power supply.
High speed zone 1X tripping is not desirable following reclosure onto a permanent fault on an
adjacent line because more of the network is lost than necessary. Therefore, tripping by zone 1X is
blocked prior to the reclosing command to the circuit breaker. Whether or not the permanent fault
is on the protected line or on an adjacent line, tripping is performed under time-stepped distance
protection.