Frequency Protection - Toshiba GRT100 Series Instruction Manual

2.7 Frequency Protection

GRT100 provides an underfrequency or overfrequency protection and/or alarms for load
shedding or for detecting such an overfrequency condition caused by disconnecting load from a
particular generation location.
The frequency element FRQ comprises two frequency elements 81-1 and 81-2, the former is used
for tripping and the latter for alarms.
Figure 2.7.1 shows the scheme logic of frequency protection. The tripping element 81-1 outputs
underfrequency and overfrequency trip signals L1 and H1. Either underfrequency or
overfrequency protection is enabled by setting the scheme switch [FRQ-UF1] to "ON" or "OFF".
The alarm element 81-2 outputs underfrequency and overfrequency alarm signals L2 and H2.
Either underfrequency or overfrequency alarms are enabled by setting the scheme switch
[FRQ-UF2] to "ON" or "OFF".
Frequency protection can perform time-delayed tripping of up to five breakers. Any of the
breaker tripping signals FRQ-1 to FRQ-5 can be blocked by the scheme switch [FRQ1] to
[FRQ5] settings.
Alarm signal FRQ-A can be blocked by the scheme switch [FRQA] setting.
Frequency protection is blocked under the condition that the system voltage is lower than the
setting of the undervoltage element UV.
FRQ
L1
L2
81-1
81-2
H1
H2
UV
1
FRQ-UF1

"ON"
FRQ-UF2

"ON"
TFRQL
t
&
0.00 - 60.00s
&
TFRQH
t
&
1
&
0.00 - 60.00s
1
1
Figure 2.7.1 Scheme Logic of Frequency Protection
0
1
[FRQ1]

0
[FRQ2]

[FRQ3]

[FRQ4]

[FRQ5]

TFRQA
t 0
[FRQA]

0.00 - 60.00s
"ON"
 32 
6 F 2 S 0 7 8 9
&
"ON"
&
"ON"
&
"ON"
&
"ON"
&
"ON"
&
FRQ-1
FRQ-2
FRQ-3
FRQ-4
FRQ-5
FRQ-A