Protection Scheme - Toshiba GRT100 Series Instruction Manual

2.2 Protection Scheme

GRT100 provides the following protection schemes with measuring elements in parentheses.
Appendix A shows block diagrams of the GRT100 series.
 Current differential protection (DIFT)
 Restricted earth fault protection (1REF-3REF)
 Time-overcurrent protection (1OC-3OC, 1OCI-3OCI, 1EF-3EF and 1EFI-3EFI)
 Thermal overload protection (THR)
 Frequency protection (FRQ)
 Overexcitation protection (V/F)
 Trip and/or indication of external devices (Buchholtz relay, pressure or temperature sensing
devices etc.)
The number of measuring elements for the restricted earth fault protection and time-overcurrent
protection is dependent on the relay models.
Figure 2.2.1 and 2.2.2 show the relationship between AC inputs and the measuring elements
applied in each model.
1CT
VT
HV
LV
2nCT
2CT
GRT100
1OC/1OCI
FRQ
1nCT
1EF/1EFI
2OC/2OCI
2EF/2EFI
Figure 2.2.1 Measuring Elements of Model 100s
 10 
THR
V/F
Calculate 3I 0
1REF
Calculate 3I 0
2REF
6 F 2 S 0 7 8 9
DIFT