Overexcitation Protection; Trip And/Or Indication Of External Protection Devices; Ac Inputs And Protection Elements; Hardware - Toshiba GRT100 Manual

GRT100

Overexcitation Protection

A single phase to phase connected voltage input is
provided to detect overexcitation. Alarms and tripping,
based on a measurement of the voltage/frequency
ratio are provided. The voltage/frequency ratio is
calculated using per unit quantities.
The alarm is definite time delayed whilst the characteristic
may be selected as either having a definite time or an
inverse time delay, as shown in Figure 5.
A: Alarm level
H: High level (definite time tripping)
V/Hz
L: Low level (pick up level)
HT: Inverse time delay-1
LT: Inverse time delay-2
H
TVFH: Definite time delay for high
TVFA: Definite time delay for alarm
L
A
TVFA HT
0
TVFH
Figure 5. Characteristic of overexcitation element

AC Inputs and Protection Elements

Figure 6 shows the typical relationship between the
AC inputs and protection elements.
GRT100-101/102
CT
1OC/1OCI
VT
FRQ
HV
CT
1EF/1EFI
LV
CT
2OC/2OCI
CT
2EF/2EFI
DIFT: Current differential protection
REF: Restricted earth fault protection
OC/OCI, EF/EFI: Overcurrent backup protection
THR: Thermal overload protection
V/F: Overexcitation protection
FRQ: Frequency protection
Figure 6. AC inputs and protection elements
level
level
LT sec
(log T)
THR
V/F
Calculate 3I 0
1REF
DIFT
Calculate 3I 0
2REF
Trip and/or Indication of External
Protection Devices
External signals such as overpressure devices and
Buchholz relay operation, can be applied through 4
binary input circuits. Logic can be arranged for alarms,
event recording and tripping. The binary input circuit
is provided with a logic level inversion function.
For redundancy it is recommended to route tripping
from the Buchholz or overpressure device in parallel
to the relay.

HARDWARE

Figure 7 shows the hardware block diagram of the
relay.
The relay is a multiple microprocessor design. The
microprocessors perform software functions such as
signal processing, protection algorithm, scheme logic,
output relay control and management of the user
interface.
Phase voltage analog inputs are provided, residual
current inputs and phase voltage inputs. The number
of analog inputs depends on the model of the relay.
The internal auxiliary transformers are used to isolate,
step down and condition the inputs from the VT and
CTs. Their output signals are then converted into
digital data for further processing.
The front panel provides a 4 x 40 character, liquid
crystal display (LCD) and 19 pushbutton keys to
provide local access to the relay menu. There are
also 8 light emitting diodes (LED) for visual indication
of the status of the relay.
The relay provides three communication ports,
RS232C for connection of a local PC, RS485 for a
remote PC and IRIG-B for an external clock.
Transformer
module
Current
- CT
Voltage
- VT
External
- IRIG-B
clock
Local PC
Figure 7. Hardware block diagram
5
Binary input
Signal
output
processing
modules
module
- DC/DC
converter
- Analog filter
- A/D - Binary input
converter - Binary output
- MPU
(trip)
- Binary output
(signal)
- RS485
- LCD
Human
- LED
machine
- Operation key
interface
- RS232C I/F
DC supply
Input
Output
Remote
PC