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1. Introduction
GRD140 series relays provide four stage non-directional and directional overcurrent protection
for distribution networks, and back-up protection for transmission and distribution networks.
The GRD140 series has three models and provides the following protection schemes in all models.
• Directional overcurrent protection and directional zero phase sequence overcurrent
protection for earth fault with definite time or inverse time characteristics
• Instantaneous directional overcurrent protection and instantaneous directional zero phase
sequence overcurrent protection for earth fault
Model 110 provides directional earth fault protection and directional sensitive earth fault
protection.
Model 400 provides three-phase directional phase fault protection and directional earth fault
protection.
Model 420 provides three-phase directional phase fault protection, and directional earth and
sensitive earth fault protection.
All models include multiple, high accuracy, overcurrent protection elements (for phase and/or
earth fault) with inverse time and definite time delay functions. All phase, earth and sensitive earth
fault overcurrent elements can be independently subject to directional control.
In addition, GRD140 provides multi-shot, three phase auto-reclose, with independent sequences
for phase fault, and earth fault and sensitive earth fault. Auto-reclosing can also be triggered by
external protection devices.
Other protection functions are available according to model type, including thermal protection to
IEC60255-8,
under/overfrequency protections. See Table 1.1.1 for details of the protection functions available
in each model.
All models provide continuous monitoring of internal circuits and of software. External circuits
are also monitored, by trip circuit supervision, CT and VT supervision, and CB condition
monitoring features.
A user-friendly HMI is provided through a backlit LCD, programmable LEDs, keypad and
menu-based operating system. PC access is also provided, either for local connection via a
front-mounted RS232 port, or for remote connection via a rear-mounted RS485 or fibre optic port.
The communication system allows the user to read and modify the relay settings, and to access
data gathered by the relay's metering and recording functions.
Data available either via the relay HMI or communications ports includes the following functions.
The GRD140 series provides the following functions for all models.
• Metering
• Fault recording
• Event recording
• Disturbance recording (available via communications ports)
Table 1.1.1 shows the members of the GRD140 series and identifies the functions to be provided
by each member.
negative
sequence
⎯
overcurrent
protection,
⎯
8
6 F 2 S 0 7 5 8
under/overvoltage
and
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