CHAPTER 2: PRODUCT DESCRIPTION
DEVICE OVERVIEW
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
17
Front panel USB port
The front panel of the D90
Plus
provides a USB 2.0 port for simple local connection.
Figure 8: Front panel USB connection
Protection features
The D90
Plus
is designed for superior performance and ease-of-use, providing a single
platform solution for protecting transmission lines from medium voltage (MV) to extra high
voltage (EHV) and cables of various voltage levels. The scalable platform consists of
protection, control, automation, monitoring, communication, digital fault recorder (DFR)
and security functionality. The incrementally scalable concept allows customization in
building the device to suit specific user requirement. The truly convergent platform
integrates multiple devices eliminating external devices and reduces the footprint of relay
panels resulting in reduced wiring, commissioning and capital costs.
Distance protection
The core of the D90
Plus
relay is the subcycle distance function providing a high degree of
sensitivity and selectivity for all types of faults. The distance function features five zones of
phase distance and ground distance protection, providing the user the utmost flexibility of
making each zone directional, non directional, or reverse. This allows customization to a
variety of applications, including primary line protection, backup protection for busbars,
and backup protection for generators, transformers, and reactors. The D90
Plus
can be
applied to power systems with different earthing conditions, lines with in-zone
transformers or tapped transformer feeders and overhead lines with series compensation.
Each zone element for the phase and ground distance can be set to the quadrilateral or
mho characteristic with the flexibility of designing different characteristic shapes to suit for
different power system conditions.
The advanced comparator based distance elements provide utmost security, sensitivity
and selectivity for different types of faults. Superior digital filtering techniques provide
secure and optimum reach accuracy even under worst-case CVT transients without
compromising the operating time. Secure direction detection is achieved by using positive
sequence memory voltage polarization providing reliable directionality for worst-case
close-in faults. The D90
Plus
employs a well-proven algorithm for phase selection, which
provides fast, secure and reliable faulted phase identification for single pole tripping and
proper fault distance calculation for a variety of power system conditions. An additional
voltage monitoring function provides extra security to the distance element, which can be
used to block the distance elements under voltage transformer fuse failure conditions.
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