VAMP Ltd Generator protection relay
Technical description
VAMP 210
VM210.EN004 Vamp 24h support phone: +358 (0)20 753 3264
5
2. Functions
The individual protection functions of the generator protection
relay VAMP 210 can independently of each other be enabled or
disabled according to the requirements of the intended
application. See the configuration instructions, Chapter 5 and
7, in the first part of this manual.
2.1. Principles of the numerical protection
technique
The generator protection relay VAMP 210 is designed using
numerical technology. This means that all signal filtering,
protection and control functions are implemented through
digital processing.
The numerical technique used in the relay is primarily based
on an adapted fast Fourier transformation (FFT), in which the
number of calculations (multiplications and additions) required
to filter out the measuring quantities remains reasonable.
By using synchronized sampling of the measured signal
(voltage or current) and a sample rate according to the 2
n
series, the FFT technique leads to a solution, which can be
realized with just a 16 bit microcontroller, without using a
separate DSP (Digital Signal Processor).
The synchronized sampling means an even number of 2
n
samples per period, e.g. 32 samples per period. This means that
the frequency must be measured and the number of samples
per period must be controlled accordingly, so that the number
of samples per period remains constant, if the frequency
changes.
Apart from the FFT calculations some protection functions also
require the symmetrical components to be calculated for
obtaining the positive, negative and zero phase sequence
components of the measured quantity. The function of the
undervoltage stage, for instance, is based on the use of the
positive phase sequence component of the voltage and the
function of the unbalanced load protection stage is based on the
use of the negative phase sequence component of the current.
Figure 2.1-1 shows a principle block diagram of a numerical
relay. The main components are the energizing inputs, digital
input elements, output relays, A/D converter and the micro
controller including memory circuits. Further a relay contains a
power supply unit and a man-machine interface (MMI).
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