REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-5
3.1.2. Control and protection function sequence
3.1.2.1. Repetition rate
The operation of the various protection functions is controlled
entirely by the protection system software. The functions are
divided into routines that are processed in sequence by the
computer. The frequency at which the processing cycle is
repeated (repetition rate) is determined according to the
technical requirements of the scheme.
For many functions, this depends essentially on the time within
which tripping is required to take place, i.e. the faster tripping
has to take place, the higher the repetition rate. Typical
relationships between operating time and repetition rate can be
seen from Table 3.1.
Repetition rate Explanation Delay time
4
³ 4 times every 20 ms
1)
< 40 ms
2
³ 2 times every 20 ms
40 ... 199 ms
1
³ 1 times every 20 ms ³ 200 ms
1)
for 50 Hz or 60 Hz
Table 3.1 Typical protection function repetition rates
The repetition rates of some of the functions, e.g. differential
protection, earth fault protection or purely logic functions, do not
depend on their settings.
The scanning of the binary inputs and the setting of the signal-
ling and tripping outputs takes place at the sampling rate of the
analogue inputs.
Whilst the operating speed of the various protection functions is
more than adequate for their purpose, they do operate in se-
quence so that the effective operating times of such outputs as
starting and tripping signals are subject to some variation. This
variation is determined by the repetition rate controlling the
operation of the function. Typical values are given in Table 3.2.
Repetition rate Variation
4 -2...+5 ms
2 -2...+10 ms
1 -2...+20 ms
Table 3.2 Variation in the operating time of output signals of
protection functions in relation to their repetition rates
To Next Page
Loading...
