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The length of the relay pulse t
R
can never be set to a lower value than the breaker
closing time, whereas t
R
can be set to a higher value if you want the max. slip
frequency (
∆
f) to be lower to limit the rush of current of the breaker (the generators) in
connection with the synchronising.
Example:
In the light of the above-mentioned examples t
R
is changed to 0.4 sec. With a slip
frequency (
∆
f) of 0.1Hz = 36°/sec. and t
R
= 0.4 sec. the phase changes 14.4° during
the 0.4 sec. If
∆ϕ
is set to
±
10° the CSQ-3 will calculate that there is space for t
R
. With
this setting the synchronising error will be identical with the synchronising error in
example 1 (-2.8°) as the breaker closing time is the same (0.2 sec.). But the max.
∆
f
can now only be 0.138Hz and not, as in example 1, 0.277Hz. The max. slip frequency
(
∆
f) could also be controlled by setting
∆ϕ
differently. If
∆ϕ
was set to
±
5° instead of
±
10° the max.
∆
f would be 0.138Hz at t
R
= 0.2 sec. With this setting and a
∆
f of 0.1Hz
the actual synchronising error will be +2.2°. Please notice that the breaker now closes
2.2° after top and not, as in example 1, 2.8° before top. The choise of setting must be
based on the knowledge of the actual installation in which the CSQ-3 is applied. But
the examples are to show that t
R
and
∆ϕ
are inextricably connected and influence the
same parameters, but with different results as to the calculation of the actual
synchronising error.
If t
R
is set to infinite (∞) the max. allowable
∆
f can no longer be controlled by means of
t
R
. When t
R
is set to infinite the setting of t
d
is automatically activated. Infinite t
R
is
primarily used where the CSQ-3 is applied as supervision of an automatic
synchronising system or in connection with closing of a tie breaker where you want to
control frequency, phase and voltage to be within certain values before the breaker is
closed.
The setting of t
d
is to be calculated from
∆ϕ
and the estimated max. allowable
∆
f.
(
∆ϕ
-) + (
∆ϕ
+)
t
d
=
360 x
∆
f
Example 1:
∆ϕ
is set to
±
7°, and a max.
∆
f of 0.05Hz at the moment of synchronising is estimated
to be allowable.
| -7 | +7
t
d
=
360 x 0.05
t
d
= 0.77 sec. ~ 0.8 sec.
Please notice that when t
R
is set to infinite (∞) the synchronising pulse (the relay
contact of the CSQ-3) is interrupted the moment the phase is outside the set phase
window. As the timer t
d
starts the moment the phase is within the set phase window
