User manual, Check synchroscope CSQ-3
4189340263L (UK)
Calculation of the actual synchronising error – not to be mistaken for the max.
synchronising error which is solely determined by the chosen
∆ϕ
window
The next examples apply to situations where t
R
is set in the range 0.1...1 sec.
Example:
With a slip frequency (
∆
f) of 0.1Hz the phase changes with a rate of 36°/sec. If
∆ϕ
is
set to
±
10° and t
R
is set to 0.2 sec. = breaker closing time, the actual synchronising
error can be calculated.
The moment the phase is within the set phase window (
∆ϕ
) the relay of the CSQ-3 is
activated on condition that there is space for the chosen t
R
, in this case 0.2 sec. If
∆
f is
too big it will cause lack of space for the chosen t
R
time within the chosen
∆ϕ
window.
Example 1:
With a phase change of 36°/sec. the phase will change 7.2° during the 0.2 sec. This
means that we can now calculate the phase displacement at the exact moment when
the breaker closes.
∆ϕ
is set to -10° and +10°. The CSQ-3 relay will be activated -10°
before top (12 o’clock position), and after 7.2° the breaker closes which means that the
breaker closes 10° - 7.2° = 2.8° before top, that is an actual synchronising error of -
2.8°. Applying the formula on page 17 the max.
∆
f with the shown settings can be
calculated to be 0.277Hz.
Example 2:
If we assume that the slip frequency in the actual case is 0.2Hz the phase changes
with a rate of 72°/sec. With a phase change of 72°/sec. the phase will change 14.4°
during the 0.2 sec. which gives a synchronising error of 10° - 14.4° = -4.4°. The
negative result means that the breaker closed 4.4° after top, that is an actual
synchronising error of +4.4°.
Example 3:
The same as examples 1 and 2 but with a slip frequency of 0.3Hz = 108°/sec. At t
R
=
0.2 sec. the phase will change 21.6°. As the
∆ϕ
window is set to
±
10°, the CSQ-3 will
calculate that there is no longer space for a t
R
pulse of 0.2 sec. and therefore no relay
pulse is emitted.
General formula for the above-mentioned:
Actual synchronising error = (
∆ϕ
-) - 360 x
∆
f x breaker closing time (t
R
).
Alternatively at negative slip frequency:
Actual synchronising error = (
∆ϕ
+) - 360 x
∆
f x breaker closing time (t
R
).
If the result is negative the synchronising will take place after top (0°) provided that
there is space for t
R
within the
∆ϕ
window.
If you want to avoid synchronising after top,
∆ϕ
is set asymmetrically. At positive slip
frequency (
∆
f) as in the shown example a setting of
∆ϕ
- to -10° and
∆ϕ
+ to +5° would
have as a result that synchronising after top of more than 5° would not be possible.
