Basler Electric BE1-25A - Manual (Page 14)

may cause winding, iron, or shaft stress. Accordingly, the selection of closing direction and permissible
limits should consider these and other pertinent application data.
Defining the Parameters
These application notes are not intended to cover every possible set of circumstances, but rather to
provide a basic description of slip frequency synchronization. The relationship between slip, advance
angle (or window), and breaker closing time is shown in Figure 1-1, and described by the formula:
𝐴
𝐴
= 360(𝑇
𝐶𝐵
+ 𝑇
𝑅
)𝐹
𝑆
where:
A
A
= advance angle in degrees. This is the time, measured in electrical degrees, between
initiation of breaker closure and the actual closure of the breaker contacts.
360 = degrees per slip cycle.
T
CB
= the closing time of the circuit breaker in seconds. This is the time required from the closure
of the synchronizer output contact to the actual closing of the circuit breaker contacts.
T
CB
is preset in synchronizer memory for each different breaker controlled by the synchronizer.
EXCEPTION: In some applications,
T
CB
may represent the characteristic closing time of a
group of breakers all having the same closing time.
T
R
= response time, in seconds, of the synchronizer breaker close output relay. (A non-
adjustable parameter approximately 0.008 second.)
F
S
= slip frequency in cycles per second. This is the oncoming generator frequency minus the
bus frequency: positive for a generator speed higher than bus, negative for lower.
The relationships defined above should prove helpful in determining the settings for the auto-
synchronizer. Note that reducing the advance angle (or window) also reduces the absolute value of the
slip frequency (which is the maximum permissible speed difference for which the machine is allowed to
close onto the bus). Lower slip frequencies are softer (i.e., less liable to produce system disturbance or
machine damage).
Higher frequencies, on the other hand, are quicker (i.e., allow synchronization to be accomplished faster).
Again, these considerations should be balanced against others such as:
1. How fast do I need to be on line?
2. How critical is the machine?
3. How expensive is the machine as against possible outage (down) times?
A proper synchronizer application will take into account the considerations mentioned above, as well as
others that may be unique to the system under consideration. See Figure 1-1.
Figure 1-1. Slip, Advance Angle, and Breaker Closing Time
1-4 BE1-25A General Information 9146600990 Rev S