Governing Fundamentals and Power Management phần 6 potx

Manual 26260 Governing Fundamentals and Power Management

Woodward 45

Assuming φ continues to rotate at a constant rate, and that the circuit-breaker

time delay (Tb), the synchronizer window (φw), and selected synchronizer window

dwell time (Twd) are known, the worst case value which the synchronizer will

allow (φs) can be predicted. φs is equal to φ at the time the synchronizer issues

the breaker closure command (φw in the worst case) plus the change in φ due to

the rate of change in φ times the breaker delay (Tb in the worst case). Therefore,

φ = φwc when φ (at the instant the breaker closure command is issued) = φw. The

rate of change of φ (φ/s) is the total degrees in the window divided by the dwell

time of the window or

2õ .

T

w

wd

then = = + 2

T wc s w (T ) w

wd

θ θθ b

θ

For Example:

Assume a synchronizer configured for a window of ±10 degrees and a window

dwell time of 1/2 second. Assume the breaker is never slower than 13 cycles.

If θw = 10°

Twd = 0.5 s

Tb = 13 cycles

60 cycles/second = 0.217 s

then = = 10 + 2(10 )

0.5 . (0.217 .)

= 18.7

wc s

wc

Θ

Θ

θ ° °

°

sec

sec

In comparison, a window of ±5° and a window dwell time of 1 second, using the

same breaker.

= =5 + 2(5 ) (0.217 .)

1 .

= 7.2

wc s

wc

θ θ

θ

° °

°

sec

sec

Figure 7-9. Phase Angle Relationship