Page 549 - Industrial Power Engineering and Applications Handbook

Captive (emergency) power generation 16/523
.
-
Existing Incoming Fl’i
system MIGG, Existing source
R Y Rl Y

VillOV laaaaal w v,/110 v
Control VT Control VT Synchronizing
@J&& voltmeters to
measure AV
and fc (A0
and Af)
Common - Incoming generator (E1, f,)
Incoming
generator-‘

Sl - Double throw switch
0 - Generator breaker
V - To compare voltages of the two sources
Vb/fb : Existing voltage and frequency-meters
€,if, : Incoming voltage and frequency-meters Figure 16.29 Synchronizing by the voltmeter method
SYN . Synchroscope
-
Figure 16.28 Circuit to check Vand f - T R’i
- Existing source

will be (.f\ +f2)/2 when it is operating in parallel with T
another generator. In an infinite bus, the bus frequency,
fh, will prevail (Section 16.9.1 C and D).

To check the phase difference Synchronizing
Some methods to do this are noted below: lamps to indicate
AVand
Ec (A0 and Af)
1 Voltmeter method
2 Dark lamp method
3 Synchroscope method
1 Check synchronizing relay
5 Auto synchroniration

1 Voltineter method (Figure 16.29) Incoming generator (E,, fl)
The incoming machine is brought up to its synchronous S, - Double throw switch
speed by controlling the torque or power input to the 0 - Generator breaker
engine and the voltage to the required level with the help V - To compare voltages of the two sources
of the AVR (Figure 16.6). When the line voltage of the
incoming machine and the other source are the same and Figure 16.30 Synchronizing by the dark lamp method
fall almost in phase with each other, i.e. when the
cumulative effect of AV, A0 and Affall within permissible
limits, the three synchronizing voltmeter readings will
read almost zero. This is the condition when the
synchronizing switch or the incoming machine breaker
can be closed.
or 480 V for a 4 IS V system 1
2 Dork lamp method (Figure 16.30)
This is a simpler method to check the phase displacement
between the incoming and the existing voltage. Normally This is a better method, for it can compare both frequency
two lamps are connected in series to make them suitable and phase displacement of the two voltages, as Af’wouid
for 480 V as shown to withstand the maximum line voltage, also result in E, and is reflected by the flickering of the
in case the two voltages fall 180” apart. This voltage, AV lamps. If the frequencies ,fl and fb are not equal, the
can rise to lamps will flicker at the rate Afi i.e. (f, -,fb) times per