INBD
T107
RIGHT GENERATOR
DPCT NO. 1
RIGHT GENERATOR POWER PANEL P32
C
SEE B
SEE C
SEE D
119AL
T115
APU TIE
BUS DPCT
T111
APU GEN
DPCT
T116
EXT PWR
TIE BUS
DPCT
T122 GROUND POWER CURRENT TRANSFORMER
APU/EXTERNAL POWER PANEL P34
D
Current Transformers Component Locations
Figure 1 (Sheet 2)
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MAINTENANCE MANUAL
~...................................................................... | NAME | LOCATION | ........................................................................ | Left generator differential | P31 (Left generator | | protection current transformer | power panel) | | (DPCT) No. 1 | | ........................................................................ | Left generator DPCT No. 2 | P6 (Main power | | | distribution panel) | ........................................................................ | Left overlap current transformer | P31 | ........................................................................ | Right generator DPCT No. 1 | P32 (Right generator | | | power panel) | ........................................................................ | Right generator DPCT No. 2 | P6 | ........................................................................ | Right overlap current transformer | P32 | ........................................................................ | APU generator DPCT | P34 (APU/external | | | power panel) | ........................................................................ | Ground power current transformer | P34 | ........................................................................ | R tie bus DPCT | P32 | ........................................................................ | L tie bus DPCT | P31 | ........................................................................ | APU tie bus DPCT | P34 | ........................................................................ | External power tie bus DPCT | P34 | 2........................................….............................1
3. Operation_________
A. Functional Description
(1) Generator Control Unit Protection
(a)
The generator control units continuously monitor power quality. Each provides the following protection functions: over/under voltage, over/under frequency, open phase, integrated drive generator (IDG) underspeed, shorted rotating diode, shorted permanent magnet generator, failed generator circuit breaker (GCB), and BTB lockout. (The rotating diode and PMG are components in the IDG.) The APU GCU functions identically but has no IDG underspeed protection.
(b)
A GCU detecting an IDG underspeed condition opens only its GCB. A GCU detecting any other protection condition opens its generator field control relay (GCR) and GCB. An APU protection function causes the APU GCU to open the APU GCR and the auxiliary power breaker (APB).
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(c) (d) (e) (f) (g) Each GCU monitors voltage on the generator side of its GCB or APB. This is the point of regulation. An overvoltage condition occurs if any phase voltage is greater than 130-volts ac. The larger the overvoltage, the faster the effected breakers are tripped.For undervoltage protection, each GCU takes the average of its three phase voltages. If this voltage remains at or below 104.5 |1.5-volts ac, an undervoltage condition exists. The breakers effected open in 9 |1 seconds. Undervoltage protection is prevented from operating by underspeed or underfrequency activation, as well as an open GCR.Each GCU monitors its associated IDG for over/under frequency protection. The underfrequency level begins at 370-375 Hz. Minimum overfrequency levels are 425-430 Hz. An overfrequency level of 425-430 Hz for 0.8 to 1.6 seconds trips the GCB and GCR. Overfrequency protection is locked out by shorted rotating diode protection (only if frequency does not exceed 435-445 Hz). An underfrequency level of 370-375 Hz for 0.8 to 1.6 seconds trips the GCB and GCR. For an underfrequency level of 345-355 Hz. the GCB and GCR trip after 0.1 to 0.2 seconds. Underfrequency detection locks out undervoltage protection. Underfrequency protection is prevented from operating by underspeed activation. Underfrequency activation locks out underspeed protection.Open phase protection is in effect when the lowest phase current is 6 |5 amps, and the next lowest phase current is 40 |5 amps or more. The effected breakers open in 4 |0.5-seconds.The right and left GCU's provide IDG underspeed protection. Each GCU monitors input shaft speed of its generator. An underspeed condition occurs when shaft speed falls to, and remains below, 4,300 |30 rpm. The GCB of the IDG effected is tripped in 0.15 |0.05 seconds. Underspeed activation prevents operation of undervoltage and underfrequency protection functions.
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