Page 226 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Electrical Design Characteristics and Issues 199

N
φ
Cogeneration tie bus

52 Cogen breaker

65
C
43
CT 52A A
kW/kvar
50 43
3 51 32 65 kWh 40 V
F
(2)
T
PT
27 81 43
25
PT
CT
90
3 C 52A 90

Field
To utility
GEN connection

R Medium voltage
2.4 to 15 kV
59

FIGURE 11-2 Typical protection for CHP generator connected to utility–generator section.

the utility if utility voltage is below nominal, and helps detect issues of islanding,
voltage regulation malfunction, or faults causing voltage dip. Because system voltage
transients are normal, this relay usually has a 2-second time delay on drop out and
a 1-second time delay on pick up. Drop out is typically at 75 to 80 percent and pick
up at 90 percent of nominal voltage.
43-Manual selector switch. These are not part of the control system, but rather allow
for multiple meter readings and are often incorporated directly into digital meters.
Three manual selector switches are shown in this example: one selects phase for