1-2
BE1-32R, -32 O/U GENERAL INFORMATION
Figure 1-2. Power Relay Start Control
The BE1-32R, Reverse Power Relay must be sensitive enough to detect power levels lower than those required
to motor the generator. Sensitivity is much more important on steam and hydro turbines than on reciprocating
engines and gas turbines.
Table 1-1 represents the reverse power requirements to motor a generator when the prime mover is rotating at
synchronous speed with no input power supplied by the prime mover.
Table 1-1. Motoring Reverse Power Requirements
Prime Mover Type
Percent Of Rated kW
Hydro turbines
0.2 to 2.0
Steam turbines (condensing/non-condensing)
3.0 /
3.0
Diesel engine (No cylinders firing)
25
Gas turbines
50 (due to compressor load)
The Reverse Power Relay is generally set for levels as low as possible with steam turbines typically being set
not higher than three percent and diesels and gas turbines slightly below ten percent.
Time delays are usually employed to avoid nuisance tripping caused by reverse power transient surges that may
result from synchronizing or other system disturbances. These time delays are typically set from 2 to 10
seconds, but may be set as high as 30 seconds or more.
Example 2, Co-Generator Control
In example 2, co-generation concepts are addressed. To illustrate, assume that the co-generation system has
automatic engine controls, an auto synchronizer, automatic kW, and kvar controls. The system operates virtually
by itself. The only lacking function is the
start/stop signals to the generators. Two system
configurations may be implemented to generate
contact closures for start/stop signals.
The first configuration (Figure 1-2) shows a
directional power relay connected to the utility to
sense kW. The pickup point of the relay is set at
the maximum desired utility power level. When
the utility power level exceeds the relay pickup
point, the output relay contact closes and the
generator is automatically started and paralleled
with the utility. A time delay is generally included
in the start circuit of about 15 or more seconds to
ignore transient overload conditions.
When the generator is paralleled and loaded, the
kW signal of the utility decreases by the amount
of load the generator has accepted. An
underpower relay can measure utility power and
generate a stop signal when the utility power
decreases below a selected level. A time delay
is typically provided for the stop signal of one
minute or more (however, time delays are totally
user controlled). The Basler Electric Model BE1-
32 O/U Power Relay incorporates both
overpower and underpower sensing in a single
relay unit and is ideal for this type of application.
In the second configuration the start signal is generated in the same manner as that of Figure 1-2. The start
signal setpoint may be set above the import power setting. The stop signal will require an underpower relay on
the generator output. This system is illustrated in Figure 1-3.
www
. ElectricalPartManuals
. com
