2
BE1-32R, BE1-32R O/U
APPLICATION
PURPOSE
The BE1-32R Directional Overpower Relay and the BE1-
32 O/U, Directional Over/Underpower Relays sense real
power flow (El cos
Θ
). These relays are solid-state
devices designed for use in single-phase or three-phase
systems to provide equipment protection for overpower
and/or underpower or to be used for supervisory control
of circuits. Both relay configurations may be used to
monitor either forward or reverse power. In the following
application examples, single-phase connections are
shown for simplicity.
APPLICATION EXAMPLES
The BE1-32 relays (R and O/U) are typically used in
applications where excessive power flow in the tripping
direction is indicative of undesirable situations. Typical
examples are discussed below:
Figure 1 - Power Relay Motoring Protection
Figure 2 - Power Relay Start Control
EXAMPLE 1 - ANTI MOTORING
In this example, the power relay is used to protect the
prime mover rather than the generator. When an ac
generator, operating in parallel with a power system,
loses prime mover torque, it remains in synchronism
with the system and continues to run as a synchronous
motor drawing sufficient power from the system to
drive the prime mover. Sustained motoring can cause
severe damage to the prime mover. The Directional
Power Relay, with its wide sensitivity range, can detect
levels of reverse real power flow as low as 0.5 Watts
secondary and provide an alarm or trip the unit off line
(See Figure 1). In this example, single phase sensing is
usually considered sufficient, since motoring is a
balanced condition.
EXAMPLE 2 - COGENERATOR CONTROL
Given that a co-generation system has automatic
engine controls, auto synchronizer, and automatic kW
and kVar controls, the system will virtually operate by
itself. The only functions not readily apparent are the
start/stop signals to the generators. Two system
configurations using a Power Relay may be utilized to
generate contact closures for start and/or stop signals.
The first configuration (Figure 2) shows a power relay
connected to the utility to sense kW. The pickup point
of the relay is set at the maximum desired utility power
level. If the power relay contact closes, the generator
will be started and automatically paralleled with the
utility system. A time delay of 15 seconds or more is
generally included in the “start” circuit to ignore
transient overload conditions.
