Introduction; Application; Characteristics - GE NBVllA Series Instructions Manual

The NBV1 1A relay is a high-speed sensitive three-phase voltage unbalance relay that
is capable of detecting a small voltage unbalance in a three-phase system.
NBV 1 1A, when applied as a protective device, is normally used in con
time-delay relay such as the IAV5 1D relay shown in Figure 12.
one timing relay
operating a three-phase system on single phase.
The NBVllA relay is
principal parts and show their locations.
The principal application of the NBV 1 1A relay is to protect three-phase motors from
the damage that may be caused by single-phase operation.
three-phase supply to
single-phase power.
motors will maintain
voltage unbalance relay
motors will overheat and be damaged if they are more than fractionally loaded on
single-phase power,
sound an alarm. Since the NBV operates on a percentage of the unbalance in line
voltages, it will detect a single-phase condition on light load as well as on heavy
load. The NBV is usua lly connected to a bus,
group of many motors when the open circuit is between the source and the bus.
shown in Figure 4, the NBVllA is a high-speed relay,
used to prevent false tripping or alarm.
the scheme using a 27 device should be used.
available, a DC timing relay such as the RPM may be used.
the relay also provides protection against reverse phase-sequence operation.
Another application of the NBVllA relay is to block tripping when a fuse blows in
the potential transformer circuit supplying a
The NBVllA relay is
connected to the three line voltages and does not see any zero-sequence voltage.
These instructions do not purport to cover all details or variations in equipment nor to provide for
every possible contingency to be met in connection with installation,
further information be desired or should particular problems arise which are not covered sufficiently for
the purchaser's purposes,
To the extent required the products described herein meet applicable
bu t no such assurance is given with respect to local codes and ordinances because they vary greatly.
GEI-50261
VOLTAGE
TYPE

INTRODUCTION

are required at each
mounted in an

APPLICATION

a group of motors,
At this time, the voltage unbalance will be small, since the
near ly full voltage across
is required
so the NBVllA relay is used to trip the supply breaker or to

CHARACTERISTICS

basically a negative-sequence
the matter should be referred to the General Electric Company.
URBALANCE RELAY
NBVllA
terminal to
8 1 case. Figures
these motors
the open
to detect the single-phase
and it will effectively protect a
and a timing relay should be
When undervoltage tripping is permissible,
If a reliable source of DC power is
relay.
CEH
voltage
operation or maintenance.
unction with a
j
One NBV 1 1A relay and
provide protection
1, 2 and 3 identify
When one fuse blows in a
will continue to
phase and a
operation.
In this last application,
relay. The relay is
Should
ANSI, NEHA
IEEE and standards1
The
against
the
run on
sensitive
The
As